Sync from upstream

This commit is contained in:
吴凡
2016-07-01 11:03:25 +08:00
296 changed files with 16524 additions and 8059 deletions

3
.gitignore vendored
View File

@@ -58,3 +58,6 @@ java/*.iml
java/target
**/*.pyc
.idea
build/VS2010/FlatBuffers.sdf
build/VS2010/FlatBuffers.opensdf
build/VS2010/ipch/**/*.ipch

View File

@@ -12,8 +12,9 @@ env:
matrix:
- BUILD_TYPE=Debug BIICODE=false
- BUILD_TYPE=Release BIICODE=false
- BUILD_TYPE=Release BIICODE=true
- BUILD_TYPE=Debug BIICODE=true
# biicode .deb files no longer available.
# - BUILD_TYPE=Release BIICODE=true
# - BUILD_TYPE=Debug BIICODE=true
global:
- GCC_VERSION="4.9"

View File

@@ -63,6 +63,13 @@ function(build_flatbuffers flatbuffers_schemas
set(FLATC_TARGET flatc)
set(FLATC flatc)
endif()
set(FLATC_SCHEMA_ARGS --gen-mutable)
if(FLATBUFFERS_FLATC_SCHEMA_EXTRA_ARGS)
set(FLATC_SCHEMA_ARGS
${FLATBUFFERS_FLATC_SCHEMA_EXTRA_ARGS}
${FLATC_SCHEMA_ARGS}
)
endif()
set(schema_glob "*.fbs")
# Generate the include files parameters.
@@ -86,7 +93,7 @@ function(build_flatbuffers flatbuffers_schemas
set(generated_include ${generated_includes_dir}/${filename}_generated.h)
add_custom_command(
OUTPUT ${generated_include}
COMMAND ${FLATC} --gen-mutable
COMMAND ${FLATC} ${FLATC_SCHEMA_ARGS}
-o ${generated_includes_dir}
${include_params}
-c ${schema}

View File

@@ -9,6 +9,7 @@ option(FLATBUFFERS_INSTALL "Enable the installation of targets." ON)
option(FLATBUFFERS_BUILD_FLATLIB "Enable the build of the flatbuffers library" ON)
option(FLATBUFFERS_BUILD_FLATC "Enable the build of the flatbuffers compiler" ON)
option(FLATBUFFERS_BUILD_FLATHASH "Enable the build of flathash" ON)
option(FLATBUFFERS_BUILD_GRPCTEST "Enable the build of grpctest" OFF)
if(NOT FLATBUFFERS_BUILD_FLATC AND FLATBUFFERS_BUILD_TESTS)
message(WARNING
@@ -17,6 +18,7 @@ if(NOT FLATBUFFERS_BUILD_FLATC AND FLATBUFFERS_BUILD_TESTS)
endif()
set(FlatBuffers_Library_SRCS
include/flatbuffers/code_generators.h
include/flatbuffers/flatbuffers.h
include/flatbuffers/hash.h
include/flatbuffers/idl.h
@@ -26,6 +28,7 @@ set(FlatBuffers_Library_SRCS
src/idl_parser.cpp
src/idl_gen_text.cpp
src/reflection.cpp
src/util.cpp
)
set(FlatBuffers_Compiler_SRCS
@@ -37,7 +40,10 @@ set(FlatBuffers_Compiler_SRCS
src/idl_gen_php.cpp
src/idl_gen_python.cpp
src/idl_gen_fbs.cpp
src/idl_gen_grpc.cpp
src/flatc.cpp
grpc/src/compiler/cpp_generator.h
grpc/src/compiler/cpp_generator.cc
)
set(FlatHash_SRCS
@@ -68,11 +74,22 @@ set(FlatBuffers_Sample_Text_SRCS
include/flatbuffers/util.h
src/idl_parser.cpp
src/idl_gen_text.cpp
src/util.cpp
samples/sample_text.cpp
# file generated by running compiler on samples/monster.fbs
${CMAKE_CURRENT_BINARY_DIR}/samples/monster_generated.h
)
set(FlatBuffers_GRPCTest_SRCS
include/flatbuffers/flatbuffers.h
include/flatbuffers/grpc.h
tests/monster_test.grpc.fb.h
tests/monster_test.grpc.fb.cc
grpc/tests/grpctest.cpp
# file generated by running compiler on samples/monster.fbs
${CMAKE_CURRENT_BINARY_DIR}/samples/monster_generated.h
)
# source_group(Compiler FILES ${FlatBuffers_Compiler_SRCS})
# source_group(Tests FILES ${FlatBuffers_Tests_SRCS})
@@ -80,13 +97,47 @@ if(APPLE)
set(CMAKE_CXX_FLAGS
"${CMAKE_CXX_FLAGS} -std=c++11 -stdlib=libc++ -Wall -pedantic -Werror -Wextra")
elseif(CMAKE_COMPILER_IS_GNUCXX)
if(CYGWIN)
set(CMAKE_CXX_FLAGS
"${CMAKE_CXX_FLAGS} -std=gnu++11")
else(CYGWIN)
set(CMAKE_CXX_FLAGS
"${CMAKE_CXX_FLAGS} -std=c++0x")
endif(CYGWIN)
set(CMAKE_CXX_FLAGS
<<<<<<< HEAD
"${CMAKE_CXX_FLAGS} -std=c++0x -Wall -pedantic -Werror -Wextra -Werror=shadow")
elseif("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
set(CMAKE_CXX_FLAGS
"${CMAKE_CXX_FLAGS} -std=c++0x -stdlib=libc++ -Wall -pedantic -Werror -Wextra")
set(CMAKE_EXE_LINKER_FLAGS
"${CMAKE_EXE_LINKER_FLAGS} -lc++abi")
=======
"${CMAKE_CXX_FLAGS} -Wall -pedantic -Werror -Wextra -Werror=shadow")
if (GCC_VERSION VERSION_GREATER 4.4)
set(CMAKE_CXX_FLAGS
"${CMAKE_CXX_FLAGS} -Wunused-result -Werror=unused-result")
endif()
# Certain platforms such as ARM do not use signed chars by default
# which causes issues with certain bounds checks.
set(CMAKE_CXX_FLAGS
"${CMAKE_CXX_FLAGS} -fsigned-char")
elseif("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
set(CMAKE_CXX_FLAGS
"${CMAKE_CXX_FLAGS} -std=c++0x -stdlib=libc++ -Wall -pedantic -Werror -Wextra")
if(NOT "${CMAKE_SYSTEM_NAME}" MATCHES "FreeBSD")
set(CMAKE_EXE_LINKER_FLAGS
"${CMAKE_EXE_LINKER_FLAGS} -lc++abi")
endif()
# Certain platforms such as ARM do not use signed chars by default
# which causes issues with certain bounds checks.
set(CMAKE_CXX_FLAGS
"${CMAKE_CXX_FLAGS} -fsigned-char")
>>>>>>> 48f37f9e0a04f2b60046dda7fef20a8b0ebc1a70
endif()
if(FLATBUFFERS_CODE_COVERAGE)
@@ -101,6 +152,7 @@ if(BIICODE)
endif()
include_directories(include)
include_directories(grpc)
if(FLATBUFFERS_BUILD_FLATLIB)
add_library(flatbuffers STATIC ${FlatBuffers_Library_SRCS})
@@ -108,6 +160,9 @@ endif()
if(FLATBUFFERS_BUILD_FLATC)
add_executable(flatc ${FlatBuffers_Compiler_SRCS})
if(NOT FLATBUFFERS_FLATC_EXECUTABLE)
set(FLATBUFFERS_FLATC_EXECUTABLE $<TARGET_FILE:flatc>)
endif()
endif()
if(FLATBUFFERS_BUILD_FLATHASH)
@@ -119,7 +174,7 @@ function(compile_flatbuffers_schema_to_cpp SRC_FBS)
string(REGEX REPLACE "\\.fbs$" "_generated.h" GEN_HEADER ${SRC_FBS})
add_custom_command(
OUTPUT ${GEN_HEADER}
COMMAND flatc -c --no-includes --gen-mutable -o "${SRC_FBS_DIR}" "${CMAKE_CURRENT_SOURCE_DIR}/${SRC_FBS}"
COMMAND "${FLATBUFFERS_FLATC_EXECUTABLE}" -c --no-includes --gen-mutable -o "${SRC_FBS_DIR}" "${CMAKE_CURRENT_SOURCE_DIR}/${SRC_FBS}"
DEPENDS flatc)
endfunction()
@@ -128,7 +183,7 @@ function(compile_flatbuffers_schema_to_binary SRC_FBS)
string(REGEX REPLACE "\\.fbs$" ".bfbs" GEN_BINARY_SCHEMA ${SRC_FBS})
add_custom_command(
OUTPUT ${GEN_BINARY_SCHEMA}
COMMAND flatc -b --schema -o "${SRC_FBS_DIR}" "${CMAKE_CURRENT_SOURCE_DIR}/${SRC_FBS}"
COMMAND "${FLATBUFFERS_FLATC_EXECUTABLE}" -b --schema -o "${SRC_FBS_DIR}" "${CMAKE_CURRENT_SOURCE_DIR}/${SRC_FBS}"
DEPENDS flatc)
endfunction()
@@ -143,6 +198,14 @@ if(FLATBUFFERS_BUILD_TESTS)
add_executable(flatsampletext ${FlatBuffers_Sample_Text_SRCS})
endif()
if(FLATBUFFERS_BUILD_GRPCTEST)
if(CMAKE_COMPILER_IS_GNUCXX)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-unused-parameter")
endif()
add_executable(grpctest ${FlatBuffers_GRPCTest_SRCS})
target_link_libraries(grpctest grpc++_unsecure grpc pthread dl)
endif()
if(FLATBUFFERS_INSTALL)
install(DIRECTORY include/flatbuffers DESTINATION include)
if(FLATBUFFERS_BUILD_FLATLIB)

View File

@@ -1,4 +1,5 @@
#!/bin/bash -eu
#
# Copyright (c) 2013 Google, Inc.
#
# This software is provided 'as-is', without any express or implied

View File

@@ -19,26 +19,34 @@ LOCAL_PATH := $(call my-dir)/../..
include $(LOCAL_PATH)/android/jni/include.mk
LOCAL_PATH := $(call realpath-portable,$(LOCAL_PATH))
# Empty static library so that other projects can include FlatBuffers as a
# module.
# Empty static library so that other projects can include just the basic
# FlatBuffers headers as a module.
include $(CLEAR_VARS)
LOCAL_MODULE := flatbuffers
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
LOCAL_EXPORT_CPPFLAGS := -std=c++11 -fexceptions -Wall -Wno-literal-suffix
include $(BUILD_STATIC_LIBRARY)
# static library that additionally includes text parsing/generation/reflection
# for projects that want richer functionality.
include $(CLEAR_VARS)
LOCAL_MODULE := flatbuffers_extra
LOCAL_SRC_FILES := src/idl_parser.cpp \
src/idl_gen_text.cpp \
src/reflection.cpp \
src/util.cpp
LOCAL_STATIC_LIBRARIES := flatbuffers
include $(BUILD_STATIC_LIBRARY)
# FlatBuffers test
include $(CLEAR_VARS)
LOCAL_MODULE := FlatBufferTest
LOCAL_SRC_FILES := android/jni/main.cpp \
tests/test.cpp \
src/idl_parser.cpp \
src/idl_gen_text.cpp \
src/idl_gen_fbs.cpp \
src/idl_gen_general.cpp \
src/reflection.cpp
src/idl_gen_general.cpp
LOCAL_LDLIBS := -llog -landroid
LOCAL_STATIC_LIBRARIES := android_native_app_glue flatbuffers
LOCAL_STATIC_LIBRARIES := android_native_app_glue flatbuffers_extra
LOCAL_ARM_MODE := arm
include $(BUILD_SHARED_LIBRARY)

View File

@@ -18,5 +18,5 @@ APP_PROJECT_PATH := $(call my-dir)/..
APP_STL := gnustl_static
APP_ABI := armeabi-v7a
NDK_TOOLCHAIN_VERSION := 4.8
APP_CPPFLAGS += -std=c++11

View File

@@ -1,4 +1,18 @@
#!/bin/bash
#
# Copyright 2016 Google Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
sudo apt-get update -qq
sudo apt-get install libglu1-mesa-dev xorg-dev

View File

@@ -263,6 +263,7 @@
</ProjectReference>
</ItemDefinitionGroup>
<ItemGroup>
<ClCompile Include="..\..\src\util.cpp" />
<ClInclude Include="..\..\include\flatbuffers\flatbuffers.h" />
<ClInclude Include="..\..\include\flatbuffers\idl.h" />
<ClInclude Include="..\..\include\flatbuffers\util.h" />

View File

@@ -263,6 +263,7 @@
</ProjectReference>
</ItemDefinitionGroup>
<ItemGroup>
<ClCompile Include="..\..\src\util.cpp" />
<ClInclude Include="..\..\include\flatbuffers\flatbuffers.h" />
<ClInclude Include="..\..\include\flatbuffers\idl.h" />
<ClInclude Include="..\..\include\flatbuffers\util.h" />

View File

@@ -273,6 +273,7 @@
<ClCompile Include="..\..\src\idl_parser.cpp" />
<ClCompile Include="..\..\src\idl_gen_text.cpp" />
<ClCompile Include="..\..\src\reflection.cpp" />
<ClCompile Include="..\..\src\util.cpp" />
<ClCompile Include="..\..\tests\test.cpp" />
</ItemGroup>
<Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />

View File

@@ -11,6 +11,9 @@
5AC48C391ACA9A0A008132C5 /* idl_gen_general.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 8CD8717A19CB937D0012A827 /* idl_gen_general.cpp */; };
61823BBC53544106B6DBC38E /* idl_parser.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 3709AC883348409592530AE6 /* idl_parser.cpp */; settings = {COMPILER_FLAGS = ""; }; };
61FF3C34FBEC4819A1C30F92 /* sample_text.cpp in Sources */ = {isa = PBXBuildFile; fileRef = ECCEBFFA6977404F858F9739 /* sample_text.cpp */; settings = {COMPILER_FLAGS = ""; }; };
8C2AAE0A1CB338A8000CC78D /* util.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 8C2AAE091CB338A8000CC78D /* util.cpp */; settings = {ASSET_TAGS = (); }; };
8C2AAE0B1CB338CD000CC78D /* util.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 8C2AAE091CB338A8000CC78D /* util.cpp */; settings = {ASSET_TAGS = (); }; };
8C2AAE0C1CB338CE000CC78D /* util.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 8C2AAE091CB338A8000CC78D /* util.cpp */; settings = {ASSET_TAGS = (); }; };
8C303C591975D6A700D7C1C5 /* idl_gen_go.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 8C303C581975D6A700D7C1C5 /* idl_gen_go.cpp */; };
8C6905FD19F835B400CB8866 /* idl_gen_fbs.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 8C6905EC19F8357300CB8866 /* idl_gen_fbs.cpp */; };
8C78573E1BD5AE2C00C53C34 /* idl_gen_js.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 8C78573D1BD5AE2C00C53C34 /* idl_gen_js.cpp */; };
@@ -38,6 +41,7 @@
420E3BC724ED4A008D79297F /* flatsampletext */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; path = flatsampletext; sourceTree = BUILT_PRODUCTS_DIR; };
5EE44BFFAF8E43F485859145 /* sample_binary.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = sample_binary.cpp; path = samples/sample_binary.cpp; sourceTree = SOURCE_ROOT; };
6AD24EEB3D024825A37741FF /* test.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = test.cpp; path = tests/test.cpp; sourceTree = SOURCE_ROOT; };
8C2AAE091CB338A8000CC78D /* util.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = util.cpp; path = src/util.cpp; sourceTree = "<group>"; };
8C303C581975D6A700D7C1C5 /* idl_gen_go.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = idl_gen_go.cpp; path = src/idl_gen_go.cpp; sourceTree = "<group>"; };
8C6905EC19F8357300CB8866 /* idl_gen_fbs.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = idl_gen_fbs.cpp; path = src/idl_gen_fbs.cpp; sourceTree = "<group>"; };
8C78573D1BD5AE2C00C53C34 /* idl_gen_js.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = idl_gen_js.cpp; path = src/idl_gen_js.cpp; sourceTree = "<group>"; };
@@ -58,6 +62,7 @@
28237E300FE042DEADA302D3 /* Source Files */ = {
isa = PBXGroup;
children = (
8C2AAE091CB338A8000CC78D /* util.cpp */,
D2DA271C1BFFBC06000F9168 /* idl_gen_php.cpp */,
8C78573D1BD5AE2C00C53C34 /* idl_gen_js.cpp */,
8CA854B21B04244A00040A06 /* idl_gen_python.cpp */,
@@ -246,6 +251,7 @@
61FF3C34FBEC4819A1C30F92 /* sample_text.cpp in Sources */,
AE5F47A7DCB44781B657F062 /* idl_gen_text.cpp in Sources */,
1963D7D2A57344A3B1C1713F /* idl_parser.cpp in Sources */,
8C2AAE0B1CB338CD000CC78D /* util.cpp in Sources */,
);
runOnlyForDeploymentPostprocessing = 0;
};
@@ -265,6 +271,7 @@
AA9BACF55EB3456BA2F633BB /* flatc.cpp in Sources */,
BE03D7B0C9584DD58B50ED34 /* idl_gen_cpp.cpp in Sources */,
AD71FEBEE4E846529002C1F0 /* idl_gen_text.cpp in Sources */,
8C2AAE0A1CB338A8000CC78D /* util.cpp in Sources */,
8C8774641B703E1200E693F5 /* idl_gen_fbs.cpp in Sources */,
A9C9A99F719A4ED58DC2D2FC /* idl_parser.cpp in Sources */,
8CA854B31B04244A00040A06 /* idl_gen_python.cpp in Sources */,
@@ -280,6 +287,7 @@
files = (
8C8774631B703D4800E693F5 /* reflection.cpp in Sources */,
5AC48C391ACA9A0A008132C5 /* idl_gen_general.cpp in Sources */,
8C2AAE0C1CB338CE000CC78D /* util.cpp in Sources */,
8C6905FD19F835B400CB8866 /* idl_gen_fbs.cpp in Sources */,
E0680D6B5BFD484BA9D88EE8 /* idl_gen_text.cpp in Sources */,
61823BBC53544106B6DBC38E /* idl_parser.cpp in Sources */,

View File

@@ -1,8 +0,0 @@
<html>
<head>
<meta http-equiv="refresh" content="0;url=html/index.html">
</head>
<body>
<a href="html/index.html">Click here if you are not redirected.</a>
</body>
</html>

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@@ -1,97 +0,0 @@
function toggleVisibility(linkObj)
{
var base = $(linkObj).attr('id');
var summary = $('#'+base+'-summary');
var content = $('#'+base+'-content');
var trigger = $('#'+base+'-trigger');
var src=$(trigger).attr('src');
if (content.is(':visible')===true) {
content.hide();
summary.show();
$(linkObj).addClass('closed').removeClass('opened');
$(trigger).attr('src',src.substring(0,src.length-8)+'closed.png');
} else {
content.show();
summary.hide();
$(linkObj).removeClass('closed').addClass('opened');
$(trigger).attr('src',src.substring(0,src.length-10)+'open.png');
}
return false;
}
function updateStripes()
{
$('table.directory tr').
removeClass('even').filter(':visible:even').addClass('even');
}
function toggleLevel(level)
{
$('table.directory tr').each(function() {
var l = this.id.split('_').length-1;
var i = $('#img'+this.id.substring(3));
var a = $('#arr'+this.id.substring(3));
if (l<level+1) {
i.removeClass('iconfopen iconfclosed').addClass('iconfopen');
a.html('&#9660;');
$(this).show();
} else if (l==level+1) {
i.removeClass('iconfclosed iconfopen').addClass('iconfclosed');
a.html('&#9658;');
$(this).show();
} else {
$(this).hide();
}
});
updateStripes();
}
function toggleFolder(id)
{
// the clicked row
var currentRow = $('#row_'+id);
// all rows after the clicked row
var rows = currentRow.nextAll("tr");
var re = new RegExp('^row_'+id+'\\d+_$', "i"); //only one sub
// only match elements AFTER this one (can't hide elements before)
var childRows = rows.filter(function() { return this.id.match(re); });
// first row is visible we are HIDING
if (childRows.filter(':first').is(':visible')===true) {
// replace down arrow by right arrow for current row
var currentRowSpans = currentRow.find("span");
currentRowSpans.filter(".iconfopen").removeClass("iconfopen").addClass("iconfclosed");
currentRowSpans.filter(".arrow").html('&#9658;');
rows.filter("[id^=row_"+id+"]").hide(); // hide all children
} else { // we are SHOWING
// replace right arrow by down arrow for current row
var currentRowSpans = currentRow.find("span");
currentRowSpans.filter(".iconfclosed").removeClass("iconfclosed").addClass("iconfopen");
currentRowSpans.filter(".arrow").html('&#9660;');
// replace down arrows by right arrows for child rows
var childRowsSpans = childRows.find("span");
childRowsSpans.filter(".iconfopen").removeClass("iconfopen").addClass("iconfclosed");
childRowsSpans.filter(".arrow").html('&#9658;');
childRows.show(); //show all children
}
updateStripes();
}
function toggleInherit(id)
{
var rows = $('tr.inherit.'+id);
var img = $('tr.inherit_header.'+id+' img');
var src = $(img).attr('src');
if (rows.filter(':first').is(':visible')===true) {
rows.css('display','none');
$(img).attr('src',src.substring(0,src.length-8)+'closed.png');
} else {
rows.css('display','table-row'); // using show() causes jump in firefox
$(img).attr('src',src.substring(0,src.length-10)+'open.png');
}
}

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@@ -1,149 +0,0 @@
<!-- HTML header for doxygen 1.8.6-->
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/>
<meta http-equiv="X-UA-Compatible" content="IE=9"/>
<meta name="generator" content="Doxygen 1.8.7"/>
<title>FlatBuffers: Main Page</title>
<link href="tabs.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="dynsections.js"></script>
<link href="navtree.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="resize.js"></script>
<script type="text/javascript" src="navtree.js"></script>
<script type="text/javascript">
$(document).ready(initResizable);
$(window).load(resizeHeight);
</script>
<link href="style.css" rel="stylesheet" type="text/css" />
<link href="https://fonts.googleapis.com/css?family=Roboto:300,400,400italic,500,500italic,700,700italic|Roboto+Mono:400,700" rel="stylesheet">
</head>
<body>
<div id="top"><!-- do not remove this div, it is closed by doxygen! -->
<div id="titlearea" style="height: 110px;">
<table cellspacing="0" cellpadding="0">
<tbody>
<tr style="height: 56px;">
<td id="commonprojectlogo">
<img alt="Logo" src="fpl_logo_small.png"/>
</td>
<td style="padding-left: 0.5em;">
<div id="projectname">FlatBuffers
</div>
<div style="font-size:12px;">
An open source project by <a href="https://developers.google.com/games/#Tools">FPL</a>.
</div>
</td>
</tr>
</tbody>
</table>
</div>
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<div class="textblock"><p>FlatBuffers is an efficient cross platform serialization library for C++, Java, C#, Go, Python and JavaScript (C, PHP &amp; Ruby in progress). It was originally created at Google for game development and other performance-critical applications.</p>
<p>It is available as Open Source on <a href="http://github.com/google/flatbuffers">GitHub</a> under the Apache license, v2 (see LICENSE.txt).</p>
<h2>Why use FlatBuffers?</h2>
<ul>
<li><b>Access to serialized data without parsing/unpacking</b> - What sets FlatBuffers apart is that it represents hierarchical data in a flat binary buffer in such a way that it can still be accessed directly without parsing/unpacking, while also still supporting data structure evolution (forwards/backwards compatibility).</li>
<li><b>Memory efficiency and speed</b> - The only memory needed to access your data is that of the buffer. It requires 0 additional allocations (in C++, other languages may vary). FlatBuffers is also very suitable for use with mmap (or streaming), requiring only part of the buffer to be in memory. Access is close to the speed of raw struct access with only one extra indirection (a kind of vtable) to allow for format evolution and optional fields. It is aimed at projects where spending time and space (many memory allocations) to be able to access or construct serialized data is undesirable, such as in games or any other performance sensitive applications. See the <a href="md__benchmarks.html">benchmarks</a> for details.</li>
<li><b>Flexible</b> - Optional fields means not only do you get great forwards and backwards compatibility (increasingly important for long-lived games: don't have to update all data with each new version!). It also means you have a lot of choice in what data you write and what data you don't, and how you design data structures.</li>
<li><b>Tiny code footprint</b> - Small amounts of generated code, and just a single small header as the minimum dependency, which is very easy to integrate. Again, see the benchmark section for details.</li>
<li><b>Strongly typed</b> - Errors happen at compile time rather than manually having to write repetitive and error prone run-time checks. Useful code can be generated for you.</li>
<li><p class="startli"><b>Convenient to use</b> - Generated C++ code allows for terse access &amp; construction code. Then there's optional functionality for parsing schemas and JSON-like text representations at runtime efficiently if needed (faster and more memory efficient than other JSON parsers).</p>
<p class="startli">Java and Go code supports object-reuse. C# has efficient struct based accessors.</p>
</li>
<li><b>Cross platform code with no dependencies</b> - C++ code will work with any recent gcc/clang and VS2010. Comes with build files for the tests &amp; samples (Android .mk files, and cmake for all other platforms).</li>
</ul>
<h3>Why not use Protocol Buffers, or .. ?</h3>
<p>Protocol Buffers is indeed relatively similar to FlatBuffers, with the primary difference being that FlatBuffers does not need a parsing/ unpacking step to a secondary representation before you can access data, often coupled with per-object memory allocation. The code is an order of magnitude bigger, too. Protocol Buffers has neither optional text import/export nor schema language features like unions.</p>
<h3>But all the cool kids use JSON!</h3>
<p>JSON is very readable (which is why we use it as our optional text format) and very convenient when used together with dynamically typed languages (such as JavaScript). When serializing data from statically typed languages, however, JSON not only has the obvious drawback of runtime inefficiency, but also forces you to write <em>more</em> code to access data (counterintuitively) due to its dynamic-typing serialization system. In this context, it is only a better choice for systems that have very little to no information ahead of time about what data needs to be stored.</p>
<p>Read more about the "why" of FlatBuffers in the <a href="md__white_paper.html">white paper</a>.</p>
<h3>Who uses FlatBuffers?</h3>
<ul>
<li><a href="http://www.cocos2d-x.org/">Cocos2d-x</a>, the #1 open source mobile game engine, uses it to serialize all their <a href="http://www.cocos2d-x.org/reference/native-cpp/V3.5/d7/d2d/namespaceflatbuffers.html">game data</a>.</li>
<li><a href="http://facebook.com/">Facebook</a> uses it for client-server communication in their Android app. They have a nice <a href="https://code.facebook.com/posts/872547912839369/improving-facebook-s-performance-on-android-with-flatbuffers/">article</a> explaining how it speeds up loading their posts.</li>
<li><a href="https://developers.google.com/games/#Tools">Fun Propulsion Labs</a> at Google uses it extensively in all their libraries and games.</li>
</ul>
<h2>Usage in brief</h2>
<p>This section is a quick rundown of how to use this system. Subsequent sections provide a more in-depth usage guide.</p>
<ul>
<li>Write a schema file that allows you to define the data structures you may want to serialize. Fields can have a scalar type (ints/floats of all sizes), or they can be a: string; array of any type; reference to yet another object; or, a set of possible objects (unions). Fields are optional and have defaults, so they don't need to be present for every object instance.</li>
<li>Use <code>flatc</code> (the FlatBuffer compiler) to generate a C++ header (or Java/C#/Go/Python.. classes) with helper classes to access and construct serialized data. This header (say <code>mydata_generated.h</code>) only depends on <code>flatbuffers.h</code>, which defines the core functionality.</li>
<li>Use the <code>FlatBufferBuilder</code> class to construct a flat binary buffer. The generated functions allow you to add objects to this buffer recursively, often as simply as making a single function call.</li>
<li>Store or send your buffer somewhere!</li>
<li>When reading it back, you can obtain the pointer to the root object from the binary buffer, and from there traverse it conveniently in-place with <code>object-&gt;field()</code>.</li>
</ul>
<h2>In-depth documentation</h2>
<ul>
<li>How to <a href="md__building.html">build the compiler</a> and samples on various platforms.</li>
<li>How to <a href="md__compiler.html">use the compiler</a>.</li>
<li>How to <a href="md__schemas.html">write a schema</a>.</li>
<li>How to <a href="md__cpp_usage.html">use the generated C++ code</a> in your own programs.</li>
<li>How to <a href="md__java_usage.html">use the generated Java/C# code</a> in your own programs.</li>
<li>How to <a href="md__go_usage.html">use the generated Go code</a> in your own programs.</li>
<li><a href="md__support.html">Support matrix</a> for platforms/languages/features.</li>
<li>Some <a href="md__benchmarks.html">benchmarks</a> showing the advantage of using FlatBuffers.</li>
<li>A <a href="md__white_paper.html">white paper</a> explaining the "why" of FlatBuffers.</li>
<li>A description of the <a href="md__internals.html">internals</a> of FlatBuffers.</li>
<li>A formal <a href="md__grammar.html">grammar</a> of the schema language.</li>
</ul>
<h2>Online resources</h2>
<ul>
<li><a href="http://github.com/google/flatbuffers">GitHub repository</a></li>
<li><a href="http://google.github.io/flatbuffers">Landing page</a></li>
<li><a href="http://group.google.com/group/flatbuffers">FlatBuffers Google Group</a></li>
<li><a href="http://github.com/google/flatbuffers/issues">FlatBuffers Issues Tracker</a></li>
<li>Independent implementations &amp; tools:<ul>
<li><a href="https://github.com/dvidelabs/flatcc">FlatCC</a> Alternative FlatBuffers parser, code generator and runtime all in C.</li>
</ul>
</li>
<li>Videos:<ul>
<li>Colt's <a href="https://www.youtube.com/watch?v=iQTxMkSJ1dQ">DevByte</a>.</li>
<li>GDC 2015 <a href="https://www.youtube.com/watch?v=olmL1fUnQAQ">Lightning Talk</a>.</li>
<li>FlatBuffers for <a href="https://www.youtube.com/watch?v=-BPVId_lA5w">Go</a>.</li>
<li>Evolution of FlatBuffers <a href="https://www.youtube.com/watch?v=a0QE0xS8rKM">visualization</a>.</li>
</ul>
</li>
<li>Useful documentation created by others:<ul>
<li><a href="https://rwinslow.com/tags/flatbuffers/">FlatBuffers in Go</a></li>
<li><a href="http://frogermcs.github.io/flatbuffers-in-android-introdution/">FlatBuffers in Android</a></li>
<li><a href="http://frogermcs.github.io/json-parsing-with-flatbuffers-in-android/">Parsing JSON to FlatBuffers in Java</a></li>
<li><a href="http://exiin.com/blog/flatbuffers-for-unity-sample-code/">FlatBuffers in Unity</a> </li>
</ul>
</li>
</ul>
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<div style="font-size:12px;">
An open source project by <a href="https://developers.google.com/games/#Tools">FPL</a>.
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<div class="textblock"><p>Comparing against other serialization solutions, running on Windows 7 64bit. We use the LITE runtime for Protocol Buffers (less code / lower overhead), Rapid JSON (one of the fastest C++ JSON parsers around), and pugixml, also one of the fastest XML parsers.</p>
<p>We also compare against code that doesn't use a serialization library at all (the column "Raw structs"), which is what you get if you write hardcoded code that just writes structs. This is the fastest possible, but of course is not cross platform nor has any kind of forwards / backwards compatibility.</p>
<p>We compare against Flatbuffers with the binary wire format (as intended), and also with JSON as the wire format with the optional JSON parser (which, using a schema, parses JSON into a binary buffer that can then be accessed as before).</p>
<p>The benchmark object is a set of about 10 objects containing an array, 4 strings, and a large variety of int/float scalar values of all sizes, meant to be representative of game data, e.g. a scene format.</p>
<table class="doxtable">
<tr>
<th></th><th>FlatBuffers (binary) </th><th>Protocol Buffers LITE </th><th>Rapid JSON </th><th>FlatBuffers (JSON) </th><th>pugixml </th><th>Raw structs </th></tr>
<tr>
<td>Decode + Traverse + Dealloc (1 million times, seconds) </td><td>0.08 </td><td>302 </td><td>583 </td><td>105 </td><td>196 </td><td>0.02 </td></tr>
<tr>
<td>Decode / Traverse / Dealloc (breakdown) </td><td>0 / 0.08 / 0 </td><td>220 / 0.15 / 81 </td><td>294 / 0.9 / 287 </td><td>70 / 0.08 / 35 </td><td>41 / 3.9 / 150 </td><td>0 / 0.02 / 0 </td></tr>
<tr>
<td>Encode (1 million times, seconds) </td><td>3.2 </td><td>185 </td><td>650 </td><td>169 </td><td>273 </td><td>0.15 </td></tr>
<tr>
<td>Wire format size (normal / zlib, bytes) </td><td>344 / 220 </td><td>228 / 174 </td><td>1475 / 322 </td><td>1029 / 298 </td><td>1137 / 341 </td><td>312 / 187 </td></tr>
<tr>
<td>Memory needed to store decoded wire (bytes / blocks) </td><td>0 / 0 </td><td>760 / 20 </td><td>65689 / 4 </td><td>328 / 1 </td><td>34194 / 3 </td><td>0 / 0 </td></tr>
<tr>
<td>Transient memory allocated during decode (KB) </td><td>0 </td><td>1 </td><td>131 </td><td>4 </td><td>34 </td><td>0 </td></tr>
<tr>
<td>Generated source code size (KB) </td><td>4 </td><td>61 </td><td>0 </td><td>4 </td><td>0 </td><td>0 </td></tr>
<tr>
<td>Field access in handwritten traversal code </td><td>typed accessors </td><td>typed accessors </td><td>manual error checking </td><td>typed accessors </td><td>manual error checking </td><td>typed but no safety </td></tr>
<tr>
<td>Library source code (KB) </td><td>15 </td><td>some subset of 3800 </td><td>87 </td><td>43 </td><td>327 </td><td>0 </td></tr>
</table>
<h3>Some other serialization systems we compared against but did not benchmark (yet), in rough order of applicability:</h3>
<ul>
<li>Cap'n'Proto promises to reduce Protocol Buffers much like FlatBuffers does, though with a more complicated binary encoding and less flexibility (no optional fields to allow deprecating fields or serializing with missing fields for which defaults exist). It currently also isn't fully cross-platform portable (lack of VS support).</li>
<li>msgpack: has very minimal forwards/backwards compatibility support when used with the typed C++ interface. Also lacks VS2010 support.</li>
<li>Thrift: very similar to Protocol Buffers, but appears to be less efficient, and have more dependencies.</li>
<li>YAML: a superset of JSON and otherwise very similar. Used by e.g. Unity.</li>
<li>C# comes with built-in serialization functionality, as used by Unity also. Being tied to the language, and having no automatic versioning support limits its applicability.</li>
<li>Project Anarchy (the free mobile engine by Havok) comes with a serialization system, that however does no automatic versioning (have to code around new fields manually), is very much tied to the rest of the engine, and works without a schema to generate code (tied to your C++ class definition). </li>
</ul>
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<div class="textblock"><p>There are project files for Visual Studio and Xcode that should allow you to build the compiler <code>flatc</code>, the samples and the tests out of the box.</p>
<p>Alternatively, the distribution comes with a <code>cmake</code> file that should allow you to build project/make files for any platform. For details on <code>cmake</code>, see <a href="http://www.cmake.org">http://www.cmake.org</a>. In brief, depending on your platform, use one of e.g.: </p><pre class="fragment">cmake -G "Unix Makefiles"
cmake -G "Visual Studio 10"
cmake -G "Xcode"
</pre><p>Then, build as normal for your platform. This should result in a <code>flatc</code> executable, essential for the next steps. Note that to use clang instead of gcc, you may need to set up your environment variables, e.g. <code>CC=/usr/bin/clang CXX=/usr/bin/clang++ cmake -G "Unix Makefiles"</code>.</p>
<p>Optionally, run the <code>flattests</code> executable to ensure everything is working correctly on your system. If this fails, please contact us!</p>
<p>Note that you MUST be in the root of the FlatBuffers distribution when you run 'flattests' (and the samples), or it will fail to load its files.</p>
<p>Building should also produce two sample executables, <code>sample_binary</code> and <code>sample_text</code>, see the corresponding <code>.cpp</code> file in the samples directory.</p>
<p>There is an <code>android</code> directory that contains all you need to build the test executable on android (use the included <code>build_apk.sh</code> script, or use <code>ndk_build</code> / <code>adb</code> etc. as usual). Upon running, it will output to the log if tests succeeded or not.</p>
<p>There is usually no runtime to compile, as the code consists of a single header, <code>include/flatbuffers/flatbuffers.h</code>. You should add the <code>include</code> folder to your include paths. If you wish to be able to load schemas and/or parse text into binary buffers at runtime, you additionally need the other headers in <code>include/flatbuffers</code>. You must also compile/link <code>src/idl_parser.cpp</code> (and <code>src/idl_gen_text.cpp</code> if you also want to be able convert binary to text).</p>
<p>For applications on Google Play that integrate this library, usage is tracked. This tracking is done automatically using the embedded version string (flatbuffer_version_string), and helps us continue to optimize it. Aside from consuming a few extra bytes in your application binary, it shouldn't affect your application at all. We use this information to let us know if FlatBuffers is useful and if we should continue to invest in it. Since this is open source, you are free to remove the version string but we would appreciate if you would leave it in. </p>
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<div class="textblock"><p>Assuming you have written a schema using the above language in say <code>mygame.fbs</code> (FlatBuffer Schema, though the extension doesn't matter), you've generated a C++ header called <code>mygame_generated.h</code> using the compiler (e.g. <code>flatc -c mygame.fbs</code>), you can now start using this in your program by including the header. As noted, this header relies on <code>flatbuffers/flatbuffers.h</code>, which should be in your include path.</p>
<h3>Writing in C++</h3>
<p>To start creating a buffer, create an instance of <code>FlatBufferBuilder</code> which will contain the buffer as it grows:</p>
<div class="fragment"><div class="line">FlatBufferBuilder fbb;</div>
</div><!-- fragment --><p>Before we serialize a Monster, we need to first serialize any objects that are contained there-in, i.e. we serialize the data tree using depth first, pre-order traversal. This is generally easy to do on any tree structures. For example:</p>
<div class="fragment"><div class="line"><span class="keyword">auto</span> name = fbb.CreateString(<span class="stringliteral">&quot;MyMonster&quot;</span>);</div>
<div class="line"></div>
<div class="line"><span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> inv[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };</div>
<div class="line"><span class="keyword">auto</span> inventory = fbb.CreateVector(inv, 10);</div>
</div><!-- fragment --><p><code>CreateString</code> and <code>CreateVector</code> serialize these two built-in datatypes, and return offsets into the serialized data indicating where they are stored, such that <code>Monster</code> below can refer to them.</p>
<p><code>CreateString</code> can also take an <code>std::string</code>, or a <code>const char *</code> with an explicit length, and is suitable for holding UTF-8 and binary data if needed.</p>
<p><code>CreateVector</code> can also take an <code>std::vector</code>. The offset it returns is typed, i.e. can only be used to set fields of the correct type below. To create a vector of struct objects (which will be stored as contiguous memory in the buffer, use <code>CreateVectorOfStructs</code> instead.</p>
<p>To create a vector of nested objects (e.g. tables, strings or other vectors) collect their offsets in a temporary array/vector, then call <code>CreateVector</code> on that (see e.g. the array of strings example in <code>test.cpp</code> <code>CreateFlatBufferTest</code>).</p>
<div class="fragment"><div class="line">Vec3 vec(1, 2, 3);</div>
</div><!-- fragment --><p><code>Vec3</code> is the first example of code from our generated header. Structs (unlike tables) translate to simple structs in C++, so we can construct them in a familiar way.</p>
<p>We have now serialized the non-scalar components of of the monster example, so we could create the monster something like this:</p>
<div class="fragment"><div class="line"><span class="keyword">auto</span> mloc = CreateMonster(fbb, &amp;vec, 150, 80, name, inventory, Color_Red, 0, Any_NONE);</div>
</div><!-- fragment --><p>Note that we're passing <code>150</code> for the <code>mana</code> field, which happens to be the default value: this means the field will not actually be written to the buffer, since we'll get that value anyway when we query it. This is a nice space savings, since it is very common for fields to be at their default. It means we also don't need to be scared to add fields only used in a minority of cases, since they won't bloat up the buffer sizes if they're not actually used.</p>
<p>We do something similarly for the union field <code>test</code> by specifying a <code>0</code> offset and the <code>NONE</code> enum value (part of every union) to indicate we don't actually want to write this field. You can use <code>0</code> also as a default for other non-scalar types, such as strings, vectors and tables. To pass an actual table, pass a preconstructed table as <code>mytable.Union()</code> that corresponds to union enum you're passing.</p>
<p>Tables (like <code>Monster</code>) give you full flexibility on what fields you write (unlike <code>Vec3</code>, which always has all fields set because it is a <code>struct</code>). If you want even more control over this (i.e. skip fields even when they are not default), instead of the convenient <code>CreateMonster</code> call we can also build the object field-by-field manually:</p>
<div class="fragment"><div class="line">MonsterBuilder mb(fbb);</div>
<div class="line">mb.add_pos(&amp;vec);</div>
<div class="line">mb.add_hp(80);</div>
<div class="line">mb.add_name(name);</div>
<div class="line">mb.add_inventory(inventory);</div>
<div class="line"><span class="keyword">auto</span> mloc = mb.Finish();</div>
</div><!-- fragment --><p>We start with a temporary helper class <code>MonsterBuilder</code> (which is defined in our generated code also), then call the various <code>add_</code> methods to set fields, and <code>Finish</code> to complete the object. This is pretty much the same code as you find inside <code>CreateMonster</code>, except we're leaving out a few fields. Fields may also be added in any order, though orderings with fields of the same size adjacent to each other most efficient in size, due to alignment. You should not nest these Builder classes (serialize your data in pre-order).</p>
<p>Regardless of whether you used <code>CreateMonster</code> or <code>MonsterBuilder</code>, you now have an offset to the root of your data, and you can finish the buffer using:</p>
<div class="fragment"><div class="line">FinishMonsterBuffer(fbb, mloc);</div>
</div><!-- fragment --><p>The buffer is now ready to be stored somewhere, sent over the network, be compressed, or whatever you'd like to do with it. You can access the start of the buffer with <code>fbb.GetBufferPointer()</code>, and it's size from <code>fbb.GetSize()</code>.</p>
<p>Calling code may take ownership of the buffer with <code>fbb.ReleaseBufferPointer()</code>. Should you do it, the <code>FlatBufferBuilder</code> will be in an invalid state, and <em>must</em> be cleared before it can be used again. However, it also means you are able to destroy the builder while keeping the buffer in your application.</p>
<p><code>samples/sample_binary.cpp</code> is a complete code sample similar to the code above, that also includes the reading code below.</p>
<h3>Reading in C++</h3>
<p>If you've received a buffer from somewhere (disk, network, etc.) you can directly start traversing it using:</p>
<div class="fragment"><div class="line"><span class="keyword">auto</span> monster = GetMonster(buffer_pointer);</div>
</div><!-- fragment --><p><code>monster</code> is of type <code>Monster *</code>, and points to somewhere <em>inside</em> your buffer (root object pointers are not the same as <code>buffer_pointer</code> !). If you look in your generated header, you'll see it has convenient accessors for all fields, e.g.</p>
<div class="fragment"><div class="line">assert(monster-&gt;hp() == 80);</div>
<div class="line">assert(monster-&gt;mana() == 150); <span class="comment">// default</span></div>
<div class="line">assert(strcmp(monster-&gt;name()-&gt;c_str(), <span class="stringliteral">&quot;MyMonster&quot;</span>) == 0);</div>
</div><!-- fragment --><p>These should all be true. Note that we never stored a <code>mana</code> value, so it will return the default.</p>
<p>To access sub-objects, in this case the <code>Vec3</code>:</p>
<div class="fragment"><div class="line"><span class="keyword">auto</span> pos = monster-&gt;pos();</div>
<div class="line">assert(pos);</div>
<div class="line">assert(pos-&gt;z() == 3);</div>
</div><!-- fragment --><p>If we had not set the <code>pos</code> field during serialization, it would be <code>NULL</code>.</p>
<p>Similarly, we can access elements of the inventory array:</p>
<div class="fragment"><div class="line"><span class="keyword">auto</span> inv = monster-&gt;inventory();</div>
<div class="line">assert(inv);</div>
<div class="line">assert(inv-&gt;Get(9) == 9);</div>
</div><!-- fragment --><h3>Mutating FlatBuffers</h3>
<p>As you saw above, typically once you have created a FlatBuffer, it is read-only from that moment on. There are however cases where you have just received a FlatBuffer, and you'd like to modify something about it before sending it on to another recipient. With the above functionality, you'd have to generate an entirely new FlatBuffer, while tracking what you modify in your own data structures. This is inconvenient.</p>
<p>For this reason FlatBuffers can also be mutated in-place. While this is great for making small fixes to an existing buffer, you generally want to create buffers from scratch whenever possible, since it is much more efficient and the API is much more general purpose.</p>
<p>To get non-const accessors, invoke <code>flatc</code> with <code>--gen-mutable</code>.</p>
<p>Similar to the reading API above, you now can:</p>
<div class="fragment"><div class="line"><span class="keyword">auto</span> monster = GetMutableMonster(buffer_pointer); <span class="comment">// non-const</span></div>
<div class="line">monster-&gt;mutate_hp(10); <span class="comment">// Set table field.</span></div>
<div class="line">monster-&gt;mutable_pos()-&gt;mutate_z(4); <span class="comment">// Set struct field.</span></div>
<div class="line">monster-&gt;mutable_inventory()-&gt;Mutate(0, 1); <span class="comment">// Set vector element.</span></div>
</div><!-- fragment --><p>We use the somewhat verbose term <code>mutate</code> instead of <code>set</code> to indicate that this is a special use case, not to be confused with the default way of constructing FlatBuffer data.</p>
<p>After the above mutations, you can send on the FlatBuffer to a new recipient without any further work!</p>
<p>Note that any <code>mutate_</code> functions on tables return a bool, which is false if the field we're trying to set isn't present in the buffer. Fields are not present if they weren't set, or even if they happen to be equal to the default value. For example, in the creation code above we set the <code>mana</code> field to <code>150</code>, which is the default value, so it was never stored in the buffer. Trying to call mutate_mana() on such data will return false, and the value won't actually be modified!</p>
<p>One way to solve this is to call <code>ForceDefaults()</code> on a <code>FlatBufferBuilder</code> to force all fields you set to actually be written. This of course increases the size of the buffer somewhat, but this may be acceptable for a mutable buffer.</p>
<p>Alternatively, you can use the more powerful reflection functionality:</p>
<h3>Reflection (&amp; Resizing)</h3>
<p>If the above ways of accessing a buffer are still too static for you, there is experimental support for reflection in FlatBuffers, allowing you to read and write data even if you don't know the exact format of a buffer, and even allows you to change sizes of strings and vectors in-place.</p>
<p>The way this works is very elegant, there is actually a FlatBuffer schema that describes schemas (!) which you can find in <code>reflection/reflection.fbs</code>. The compiler <code>flatc</code> can write out any schemas it has just parsed as a binary FlatBuffer, corresponding to this meta-schema.</p>
<p>Loading in one of these binary schemas at runtime allows you traverse any FlatBuffer data that corresponds to it without knowing the exact format. You can query what fields are present, and then read/write them after.</p>
<p>For convenient field manipulation, you can include the header <code>flatbuffers/reflection.h</code> which includes both the generated code from the meta schema, as well as a lot of helper functions.</p>
<p>And example of usage for the moment you can find in <code>test.cpp/ReflectionTest()</code>.</p>
<h3>Storing maps / dictionaries in a FlatBuffer</h3>
<p>FlatBuffers doesn't support maps natively, but there is support to emulate their behavior with vectors and binary search, which means you can have fast lookups directly from a FlatBuffer without having to unpack your data into a <code>std::map</code> or similar.</p>
<p>To use it:</p><ul>
<li>Designate one of the fields in a table as they "key" field. You do this by setting the <code>key</code> attribute on this field, e.g. <code>name:string (key)</code>. You may only have one key field, and it must be of string or scalar type.</li>
<li>Write out tables of this type as usual, collect their offsets in an array or vector.</li>
<li>Instead of <code>CreateVector</code>, call <code>CreateVectorOfSortedTables</code>, which will first sort all offsets such that the tables they refer to are sorted by the key field, then serialize it.</li>
<li>Now when you're accessing the FlatBuffer, you can use <code>Vector::LookupByKey</code> instead of just <code>Vector::Get</code> to access elements of the vector, e.g.: <code>myvector-&gt;LookupByKey("Fred")</code>, which returns a pointer to the corresponding table type, or <code>nullptr</code> if not found. <code>LookupByKey</code> performs a binary search, so should have a similar speed to <code>std::map</code>, though may be faster because of better caching. <code>LookupByKey</code> only works if the vector has been sorted, it will likely not find elements if it hasn't been sorted.</li>
</ul>
<h3>Direct memory access</h3>
<p>As you can see from the above examples, all elements in a buffer are accessed through generated accessors. This is because everything is stored in little endian format on all platforms (the accessor performs a swap operation on big endian machines), and also because the layout of things is generally not known to the user.</p>
<p>For structs, layout is deterministic and guaranteed to be the same accross platforms (scalars are aligned to their own size, and structs themselves to their largest member), and you are allowed to access this memory directly by using <code>sizeof()</code> and <code>memcpy</code> on the pointer to a struct, or even an array of structs.</p>
<p>To compute offsets to sub-elements of a struct, make sure they are a structs themselves, as then you can use the pointers to figure out the offset without having to hardcode it. This is handy for use of arrays of structs with calls like <code>glVertexAttribPointer</code> in OpenGL or similar APIs.</p>
<p>It is important to note is that structs are still little endian on all machines, so only use tricks like this if you can guarantee you're not shipping on a big endian machine (an <code>assert(FLATBUFFERS_LITTLEENDIAN)</code> would be wise).</p>
<h3>Access of untrusted buffers</h3>
<p>The generated accessor functions access fields over offsets, which is very quick. These offsets are not verified at run-time, so a malformed buffer could cause a program to crash by accessing random memory.</p>
<p>When you're processing large amounts of data from a source you know (e.g. your own generated data on disk), this is acceptable, but when reading data from the network that can potentially have been modified by an attacker, this is undesirable.</p>
<p>For this reason, you can optionally use a buffer verifier before you access the data. This verifier will check all offsets, all sizes of fields, and null termination of strings to ensure that when a buffer is accessed, all reads will end up inside the buffer.</p>
<p>Each root type will have a verification function generated for it, e.g. for <code>Monster</code>, you can call:</p>
<div class="fragment"><div class="line"><span class="keywordtype">bool</span> ok = VerifyMonsterBuffer(Verifier(buf, len));</div>
</div><!-- fragment --><p>if <code>ok</code> is true, the buffer is safe to read.</p>
<p>Besides untrusted data, this function may be useful to call in debug mode, as extra insurance against data being corrupted somewhere along the way.</p>
<p>While verifying a buffer isn't "free", it is typically faster than a full traversal (since any scalar data is not actually touched), and since it may cause the buffer to be brought into cache before reading, the actual overhead may be even lower than expected.</p>
<p>In specialized cases where a denial of service attack is possible, the verifier has two additional constructor arguments that allow you to limit the nesting depth and total amount of tables the verifier may encounter before declaring the buffer malformed. The default is <code>Verifier(buf, len, 64 /* max depth */, 1000000, /* max tables */)</code> which should be sufficient for most uses.</p>
<h2>Text &amp; schema parsing</h2>
<p>Using binary buffers with the generated header provides a super low overhead use of FlatBuffer data. There are, however, times when you want to use text formats, for example because it interacts better with source control, or you want to give your users easy access to data.</p>
<p>Another reason might be that you already have a lot of data in JSON format, or a tool that generates JSON, and if you can write a schema for it, this will provide you an easy way to use that data directly.</p>
<p>(see the schema documentation for some specifics on the JSON format accepted).</p>
<p>There are two ways to use text formats:</p>
<h3>Using the compiler as a conversion tool</h3>
<p>This is the preferred path, as it doesn't require you to add any new code to your program, and is maximally efficient since you can ship with binary data. The disadvantage is that it is an extra step for your users/developers to perform, though you might be able to automate it. </p><pre class="fragment">flatc -b myschema.fbs mydata.json
</pre><p>This will generate the binary file <code>mydata_wire.bin</code> which can be loaded as before.</p>
<h3>Making your program capable of loading text directly</h3>
<p>This gives you maximum flexibility. You could even opt to support both, i.e. check for both files, and regenerate the binary from text when required, otherwise just load the binary.</p>
<p>This option is currently only available for C++, or Java through JNI.</p>
<p>As mentioned in the section "Building" above, this technique requires you to link a few more files into your program, and you'll want to include <code>flatbuffers/idl.h</code>.</p>
<p>Load text (either a schema or json) into an in-memory buffer (there is a convenient <code>LoadFile()</code> utility function in <code>flatbuffers/util.h</code> if you wish). Construct a parser:</p>
<div class="fragment"><div class="line">flatbuffers::Parser parser;</div>
</div><!-- fragment --><p>Now you can parse any number of text files in sequence:</p>
<div class="fragment"><div class="line">parser.Parse(text_file.c_str());</div>
</div><!-- fragment --><p>This works similarly to how the command-line compiler works: a sequence of files parsed by the same <code>Parser</code> object allow later files to reference definitions in earlier files. Typically this means you first load a schema file (which populates <code>Parser</code> with definitions), followed by one or more JSON files.</p>
<p>As optional argument to <code>Parse</code>, you may specify a null-terminated list of include paths. If not specified, any include statements try to resolve from the current directory.</p>
<p>If there were any parsing errors, <code>Parse</code> will return <code>false</code>, and <code>Parser::err</code> contains a human readable error string with a line number etc, which you should present to the creator of that file.</p>
<p>After each JSON file, the <code>Parser::fbb</code> member variable is the <code>FlatBufferBuilder</code> that contains the binary buffer version of that file, that you can access as described above.</p>
<p><code>samples/sample_text.cpp</code> is a code sample showing the above operations.</p>
<h3>Threading</h3>
<p>Reading a FlatBuffer does not touch any memory outside the original buffer, and is entirely read-only (all const), so is safe to access from multiple threads even without synchronisation primitives.</p>
<p>Creating a FlatBuffer is not thread safe. All state related to building a FlatBuffer is contained in a FlatBufferBuilder instance, and no memory outside of it is touched. To make this thread safe, either do not share instances of FlatBufferBuilder between threads (recommended), or manually wrap it in synchronisation primites. There's no automatic way to accomplish this, by design, as we feel multithreaded construction of a single buffer will be rare, and synchronisation overhead would be costly. </p>
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<div class="textblock"><p>There's experimental support for reading FlatBuffers in Go. Generate code for Go with the <code>-g</code> option to <code>flatc</code>.</p>
<p>See <code>go_test.go</code> for an example. You import the generated code, read a FlatBuffer binary file into a <code>[]byte</code>, which you pass to the <code>GetRootAsMonster</code> function:</p>
<div class="fragment"><div class="line"><span class="keyword">import</span> (</div>
<div class="line"> example <span class="stringliteral">&quot;MyGame/Example&quot;</span></div>
<div class="line"> flatbuffers <span class="stringliteral">&quot;github.com/google/flatbuffers/go&quot;</span></div>
<div class="line"></div>
<div class="line"> io/ioutil</div>
<div class="line">)</div>
<div class="line"></div>
<div class="line">buf, err := ioutil.ReadFile(<span class="stringliteral">&quot;monster.dat&quot;</span>)</div>
<div class="line"><span class="comment">// handle err</span></div>
<div class="line">monster := example.GetRootAsMonster(buf, 0)</div>
</div><!-- fragment --><p>Now you can access values like this:</p>
<div class="fragment"><div class="line">hp := monster.Hp()</div>
<div class="line">pos := monster.Pos(nil)</div>
</div><!-- fragment --><p>Note that whenever you access a new object like in the <code>Pos</code> example above, a new temporary accessor object gets created. If your code is very performance sensitive (you iterate through a lot of objects), you can replace nil with a pointer to a <code>Vec3</code> object you've already created. This allows you to reuse it across many calls and reduce the amount of object allocation (and thus garbage collection) your program does.</p>
<p>To access vectors you pass an extra index to the vector field accessor. Then a second method with the same name suffixed by <code>Length</code> let's you know the number of elements you can access:</p>
<div class="fragment"><div class="line"><span class="keywordflow">for</span> i := 0; i &lt; monster.InventoryLength(); i++ {</div>
<div class="line"> monster.Inventory(i) <span class="comment">// do something here</span></div>
<div class="line">}</div>
</div><!-- fragment --><p>You can also construct these buffers in Go using the functions found in the generated code, and the FlatBufferBuilder class:</p>
<div class="fragment"><div class="line">builder := flatbuffers.NewBuilder(0)</div>
</div><!-- fragment --><p>Create strings:</p>
<div class="fragment"><div class="line">str := builder.CreateString(<span class="stringliteral">&quot;MyMonster&quot;</span>)</div>
</div><!-- fragment --><p>Create a table with a struct contained therein:</p>
<div class="fragment"><div class="line">example.MonsterStart(builder)</div>
<div class="line">example.MonsterAddPos(builder, example.CreateVec3(builder, 1.0, 2.0, 3.0, 3.0, 4, 5, 6))</div>
<div class="line">example.MonsterAddHp(builder, 80)</div>
<div class="line">example.MonsterAddName(builder, str)</div>
<div class="line">example.MonsterAddInventory(builder, inv)</div>
<div class="line">example.MonsterAddTest_Type(builder, 1)</div>
<div class="line">example.MonsterAddTest(builder, mon2)</div>
<div class="line">example.MonsterAddTest4(builder, test4s)</div>
<div class="line">mon := example.MonsterEnd(builder)</div>
</div><!-- fragment --><p>Unlike C++, Go does not support table creation functions like 'createMonster()'. This is to create the buffer without using temporary object allocation (since the <code>Vec3</code> is an inline component of <code>Monster</code>, it has to be created right where it is added, whereas the name and the inventory are not inline, and <b>must</b> be created outside of the table creation sequence). Structs do have convenient methods that allow you to construct them in one call. These also have arguments for nested structs, e.g. if a struct has a field <code>a</code> and a nested struct field <code>b</code> (which has fields <code>c</code> and <code>d</code>), then the arguments will be <code>a</code>, <code>c</code> and <code>d</code>.</p>
<p>Vectors also use this start/end pattern to allow vectors of both scalar types and structs:</p>
<div class="fragment"><div class="line">example.MonsterStartInventoryVector(builder, 5)</div>
<div class="line"><span class="keywordflow">for</span> i := 4; i &gt;= 0; i-- {</div>
<div class="line"> builder.PrependByte(byte(i))</div>
<div class="line">}</div>
<div class="line">inv := builder.EndVector(5)</div>
</div><!-- fragment --><p>The generated method 'StartInventoryVector' is provided as a convenience function which calls 'StartVector' with the correct element size of the vector type which in this case is 'ubyte' or 1 byte per vector element. You pass the number of elements you want to write. You write the elements backwards since the buffer is being constructed back to front. Use the correct <code>Prepend</code> call for the type, or <code>PrependUOffsetT</code> for offsets. You then pass <code>inv</code> to the corresponding <code>Add</code> call when you construct the table containing it afterwards.</p>
<p>There are <code>Prepend</code> functions for all the scalar types. You use <code>PrependUOffset</code> for any previously constructed objects (such as other tables, strings, vectors). For structs, you use the appropriate <code>create</code> function in-line, as shown above in the <code>Monster</code> example.</p>
<p>Once you're done constructing a buffer, you call <code>Finish</code> with the root object offset (<code>mon</code> in the example above). Your data now resides in Builder.Bytes. Important to note is that the real data starts at the index indicated by Head(), for Offset() bytes (this is because the buffer is constructed backwards). If you wanted to read the buffer right after creating it (using <code>GetRootAsMonster</code> above), the second argument, instead of <code>0</code> would thus also be <code>Head()</code>.</p>
<h2>Text Parsing</h2>
<p>There currently is no support for parsing text (Schema's and JSON) directly from Go, though you could use the C++ parser through cgo. Please see the C++ documentation for more on text parsing. </p>
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<div class="textblock"><p>schema = include* ( namespace_decl | type_decl | enum_decl | root_decl | file_extension_decl | file_identifier_decl | attribute_decl | object )*</p>
<p>include = <code>include</code> string_constant <code>;</code></p>
<p>namespace_decl = <code>namespace</code> ident ( <code>.</code> ident )* <code>;</code></p>
<p>attribute_decl = <code>attribute</code> string_constant <code>;</code></p>
<p>type_decl = ( <code>table</code> | <code>struct</code> ) ident metadata <code>{</code> field_decl+ <code>}</code></p>
<p>enum_decl = ( <code>enum</code> | <code>union</code> ) ident [ <code>:</code> type ] metadata <code>{</code> commasep( enumval_decl ) <code>}</code></p>
<p>root_decl = <code>root_type</code> ident <code>;</code></p>
<p>field_decl = ident <code>:</code> type [ <code>=</code> scalar ] metadata <code>;</code></p>
<p>type = <code>bool</code> | <code>byte</code> | <code>ubyte</code> | <code>short</code> | <code>ushort</code> | <code>int</code> | <code>uint</code> | <code>float</code> | <code>long</code> | <code>ulong</code> | <code>double</code> | <code>string</code> | <code>[</code> type <code>]</code> | ident</p>
<p>enumval_decl = ident [ <code>=</code> integer_constant ]</p>
<p>metadata = [ <code>(</code> commasep( ident [ <code>:</code> single_value ] ) <code>)</code> ]</p>
<p>scalar = integer_constant | float_constant</p>
<p>object = { commasep( ident <code>:</code> value ) }</p>
<p>single_value = scalar | string_constant</p>
<p>value = single_value | object | <code>[</code> commasep( value ) <code>]</code></p>
<p>commasep(x) = [ x ( <code>,</code> x )* ]</p>
<p>file_extension_decl = <code>file_extension</code> string_constant <code>;</code></p>
<p>file_identifier_decl = <code>file_identifier</code> string_constant <code>;</code></p>
<p>integer_constant = -?[0-9]+ | <code>true</code> | <code>false</code></p>
<p>float_constant = -?[0-9]+.[0-9]+((e|E)(+|-)?[0-9]+)? </p>
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<div class="textblock"><p>This section is entirely optional for the use of FlatBuffers. In normal usage, you should never need the information contained herein. If you're interested however, it should give you more of an appreciation of why FlatBuffers is both efficient and convenient.</p>
<h3>Format components</h3>
<p>A FlatBuffer is a binary file and in-memory format consisting mostly of scalars of various sizes, all aligned to their own size. Each scalar is also always represented in little-endian format, as this corresponds to all commonly used CPUs today. FlatBuffers will also work on big-endian machines, but will be slightly slower because of additional byte-swap intrinsics.</p>
<p>On purpose, the format leaves a lot of details about where exactly things live in memory undefined, e.g. fields in a table can have any order, and objects to some extend can be stored in many orders. This is because the format doesn't need this information to be efficient, and it leaves room for optimization and extension (for example, fields can be packed in a way that is most compact). Instead, the format is defined in terms of offsets and adjacency only. This may mean two different implementations may produce different binaries given the same input values, and this is perfectly valid.</p>
<h3>Format identification</h3>
<p>The format also doesn't contain information for format identification and versioning, which is also by design. FlatBuffers is a statically typed system, meaning the user of a buffer needs to know what kind of buffer it is. FlatBuffers can of course be wrapped inside other containers where needed, or you can use its union feature to dynamically identify multiple possible sub-objects stored. Additionally, it can be used together with the schema parser if full reflective capabilities are desired.</p>
<p>Versioning is something that is intrinsically part of the format (the optionality / extensibility of fields), so the format itself does not need a version number (it's a meta-format, in a sense). We're hoping that this format can accommodate all data needed. If format breaking changes are ever necessary, it would become a new kind of format rather than just a variation.</p>
<h3>Offsets</h3>
<p>The most important and generic offset type (see <code>flatbuffers.h</code>) is <code>uoffset_t</code>, which is currently always a <code>uint32_t</code>, and is used to refer to all tables/unions/strings/vectors (these are never stored in-line). 32bit is intentional, since we want to keep the format binary compatible between 32 and 64bit systems, and a 64bit offset would bloat the size for almost all uses. A version of this format with 64bit (or 16bit) offsets is easy to set when needed. Unsigned means they can only point in one direction, which typically is forward (towards a higher memory location). Any backwards offsets will be explicitly marked as such.</p>
<p>The format starts with an <code>uoffset_t</code> to the root object in the buffer.</p>
<p>We have two kinds of objects, structs and tables.</p>
<h3>Structs</h3>
<p>These are the simplest, and as mentioned, intended for simple data that benefits from being extra efficient and doesn't need versioning / extensibility. They are always stored inline in their parent (a struct, table, or vector) for maximum compactness. Structs define a consistent memory layout where all components are aligned to their size, and structs aligned to their largest scalar member. This is done independent of the alignment rules of the underlying compiler to guarantee a cross platform compatible layout. This layout is then enforced in the generated code.</p>
<h3>Tables</h3>
<p>These start with an <code>soffset_t</code> to a vtable. This is a signed version of <code>uoffset_t</code>, since vtables may be stored anywhere relative to the object. This offset is substracted (not added) from the object start to arrive at the vtable start. This offset is followed by all the fields as aligned scalars (or offsets). Unlike structs, not all fields need to be present. There is no set order and layout.</p>
<p>To be able to access fields regardless of these uncertainties, we go through a vtable of offsets. Vtables are shared between any objects that happen to have the same vtable values.</p>
<p>The elements of a vtable are all of type <code>voffset_t</code>, which is a <code>uint16_t</code>. The first element is the size of the vtable in bytes, including the size element. The second one is the size of the object, in bytes (including the vtable offset). This size could be used for streaming, to know how many bytes to read to be able to access all fields of the object. The remaining elements are the N offsets, where N is the amount of fields declared in the schema when the code that constructed this buffer was compiled (thus, the size of the table is N + 2).</p>
<p>All accessor functions in the generated code for tables contain the offset into this table as a constant. This offset is checked against the first field (the number of elements), to protect against newer code reading older data. If this offset is out of range, or the vtable entry is 0, that means the field is not present in this object, and the default value is return. Otherwise, the entry is used as offset to the field to be read.</p>
<h3>Strings and Vectors</h3>
<p>Strings are simply a vector of bytes, and are always null-terminated. Vectors are stored as contiguous aligned scalar elements prefixed by a 32bit element count (not including any null termination).</p>
<h3>Construction</h3>
<p>The current implementation constructs these buffers backwards (starting at the highest memory address of the buffer), since that significantly reduces the amount of bookkeeping and simplifies the construction API.</p>
<h3>Code example</h3>
<p>Here's an example of the code that gets generated for the <code>samples/monster.fbs</code>. What follows is the entire file, broken up by comments: </p><pre class="fragment">// automatically generated, do not modify
#include "flatbuffers/flatbuffers.h"
namespace MyGame {
namespace Sample {
</pre><p>Nested namespace support. </p><pre class="fragment">enum {
Color_Red = 0,
Color_Green = 1,
Color_Blue = 2,
};
inline const char **EnumNamesColor() {
static const char *names[] = { "Red", "Green", "Blue", nullptr };
return names;
}
inline const char *EnumNameColor(int e) { return EnumNamesColor()[e]; }
</pre><p>Enums and convenient reverse lookup. </p><pre class="fragment">enum {
Any_NONE = 0,
Any_Monster = 1,
};
inline const char **EnumNamesAny() {
static const char *names[] = { "NONE", "Monster", nullptr };
return names;
}
inline const char *EnumNameAny(int e) { return EnumNamesAny()[e]; }
</pre><p>Unions share a lot with enums. </p><pre class="fragment">struct Vec3;
struct Monster;
</pre><p>Predeclare all data types since circular references between types are allowed (circular references between object are not, though). </p><pre class="fragment">MANUALLY_ALIGNED_STRUCT(4) Vec3 {
private:
float x_;
float y_;
float z_;
public:
Vec3(float x, float y, float z)
: x_(flatbuffers::EndianScalar(x)), y_(flatbuffers::EndianScalar(y)), z_(flatbuffers::EndianScalar(z)) {}
float x() const { return flatbuffers::EndianScalar(x_); }
float y() const { return flatbuffers::EndianScalar(y_); }
float z() const { return flatbuffers::EndianScalar(z_); }
};
STRUCT_END(Vec3, 12);
</pre><p>These ugly macros do a couple of things: they turn off any padding the compiler might normally do, since we add padding manually (though none in this example), and they enforce alignment chosen by FlatBuffers. This ensures the layout of this struct will look the same regardless of compiler and platform. Note that the fields are private: this is because these store little endian scalars regardless of platform (since this is part of the serialized data). <code>EndianScalar</code> then converts back and forth, which is a no-op on all current mobile and desktop platforms, and a single machine instruction on the few remaining big endian platforms. </p><pre class="fragment">struct Monster : private flatbuffers::Table {
const Vec3 *pos() const { return GetStruct&lt;const Vec3 *&gt;(4); }
int16_t mana() const { return GetField&lt;int16_t&gt;(6, 150); }
int16_t hp() const { return GetField&lt;int16_t&gt;(8, 100); }
const flatbuffers::String *name() const { return GetPointer&lt;const flatbuffers::String *&gt;(10); }
const flatbuffers::Vector&lt;uint8_t&gt; *inventory() const { return GetPointer&lt;const flatbuffers::Vector&lt;uint8_t&gt; *&gt;(14); }
int8_t color() const { return GetField&lt;int8_t&gt;(16, 2); }
};
</pre><p>Tables are a bit more complicated. A table accessor struct is used to point at the serialized data for a table, which always starts with an offset to its vtable. It derives from <code>Table</code>, which contains the <code>GetField</code> helper functions. GetField takes a vtable offset, and a default value. It will look in the vtable at that offset. If the offset is out of bounds (data from an older version) or the vtable entry is 0, the field is not present and the default is returned. Otherwise, it uses the entry as an offset into the table to locate the field. </p><pre class="fragment">struct MonsterBuilder {
flatbuffers::FlatBufferBuilder &amp;fbb_;
flatbuffers::uoffset_t start_;
void add_pos(const Vec3 *pos) { fbb_.AddStruct(4, pos); }
void add_mana(int16_t mana) { fbb_.AddElement&lt;int16_t&gt;(6, mana, 150); }
void add_hp(int16_t hp) { fbb_.AddElement&lt;int16_t&gt;(8, hp, 100); }
void add_name(flatbuffers::Offset&lt;flatbuffers::String&gt; name) { fbb_.AddOffset(10, name); }
void add_inventory(flatbuffers::Offset&lt;flatbuffers::Vector&lt;uint8_t&gt;&gt; inventory) { fbb_.AddOffset(14, inventory); }
void add_color(int8_t color) { fbb_.AddElement&lt;int8_t&gt;(16, color, 2); }
MonsterBuilder(flatbuffers::FlatBufferBuilder &amp;_fbb) : fbb_(_fbb) { start_ = fbb_.StartTable(); }
flatbuffers::Offset&lt;Monster&gt; Finish() { return flatbuffers::Offset&lt;Monster&gt;(fbb_.EndTable(start_, 7)); }
};
</pre><p><code>MonsterBuilder</code> is the base helper struct to construct a table using a <code>FlatBufferBuilder</code>. You can add the fields in any order, and the <code>Finish</code> call will ensure the correct vtable gets generated. </p><pre class="fragment">inline flatbuffers::Offset&lt;Monster&gt; CreateMonster(flatbuffers::FlatBufferBuilder &amp;_fbb, const Vec3 *pos, int16_t mana, int16_t hp, flatbuffers::Offset&lt;flatbuffers::String&gt; name, flatbuffers::Offset&lt;flatbuffers::Vector&lt;uint8_t&gt;&gt; inventory, int8_t color) {
MonsterBuilder builder_(_fbb);
builder_.add_inventory(inventory);
builder_.add_name(name);
builder_.add_pos(pos);
builder_.add_hp(hp);
builder_.add_mana(mana);
builder_.add_color(color);
return builder_.Finish();
}
</pre><p><code>CreateMonster</code> is a convenience function that calls all functions in <code>MonsterBuilder</code> above for you. Note that if you pass values which are defaults as arguments, it will not actually construct that field, so you can probably use this function instead of the builder class in almost all cases. </p><pre class="fragment">inline const Monster *GetMonster(const void *buf) { return flatbuffers::GetRoot&lt;Monster&gt;(buf); }
</pre><p>This function is only generated for the root table type, to be able to start traversing a FlatBuffer from a raw buffer pointer. </p><pre class="fragment">}; // namespace MyGame
}; // namespace Sample</pre> </div></div><!-- contents -->
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<div class="textblock"><p>FlatBuffers supports reading and writing binary FlatBuffers in Java and C#. Generate code for Java with the <code>-j</code> option to <code>flatc</code>, or for C# with <code>-n</code> (think .Net).</p>
<p>Note that this document is from the perspective of Java. Code for both languages is generated in the same way, with only minor differences. These differences are <a href="#differences-in-c-sharp">explained in a section below</a>.</p>
<p>See <code>javaTest.java</code> for an example. Essentially, you read a FlatBuffer binary file into a <code>byte[]</code>, which you then turn into a <code>ByteBuffer</code>, which you pass to the <code>getRootAsMyRootType</code> function:</p>
<div class="fragment"><div class="line">ByteBuffer bb = ByteBuffer.wrap(data);</div>
<div class="line">Monster monster = Monster.getRootAsMonster(bb);</div>
</div><!-- fragment --><p>Now you can access values much like C++:</p>
<div class="fragment"><div class="line"><span class="keywordtype">short</span> hp = monster.hp();</div>
<div class="line">Vec3 pos = monster.pos();</div>
</div><!-- fragment --><p>Note that whenever you access a new object like in the <code>pos</code> example above, a new temporary accessor object gets created. If your code is very performance sensitive (you iterate through a lot of objects), there's a second <code>pos()</code> method to which you can pass a <code>Vec3</code> object you've already created. This allows you to reuse it across many calls and reduce the amount of object allocation (and thus garbage collection) your program does.</p>
<p>Java does not support unsigned scalars. This means that any unsigned types you use in your schema will actually be represented as a signed value. This means all bits are still present, but may represent a negative value when used. For example, to read a <code>byte b</code> as an unsigned number, you can do: <code>(short)(b &amp; 0xFF)</code></p>
<p>The default string accessor (e.g. <code>monster.name()</code>) currently always create a new Java <code>String</code> when accessed, since FlatBuffer's UTF-8 strings can't be used in-place by <code>String</code>. Alternatively, use <code>monster.nameAsByteBuffer()</code> which returns a <code>ByteBuffer</code> referring to the UTF-8 data in the original <code>ByteBuffer</code>, which is much more efficient. The <code>ByteBuffer</code>'s <code>position</code> points to the first character, and its <code>limit</code> to just after the last.</p>
<p>Vector access is also a bit different from C++: you pass an extra index to the vector field accessor. Then a second method with the same name suffixed by <code>Length</code> let's you know the number of elements you can access:</p>
<div class="fragment"><div class="line"><span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 0; i &lt; monster.inventoryLength(); i++)</div>
<div class="line"> monster.inventory(i); <span class="comment">// do something here</span></div>
</div><!-- fragment --><p>Alternatively, much like strings, you can use <code>monster.inventoryAsByteBuffer()</code> to get a <code>ByteBuffer</code> referring to the whole vector. Use <code>ByteBuffer</code> methods like <code>asFloatBuffer</code> to get specific views if needed.</p>
<p>If you specified a file_indentifier in the schema, you can query if the buffer is of the desired type before accessing it using:</p>
<div class="fragment"><div class="line"><span class="keywordflow">if</span> (Monster.MonsterBufferHasIdentifier(bb)) ...</div>
</div><!-- fragment --><h2>Buffer construction in Java</h2>
<p>You can also construct these buffers in Java using the static methods found in the generated code, and the FlatBufferBuilder class:</p>
<div class="fragment"><div class="line">FlatBufferBuilder fbb = <span class="keyword">new</span> FlatBufferBuilder();</div>
</div><!-- fragment --><p>Create strings:</p>
<div class="fragment"><div class="line"><span class="keywordtype">int</span> str = fbb.createString(<span class="stringliteral">&quot;MyMonster&quot;</span>);</div>
</div><!-- fragment --><p>Create a table with a struct contained therein:</p>
<div class="fragment"><div class="line">Monster.startMonster(fbb);</div>
<div class="line">Monster.addPos(fbb, Vec3.createVec3(fbb, 1.0f, 2.0f, 3.0f, 3.0, (byte)4, (<span class="keywordtype">short</span>)5, (byte)6));</div>
<div class="line">Monster.addHp(fbb, (short)80);</div>
<div class="line">Monster.addName(fbb, str);</div>
<div class="line">Monster.addInventory(fbb, inv);</div>
<div class="line">Monster.addTest_type(fbb, (byte)1);</div>
<div class="line">Monster.addTest(fbb, mon2);</div>
<div class="line">Monster.addTest4(fbb, test4s);</div>
<div class="line"><span class="keywordtype">int</span> mon = Monster.endMonster(fbb);</div>
</div><!-- fragment --><p>For some simpler types, you can use a convenient <code>create</code> function call that allows you to construct tables in one function call. This example definition however contains an inline struct field, so we have to create the table manually. This is to create the buffer without using temporary object allocation.</p>
<p>It's important to understand that fields that are structs are inline (like <code>Vec3</code> above), and MUST thus be created between the start and end calls of a table. Everything else (other tables, strings, vectors) MUST be created before the start of the table they are referenced in.</p>
<p>Structs do have convenient methods that even have arguments for nested structs.</p>
<p>As you can see, references to other objects (e.g. the string above) are simple ints, and thus do not have the type-safety of the Offset type in C++. Extra care must thus be taken that you set the right offset on the right field.</p>
<p>Vectors can be created from the corresponding Java array like so:</p>
<div class="fragment"><div class="line"><span class="keywordtype">int</span> inv = Monster.createInventoryVector(fbb, <span class="keyword">new</span> byte[] { 0, 1, 2, 3, 4 });</div>
</div><!-- fragment --><p>This works for arrays of scalars and (int) offsets to strings/tables, but not structs. If you want to write structs, or what you want to write does not sit in an array, you can also use the start/end pattern:</p>
<div class="fragment"><div class="line">Monster.startInventoryVector(fbb, 5);</div>
<div class="line"><span class="keywordflow">for</span> (byte i = 4; i &gt;=0; i--) fbb.addByte(i);</div>
<div class="line"><span class="keywordtype">int</span> inv = fbb.endVector();</div>
</div><!-- fragment --><p>You can use the generated method <code>startInventoryVector</code> to conveniently call <code>startVector</code> with the right element size. You pass the number of elements you want to write. Note how you write the elements backwards since the buffer is being constructed back to front. You then pass <code>inv</code> to the corresponding <code>Add</code> call when you construct the table containing it afterwards.</p>
<p>There are <code>add</code> functions for all the scalar types. You use <code>addOffset</code> for any previously constructed objects (such as other tables, strings, vectors). For structs, you use the appropriate <code>create</code> function in-line, as shown above in the <code>Monster</code> example.</p>
<p>To finish the buffer, call:</p>
<div class="fragment"><div class="line">Monster.finishMonsterBuffer(fbb, mon);</div>
</div><!-- fragment --><p>The buffer is now ready to be transmitted. It is contained in the <code>ByteBuffer</code> which you can obtain from <code>fbb.dataBuffer()</code>. Importantly, the valid data does not start from offset 0 in this buffer, but from <code>fbb.dataBuffer().position()</code> (this is because the data was built backwards in memory). It ends at <code>fbb.capacity()</code>.</p>
<h2>Differences in C-sharp</h2>
<p>C# code works almost identically to Java, with only a few minor differences. You can see an example of C# code in <code>tests/FlatBuffers.Test/FlatBuffersExampleTests.cs</code>.</p>
<p>First of all, naming follows standard C# style with <code>PascalCasing</code> identifiers, e.g. <code>GetRootAsMyRootType</code>. Also, values (except vectors and unions) are available as properties instead of parameterless accessor methods as in Java. The performance-enhancing methods to which you can pass an already created object are prefixed with <code>Get</code>, e.g.:</p>
<div class="fragment"><div class="line"><span class="comment">// property</span></div>
<div class="line">var pos = monster.Pos;</div>
<div class="line"><span class="comment">// method filling a preconstructed object</span></div>
<div class="line">var preconstructedPos = <span class="keyword">new</span> Vec3();</div>
<div class="line">monster.GetPos(preconstructedPos);</div>
</div><!-- fragment --><h2>Text parsing</h2>
<p>There currently is no support for parsing text (Schema's and JSON) directly from Java or C#, though you could use the C++ parser through native call interfaces available to each language. Please see the C++ documentation for more on text parsing.</p>
<h3>Mutating FlatBuffers</h3>
<p>As you saw above, typically once you have created a FlatBuffer, it is read-only from that moment on. There are however cases where you have just received a FlatBuffer, and you'd like to modify something about it before sending it on to another recipient. With the above functionality, you'd have to generate an entirely new FlatBuffer, while tracking what you modify in your own data structures. This is inconvenient.</p>
<p>For this reason FlatBuffers can also be mutated in-place. While this is great for making small fixes to an existing buffer, you generally want to create buffers from scratch whenever possible, since it is much more efficient and the API is much more general purpose.</p>
<p>To get non-const accessors, invoke <code>flatc</code> with <code>--gen-mutable</code>.</p>
<p>You now can:</p>
<div class="fragment"><div class="line">Monster monster = Monster.getRootAsMonster(bb);</div>
<div class="line">monster.mutateHp(10); <span class="comment">// Set table field.</span></div>
<div class="line">monster.pos().mutateZ(4); <span class="comment">// Set struct field.</span></div>
<div class="line">monster.mutateInventory(0, 1); <span class="comment">// Set vector element.</span></div>
</div><!-- fragment --><p>We use the somewhat verbose term <code>mutate</code> instead of <code>set</code> to indicate that this is a special use case, not to be confused with the default way of constructing FlatBuffer data.</p>
<p>After the above mutations, you can send on the FlatBuffer to a new recipient without any further work!</p>
<p>Note that any <code>mutate</code> functions on tables return a boolean, which is false if the field we're trying to set isn't present in the buffer. Fields are not present if they weren't set, or even if they happen to be equal to the default value. For example, in the creation code above we set the <code>mana</code> field to <code>150</code>, which is the default value, so it was never stored in the buffer. Trying to call mutateMana() on such data will return false, and the value won't actually be modified!</p>
<p>One way to solve this is to call <code>forceDefaults()</code> on a <code>FlatBufferBuilder</code> to force all fields you set to actually be written. This of course increases the size of the buffer somewhat, but this may be acceptable for a mutable buffer. </p>
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<div class="textblock"><p>There's experimental support for reading FlatBuffers in Python. Generate code for Python with the <code>-p</code> option to <code>flatc</code>.</p>
<p>See <code>py_test.py</code> for an example. You import the generated code, read a FlatBuffer binary file into a <code>bytearray</code>, which you pass to the <code>GetRootAsMonster</code> function:</p>
<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span>&#160;import MyGame.Example <span class="keyword">as</span> example</div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span>&#160;<span class="keyword">import</span> flatbuffers</div>
<div class="line"><a name="l00003"></a><span class="lineno"> 3</span>&#160;</div>
<div class="line"><a name="l00004"></a><span class="lineno"> 4</span>&#160;buf = open(<span class="stringliteral">&#39;monster.dat&#39;</span>, <span class="stringliteral">&#39;rb&#39;</span>).read()</div>
<div class="line"><a name="l00005"></a><span class="lineno"> 5</span>&#160;buf = bytearray(buf)</div>
<div class="line"><a name="l00006"></a><span class="lineno"> 6</span>&#160;monster = example.GetRootAsMonster(buf, 0)</div>
</div><!-- fragment --><p>Now you can access values like this:</p>
<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span>&#160;hp = monster.Hp()</div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span>&#160;pos = monster.Pos()</div>
</div><!-- fragment --><p>To access vectors you pass an extra index to the vector field accessor. Then a second method with the same name suffixed by <code>Length</code> let's you know the number of elements you can access:</p>
<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span>&#160;<span class="keywordflow">for</span> i <span class="keywordflow">in</span> xrange(monster.InventoryLength()):</div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span>&#160; monster.Inventory(i) <span class="comment"># do something here</span></div>
</div><!-- fragment --><p>You can also construct these buffers in Python using the functions found in the generated code, and the FlatBufferBuilder class:</p>
<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span>&#160;builder = flatbuffers.Builder(0)</div>
</div><!-- fragment --><p>Create strings:</p>
<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span>&#160;s = builder.CreateString(<span class="stringliteral">&quot;MyMonster&quot;</span>)</div>
</div><!-- fragment --><p>Create a table with a struct contained therein:</p>
<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span>&#160;example.MonsterStart(builder)</div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span>&#160;example.MonsterAddPos(builder, example.CreateVec3(builder, 1.0, 2.0, 3.0, 3.0, 4, 5, 6))</div>
<div class="line"><a name="l00003"></a><span class="lineno"> 3</span>&#160;example.MonsterAddHp(builder, 80)</div>
<div class="line"><a name="l00004"></a><span class="lineno"> 4</span>&#160;example.MonsterAddName(builder, str)</div>
<div class="line"><a name="l00005"></a><span class="lineno"> 5</span>&#160;example.MonsterAddInventory(builder, inv)</div>
<div class="line"><a name="l00006"></a><span class="lineno"> 6</span>&#160;example.MonsterAddTest_Type(builder, 1)</div>
<div class="line"><a name="l00007"></a><span class="lineno"> 7</span>&#160;example.MonsterAddTest(builder, mon2)</div>
<div class="line"><a name="l00008"></a><span class="lineno"> 8</span>&#160;example.MonsterAddTest4(builder, test4s)</div>
<div class="line"><a name="l00009"></a><span class="lineno"> 9</span>&#160;mon = example.MonsterEnd(builder)</div>
<div class="line"><a name="l00010"></a><span class="lineno"> 10</span>&#160;</div>
<div class="line"><a name="l00011"></a><span class="lineno"> 11</span>&#160;final_flatbuffer = builder.Output()</div>
</div><!-- fragment --><p>Unlike C++, Python does not support table creation functions like 'createMonster()'. This is to create the buffer without using temporary object allocation (since the <code>Vec3</code> is an inline component of <code>Monster</code>, it has to be created right where it is added, whereas the name and the inventory are not inline, and <b>must</b> be created outside of the table creation sequence). Structs do have convenient methods that allow you to construct them in one call. These also have arguments for nested structs, e.g. if a struct has a field <code>a</code> and a nested struct field <code>b</code> (which has fields <code>c</code> and <code>d</code>), then the arguments will be <code>a</code>, <code>c</code> and <code>d</code>.</p>
<p>Vectors also use this start/end pattern to allow vectors of both scalar types and structs:</p>
<div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span>&#160;example.MonsterStartInventoryVector(builder, 5)</div>
<div class="line"><a name="l00002"></a><span class="lineno"> 2</span>&#160;i = 4</div>
<div class="line"><a name="l00003"></a><span class="lineno"> 3</span>&#160;<span class="keywordflow">while</span> i &gt;= 0:</div>
<div class="line"><a name="l00004"></a><span class="lineno"> 4</span>&#160; builder.PrependByte(byte(i))</div>
<div class="line"><a name="l00005"></a><span class="lineno"> 5</span>&#160; i -= 1</div>
<div class="line"><a name="l00006"></a><span class="lineno"> 6</span>&#160;</div>
<div class="line"><a name="l00007"></a><span class="lineno"> 7</span>&#160;inv = builder.EndVector(5)</div>
</div><!-- fragment --><p>The generated method 'StartInventoryVector' is provided as a convenience function which calls 'StartVector' with the correct element size of the vector type which in this case is 'ubyte' or 1 byte per vector element. You pass the number of elements you want to write. You write the elements backwards since the buffer is being constructed back to front. Use the correct <code>Prepend</code> call for the type, or <code>PrependUOffsetT</code> for offsets. You then pass <code>inv</code> to the corresponding <code>Add</code> call when you construct the table containing it afterwards.</p>
<p>There are <code>Prepend</code> functions for all the scalar types. You use <code>PrependUOffset</code> for any previously constructed objects (such as other tables, strings, vectors). For structs, you use the appropriate <code>create</code> function in-line, as shown above in the <code>Monster</code> example.</p>
<p>Once you're done constructing a buffer, you call <code>Finish</code> with the root object offset (<code>mon</code> in the example above). Your data now resides in Builder.Bytes. Important to note is that the real data starts at the index indicated by Head(), for Offset() bytes (this is because the buffer is constructed backwards). If you wanted to read the buffer right after creating it (using <code>GetRootAsMonster</code> above), the second argument, instead of <code>0</code> would thus also be <code>Head()</code>.</p>
<h2>Text Parsing</h2>
<p>There currently is no support for parsing text (Schema's and JSON) directly from Python, though you could use the C++ parser through SWIG or ctypes. Please see the C++ documentation for more on text parsing. </p>
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<div class="textblock"><p>The syntax of the schema language (aka IDL, Interface Definition Language) should look quite familiar to users of any of the C family of languages, and also to users of other IDLs. Let's look at an example first: </p><pre class="fragment">// example IDL file
namespace MyGame;
attribute "priority";
enum Color : byte { Red = 1, Green, Blue }
union Any { Monster, Weapon, Pickup }
struct Vec3 {
x:float;
y:float;
z:float;
}
table Monster {
pos:Vec3;
mana:short = 150;
hp:short = 100;
name:string;
friendly:bool = false (deprecated, priority: 1);
inventory:[ubyte];
color:Color = Blue;
test:Any;
}
root_type Monster;
</pre><p>(Weapon &amp; Pickup not defined as part of this example).</p>
<h3>Tables</h3>
<p>Tables are the main way of defining objects in FlatBuffers, and consist of a name (here <code>Monster</code>) and a list of fields. Each field has a name, a type, and optionally a default value (if omitted, it defaults to 0 / NULL).</p>
<p>Each field is optional: It does not have to appear in the wire representation, and you can choose to omit fields for each individual object. As a result, you have the flexibility to add fields without fear of bloating your data. This design is also FlatBuffer's mechanism for forward and backwards compatibility. Note that:</p>
<ul>
<li>You can add new fields in the schema ONLY at the end of a table definition. Older data will still read correctly, and give you the default value when read. Older code will simply ignore the new field. If you want to have flexibility to use any order for fields in your schema, you can manually assign ids (much like Protocol Buffers), see the <code>id</code> attribute below.</li>
<li>You cannot delete fields you don't use anymore from the schema, but you can simply stop writing them into your data for almost the same effect. Additionally you can mark them as <code>deprecated</code> as in the example above, which will prevent the generation of accessors in the generated C++, as a way to enforce the field not being used any more. (careful: this may break code!).</li>
<li>You may change field names and table names, if you're ok with your code breaking until you've renamed them there too.</li>
</ul>
<h3>Structs</h3>
<p>Similar to a table, only now none of the fields are optional (so no defaults either), and fields may not be added or be deprecated. Structs may only contain scalars or other structs. Use this for simple objects where you are very sure no changes will ever be made (as quite clear in the example <code>Vec3</code>). Structs use less memory than tables and are even faster to access (they are always stored in-line in their parent object, and use no virtual table).</p>
<h3>Types</h3>
<p>Built-in scalar types are:</p>
<ul>
<li>8 bit: <code>byte ubyte bool</code></li>
<li>16 bit: <code>short ushort</code></li>
<li>32 bit: <code>int uint float</code></li>
<li>64 bit: <code>long ulong double</code></li>
</ul>
<p>Built-in non-scalar types:</p>
<ul>
<li>Vector of any other type (denoted with <code>[type]</code>). Nesting vectors is not supported, instead you can wrap the inner vector in a table.</li>
<li><code>string</code>, which may only hold UTF-8 or 7-bit ASCII. For other text encodings or general binary data use vectors (<code>[byte]</code> or <code>[ubyte]</code>) instead.</li>
<li>References to other tables or structs, enums or unions (see below).</li>
</ul>
<p>You can't change types of fields once they're used, with the exception of same-size data where a <code>reinterpret_cast</code> would give you a desirable result, e.g. you could change a <code>uint</code> to an <code>int</code> if no values in current data use the high bit yet.</p>
<h3>(Default) Values</h3>
<p>Values are a sequence of digits, optionally followed by a <code>.</code> and more digits for float constants, and optionally prefixed by a <code>-</code>. Floats may end with an <code>e</code> or <code>E</code>, followed by a <code>+</code> or <code>-</code> and more digits (scientific notation).</p>
<p>Only scalar values can have defaults, non-scalar (string/vector/table) fields default to NULL when not present.</p>
<p>You generally do not want to change default values after they're initially defined. Fields that have the default value are not actually stored in the serialized data but are generated in code, so when you change the default, you'd now get a different value than from code generated from an older version of the schema. There are situations however where this may be desirable, especially if you can ensure a simultaneous rebuild of all code.</p>
<h3>Enums</h3>
<p>Define a sequence of named constants, each with a given value, or increasing by one from the previous one. The default first value is <code>0</code>. As you can see in the enum declaration, you specify the underlying integral type of the enum with <code>:</code> (in this case <code>byte</code>), which then determines the type of any fields declared with this enum type.</p>
<h3>Unions</h3>
<p>Unions share a lot of properties with enums, but instead of new names for constants, you use names of tables. You can then declare a union field which can hold a reference to any of those types, and additionally a hidden field with the suffix <code>_type</code> is generated that holds the corresponding enum value, allowing you to know which type to cast to at runtime.</p>
<p>Unions are a good way to be able to send multiple message types as a FlatBuffer. Note that because a union field is really two fields, it must always be part of a table, it cannot be the root of a FlatBuffer by itself.</p>
<p>If you have a need to distinguish between different FlatBuffers in a more open-ended way, for example for use as files, see the file identification feature below.</p>
<h3>Namespaces</h3>
<p>These will generate the corresponding namespace in C++ for all helper code, and packages in Java. You can use <code>.</code> to specify nested namespaces / packages.</p>
<h3>Includes</h3>
<p>You can include other schemas files in your current one, e.g.: </p><pre class="fragment">include "mydefinitions.fbs";
</pre><p>This makes it easier to refer to types defined elsewhere. <code>include</code> automatically ensures each file is parsed just once, even when referred to more than once.</p>
<p>When using the <code>flatc</code> compiler to generate code for schema definitions, only definitions in the current file will be generated, not those from the included files (those you still generate separately).</p>
<h3>Root type</h3>
<p>This declares what you consider to be the root table (or struct) of the serialized data. This is particular important for parsing JSON data, which doesn't include object type information.</p>
<h3>File identification and extension</h3>
<p>Typically, a FlatBuffer binary buffer is not self-describing, i.e. it needs you to know its schema to parse it correctly. But if you want to use a FlatBuffer as a file format, it would be convenient to be able to have a "magic number" in there, like most file formats have, to be able to do a sanity check to see if you're reading the kind of file you're expecting.</p>
<p>Now, you can always prefix a FlatBuffer with your own file header, but FlatBuffers has a built-in way to add an identifier to a FlatBuffer that takes up minimal space, and keeps the buffer compatible with buffers that don't have such an identifier.</p>
<p>You can specify in a schema, similar to <code>root_type</code>, that you intend for this type of FlatBuffer to be used as a file format: </p><pre class="fragment">file_identifier "MYFI";
</pre><p>Identifiers must always be exactly 4 characters long. These 4 characters will end up as bytes at offsets 4-7 (inclusive) in the buffer.</p>
<p>For any schema that has such an identifier, <code>flatc</code> will automatically add the identifier to any binaries it generates (with <code>-b</code>), and generated calls like <code>FinishMonsterBuffer</code> also add the identifier. If you have specified an identifier and wish to generate a buffer without one, you can always still do so by calling <code>FlatBufferBuilder::Finish</code> explicitly.</p>
<p>After loading a buffer, you can use a call like <code>MonsterBufferHasIdentifier</code> to check if the identifier is present.</p>
<p>Note that this is best for open-ended uses such as files. If you simply wanted to send one of a set of possible messages over a network for example, you'd be better off with a union.</p>
<p>Additionally, by default <code>flatc</code> will output binary files as <code>.bin</code>. This declaration in the schema will change that to whatever you want: </p><pre class="fragment">file_extension "ext";
</pre><h3>Comments &amp; documentation</h3>
<p>May be written as in most C-based languages. Additionally, a triple comment (<code>///</code>) on a line by itself signals that a comment is documentation for whatever is declared on the line after it (table/struct/field/enum/union/element), and the comment is output in the corresponding C++ code. Multiple such lines per item are allowed.</p>
<h3>Attributes</h3>
<p>Attributes may be attached to a declaration, behind a field, or after the name of a table/struct/enum/union. These may either have a value or not. Some attributes like <code>deprecated</code> are understood by the compiler, user defined ones need to be declared with the attribute declaration (like <code>priority</code> in the example above), and are available to query if you parse the schema at runtime. This is useful if you write your own code generators/editors etc., and you wish to add additional information specific to your tool (such as a help text).</p>
<p>Current understood attributes:</p>
<ul>
<li><code>id: n</code> (on a table field): manually set the field identifier to <code>n</code>. If you use this attribute, you must use it on ALL fields of this table, and the numbers must be a contiguous range from 0 onwards. Additionally, since a union type effectively adds two fields, its id must be that of the second field (the first field is the type field and not explicitly declared in the schema). For example, if the last field before the union field had id 6, the union field should have id 8, and the unions type field will implicitly be 7. IDs allow the fields to be placed in any order in the schema. When a new field is added to the schema is must use the next available ID.</li>
<li><code>deprecated</code> (on a field): do not generate accessors for this field anymore, code should stop using this data.</li>
<li><code>required</code> (on a non-scalar table field): this field must always be set. By default, all fields are optional, i.e. may be left out. This is desirable, as it helps with forwards/backwards compatibility, and flexibility of data structures. It is also a burden on the reading code, since for non-scalar fields it requires you to check against NULL and take appropriate action. By specifying this field, you force code that constructs FlatBuffers to ensure this field is initialized, so the reading code may access it directly, without checking for NULL. If the constructing code does not initialize this field, they will get an assert, and also the verifier will fail on buffers that have missing required fields.</li>
<li><code>original_order</code> (on a table): since elements in a table do not need to be stored in any particular order, they are often optimized for space by sorting them to size. This attribute stops that from happening.</li>
<li><code>force_align: size</code> (on a struct): force the alignment of this struct to be something higher than what it is naturally aligned to. Causes these structs to be aligned to that amount inside a buffer, IF that buffer is allocated with that alignment (which is not necessarily the case for buffers accessed directly inside a <code>FlatBufferBuilder</code>).</li>
<li><code>bit_flags</code> (on an enum): the values of this field indicate bits, meaning that any value N specified in the schema will end up representing 1&lt;&lt;N, or if you don't specify values at all, you'll get the sequence 1, 2, 4, 8, ...</li>
<li><code>nested_flatbuffer: "table_name"</code> (on a field): this indicates that the field (which must be a vector of ubyte) contains flatbuffer data, for which the root type is given by <code>table_name</code>. The generated code will then produce a convenient accessor for the nested FlatBuffer.</li>
<li><code>key</code> (on a field): this field is meant to be used as a key when sorting a vector of the type of table it sits in. Can be used for in-place binary search.</li>
</ul>
<h2>JSON Parsing</h2>
<p>The same parser that parses the schema declarations above is also able to parse JSON objects that conform to this schema. So, unlike other JSON parsers, this parser is strongly typed, and parses directly into a FlatBuffer (see the compiler documentation on how to do this from the command line, or the C++ documentation on how to do this at runtime).</p>
<p>Besides needing a schema, there are a few other changes to how it parses JSON:</p>
<ul>
<li>It accepts field names with and without quotes, like many JSON parsers already do. It outputs them without quotes as well, though can be made to output them using the <code>strict_json</code> flag.</li>
<li>If a field has an enum type, the parser will recognize symbolic enum values (with or without quotes) instead of numbers, e.g. <code>field: EnumVal</code>. If a field is of integral type, you can still use symbolic names, but values need to be prefixed with their type and need to be quoted, e.g. <code>field: "Enum.EnumVal"</code>. For enums representing flags, you may place multiple inside a string separated by spaces to OR them, e.g. <code>field: "EnumVal1 EnumVal2"</code> or <code>field: "Enum.EnumVal1 Enum.EnumVal2"</code>.</li>
<li>Similarly, for unions, these need to specified with two fields much like you do when serializing from code. E.g. for a field <code>foo</code>, you must add a field <code>foo_type: FooOne</code> right before the <code>foo</code> field, where <code>FooOne</code> would be the table out of the union you want to use.</li>
</ul>
<p>When parsing JSON, it recognizes the following escape codes in strings:</p>
<ul>
<li><code>\n</code> - linefeed.</li>
<li><code>\t</code> - tab.</li>
<li><code>\r</code> - carriage return.</li>
<li><code>\b</code> - backspace.</li>
<li><code>\f</code> - form feed.</li>
<li><code>\"</code> - double quote.</li>
<li><code>\\</code> - backslash.</li>
<li><code>\/</code> - forward slash.</li>
<li><code>\uXXXX</code> - 16-bit unicode code point, converted to the equivalent UTF-8 representation.</li>
<li><code>\xXX</code> - 8-bit binary hexadecimal number XX. This is the only one that is not in the JSON spec (see <a href="http://json.org/">http://json.org/</a>), but is needed to be able to encode arbitrary binary in strings to text and back without losing information (e.g. the byte 0xFF can't be represented in standard JSON).</li>
</ul>
<p>It also generates these escape codes back again when generating JSON from a binary representation.</p>
<h2>Gotchas</h2>
<h3>Schemas and version control</h3>
<p>FlatBuffers relies on new field declarations being added at the end, and earlier declarations to not be removed, but be marked deprecated when needed. We think this is an improvement over the manual number assignment that happens in Protocol Buffers (and which is still an option using the <code>id</code> attribute mentioned above).</p>
<p>One place where this is possibly problematic however is source control. If user A adds a field, generates new binary data with this new schema, then tries to commit both to source control after user B already committed a new field also, and just auto-merges the schema, the binary files are now invalid compared to the new schema.</p>
<p>The solution of course is that you should not be generating binary data before your schema changes have been committed, ensuring consistency with the rest of the world. If this is not practical for you, use explicit field ids, which should always generate a merge conflict if two people try to allocate the same id. </p>
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An open source project by <a href="https://developers.google.com/games/#Tools">FPL</a>.
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<div class="textblock"><p>FlatBuffers is actively being worked on, which means that certain platform / language / feature combinations may not be available yet.</p>
<p>This page tries to track those issues, to make informed decisions easier. In general:</p>
<ul>
<li>Languages: language support beyond the ones created by the original FlatBuffer authors typically depends on community contributions.</li>
<li>Features: C++ was the first language supported, since our original target was high performance game development. It thus has the richest feature set, and is likely most robust. Other languages are catching up however.</li>
<li>Platforms: All language implementations are typically portable to most platforms, unless where noted otherwise.</li>
</ul>
<p>NOTE: this table is a start, it needs to be extended.</p>
<table class="doxtable">
<tr>
<th>Feature </th><th>C++ </th><th>Java </th><th>C# </th><th>Go </th><th>Python </th><th>JS </th><th>C </th><th>PHP </th><th>Ruby </th></tr>
<tr>
<td>Codegen for all basic features </td><td>Yes </td><td>Yes </td><td>Yes </td><td>Yes </td><td>Yes </td><td>Yes </td><td>WiP </td><td>WiP </td><td>WiP </td></tr>
<tr>
<td>JSON parsing </td><td>Yes </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td></tr>
<tr>
<td>Simple mutation </td><td>Yes </td><td>WIP </td><td>WIP </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td></tr>
<tr>
<td>Reflection </td><td>Yes </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td></tr>
<tr>
<td>Buffer verifier </td><td>Yes </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td><td>No </td></tr>
<tr>
<td>Testing: basic </td><td>Yes </td><td>Yes </td><td>Yes </td><td>Yes </td><td>Yes </td><td>Yes </td><td>? </td><td>? </td><td>? </td></tr>
<tr>
<td>Testing: fuzz </td><td>Yes </td><td>No </td><td>No </td><td>Yes </td><td>Yes </td><td>No </td><td>? </td><td>? </td><td>? </td></tr>
<tr>
<td>Performance: </td><td>Superb </td><td>Great </td><td>Great </td><td>Great </td><td>Ok </td><td>? </td><td>Superb</td><td>? </td><td>? </td></tr>
<tr>
<td>Platform: Windows </td><td>VS2010 </td><td>Yes </td><td>Yes </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td></tr>
<tr>
<td>Platform: Linux </td><td>GCC282 </td><td>Yes </td><td>? </td><td>Yes </td><td>Yes </td><td>? </td><td>? </td><td>? </td><td>? </td></tr>
<tr>
<td>Platform: OS X </td><td>Xcode4 </td><td>? </td><td>? </td><td>? </td><td>Yes </td><td>? </td><td>? </td><td>? </td><td>? </td></tr>
<tr>
<td>Platform: Android </td><td>NDK10d </td><td>Yes </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td></tr>
<tr>
<td>Platform: iOS </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td></tr>
<tr>
<td>Engine: Unity </td><td>? </td><td>? </td><td>Yes </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td><td>? </td></tr>
<tr>
<td>Primary authors (github) </td><td>gwvo </td><td>gwvo </td><td>ev*/js*</td><td>rw </td><td>rw </td><td>evanw/ev* </td><td>mik* </td><td>ch* </td><td>rw </td></tr>
</table>
<ul>
<li>ev = evolutional</li>
<li>js = jonsimantov</li>
<li>mik = mikkelfj</li>
<li>ch = chobie </li>
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<div class="textblock"><p>This document tries to shed some light on to the "why" of FlatBuffers, a new serialization library.</p>
<h2>Motivation</h2>
<p>Back in the good old days, performance was all about instructions and cycles. Nowadays, processing units have run so far ahead of the memory subsystem, that making an efficient application should start and finish with thinking about memory. How much you use of it. How you lay it out and access it. How you allocate it. When you copy it.</p>
<p>Serialization is a pervasive activity in a lot programs, and a common source of memory inefficiency, with lots of temporary data structures needed to parse and represent data, and inefficient allocation patterns and locality.</p>
<p>If it would be possible to do serialization with no temporary objects, no additional allocation, no copying, and good locality, this could be of great value. The reason serialization systems usually don't manage this is because it goes counter to forwards/backwards compatability, and platform specifics like endianness and alignment.</p>
<p>FlatBuffers is what you get if you try anyway.</p>
<p>In particular, FlatBuffers focus is on mobile hardware (where memory size and memory bandwidth is even more constrained than on desktop hardware), and applications that have the highest performance needs: games.</p>
<h2>FlatBuffers</h2>
<p><em>This is a summary of FlatBuffers functionality, with some rationale. A more detailed description can be found in the FlatBuffers documentation.</em></p>
<h3>Summary</h3>
<p>A FlatBuffer is a binary buffer containing nested objects (structs, tables, vectors,..) organized using offsets so that the data can be traversed in-place just like any pointer-based data structure. Unlike most in-memory data structures however, it uses strict rules of alignment and endianness (always little) to ensure these buffers are cross platform. Additionally, for objects that are tables, FlatBuffers provides forwards/backwards compatibility and general optionality of fields, to support most forms of format evolution.</p>
<p>You define your object types in a schema, which can then be compiled to C++ or Java for low to zero overhead reading &amp; writing. Optionally, JSON data can be dynamically parsed into buffers.</p>
<h3>Tables</h3>
<p>Tables are the cornerstone of FlatBuffers, since format evolution is essential for most applications of serialization. Typically, dealing with format changes is something that can be done transparently during the parsing process of most serialization solutions out there. But a FlatBuffer isn't parsed before it is accessed.</p>
<p>Tables get around this by using an extra indirection to access fields, through a <em>vtable</em>. Each table comes with a vtable (which may be shared between multiple tables with the same layout), and contains information where fields for this particular kind of instance of vtable are stored. The vtable may also indicate that the field is not present (because this FlatBuffer was written with an older version of the software, of simply because the information was not necessary for this instance, or deemed deprecated), in which case a default value is returned.</p>
<p>Tables have a low overhead in memory (since vtables are small and shared) and in access cost (an extra indirection), but provide great flexibility. Tables may even cost less memory than the equivalent struct, since fields do not need to be stored when they are equal to their default.</p>
<p>FlatBuffers additionally offers "naked" structs, which do not offer forwards/backwards compatibility, but can be even smaller (useful for very small objects that are unlikely to change, like e.g. a coordinate pair or a RGBA color).</p>
<h3>Schemas</h3>
<p>While schemas reduce some generality (you can't just read any data without having its schema), they have a lot of upsides:</p>
<ul>
<li>Most information about the format can be factored into the generated code, reducing memory needed to store data, and time to access it.</li>
<li>The strong typing of the data definitions means less error checking/handling at runtime (less can go wrong).</li>
<li>A schema enables us to access a buffer without parsing.</li>
</ul>
<p>FlatBuffer schemas are fairly similar to those of the incumbent, Protocol Buffers, and generally should be readable to those familiar with the C family of languages. We chose to improve upon the features offered by .proto files in the following ways:</p>
<ul>
<li>Deprecation of fields instead of manual field id assignment. Extending an object in a .proto means hunting for a free slot among the numbers (preferring lower numbers since they have a more compact representation). Besides being inconvenient, it also makes removing fields problematic: you either have to keep them, not making it obvious that this field shouldn't be read/written anymore, and still generating accessors. Or you remove it, but now you risk that there's still old data around that uses that field by the time someone reuses that field id, with nasty consequences.</li>
<li>Differentiating between tables and structs (see above). Effectively all table fields are <code>optional</code>, and all struct fields are <code>required</code>.</li>
<li>Having a native vector type instead of <code>repeated</code>. This gives you a length without having to collect all items, and in the case of scalars provides for a more compact representation, and one that guarantees adjacency.</li>
<li>Having a native <code>union</code> type instead of using a series of <code>optional</code> fields, all of which must be checked individually.</li>
<li>Being able to define defaults for all scalars, instead of having to deal with their optionality at each access.</li>
<li>A parser that can deal with both schemas and data definitions (JSON compatible) uniformly. </li>
</ul>
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An open source project by <a href="https://developers.google.com/games/#Tools">FPL</a>.
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<tr id="row_0_" class="even"><td class="entry"><span style="width:16px;display:inline-block;">&#160;</span><a class="el" href="md__building.html" target="_self">Building</a></td><td class="desc"></td></tr>
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# Benchmarks
Benchmarks {#flatbuffers_benchmarks}
==========
Comparing against other serialization solutions, running on Windows 7
64bit. We use the LITE runtime for Protocol Buffers (less code / lower
@@ -21,7 +22,7 @@ strings, and a large variety of int/float scalar values of all sizes,
meant to be representative of game data, e.g. a scene format.
| | FlatBuffers (binary) | Protocol Buffers LITE | Rapid JSON | FlatBuffers (JSON) | pugixml | Raw structs |
|--------------------------------------------------------|-----------------------|-----------------------|-----------------------|-----------------------| ----------------------| ----------------------|
|--------------------------------------------------------|-----------------------|-----------------------|-----------------------|------------------------| ----------------------| ----------------------|
| Decode + Traverse + Dealloc (1 million times, seconds) | 0.08 | 302 | 583 | 105 | 196 | 0.02 |
| Decode / Traverse / Dealloc (breakdown) | 0 / 0.08 / 0 | 220 / 0.15 / 81 | 294 / 0.9 / 287 | 70 / 0.08 / 35 | 41 / 3.9 / 150 | 0 / 0.02 / 0 |
| Encode (1 million times, seconds) | 3.2 | 185 | 650 | 169 | 273 | 0.15 |
@@ -52,3 +53,11 @@ meant to be representative of game data, e.g. a scene format.
fields manually), is very much tied to the rest of the engine, and works
without a schema to generate code (tied to your C++ class definition).
### Code for benchmarks
Code for these benchmarks sits in `benchmarks/` in git branch `benchmarks`.
It sits in its own branch because it has submodule dependencies that the main
project doesn't need, and the code standards do not meet those of the main
project. Please read `benchmarks/cpp/README.txt` before working with the code.
<br>

View File

@@ -1,8 +1,13 @@
# Building
Building {#flatbuffers_guide_building}
========
## Building with Visual Studio or Xcode projects
There are project files for Visual Studio and Xcode that should allow you
to build the compiler `flatc`, the samples and the tests out of the box.
## Building with CMake
Alternatively, the distribution comes with a `cmake` file that should allow
you to build project/make files for any platform. For details on `cmake`, see
<http://www.cmake.org>. In brief, depending on your platform, use one of
@@ -18,28 +23,45 @@ Note that to use clang instead of gcc, you may need to set up your environment
variables, e.g.
`CC=/usr/bin/clang CXX=/usr/bin/clang++ cmake -G "Unix Makefiles"`.
Optionally, run the `flattests` executable to ensure everything is working
correctly on your system. If this fails, please contact us!
Optionally, run the `flattests` executable from the root `flatbuffers/`
directory to ensure everything is working correctly on your system. If this
fails, please contact us!
Note that you MUST be in the root of the FlatBuffers distribution when you
run 'flattests' (and the samples), or it will fail to load its files.
Building should also produce two sample executables, `flatsamplebinary` and
`flatsampletext`, see the corresponding `.cpp` files in the
`flatbuffers/samples` directory.
Building should also produce two sample executables, `sample_binary` and
`sample_text`, see the corresponding `.cpp` file in the samples directory.
*Note that you MUST be in the root of the FlatBuffers distribution when you
run 'flattests' or `flatsampletext`, or it will fail to load its files.*
There is an `android` directory that contains all you need to build the test
executable on android (use the included `build_apk.sh` script, or use
## Building for Android
There is a `flatbuffers/android` directory that contains all you need to build
the test executable on android (use the included `build_apk.sh` script, or use
`ndk_build` / `adb` etc. as usual). Upon running, it will output to the log
if tests succeeded or not.
There is usually no runtime to compile, as the code consists of a single
header, `include/flatbuffers/flatbuffers.h`. You should add the
You may also run an android sample from inside the `flatbuffers/samples`, by
running the `android_sample.sh` script. Optionally, you may go to the
`flatbuffers/samples/android` folder and build the sample with the
`build_apk.sh` script or `ndk_build` / `adb` etc.
## Using FlatBuffers in your own projects.
For C++, there is usually no runtime to compile, as the code consists of a
single header, `include/flatbuffers/flatbuffers.h`. You should add the
`include` folder to your include paths. If you wish to be
able to load schemas and/or parse text into binary buffers at runtime,
you additionally need the other headers in `include/flatbuffers`. You must
also compile/link `src/idl_parser.cpp` (and `src/idl_gen_text.cpp` if you
also want to be able convert binary to text).
To see how to include FlatBuffers in any of our supported languages, please
view the [Tutorial](@ref flatbuffers_guide_tutorial) and select your appropriate
language using the radio buttons.
#### For Google Play apps
For applications on Google Play that integrate this library, usage is tracked.
This tracking is done automatically using the embedded version string
(flatbuffer_version_string), and helps us continue to optimize it.

1
docs/source/CONTRIBUTING.md Symbolic link
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@@ -0,0 +1 @@
../../CONTRIBUTING

224
docs/source/CUsage.md Normal file
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@@ -0,0 +1,224 @@
Use in C {#flatbuffers_guide_use_c}
==========
The C language binding exists in a separate project named [FlatCC](https://github.com/dvidelabs/flatcc).
The `flatcc` C schema compiler can generate code offline as well as
online via a C library. It can also generate buffer verifiers and fast
JSON parsers, printers.
Great care has been taken to ensure compatibily with the main `flatc`
project.
## General Documention
- [Tutorial](@ref flatbuffers_guide_tutorial) - select C as language
when scrolling down
- [FlatCC Guide](https://github.com/dvidelabs/flatcc#flatcc-flatbuffers-in-c-for-c)
- [The C Builder Interface](https://github.com/dvidelabs/flatcc/blob/master/doc/builder.md#the-builder-interface)
- [The Monster Sample in C](https://github.com/dvidelabs/flatcc/blob/master/samples/monster/monster.c)
- [GitHub](https://github.com/dvidelabs/flatcc)
## Supported Platforms
- Ubuntu (clang / gcc, ninja / gnu make)
- OS-X (clang / gcc, ninja / gnu make)
- Windows MSVC 2010, 2013, 2015
CI builds recent versions of gcc, clang and MSVC on OS-X, Ubuntu, and
Windows, and occasionally older compiler versions. See main project [Status](https://github.com/dvidelabs/flatcc#status).
Other platforms may well work, including Centos, but are not tested
regularly.
The monster sample project was specifically written for C99 in order to
follow the C++ version and for that reason it will not work with MSVC
2010.
## Modular Object Creation
In the tutorial we used the call `Monster_create_as_root` to create the
root buffer object since this is easier in simple use cases. Sometimes
we need more modularity so we can reuse a function to create nested
tables and root tables the same way. For this we need the
`flatcc_builder_buffer_create_call`. It is best to keep `flatcc_builder`
calls isolated at the top driver level, so we get:
<div class="language-c">
~~~{.c}
ns(Monster_ref_t) create_orc(flatcc_builder_t *B)
{
// ... same as in the tutorial.
return s(Monster_create(B, ...));
}
void create_monster_buffer()
{
uint8_t *buf;
size_t size;
flatcc_builder_t builder, *B;
// Initialize the builder object.
B = &builder;
flatcc_builder_init(B);
// Only use `buffer_create` without `create/start/end_as_root`.
flatcc_builder_buffer_create(create_orc(B));
// Allocate and copy buffer to user memory.
buf = flatcc_builder_finalize_buffer(B, &size);
// ... write the buffer to disk or network, or something.
free(buf);
flatcc_builder_clear(B);
}
~~~
</div>
The same principle applies with `start/end` vs `start/end_as_root` in
the top-down approach.
## Top Down Example
The tutorial uses a bottom up approach. In C it is also possible to use
a top-down approach by starting and ending objects nested within each
other. In the tutorial there is no deep nesting, so the difference is
limited, but it shows the idea:
<div class="language-c">
<br>
~~~{.c}
uint8_t treasure[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
size_t treasure_count = c_vec_len(treasure);
ns(Weapon_ref_t) axe;
// NOTE: if we use end_as_root, we MUST also start as root.
ns(Monster_start_as_root(B));
ns(Monster_pos_create(B, 1.0f, 2.0f, 3.0f));
ns(Monster_hp_add(B, 300));
ns(Monster_mana_add(B, 150));
// We use create_str instead of add because we have no existing string reference.
ns(Monster_name_create_str(B, "Orc"));
// Again we use create because we no existing vector object, only a C-array.
ns(Monster_inventory_create(B, treasure, treasure_count));
ns(Monster_color_add(B, ns(Color_Red)));
if (1) {
ns(Monster_weapons_start(B));
ns(Monster_weapons_push_create(B, flatbuffers_string_create_str(B, "Sword"), 3));
// We reuse the axe object later. Note that we dereference a pointer
// because push always returns a short-term pointer to the stored element.
// We could also have created the axe object first and simply pushed it.
axe = *ns(Monster_weapons_push_create(B, flatbuffers_string_create_str(B, "Axe"), 5));
ns(Monster_weapons_end(B));
} else {
// We can have more control with the table elements added to a vector:
//
ns(Monster_weapons_start(B));
ns(Monster_weapons_push_start(B));
ns(Weapon_name_create_str(B, "Sword"));
ns(Weapon_damage_add(B, 3));
ns(Monster_weapons_push_end(B));
ns(Monster_weapons_push_start(B));
ns(Monster_weapons_push_start(B));
ns(Weapon_name_create_str(B, "Axe"));
ns(Weapon_damage_add(B, 5));
axe = *ns(Monster_weapons_push_end(B));
ns(Monster_weapons_end(B));
}
// Unions can get their type by using a type-specific add/create/start method.
ns(Monster_equipped_Weapon_add(B, axe));
ns(Monster_end_as_root(B));
~~~
</div>
## Basic Reflection
The C-API does support reading binary schema (.bfbs)
files via code generated from the `reflection.fbs` schema, and an
[example usage](https://github.com/dvidelabs/flatcc/tree/master/samples/reflection)
shows how to use this. The reflection schema files are pre-generated
in the [runtime distribution](https://github.com/dvidelabs/flatcc/tree/master/include/flatcc/reflection).
## Mutations and Reflection
The C-API does not support mutating reflection like C++ does, nor does
the reader interface support mutating scalars (and it is generally
unsafe to do so even after verification).
The generated reader interface supports sorting vectors in-place after
casting them to a mutating type because it is not practical to do so
while building a buffer. This is covered in the builder documentation.
The reflection example makes use of this feature to look up objects by
name.
It is possible to build new buffers using complex objects from existing
buffers as source. This can be very efficient due to direct copy
semantics without endian conversion or temporary stack allocation.
Scalars, structs and strings can be used as source, as well vectors of
these.
It is currently not possible to use an existing table or vector of table
as source, but it would be possible to add support for this at some
point.
## Namespaces
The `FLATBUFFERS_WRAP_NAMESPACE` approach used in the tutorial is convenient
when each function has a very long namespace prefix. But it isn't always
the best approach. If the namespace is absent, or simple and
informative, we might as well use the prefix directly. The
[reflection example](https://github.com/dvidelabs/flatcc/blob/master/samples/reflection/bfbs2json.c)
mentioned above uses this approach.
## Checking for Present Members
Not all languages support testing if a field is present, but in C we can
elaborate the reader section of the tutorial with tests for this. Recall
that `mana` was set to the default value `150` and therefore shouldn't
be present.
<div class="language-c">
~~~{.c}
int hp_present = ns(Monster_hp_is_present(monster)); // 1
int mana_present = ns(Monster_mana_is_present(monster)); // 0
~~~
</div>
## Alternative ways to add a Union
In the tutorial we used a single call to add a union. Here we show
different ways to accomplish the same thing. The last form is rarely
used, but is the low-level way to do it. It can be used to group small
values together in the table by adding type and data at different
points in time.
<div class="language-c">
~~~{.c}
ns(Equipment_union_ref_t) equipped = ns(Equipment_as_Weapon(axe));
ns(Monster_equipped_add(B, equipped));
// or alternatively
ns(Monster_equipped_Weapon_add(B, axe);
// or alternatively
ns(Monster_equipped_add_type(B, ns(Equipment_Weapon));
ns(Monster_equipped_add_member(B, axe));
~~~
</div>
## Why not integrate with the `flatc` tool?
[It was considered how the C code generator could be integrated into the
`flatc` tool](https://github.com/dvidelabs/flatcc/issues/1), but it
would either require that the standalone C implementation of the schema
compiler was dropped, or it would lead to excessive code duplication, or
a complicated intermediate representation would have to be invented.
Neither of these alternatives are very attractive, and it isn't a big
deal to use the `flatcc` tool instead of `flatc` given that the
FlatBuffers C runtime library needs to be made available regardless.

View File

@@ -1,4 +1,5 @@
# Using the schema compiler
Using the schema compiler {#flatbuffers_guide_using_schema_compiler}
=========================
Usage:
@@ -32,6 +33,11 @@ For any schema input files, one or more generators can be specified:
- `--php`: Generate PHP code.
<<<<<<< HEAD
=======
- `--grpc`: Generate RPC stub code for GRPC.
>>>>>>> 48f37f9e0a04f2b60046dda7fef20a8b0ebc1a70
For any data input files:
- `--binary`, `-b` : If data is contained in this file, generate a
@@ -80,6 +86,11 @@ Additional options:
- `--gen-onefile` : Generate single output file (useful for C#)
- `--gen-all`: Generate not just code for the current schema files, but
for all files it includes as well. If the language uses a single file for
output (by default the case for C++ and JS), all code will end up in
this one file.
- `--raw-binary` : Allow binaries without a file_indentifier to be read.
This may crash flatc given a mismatched schema.

View File

@@ -1,227 +1,99 @@
# Use in C++
Use in C++ {#flatbuffers_guide_use_cpp}
==========
Assuming you have written a schema using the above language in say
`mygame.fbs` (FlatBuffer Schema, though the extension doesn't matter),
you've generated a C++ header called `mygame_generated.h` using the
## Before you get started
Before diving into the FlatBuffers usage in C++, it should be noted that
the [Tutorial](@ref flatbuffers_guide_tutorial) page has a complete guide
to general FlatBuffers usage in all of the supported languages (including C++).
This page is designed to cover the nuances of FlatBuffers usage, specific to
C++.
#### Prerequisites
This page assumes you have written a FlatBuffers schema and compiled it
with the Schema Compiler. If you have not, please see
[Using the schema compiler](@ref flatbuffers_guide_using_schema_compiler)
and [Writing a schema](@ref flatbuffers_guide_writing_schema).
Assuming you wrote a schema, say `mygame.fbs` (though the extension doesn't
matter), you've generated a C++ header called `mygame_generated.h` using the
compiler (e.g. `flatc -c mygame.fbs`), you can now start using this in
your program by including the header. As noted, this header relies on
`flatbuffers/flatbuffers.h`, which should be in your include path.
### Writing in C++
## FlatBuffers C++ library code location
To start creating a buffer, create an instance of `FlatBufferBuilder`
which will contain the buffer as it grows:
The code for the FlatBuffers C++ library can be found at
`flatbuffers/include/flatbuffers`. You can browse the library code on the
[FlatBuffers GitHub page](https://github.com/google/flatbuffers/tree/master/include/flatbuffers).
## Testing the FlatBuffers C++ library
The code to test the C++ library can be found at `flatbuffers/tests`.
The test code itself is located in
[test.cpp](https://github.com/google/flatbuffers/blob/master/tests/test.cpp).
This test file is built alongside `flatc`. To review how to build the project,
please read the [Building](@ref flatbuffers_guide_building) documenation.
To run the tests, execute `flattests` from the root `flatbuffers/` directory.
For example, on [Linux](https://en.wikipedia.org/wiki/Linux), you would simply
run: `./flattests`.
## Using the FlatBuffers C++ library
*Note: See [Tutorial](@ref flatbuffers_guide_tutorial) for a more in-depth
example of how to use FlatBuffers in C++.*
FlatBuffers supports both reading and writing FlatBuffers in C++.
To use FlatBuffers in your code, first generate the C++ classes from your
schema with the `--cpp` option to `flatc`. Then you can include both FlatBuffers
and the generated code to read or write FlatBuffers.
For example, here is how you would read a FlatBuffer binary file in C++:
First, include the library and generated code. Then read the file into
a `char *` array, which you pass to `GetMonster()`.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
FlatBufferBuilder fbb;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include "flatbuffers/flatbuffers.h"
#include "monster_test_generate.h"
#include <cstdio> // For printing and file access.
Before we serialize a Monster, we need to first serialize any objects
that are contained there-in, i.e. we serialize the data tree using
depth first, pre-order traversal. This is generally easy to do on
any tree structures. For example:
FILE* file = fopen("monsterdata_test.mon", "rb");
fseek(file, 0L, SEEK_END);
int length = ftell(file);
fseek(file, 0L, SEEK_SET);
char *data = new char[length];
fread(data, sizeof(char), length, file);
fclose(file);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
auto name = fbb.CreateString("MyMonster");
unsigned char inv[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
auto inventory = fbb.CreateVector(inv, 10);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
`CreateString` and `CreateVector` serialize these two built-in
datatypes, and return offsets into the serialized data indicating where
they are stored, such that `Monster` below can refer to them.
`CreateString` can also take an `std::string`, or a `const char *` with
an explicit length, and is suitable for holding UTF-8 and binary
data if needed.
`CreateVector` can also take an `std::vector`. The
offset it returns is typed, i.e. can only be used to set fields of the
correct type below. To create a vector of struct objects (which will
be stored as contiguous memory in the buffer, use `CreateVectorOfStructs`
instead.
To create a vector of nested objects (e.g. tables, strings or other vectors)
collect their offsets in a temporary array/vector, then call `CreateVector`
on that (see e.g. the array of strings example in `test.cpp`
`CreateFlatBufferTest`).
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
Vec3 vec(1, 2, 3);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
`Vec3` is the first example of code from our generated
header. Structs (unlike tables) translate to simple structs in C++, so
we can construct them in a familiar way.
We have now serialized the non-scalar components of of the monster
example, so we could create the monster something like this:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
auto mloc = CreateMonster(fbb, &vec, 150, 80, name, inventory, Color_Red, 0, Any_NONE);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Note that we're passing `150` for the `mana` field, which happens to be the
default value: this means the field will not actually be written to the buffer,
since we'll get that value anyway when we query it. This is a nice space
savings, since it is very common for fields to be at their default. It means
we also don't need to be scared to add fields only used in a minority of cases,
since they won't bloat up the buffer sizes if they're not actually used.
We do something similarly for the union field `test` by specifying a `0` offset
and the `NONE` enum value (part of every union) to indicate we don't actually
want to write this field. You can use `0` also as a default for other
non-scalar types, such as strings, vectors and tables. To pass an actual
table, pass a preconstructed table as `mytable.Union()` that corresponds to
union enum you're passing.
Tables (like `Monster`) give you full flexibility on what fields you write
(unlike `Vec3`, which always has all fields set because it is a `struct`).
If you want even more control over this (i.e. skip fields even when they are
not default), instead of the convenient `CreateMonster` call we can also
build the object field-by-field manually:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
MonsterBuilder mb(fbb);
mb.add_pos(&vec);
mb.add_hp(80);
mb.add_name(name);
mb.add_inventory(inventory);
auto mloc = mb.Finish();
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We start with a temporary helper class `MonsterBuilder` (which is
defined in our generated code also), then call the various `add_`
methods to set fields, and `Finish` to complete the object. This is
pretty much the same code as you find inside `CreateMonster`, except
we're leaving out a few fields. Fields may also be added in any order,
though orderings with fields of the same size adjacent
to each other most efficient in size, due to alignment. You should
not nest these Builder classes (serialize your
data in pre-order).
Regardless of whether you used `CreateMonster` or `MonsterBuilder`, you
now have an offset to the root of your data, and you can finish the
buffer using:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
FinishMonsterBuffer(fbb, mloc);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The buffer is now ready to be stored somewhere, sent over the network,
be compressed, or whatever you'd like to do with it. You can access the
start of the buffer with `fbb.GetBufferPointer()`, and it's size from
`fbb.GetSize()`.
Calling code may take ownership of the buffer with `fbb.ReleaseBufferPointer()`.
Should you do it, the `FlatBufferBuilder` will be in an invalid state,
and *must* be cleared before it can be used again.
However, it also means you are able to destroy the builder while keeping
the buffer in your application.
`samples/sample_binary.cpp` is a complete code sample similar to
the code above, that also includes the reading code below.
### Reading in C++
If you've received a buffer from somewhere (disk, network, etc.) you can
directly start traversing it using:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
auto monster = GetMonster(buffer_pointer);
auto monster = GetMonster(data);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
`monster` is of type `Monster *`, and points to somewhere *inside* your
buffer (root object pointers are not the same as `buffer_pointer` !).
If you look in your generated header, you'll see it has
convenient accessors for all fields, e.g.
convenient accessors for all fields, e.g. `hp()`, `mana()`, etc:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
assert(monster->hp() == 80);
assert(monster->mana() == 150); // default
assert(strcmp(monster->name()->c_str(), "MyMonster") == 0);
printf("%d\n", monster->hp()); // `80`
printf("%d\n", monster->mana()); // default value of `150`
printf("%s\n", monster->name()->c_str()); // "MyMonster"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
These should all be true. Note that we never stored a `mana` value, so
it will return the default.
*Note: That we never stored a `mana` value, so it will return the default.*
To access sub-objects, in this case the `Vec3`:
## Reflection (& Resizing)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
auto pos = monster->pos();
assert(pos);
assert(pos->z() == 3);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
There is experimental support for reflection in FlatBuffers, allowing you to
read and write data even if you don't know the exact format of a buffer, and
even allows you to change sizes of strings and vectors in-place.
If we had not set the `pos` field during serialization, it would be
`NULL`.
Similarly, we can access elements of the inventory array:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
auto inv = monster->inventory();
assert(inv);
assert(inv->Get(9) == 9);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
### Mutating FlatBuffers
As you saw above, typically once you have created a FlatBuffer, it is
read-only from that moment on. There are however cases where you have just
received a FlatBuffer, and you'd like to modify something about it before
sending it on to another recipient. With the above functionality, you'd have
to generate an entirely new FlatBuffer, while tracking what you modify in your
own data structures. This is inconvenient.
For this reason FlatBuffers can also be mutated in-place. While this is great
for making small fixes to an existing buffer, you generally want to create
buffers from scratch whenever possible, since it is much more efficient and
the API is much more general purpose.
To get non-const accessors, invoke `flatc` with `--gen-mutable`.
Similar to the reading API above, you now can:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
auto monster = GetMutableMonster(buffer_pointer); // non-const
monster->mutate_hp(10); // Set table field.
monster->mutable_pos()->mutate_z(4); // Set struct field.
monster->mutable_inventory()->Mutate(0, 1); // Set vector element.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We use the somewhat verbose term `mutate` instead of `set` to indicate that
this is a special use case, not to be confused with the default way of
constructing FlatBuffer data.
After the above mutations, you can send on the FlatBuffer to a new recipient
without any further work!
Note that any `mutate_` functions on tables return a bool, which is false
if the field we're trying to set isn't present in the buffer. Fields are not
present if they weren't set, or even if they happen to be equal to the
default value. For example, in the creation code above we set the `mana` field
to `150`, which is the default value, so it was never stored in the buffer.
Trying to call mutate_mana() on such data will return false, and the value won't
actually be modified!
One way to solve this is to call `ForceDefaults()` on a
`FlatBufferBuilder` to force all fields you set to actually be written. This
of course increases the size of the buffer somewhat, but this may be
acceptable for a mutable buffer.
Alternatively, you can use the more powerful reflection functionality:
### Reflection (& Resizing)
If the above ways of accessing a buffer are still too static for you, there is
experimental support for reflection in FlatBuffers, allowing you to read and
write data even if you don't know the exact format of a buffer, and even allows
you to change sizes of strings and vectors in-place.
The way this works is very elegant, there is actually a FlatBuffer schema that
The way this works is very elegant; there is actually a FlatBuffer schema that
describes schemas (!) which you can find in `reflection/reflection.fbs`.
The compiler `flatc` can write out any schemas it has just parsed as a binary
The compiler, `flatc`, can write out any schemas it has just parsed as a binary
FlatBuffer, corresponding to this meta-schema.
Loading in one of these binary schemas at runtime allows you traverse any
@@ -232,9 +104,10 @@ For convenient field manipulation, you can include the header
`flatbuffers/reflection.h` which includes both the generated code from the meta
schema, as well as a lot of helper functions.
And example of usage for the moment you can find in `test.cpp/ReflectionTest()`.
And example of usage, for the time being, can be found in
`test.cpp/ReflectionTest()`.
### Storing maps / dictionaries in a FlatBuffer
## Storing maps / dictionaries in a FlatBuffer
FlatBuffers doesn't support maps natively, but there is support to
emulate their behavior with vectors and binary search, which means you
@@ -260,7 +133,7 @@ To use it:
only works if the vector has been sorted, it will likely not find elements
if it hasn't been sorted.
### Direct memory access
## Direct memory access
As you can see from the above examples, all elements in a buffer are
accessed through generated accessors. This is because everything is
@@ -285,7 +158,7 @@ machines, so only use tricks like this if you can guarantee you're not
shipping on a big endian machine (an `assert(FLATBUFFERS_LITTLEENDIAN)`
would be wise).
### Access of untrusted buffers
## Access of untrusted buffers
The generated accessor functions access fields over offsets, which is
very quick. These offsets are not verified at run-time, so a malformed
@@ -342,7 +215,7 @@ accepted).
There are two ways to use text formats:
### Using the compiler as a conversion tool
#### Using the compiler as a conversion tool
This is the preferred path, as it doesn't require you to add any new
code to your program, and is maximally efficient since you can ship with
@@ -354,7 +227,7 @@ users/developers to perform, though you might be able to automate it.
This will generate the binary file `mydata_wire.bin` which can be loaded
as before.
### Making your program capable of loading text directly
#### Making your program capable of loading text directly
This gives you maximum flexibility. You could even opt to support both,
i.e. check for both files, and regenerate the binary from text when
@@ -400,7 +273,7 @@ file, that you can access as described above.
`samples/sample_text.cpp` is a code sample showing the above operations.
### Threading
## Threading
Reading a FlatBuffer does not touch any memory outside the original buffer,
and is entirely read-only (all const), so is safe to access from multiple
@@ -413,3 +286,5 @@ share instances of FlatBufferBuilder between threads (recommended), or
manually wrap it in synchronisation primites. There's no automatic way to
accomplish this, by design, as we feel multithreaded construction
of a single buffer will be rare, and synchronisation overhead would be costly.
<br>

View File

@@ -1,7 +1,10 @@
# FlatBuffers
FlatBuffers {#flatbuffers_index}
===========
FlatBuffers is an efficient cross platform serialization library for C++, Java,
C#, Go, Python and JavaScript (C, PHP & Ruby in progress).
# Overview {#flatbuffers_overview}
[FlatBuffers](@ref flatbuffers_overview) is an efficient cross platform
serialization library for C++, C#, C, Go, Java, JavaScript, PHP, and Python.
It was originally created at Google for game development and other
performance-critical applications.
@@ -26,7 +29,7 @@ under the Apache license, v2 (see LICENSE.txt).
projects where spending time and space (many memory allocations) to
be able to access or construct serialized data is undesirable, such
as in games or any other performance sensitive applications. See the
[benchmarks](md__benchmarks.html) for details.
[benchmarks](@ref flatbuffers_benchmarks) for details.
- **Flexible** - Optional fields means not only do you get great
forwards and backwards compatibility (increasingly important for
@@ -76,7 +79,7 @@ In this context, it is only a better choice for systems that have very
little to no information ahead of time about what data needs to be stored.
Read more about the "why" of FlatBuffers in the
[white paper](md__white_paper.html).
[white paper](@ref flatbuffers_white_paper).
### Who uses FlatBuffers?
- [Cocos2d-x](http://www.cocos2d-x.org/), the #1 open source mobile game
@@ -118,28 +121,31 @@ sections provide a more in-depth usage guide.
## In-depth documentation
- How to [build the compiler](md__building.html) and samples on various
platforms.
- How to [use the compiler](md__compiler.html).
- How to [write a schema](md__schemas.html).
- How to [use the generated C++ code](md__cpp_usage.html) in your own
programs.
- How to [use the generated Java/C# code](md__java_usage.html) in your own
programs.
- How to [use the generated Go code](md__go_usage.html) in your own
programs.
- [Support matrix](md__support.html) for platforms/languages/features.
- Some [benchmarks](md__benchmarks.html) showing the advantage of using
- How to [build the compiler](@ref flatbuffers_guide_building) and samples on
various platforms.
- How to [use the compiler](@ref flatbuffers_guide_using_schema_compiler).
- How to [write a schema](@ref flatbuffers_guide_writing_schema).
- How to [use the generated C++ code](@ref flatbuffers_guide_use_cpp) in your
own programs.
- How to [use the generated Java/C# code](@ref flatbuffers_guide_use_java_c-sharp)
in your own programs.
- How to [use the generated Go code](@ref flatbuffers_guide_use_go) in your
own programs.
- How to [use FlatBuffers in C with `flatcc`](@ref flatbuffers_guide_use_c) in your
own programs.
- [Support matrix](@ref flatbuffers_support) for platforms/languages/features.
- Some [benchmarks](@ref flatbuffers_benchmarks) showing the advantage of
using FlatBuffers.
- A [white paper](@ref flatbuffers_white_paper) explaining the "why" of
FlatBuffers.
- A [white paper](md__white_paper.html) explaining the "why" of FlatBuffers.
- A description of the [internals](md__internals.html) of FlatBuffers.
- A formal [grammar](md__grammar.html) of the schema language.
- A description of the [internals](@ref flatbuffers_internals) of FlatBuffers.
- A formal [grammar](@ref flatbuffers_grammar) of the schema language.
## Online resources
- [GitHub repository](http://github.com/google/flatbuffers)
- [Landing page](http://google.github.io/flatbuffers)
- [FlatBuffers Google Group](http://group.google.com/group/flatbuffers)
- [FlatBuffers Google Group](https://groups.google.com/forum/#!forum/flatbuffers)
- [FlatBuffers Issues Tracker](http://github.com/google/flatbuffers/issues)
- Independent implementations & tools:
- [FlatCC](https://github.com/dvidelabs/flatcc) Alternative FlatBuffers

26
docs/source/GoApi.md Normal file
View File

@@ -0,0 +1,26 @@
Go API
======
\addtogroup flatbuffers_go_api
<!-- Note: The `GoApi_generate.txt` code snippet was generated using `godoc` and
customized for use with this markdown file. To regenerate the file, use the
`godoc` tool (http://godoc.org) with the files in the `flatbuffers/go`
folder.
You may need to ensure that copies of the files exist in the `src/`
subfolder at the path set by the `$GOROOT` environment variable. You can
either move the files to `$GOROOT/src/flatbuffers` manually, if `$GOROOT`
is already set, otherwise you will need to manually set the `$GOROOT`
variable to a path and create `src/flatbuffers` subfolders at that path.
Then copy the flatbuffers files into `$GOROOT/src/flatbuffers`. (Some
versions of `godoc` include a `-path` flag. This could be used instead, if
available).
Once the files exist at the `$GOROOT/src/flatbuffers` location, you can
regenerate this doc using the following command:
`godoc flatbuffers > GoApi_generated.txt`.
After the documentation is generated, you will have to manually remove any
non-user facing documentation from this file. -->
\snippet GoApi_generated.txt Go API

View File

@@ -0,0 +1,125 @@
// This file was generated using `godoc` and customized for use with the
// API Reference documentation. To recreate this file, use the `godoc` tool
// (http://godoc.org) with the files in the `flatbuffers/go` folder.
//
// Note: You may need to ensure that copies of the files exist in the
// `src/` subfolder at the path set by the `$GOROOT` environment variable.
// You can either move the files to `$GOROOT/src/flatbuffers` manually, if
// `$GOROOT` is already set, otherwise you will need to manually set the
// `$GOROOT` variable to a path and create `src/flatbuffers` subfolders at that
// path. Then copy these files into `$GOROOT/src/flatbuffers`. (Some versions of
// `godoc` include a `-path` flag. This could be used instead, if available).
//
// Once the files exist at the `$GOROOT/src/flatbuffers` location, you can
// regenerate this doc using the following command:
// `godoc flatbuffers > GoApi_generated.txt`.
//
// After the documentation is generated, you will have to manually remove any
// non-user facing documentation from this file.
/// [Go API]
PACKAGE DOCUMENTATION
package flatbuffers
Package flatbuffers provides facilities to read and write flatbuffers
objects.
TYPES
type Builder struct {
// `Bytes` gives raw access to the buffer. Most users will want to use
// FinishedBytes() instead.
Bytes []byte
}
Builder is a state machine for creating FlatBuffer objects. Use a
Builder to construct object(s) starting from leaf nodes.
A Builder constructs byte buffers in a last-first manner for simplicity
and performance.
FUNCTIONS
func NewBuilder(initialSize int) *Builder
NewBuilder initializes a Builder of size `initial_size`. The internal
buffer is grown as needed.
func (b *Builder) CreateByteString(s []byte) UOffsetT
CreateByteString writes a byte slice as a string (null-terminated).
func (b *Builder) CreateByteVector(v []byte) UOffsetT
CreateByteVector writes a ubyte vector
func (b *Builder) CreateString(s string) UOffsetT
CreateString writes a null-terminated string as a vector.
func (b *Builder) EndVector(vectorNumElems int) UOffsetT
EndVector writes data necessary to finish vector construction.
func (b *Builder) Finish(rootTable UOffsetT)
Finish finalizes a buffer, pointing to the given `rootTable`.
func (b *Builder) FinishedBytes() []byte
FinishedBytes returns a pointer to the written data in the byte buffer.
Panics if the builder is not in a finished state (which is caused by
calling `Finish()`).
func (b *Builder) Head() UOffsetT
Head gives the start of useful data in the underlying byte buffer. Note:
unlike other functions, this value is interpreted as from the left.
func (b *Builder) PrependBool(x bool)
PrependBool prepends a bool to the Builder buffer. Aligns and checks for
space.
func (b *Builder) PrependByte(x byte)
PrependByte prepends a byte to the Builder buffer. Aligns and checks for
space.
func (b *Builder) PrependFloat32(x float32)
PrependFloat32 prepends a float32 to the Builder buffer. Aligns and
checks for space.
func (b *Builder) PrependFloat64(x float64)
PrependFloat64 prepends a float64 to the Builder buffer. Aligns and
checks for space.
func (b *Builder) PrependInt16(x int16)
PrependInt16 prepends a int16 to the Builder buffer. Aligns and checks
for space.
func (b *Builder) PrependInt32(x int32)
PrependInt32 prepends a int32 to the Builder buffer. Aligns and checks
for space.
func (b *Builder) PrependInt64(x int64)
PrependInt64 prepends a int64 to the Builder buffer. Aligns and checks
for space.
func (b *Builder) PrependInt8(x int8)
PrependInt8 prepends a int8 to the Builder buffer. Aligns and checks for
space.
func (b *Builder) PrependUOffsetT(off UOffsetT)
PrependUOffsetT prepends an UOffsetT, relative to where it will be
written.
func (b *Builder) PrependUint16(x uint16)
PrependUint16 prepends a uint16 to the Builder buffer. Aligns and checks
for space.
func (b *Builder) PrependUint32(x uint32)
PrependUint32 prepends a uint32 to the Builder buffer. Aligns and checks
for space.
func (b *Builder) PrependUint64(x uint64)
PrependUint64 prepends a uint64 to the Builder buffer. Aligns and checks
for space.
func (b *Builder) PrependUint8(x uint8)
PrependUint8 prepends a uint8 to the Builder buffer. Aligns and checks
for space.
func (b *Builder) Reset()
Reset truncates the underlying Builder buffer, facilitating alloc-free
reuse of a Builder. It also resets bookkeeping data.
/// [Go API]

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@@ -1,11 +1,51 @@
# Use in Go
Use in Go {#flatbuffers_guide_use_go}
=========
There's experimental support for reading FlatBuffers in Go. Generate code
for Go with the `-g` option to `flatc`.
## Before you get started
See `go_test.go` for an example. You import the generated code, read a
FlatBuffer binary file into a `[]byte`, which you pass to the
`GetRootAsMonster` function:
Before diving into the FlatBuffers usage in Go, it should be noted that
the [Tutorial](@ref flatbuffers_guide_tutorial) page has a complete guide
to general FlatBuffers usage in all of the supported languages (including Go).
This page is designed to cover the nuances of FlatBuffers usage, specific to
Go.
You should also have read the [Building](@ref flatbuffers_guide_building)
documentation to build `flatc` and should be familiar with
[Using the schema compiler](@ref flatbuffers_guide_using_schema_compiler) and
[Writing a schema](@ref flatbuffers_guide_writing_schema).
## FlatBuffers Go library code location
The code for the FlatBuffers Go library can be found at
`flatbuffers/go`. You can browse the library code on the [FlatBuffers
GitHub page](https://github.com/google/flatbuffers/tree/master/go).
## Testing the FlatBuffers Go library
The code to test the Go library can be found at `flatbuffers/tests`.
The test code itself is located in [go_test.go](https://github.com/google/
flatbuffers/blob/master/tests/go_test.go).
To run the tests, use the [GoTest.sh](https://github.com/google/flatbuffers/
blob/master/tests/GoTest.sh) shell script.
*Note: The shell script requires [Go](https://golang.org/doc/install) to
be installed.*
## Using the FlatBuffers Go library
*Note: See [Tutorial](@ref flatbuffers_guide_tutorial) for a more in-depth
example of how to use FlatBuffers in Go.*
FlatBuffers supports reading and writing binary FlatBuffers in Go.
To use FlatBuffers in your own code, first generate Go classes from your
schema with the `--go` option to `flatc`. Then you can include both FlatBuffers
and the generated code to read or write a FlatBuffer.
For example, here is how you would read a FlatBuffer binary file in Go: First,
include the library and generated code. Then read a FlatBuffer binary file into
a `[]byte`, which you pass to the `GetRootAsMonster` function:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.go}
import (
@@ -27,96 +67,10 @@ Now you can access values like this:
pos := monster.Pos(nil)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Note that whenever you access a new object like in the `Pos` example above,
a new temporary accessor object gets created. If your code is very performance
sensitive (you iterate through a lot of objects), you can replace nil with a
pointer to a `Vec3` object you've already created. This allows
you to reuse it across many calls and reduce the amount of object allocation
(and thus garbage collection) your program does.
To access vectors you pass an extra index to the
vector field accessor. Then a second method with the same name suffixed
by `Length` let's you know the number of elements you can access:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.go}
for i := 0; i < monster.InventoryLength(); i++ {
monster.Inventory(i) // do something here
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
You can also construct these buffers in Go using the functions found in the
generated code, and the FlatBufferBuilder class:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.go}
builder := flatbuffers.NewBuilder(0)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Create strings:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.go}
str := builder.CreateString("MyMonster")
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Create a table with a struct contained therein:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.go}
example.MonsterStart(builder)
example.MonsterAddPos(builder, example.CreateVec3(builder, 1.0, 2.0, 3.0, 3.0, 4, 5, 6))
example.MonsterAddHp(builder, 80)
example.MonsterAddName(builder, str)
example.MonsterAddInventory(builder, inv)
example.MonsterAddTest_Type(builder, 1)
example.MonsterAddTest(builder, mon2)
example.MonsterAddTest4(builder, test4s)
mon := example.MonsterEnd(builder)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unlike C++, Go does not support table creation functions like 'createMonster()'.
This is to create the buffer without
using temporary object allocation (since the `Vec3` is an inline component of
`Monster`, it has to be created right where it is added, whereas the name and
the inventory are not inline, and **must** be created outside of the table
creation sequence).
Structs do have convenient methods that allow you to construct them in one call.
These also have arguments for nested structs, e.g. if a struct has a field `a`
and a nested struct field `b` (which has fields `c` and `d`), then the arguments
will be `a`, `c` and `d`.
Vectors also use this start/end pattern to allow vectors of both scalar types
and structs:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.go}
example.MonsterStartInventoryVector(builder, 5)
for i := 4; i >= 0; i-- {
builder.PrependByte(byte(i))
}
inv := builder.EndVector(5)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The generated method 'StartInventoryVector' is provided as a convenience
function which calls 'StartVector' with the correct element size of the vector
type which in this case is 'ubyte' or 1 byte per vector element.
You pass the number of elements you want to write.
You write the elements backwards since the buffer
is being constructed back to front. Use the correct `Prepend` call for the type,
or `PrependUOffsetT` for offsets. You then pass `inv` to the corresponding
`Add` call when you construct the table containing it afterwards.
There are `Prepend` functions for all the scalar types. You use
`PrependUOffset` for any previously constructed objects (such as other tables,
strings, vectors). For structs, you use the appropriate `create` function
in-line, as shown above in the `Monster` example.
Once you're done constructing a buffer, you call `Finish` with the root object
offset (`mon` in the example above). Your data now resides in Builder.Bytes.
Important to note is that the real data starts at the index indicated by Head(),
for Offset() bytes (this is because the buffer is constructed backwards).
If you wanted to read the buffer right after creating it (using
`GetRootAsMonster` above), the second argument, instead of `0` would thus
also be `Head()`.
## Text Parsing
There currently is no support for parsing text (Schema's and JSON) directly
from Go, though you could use the C++ parser through cgo. Please see the
C++ documentation for more on text parsing.
<br>

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@@ -1,4 +1,5 @@
# Grammar of the schema language
Grammar of the schema language {#flatbuffers_grammar}
==============================
schema = include*
( namespace\_decl | type\_decl | enum\_decl | root\_decl |

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@@ -1,4 +1,5 @@
# FlatBuffer Internals
FlatBuffer Internals {#flatbuffers_internals}
====================
This section is entirely optional for the use of FlatBuffers. In normal
usage, you should never need the information contained herein. If you're
@@ -16,7 +17,7 @@ byte-swap intrinsics.
On purpose, the format leaves a lot of details about where exactly
things live in memory undefined, e.g. fields in a table can have any
order, and objects to some extend can be stored in many orders. This is
order, and objects to some extent can be stored in many orders. This is
because the format doesn't need this information to be efficient, and it
leaves room for optimization and extension (for example, fields can be
packed in a way that is most compact). Instead, the format is defined in
@@ -73,7 +74,10 @@ code.
### Tables
These start with an `soffset_t` to a vtable. This is a signed version of
Unlike structs, these are not stored in inline in their parent, but are
referred to by offset.
They start with an `soffset_t` to a vtable. This is a signed version of
`uoffset_t`, since vtables may be stored anywhere relative to the object.
This offset is substracted (not added) from the object start to arrive at
the vtable start. This offset is followed by all the
@@ -88,7 +92,7 @@ The elements of a vtable are all of type `voffset_t`, which is
a `uint16_t`. The first element is the size of the vtable in bytes,
including the size element. The second one is the size of the object, in bytes
(including the vtable offset). This size could be used for streaming, to know
how many bytes to read to be able to access all fields of the object.
how many bytes to read to be able to access all *inline* fields of the object.
The remaining elements are the N offsets, where N is the amount of fields
declared in the schema when the code that constructed this buffer was
compiled (thus, the size of the table is N + 2).
@@ -106,7 +110,8 @@ field to be read.
Strings are simply a vector of bytes, and are always
null-terminated. Vectors are stored as contiguous aligned scalar
elements prefixed by a 32bit element count (not including any
null termination).
null termination). Neither is stored inline in their parent, but are referred to
by offset.
### Construction
@@ -224,7 +229,12 @@ Otherwise, it uses the entry as an offset into the table to locate the field.
`FlatBufferBuilder`. You can add the fields in any order, and the `Finish`
call will ensure the correct vtable gets generated.
inline flatbuffers::Offset<Monster> CreateMonster(flatbuffers::FlatBufferBuilder &_fbb, const Vec3 *pos, int16_t mana, int16_t hp, flatbuffers::Offset<flatbuffers::String> name, flatbuffers::Offset<flatbuffers::Vector<uint8_t>> inventory, int8_t color) {
inline flatbuffers::Offset<Monster> CreateMonster(flatbuffers::FlatBufferBuilder &_fbb,
const Vec3 *pos, int16_t mana,
int16_t hp,
flatbuffers::Offset<flatbuffers::String> name,
flatbuffers::Offset<flatbuffers::Vector<uint8_t>> inventory,
int8_t color) {
MonsterBuilder builder_(_fbb);
builder_.add_inventory(inventory);
builder_.add_name(name);
@@ -249,4 +259,37 @@ start traversing a FlatBuffer from a raw buffer pointer.
}; // namespace MyGame
}; // namespace Sample
### Encoding example.
Below is a sample encoding for the following JSON corresponding to the above
schema:
{ pos: { x: 1, y: 2, z: 3 }, name: "fred", hp: 50 }
Resulting in this binary buffer:
// Start of the buffer:
uint32_t 20 // Offset to the root table.
// Start of the vtable. Not shared in this example, but could be:
uint16_t 16 // Size of table, starting from here.
uint16_t 22 // Size of object inline data.
uint16_t 4, 0, 20, 16, 0, 0 // Offsets to fields from start of (root) table, 0 for not present.
// Start of the root table:
int32_t 16 // Offset to vtable used (default negative direction)
float 1, 2, 3 // the Vec3 struct, inline.
uint32_t 8 // Offset to the name string.
int16_t 50 // hp field.
int16_t 0 // Padding for alignment.
// Start of name string:
uint32_t 4 // Length of string.
int8_t 'f', 'r', 'e', 'd', 0, 0, 0, 0 // Text + 0 termination + padding.
Note that this not the only possible encoding, since the writer has some
flexibility in which of the children of root object to write first (though in
this case there's only one string), and what order to write the fields in.
Different orders may also cause different alignments to happen.
<br>

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@@ -0,0 +1,141 @@
Use in Java/C# {#flatbuffers_guide_use_java_c-sharp}
==============
## Before you get started
Before diving into the FlatBuffers usage in Java or C#, it should be noted that
the [Tutorial](@ref flatbuffers_guide_tutorial) page has a complete guide to
general FlatBuffers usage in all of the supported languages (including both Java
and C#). This page is designed to cover the nuances of FlatBuffers usage,
specific to Java and C#.
You should also have read the [Building](@ref flatbuffers_guide_building)
documentation to build `flatc` and should be familiar with
[Using the schema compiler](@ref flatbuffers_guide_using_schema_compiler) and
[Writing a schema](@ref flatbuffers_guide_writing_schema).
## FlatBuffers Java and C-sharp code location
#### Java
The code for the FlatBuffers Java library can be found at
`flatbuffers/java/com/google/flatbuffers`. You can browse the library on the
[FlatBuffers GitHub page](https://github.com/google/flatbuffers/tree/master/
java/com/google/flatbuffers).
#### C-sharp
The code for the FlatBuffers C# library can be found at
`flatbuffers/net/FlatBuffers`. You can browse the library on the
[FlatBuffers GitHub page](https://github.com/google/flatbuffers/tree/master/net/
FlatBuffers).
## Testing the FlatBuffers Java and C-sharp libraries
The code to test the libraries can be found at `flatbuffers/tests`.
#### Java
The test code for Java is located in [JavaTest.java](https://github.com/google
/flatbuffers/blob/master/tests/JavaTest.java).
To run the tests, use either [JavaTest.sh](https://github.com/google/
flatbuffers/blob/master/tests/JavaTest.sh) or [JavaTest.bat](https://github.com/
google/flatbuffers/blob/master/tests/JavaTest.bat), depending on your operating
system.
*Note: These scripts require that [Java](https://www.oracle.com/java/index.html)
is installed.*
#### C-sharp
The test code for C# is located in the [FlatBuffers.Test](https://github.com/
google/flatbuffers/tree/master/tests/FlatBuffers.Test) subfolder. To run the
tests, open `FlatBuffers.Test.csproj` in [Visual Studio](
https://www.visualstudio.com), and compile/run the project.
Optionally, you can run this using [Mono](http://www.mono-project.com/) instead.
Once you have installed `Mono`, you can run the tests from the command line
by running the following commands from inside the `FlatBuffers.Test` folder:
~~~{.sh}
mcs *.cs ../MyGame/Example/*.cs ../../net/FlatBuffers/*.cs
mono Assert.exe
~~~
## Using the FlatBuffers Java (and C#) library
*Note: See [Tutorial](@ref flatbuffers_guide_tutorial) for a more in-depth
example of how to use FlatBuffers in Java or C#.*
FlatBuffers supports reading and writing binary FlatBuffers in Java and C#.
To use FlatBuffers in your own code, first generate Java classes from your
schema with the `--java` option to `flatc`. (Or for C# with `--csharp`).
Then you can include both FlatBuffers and the generated code to read
or write a FlatBuffer.
For example, here is how you would read a FlatBuffer binary file in Java:
First, import the library and generated code. Then, you read a FlatBuffer binary
file into a `byte[]`. You then turn the `byte[]` into a `ByteBuffer`, which you
pass to the `getRootAsMyRootType` function:
*Note: The code here is written from the perspective of Java. Code for both
languages is both generated and used in nearly the exact same way, with only
minor differences. These differences are
[explained in a section below](#differences_in_c-sharp).*
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
import MyGame.Example.*;
import com.google.flatbuffers.FlatBufferBuilder;
// This snippet ignores exceptions for brevity.
File file = new File("monsterdata_test.mon");
RandomAccessFile f = new RandomAccessFile(file, "r");
byte[] data = new byte[(int)f.length()];
f.readFully(data);
f.close();
ByteBuffer bb = ByteBuffer.wrap(data);
Monster monster = Monster.getRootAsMonster(bb);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Now you can access the data from the `Monster monster`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
short hp = monster.hp();
Vec3 pos = monster.pos();
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<a name="differences_in_c-sharp">
#### Differences in C-sharp
</a>
C# code works almost identically to Java, with only a few minor differences.
You can see an example of C# code in
`tests/FlatBuffers.Test/FlatBuffersExampleTests.cs` or
`samples/SampleBinary.cs`.
First of all, naming follows standard C# style with `PascalCasing` identifiers,
e.g. `GetRootAsMyRootType`. Also, values (except vectors and unions) are
available as properties instead of parameterless accessor methods as in Java.
The performance-enhancing methods to which you can pass an already created
object are prefixed with `Get`, e.g.:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cs}
// property
var pos = monster.Pos;
// method filling a preconstructed object
var preconstructedPos = new Vec3();
monster.GetPos(preconstructedPos);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
## Text parsing
There currently is no support for parsing text (Schema's and JSON) directly
from Java or C#, though you could use the C++ parser through native call
interfaces available to each language. Please see the
C++ documentation for more on text parsing.
<br>

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@@ -0,0 +1,105 @@
Use in JavaScript {#flatbuffers_guide_use_javascript}
=================
## Before you get started
Before diving into the FlatBuffers usage in JavaScript, it should be noted that
the [Tutorial](@ref flatbuffers_guide_tutorial) page has a complete guide to
general FlatBuffers usage in all of the supported languages
(including JavaScript). This page is specifically designed to cover the nuances
of FlatBuffers usage in JavaScript.
You should also have read the [Building](@ref flatbuffers_guide_building)
documentation to build `flatc` and should be familiar with
[Using the schema compiler](@ref flatbuffers_guide_using_schema_compiler) and
[Writing a schema](@ref flatbuffers_guide_writing_schema).
## FlatBuffers JavaScript library code location
The code for the FlatBuffers JavaScript library can be found at
`flatbuffers/js`. You can browse the library code on the [FlatBuffers
GitHub page](https://github.com/google/flatbuffers/tree/master/js).
## Testing the FlatBuffers JavaScript library
The code to test the JavaScript library can be found at `flatbuffers/tests`.
The test code itself is located in [JavaScriptTest.js](https://github.com/
google/flatbuffers/blob/master/tests/JavaScriptTest.js).
To run the tests, use the [JavaScriptTest.sh](https://github.com/google/
flatbuffers/blob/master/tests/JavaScriptTest.sh) shell script.
*Note: The JavaScript test file requires [Node.js](https://nodejs.org/en/).*
## Using the FlatBuffers JavaScript libary
*Note: See [Tutorial](@ref flatbuffers_guide_tutorial) for a more in-depth
example of how to use FlatBuffers in JavaScript.*
FlatBuffers supports both reading and writing FlatBuffers in JavaScript.
To use FlatBuffers in your own code, first generate JavaScript classes from your
schema with the `--js` option to `flatc`. Then you can include both FlatBuffers
and the generated code to read or write a FlatBuffer.
For example, here is how you would read a FlatBuffer binary file in Javascript:
First, include the library and generated code. Then read the file into an
`Uint8Array`. Make a `flatbuffers.ByteBuffer` out of the `Uint8Array`, and pass
the ByteBuffer to the `getRootAsMonster` function.
*Note: Both JavaScript module loaders (e.g. Node.js) and browser-based
HTML/JavaScript code segments are shown below in the following snippet:*
~~~{.js}
// Note: These require functions are specific to JavaScript module loaders
// (namely, Node.js). See below for a browser-based example.
var fs = require('fs');
var flatbuffers = require('../flatbuffers').flatbuffers;
var MyGame = require('./monster_generated').MyGame;
var data = new Uint8Array(fs.readFileSync('monster.dat'));
var buf = new flatbuffers.ByteBuffer(data);
var monster = MyGame.Example.Monster.getRootAsMonster(buf);
//--------------------------------------------------------------------------//
// Note: This code is specific to browser-based HTML/JavaScript. See above
// for the code using JavaScript module loaders (e.g. Node.js).
<script src="../js/flatbuffers.js"></script>
<script src="monster_generated.js"></script>
<script>
function readFile() {
var reader = new FileReader(); // This example uses the HTML5 FileReader.
var file = document.getElementById(
'file_input').files[0]; // "monster.dat" from the HTML <input> field.
reader.onload = function() { // Executes after the file is read.
var data = new Uint8Array(reader.result);
var buf = new flatbuffers.ByteBuffer(data);
var monster = MyGame.Example.Monster.getRootAsMonster(buf);
}
reader.readAsArrayBuffer(file);
}
</script>
// Open the HTML file in a browser and select "monster.dat" from with the
// <input> field.
<input type="file" id="file_input" onchange="readFile();">
~~~
Now you can access values like this:
~~~{.js}
var hp = monster.hp();
var pos = monster.pos();
~~~
## Text parsing FlatBuffers in JavaScript
There currently is no support for parsing text (Schema's and JSON) directly
from JavaScript.

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@@ -1,224 +0,0 @@
# Use in Java/C-sharp
FlatBuffers supports reading and writing binary FlatBuffers in Java and C#.
Generate code for Java with the `-j` option to `flatc`, or for C# with `-n`
(think .Net).
Note that this document is from the perspective of Java. Code for both languages
is generated in the same way, with only minor differences. These differences
are [explained in a section below](#differences-in-c-sharp).
See `javaTest.java` for an example. Essentially, you read a FlatBuffer binary
file into a `byte[]`, which you then turn into a `ByteBuffer`, which you pass to
the `getRootAsMyRootType` function:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
ByteBuffer bb = ByteBuffer.wrap(data);
Monster monster = Monster.getRootAsMonster(bb);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Now you can access values much like C++:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
short hp = monster.hp();
Vec3 pos = monster.pos();
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Note that whenever you access a new object like in the `pos` example above,
a new temporary accessor object gets created. If your code is very performance
sensitive (you iterate through a lot of objects), there's a second `pos()`
method to which you can pass a `Vec3` object you've already created. This allows
you to reuse it across many calls and reduce the amount of object allocation
(and thus garbage collection) your program does.
Java does not support unsigned scalars. This means that any unsigned types you
use in your schema will actually be represented as a signed value. This means
all bits are still present, but may represent a negative value when used.
For example, to read a `byte b` as an unsigned number, you can do:
`(short)(b & 0xFF)`
The default string accessor (e.g. `monster.name()`) currently always create
a new Java `String` when accessed, since FlatBuffer's UTF-8 strings can't be
used in-place by `String`. Alternatively, use `monster.nameAsByteBuffer()`
which returns a `ByteBuffer` referring to the UTF-8 data in the original
`ByteBuffer`, which is much more efficient. The `ByteBuffer`'s `position`
points to the first character, and its `limit` to just after the last.
Vector access is also a bit different from C++: you pass an extra index
to the vector field accessor. Then a second method with the same name
suffixed by `Length` let's you know the number of elements you can access:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
for (int i = 0; i < monster.inventoryLength(); i++)
monster.inventory(i); // do something here
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Alternatively, much like strings, you can use `monster.inventoryAsByteBuffer()`
to get a `ByteBuffer` referring to the whole vector. Use `ByteBuffer` methods
like `asFloatBuffer` to get specific views if needed.
If you specified a file_indentifier in the schema, you can query if the
buffer is of the desired type before accessing it using:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
if (Monster.MonsterBufferHasIdentifier(bb)) ...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
## Buffer construction in Java
You can also construct these buffers in Java using the static methods found
in the generated code, and the FlatBufferBuilder class:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
FlatBufferBuilder fbb = new FlatBufferBuilder();
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Create strings:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
int str = fbb.createString("MyMonster");
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Create a table with a struct contained therein:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
Monster.startMonster(fbb);
Monster.addPos(fbb, Vec3.createVec3(fbb, 1.0f, 2.0f, 3.0f, 3.0, (byte)4, (short)5, (byte)6));
Monster.addHp(fbb, (short)80);
Monster.addName(fbb, str);
Monster.addInventory(fbb, inv);
Monster.addTest_type(fbb, (byte)1);
Monster.addTest(fbb, mon2);
Monster.addTest4(fbb, test4s);
int mon = Monster.endMonster(fbb);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For some simpler types, you can use a convenient `create` function call that
allows you to construct tables in one function call. This example definition
however contains an inline struct field, so we have to create the table
manually.
This is to create the buffer without using temporary object allocation.
It's important to understand that fields that are structs are inline (like
`Vec3` above), and MUST thus be created between the start and end calls of
a table. Everything else (other tables, strings, vectors) MUST be created
before the start of the table they are referenced in.
Structs do have convenient methods that even have arguments for nested structs.
As you can see, references to other objects (e.g. the string above) are simple
ints, and thus do not have the type-safety of the Offset type in C++. Extra
care must thus be taken that you set the right offset on the right field.
Vectors can be created from the corresponding Java array like so:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
int inv = Monster.createInventoryVector(fbb, new byte[] { 0, 1, 2, 3, 4 });
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This works for arrays of scalars and (int) offsets to strings/tables,
but not structs. If you want to write structs, or what you want to write
does not sit in an array, you can also use the start/end pattern:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
Monster.startInventoryVector(fbb, 5);
for (byte i = 4; i >=0; i--) fbb.addByte(i);
int inv = fbb.endVector();
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
You can use the generated method `startInventoryVector` to conveniently call
`startVector` with the right element size. You pass the number of
elements you want to write. Note how you write the elements backwards since
the buffer is being constructed back to front. You then pass `inv` to the
corresponding `Add` call when you construct the table containing it afterwards.
There are `add` functions for all the scalar types. You use `addOffset` for
any previously constructed objects (such as other tables, strings, vectors).
For structs, you use the appropriate `create` function in-line, as shown
above in the `Monster` example.
To finish the buffer, call:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
Monster.finishMonsterBuffer(fbb, mon);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The buffer is now ready to be transmitted. It is contained in the `ByteBuffer`
which you can obtain from `fbb.dataBuffer()`. Importantly, the valid data does
not start from offset 0 in this buffer, but from `fbb.dataBuffer().position()`
(this is because the data was built backwards in memory).
It ends at `fbb.capacity()`.
## Differences in C-sharp
C# code works almost identically to Java, with only a few minor differences.
You can see an example of C# code in `tests/FlatBuffers.Test/FlatBuffersExampleTests.cs`.
First of all, naming follows standard C# style with `PascalCasing` identifiers,
e.g. `GetRootAsMyRootType`. Also, values (except vectors and unions) are available
as properties instead of parameterless accessor methods as in Java. The
performance-enhancing methods to which you can pass an already created object
are prefixed with `Get`, e.g.:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cs}
// property
var pos = monster.Pos;
// method filling a preconstructed object
var preconstructedPos = new Vec3();
monster.GetPos(preconstructedPos);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
## Text parsing
There currently is no support for parsing text (Schema's and JSON) directly
from Java or C#, though you could use the C++ parser through native call
interfaces available to each language. Please see the
C++ documentation for more on text parsing.
### Mutating FlatBuffers
As you saw above, typically once you have created a FlatBuffer, it is
read-only from that moment on. There are however cases where you have just
received a FlatBuffer, and you'd like to modify something about it before
sending it on to another recipient. With the above functionality, you'd have
to generate an entirely new FlatBuffer, while tracking what you modify in your
own data structures. This is inconvenient.
For this reason FlatBuffers can also be mutated in-place. While this is great
for making small fixes to an existing buffer, you generally want to create
buffers from scratch whenever possible, since it is much more efficient and
the API is much more general purpose.
To get non-const accessors, invoke `flatc` with `--gen-mutable`.
You now can:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.java}
Monster monster = Monster.getRootAsMonster(bb);
monster.mutateHp(10); // Set table field.
monster.pos().mutateZ(4); // Set struct field.
monster.mutateInventory(0, 1); // Set vector element.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We use the somewhat verbose term `mutate` instead of `set` to indicate that
this is a special use case, not to be confused with the default way of
constructing FlatBuffer data.
After the above mutations, you can send on the FlatBuffer to a new recipient
without any further work!
Note that any `mutate` functions on tables return a boolean, which is false
if the field we're trying to set isn't present in the buffer. Fields are not
present if they weren't set, or even if they happen to be equal to the
default value. For example, in the creation code above we set the `mana` field
to `150`, which is the default value, so it was never stored in the buffer.
Trying to call mutateMana() on such data will return false, and the value won't
actually be modified!
One way to solve this is to call `forceDefaults()` on a
`FlatBufferBuilder` to force all fields you set to actually be written. This
of course increases the size of the buffer somewhat, but this may be
acceptable for a mutable buffer.

89
docs/source/PHPUsage.md Normal file
View File

@@ -0,0 +1,89 @@
Use in PHP {#flatbuffers_guide_use_php}
==========
## Before you get started
Before diving into the FlatBuffers usage in PHP, it should be noted that
the [Tutorial](@ref flatbuffers_guide_tutorial) page has a complete guide to
general FlatBuffers usage in all of the supported languages
(including PHP). This page is specifically designed to cover the nuances of
FlatBuffers usage in PHP.
You should also have read the [Building](@ref flatbuffers_guide_building)
documentation to build `flatc` and should be familiar with
[Using the schema compiler](@ref flatbuffers_guide_using_schema_compiler) and
[Writing a schema](@ref flatbuffers_guide_writing_schema).
## FlatBuffers PHP library code location
The code for FlatBuffers PHP library can be found at `flatbuffers/php`. You
can browse the library code on the [FlatBuffers
GitHub page](https://github.com/google/flatbuffers/tree/master/php).
## Testing the FlatBuffers JavaScript library
The code to test the PHP library can be found at `flatbuffers/tests`.
The test code itself is located in [phpTest.php](https://github.com/google/
flatbuffers/blob/master/tests/phpTest.php).
You can run the test with `php phpTest.php` from the command line.
*Note: The PHP test file requires
[PHP](http://php.net/manual/en/install.php) to be installed.*
## Using theFlatBuffers PHP library
*Note: See [Tutorial](@ref flatbuffers_guide_tutorial) for a more in-depth
example of how to use FlatBuffers in PHP.*
FlatBuffers supports both reading and writing FlatBuffers in PHP.
To use FlatBuffers in your own code, first generate PHP classes from your schema
with the `--php` option to `flatc`. Then you can include both FlatBuffers and
the generated code to read or write a FlatBuffer.
For example, here is how you would read a FlatBuffer binary file in PHP:
First, include the library and generated code (using the PSR `autoload`
function). Then you can read a FlatBuffer binary file, which you
pass the contents of to the `GetRootAsMonster` function:
~~~{.php}
// It is recommended that your use PSR autoload when using FlatBuffers in PHP.
// Here is an example:
function __autoload($class_name) {
// The last segment of the class name matches the file name.
$class = substr($class_name, strrpos($class_name, "\\") + 1);
$root_dir = join(DIRECTORY_SEPARATOR, array(dirname(dirname(__FILE__)))); // `flatbuffers` root.
// Contains the `*.php` files for the FlatBuffers library and the `flatc` generated files.
$paths = array(join(DIRECTORY_SEPARATOR, array($root_dir, "php")),
join(DIRECTORY_SEPARATOR, array($root_dir, "tests", "MyGame", "Example")));
foreach ($paths as $path) {
$file = join(DIRECTORY_SEPARATOR, array($path, $class . ".php"));
if (file_exists($file)) {
require($file);
break;
}
}
// Read the contents of the FlatBuffer binary file.
$filename = "monster.dat";
$handle = fopen($filename, "rb");
$contents = $fread($handle, filesize($filename));
fclose($handle);
// Pass the contents to `GetRootAsMonster`.
$monster = \MyGame\Example\Monster::GetRootAsMonster($contents);
~~~
Now you can access values like this:
~~~{.php}
$hp = $monster->GetHp();
$pos = $monster->GetPos();
~~~
## Text Parsing
There currently is no support for parsing text (Schema's and JSON) directly
from PHP.

View File

@@ -1,11 +1,52 @@
# Use in Python
Use in Python {#flatbuffers_guide_use_python}
=============
There's experimental support for reading FlatBuffers in Python. Generate
code for Python with the `-p` option to `flatc`.
## Before you get started
See `py_test.py` for an example. You import the generated code, read a
FlatBuffer binary file into a `bytearray`, which you pass to the
`GetRootAsMonster` function:
Before diving into the FlatBuffers usage in Python, it should be noted that the
[Tutorial](@ref flatbuffers_guide_tutorial) page has a complete guide to general
FlatBuffers usage in all of the supported languages (including Python). This
page is designed to cover the nuances of FlatBuffers usage, specific to
Python.
You should also have read the [Building](@ref flatbuffers_guide_building)
documentation to build `flatc` and should be familiar with
[Using the schema compiler](@ref flatbuffers_guide_using_schema_compiler) and
[Writing a schema](@ref flatbuffers_guide_writing_schema).
## FlatBuffers Python library code location
The code for the FlatBuffers Python library can be found at
`flatbuffers/python/flatbuffers`. You can browse the library code on the
[FlatBuffers GitHub page](https://github.com/google/flatbuffers/tree/master/
python).
## Testing the FlatBuffers Python library
The code to test the Python library can be found at `flatbuffers/tests`.
The test code itself is located in [py_test.py](https://github.com/google/
flatbuffers/blob/master/tests/py_test.py).
To run the tests, use the [PythonTest.sh](https://github.com/google/flatbuffers/
blob/master/tests/PythonTest.sh) shell script.
*Note: This script requires [python](https://www.python.org/) to be
installed.*
## Using the FlatBuffers Python library
*Note: See [Tutorial](@ref flatbuffers_guide_tutorial) for a more in-depth
example of how to use FlatBuffers in Python.*
There is support for both reading and writing FlatBuffers in Python.
To use FlatBuffers in your own code, first generate Python classes from your
schema with the `--python` option to `flatc`. Then you can include both
FlatBuffers and the generated code to read or write a FlatBuffer.
For example, here is how you would read a FlatBuffer binary file in Python:
First, import the library and the generated code. Then read a FlatBuffer binary
file into a `bytearray`, which you pass to the `GetRootAsMonster` function:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.py}
import MyGame.Example as example
@@ -23,93 +64,10 @@ Now you can access values like this:
pos = monster.Pos()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To access vectors you pass an extra index to the
vector field accessor. Then a second method with the same name suffixed
by `Length` let's you know the number of elements you can access:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.py}
for i in xrange(monster.InventoryLength()):
monster.Inventory(i) # do something here
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
You can also construct these buffers in Python using the functions found
in the generated code, and the FlatBufferBuilder class:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.py}
builder = flatbuffers.Builder(0)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Create strings:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.py}
s = builder.CreateString("MyMonster")
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Create a table with a struct contained therein:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.py}
example.MonsterStart(builder)
example.MonsterAddPos(builder, example.CreateVec3(builder, 1.0, 2.0, 3.0, 3.0, 4, 5, 6))
example.MonsterAddHp(builder, 80)
example.MonsterAddName(builder, str)
example.MonsterAddInventory(builder, inv)
example.MonsterAddTest_Type(builder, 1)
example.MonsterAddTest(builder, mon2)
example.MonsterAddTest4(builder, test4s)
mon = example.MonsterEnd(builder)
final_flatbuffer = builder.Output()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unlike C++, Python does not support table creation functions like 'createMonster()'.
This is to create the buffer without
using temporary object allocation (since the `Vec3` is an inline component of
`Monster`, it has to be created right where it is added, whereas the name and
the inventory are not inline, and **must** be created outside of the table
creation sequence).
Structs do have convenient methods that allow you to construct them in one call.
These also have arguments for nested structs, e.g. if a struct has a field `a`
and a nested struct field `b` (which has fields `c` and `d`), then the arguments
will be `a`, `c` and `d`.
Vectors also use this start/end pattern to allow vectors of both scalar types
and structs:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.py}
example.MonsterStartInventoryVector(builder, 5)
i = 4
while i >= 0:
builder.PrependByte(byte(i))
i -= 1
inv = builder.EndVector(5)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The generated method 'StartInventoryVector' is provided as a convenience
function which calls 'StartVector' with the correct element size of the vector
type which in this case is 'ubyte' or 1 byte per vector element.
You pass the number of elements you want to write.
You write the elements backwards since the buffer
is being constructed back to front. Use the correct `Prepend` call for the type,
or `PrependUOffsetT` for offsets. You then pass `inv` to the corresponding
`Add` call when you construct the table containing it afterwards.
There are `Prepend` functions for all the scalar types. You use
`PrependUOffset` for any previously constructed objects (such as other tables,
strings, vectors). For structs, you use the appropriate `create` function
in-line, as shown above in the `Monster` example.
Once you're done constructing a buffer, you call `Finish` with the root object
offset (`mon` in the example above). Your data now resides in Builder.Bytes.
Important to note is that the real data starts at the index indicated by Head(),
for Offset() bytes (this is because the buffer is constructed backwards).
If you wanted to read the buffer right after creating it (using
`GetRootAsMonster` above), the second argument, instead of `0` would thus
also be `Head()`.
## Text Parsing
There currently is no support for parsing text (Schema's and JSON) directly
from Python, though you could use the C++ parser through SWIG or ctypes. Please
see the C++ documentation for more on text parsing.
<br>

View File

@@ -0,0 +1,32 @@
## Prerequisites
To generate the docs for FlatBuffers from the source files, you
will first need to install two programs.
1. You will need to install `doxygen`. See
[Download Doxygen](http://www.stack.nl/~dimitri/doxygen/download.html).
2. You will need to install `doxypypy` to format python comments appropriately.
Install it from [here](https://github.com/Feneric/doxypypy).
*Note: You will need both `doxygen` and `doxypypy` to be in your
[PATH](https://en.wikipedia.org/wiki/PATH_(variable)) environment variable.*
After you have both of those files installed and in your path, you need to
set up the `py_filter` to invoke `doxypypy` from `doxygen`.
Follow the steps
[here](https://github.com/Feneric/doxypypy#invoking-doxypypy-from-doxygen).
## Generating Docs
Run the following commands to generate the docs:
`cd flatbuffers/docs/source`
`doxygen`
The output is placed in `flatbuffers/docs/html`.
*Note: The Go API Reference code must be generated ahead of time. For
instructions on how to regenerated this file, please read the comments
in `GoApi.md`.*

View File

@@ -1,7 +1,8 @@
# Writing a schema
Writing a schema {#flatbuffers_guide_writing_schema}
================
The syntax of the schema language (aka IDL, Interface Definition
Language) should look quite familiar to users of any of the C family of
The syntax of the schema language (aka IDL, [Interface Definition Language][])
should look quite familiar to users of any of the C family of
languages, and also to users of other IDLs. Let's look at an example
first:
@@ -34,14 +35,14 @@ first:
root_type Monster;
(Weapon & Pickup not defined as part of this example).
(`Weapon` & `Pickup` not defined as part of this example).
### Tables
Tables are the main way of defining objects in FlatBuffers, and consist
of a name (here `Monster`) and a list of fields. Each field has a name,
a type, and optionally a default value (if omitted, it defaults to 0 /
NULL).
a type, and optionally a default value (if omitted, it defaults to `0` /
`NULL`).
Each field is optional: It does not have to appear in the wire
representation, and you can choose to omit fields for each individual
@@ -68,7 +69,8 @@ and backwards compatibility. Note that:
- You may change field names and table names, if you're ok with your
code breaking until you've renamed them there too.
See "Schema evolution examples" below for more on this
topic.
### Structs
@@ -84,13 +86,13 @@ parent object, and use no virtual table).
Built-in scalar types are:
- 8 bit: `byte ubyte bool`
- 8 bit: `byte`, `ubyte`, `bool`
- 16 bit: `short ushort`
- 16 bit: `short`, `ushort`
- 32 bit: `int uint float`
- 32 bit: `int`, `uint`, `float`
- 64 bit: `long ulong double`
- 64 bit: `long`, `ulong`, `double`
Built-in non-scalar types:
@@ -110,18 +112,20 @@ high bit yet.
### (Default) Values
Values are a sequence of digits, optionally followed by a `.` and more digits
for float constants, and optionally prefixed by a `-`. Floats may end with an
`e` or `E`, followed by a `+` or `-` and more digits (scientific notation).
Values are a sequence of digits. Values may be optionally followed by a decimal
point (`.`) and more digits, for float constants, or optionally prefixed by
a `-`. Floats may also be in scientific notation; optionally ending with an `e`
or `E`, followed by a `+` or `-` and more digits.
Only scalar values can have defaults, non-scalar (string/vector/table) fields
default to NULL when not present.
default to `NULL` when not present.
You generally do not want to change default values after they're initially
defined. Fields that have the default value are not actually stored in the
serialized data but are generated in code, so when you change the default, you'd
serialized data (see also Gotchas below) but are generated in code,
so when you change the default, you'd
now get a different value than from code generated from an older version of
the schema. There are situations however where this may be
the schema. There are situations, however, where this may be
desirable, especially if you can ensure a simultaneous rebuild of
all code.
@@ -133,11 +137,15 @@ is `0`. As you can see in the enum declaration, you specify the underlying
integral type of the enum with `:` (in this case `byte`), which then determines
the type of any fields declared with this enum type.
Typically, enum values should only ever be added, never removed (there is no
deprecation for enums). This requires code to handle forwards compatibility
itself, by handling unknown enum values.
### Unions
Unions share a lot of properties with enums, but instead of new names
for constants, you use names of tables. You can then declare
a union field which can hold a reference to any of those types, and
a union field, which can hold a reference to any of those types, and
additionally a hidden field with the suffix `_type` is generated that
holds the corresponding enum value, allowing you to know which type to
cast to at runtime.
@@ -173,7 +181,7 @@ included files (those you still generate separately).
### Root type
This declares what you consider to be the root table (or struct) of the
serialized data. This is particular important for parsing JSON data,
serialized data. This is particularly important for parsing JSON data,
which doesn't include object type information.
### File identification and extension
@@ -217,6 +225,21 @@ This declaration in the schema will change that to whatever you want:
file_extension "ext";
### RPC interface declarations
You can declare RPC calls in a schema, that define a set of functions
that take a FlatBuffer as an argument (the request) and return a FlatBuffer
as the response (both of which must be table types):
rpc_service MonsterStorage {
Store(Monster):StoreResponse;
Retrieve(MonsterId):Monster;
}
What code this produces and how it is used depends on language and RPC system
used, there is preliminary support for GRPC through the `--grpc` code generator,
see `grpc/tests` for an example.
### Comments & documentation
May be written as in most C-based languages. Additionally, a triple
@@ -229,7 +252,7 @@ in the corresponding C++ code. Multiple such lines per item are allowed.
Attributes may be attached to a declaration, behind a field, or after
the name of a table/struct/enum/union. These may either have a value or
not. Some attributes like `deprecated` are understood by the compiler,
not. Some attributes like `deprecated` are understood by the compiler;
user defined ones need to be declared with the attribute declaration
(like `priority` in the example above), and are
available to query if you parse the schema at runtime.
@@ -308,6 +331,13 @@ JSON:
you do when serializing from code. E.g. for a field `foo`, you must
add a field `foo_type: FooOne` right before the `foo` field, where
`FooOne` would be the table out of the union you want to use.
- A field that has the value `null` (e.g. `field: null`) is intended to
have the default value for that field (thus has the same effect as if
that field wasn't specified at all).
- It has some built in conversion functions, so you can write for example
`rad(180)` where ever you'd normally write `3.14159`.
Currently supports the following functions: `rad`, `deg`, `cos`, `sin`,
`tan`, `acos`, `asin`, `atan`.
When parsing JSON, it recognizes the following escape codes in strings:
@@ -351,3 +381,92 @@ the world. If this is not practical for you, use explicit field ids, which
should always generate a merge conflict if two people try to allocate the same
id.
### Schema evolution examples
Some examples to clarify what happens as you change a schema:
If we have the following original schema:
table { a:int; b:int; }
And we extend it:
table { a:int; b:int; c:int; }
This is ok. Code compiled with the old schema reading data generated with the
new one will simply ignore the presence of the new field. Code compiled with the
new schema reading old data will get the default value for `c` (which is 0
in this case, since it is not specified).
table { a:int (deprecated); b:int; }
This is also ok. Code compiled with the old schema reading newer data will now
always get the default value for `a` since it is not present. Code compiled
with the new schema now cannot read nor write `a` anymore (any existing code
that tries to do so will result in compile errors), but can still read
old data (they will ignore the field).
table { c:int a:int; b:int; }
This is NOT ok, as this makes the schemas incompatible. Old code reading newer
data will interpret `c` as if it was `a`, and new code reading old data
accessing `a` will instead receive `b`.
table { c:int (id: 2); a:int (id: 0); b:int (id: 1); }
This is ok. If your intent was to order/group fields in a way that makes sense
semantically, you can do so using explicit id assignment. Now we are compatible
with the original schema, and the fields can be ordered in any way, as long as
we keep the sequence of ids.
table { b:int; }
NOT ok. We can only remove a field by deprecation, regardless of wether we use
explicit ids or not.
table { a:uint; b:uint; }
This is MAYBE ok, and only in the case where the type change is the same size,
like here. If old data never contained any negative numbers, this will be
safe to do.
table { a:int = 1; b:int = 2; }
Generally NOT ok. Any older data written that had 0 values were not written to
the buffer, and rely on the default value to be recreated. These will now have
those values appear to `1` and `2` instead. There may be cases in which this
is ok, but care must be taken.
table { aa:int; bb:int; }
Occasionally ok. You've renamed fields, which will break all code (and JSON
files!) that use this schema, but as long as the change is obvious, this is not
incompatible with the actual binary buffers, since those only ever address
fields by id/offset.
<br>
### Testing whether a field is present in a table
Most serialization formats (e.g. JSON or Protocol Buffers) make it very
explicit in the format whether a field is present in an object or not,
allowing you to use this as "extra" information.
In FlatBuffers, this also holds for everything except scalar values.
FlatBuffers by default will not write fields that are equal to the default
value (for scalars), sometimes resulting in a significant space savings.
However, this also means testing whether a field is "present" is somewhat
meaningless, since it does not tell you if the field was actually written by
calling `add_field` style calls, unless you're only interested in this
information for non-default values.
Some `FlatBufferBuilder` implementations have an option called `force_defaults`
that circumvents this behavior, and writes fields even if they are equal to
the default. You can then use `IsFieldPresent` to query this.
Another option that works in all languages is to wrap a scalar field in a
struct. This way it will return null if it is not present. The cool thing
is that structs don't take up any more space than the scalar they represent.
[Interface Definition Language]: https://en.wikipedia.org/wiki/Interface_description_language

View File

@@ -1,4 +1,5 @@
# Platform / Language / Feature support
Platform / Language / Feature support {#flatbuffers_support}
=====================================
FlatBuffers is actively being worked on, which means that certain platform /
language / feature combinations may not be available yet.
@@ -18,18 +19,18 @@ In general:
NOTE: this table is a start, it needs to be extended.
Feature | C++ | Java | C# | Go | Python | JS | C | PHP | Ruby
------------------------------ | ------ | ------ | ------ | ------ | ------ | --------- | ---- | --- | ----
Codegen for all basic features | Yes | Yes | Yes | Yes | Yes | Yes | WiP | WiP | WiP
JSON parsing | Yes | No | No | No | No | No | No | No | No
------------------------------ | ------ | ------ | ------ | ------ | ------ | --------- | ------ | --- | ----
Codegen for all basic features | Yes | Yes | Yes | Yes | Yes | Yes | Yes | WiP | WiP
JSON parsing | Yes | No | No | No | No | No | Yes | No | No
Simple mutation | Yes | WIP | WIP | No | No | No | No | No | No
Reflection | Yes | No | No | No | No | No | No | No | No
Buffer verifier | Yes | No | No | No | No | No | No | No | No
Testing: basic | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ?
Testing: fuzz | Yes | No | No | Yes | Yes | No | ? | ? | ?
Reflection | Yes | No | No | No | No | No | Basic | No | No
Buffer verifier | Yes | No | No | No | No | No | Yes | No | No
Testing: basic | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | ?
Testing: fuzz | Yes | No | No | Yes | Yes | No | No | ? | ?
Performance: | Superb | Great | Great | Great | Ok | ? | Superb | ? | ?
Platform: Windows | VS2010 | Yes | Yes | ? | ? | ? | ? | ? | ?
Platform: Linux | GCC282 | Yes | ? | Yes | Yes | ? | ? | ? | ?
Platform: OS X | Xcode4 | ? | ? | ? | Yes | ? | ? | ? | ?
Platform: Windows | VS2010 | Yes | Yes | ? | ? | ? | VS2010 | ? | ?
Platform: Linux | GCC282 | Yes | ? | Yes | Yes | ? | Yes | ? | ?
Platform: OS X | Xcode4 | ? | ? | ? | Yes | ? | Yes | ? | ?
Platform: Android | NDK10d | Yes | ? | ? | ? | ? | ? | ? | ?
Platform: iOS | ? | ? | ? | ? | ? | ? | ? | ? | ?
Engine: Unity | ? | ? | Yes | ? | ? | ? | ? | ? | ?
@@ -39,3 +40,5 @@ Primary authors (github) | gwvo | gwvo | ev*/js*| rw | rw | ev
* js = jonsimantov
* mik = mikkelfj
* ch = chobie
<br>

1968
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@@ -1,4 +1,5 @@
# FlatBuffers white paper
FlatBuffers white paper {#flatbuffers_white_paper}
=======================
This document tries to shed some light on to the "why" of FlatBuffers, a
new serialization library.
@@ -124,4 +125,4 @@ offered by .proto files in the following ways:
- A parser that can deal with both schemas and data definitions (JSON
compatible) uniformly.
<br>

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@@ -88,7 +88,7 @@ OUTPUT_LANGUAGE = English
# documentation (similar to Javadoc). Set to NO to disable this.
# The default value is: YES.
BRIEF_MEMBER_DESC = NO
BRIEF_MEMBER_DESC = YES
# If the REPEAT_BRIEF tag is set to YES doxygen will prepend the brief
# description of a member or function before the detailed description
@@ -97,7 +97,7 @@ BRIEF_MEMBER_DESC = NO
# brief descriptions will be completely suppressed.
# The default value is: YES.
REPEAT_BRIEF = NO
REPEAT_BRIEF = YES
# This tag implements a quasi-intelligent brief description abbreviator that is
# used to form the text in various listings. Each string in this list, if found
@@ -177,7 +177,7 @@ SHORT_NAMES = NO
# description.)
# The default value is: NO.
JAVADOC_AUTOBRIEF = NO
JAVADOC_AUTOBRIEF = YES
# If the QT_AUTOBRIEF tag is set to YES then doxygen will interpret the first
# line (until the first dot) of a Qt-style comment as the brief description. If
@@ -203,7 +203,7 @@ MULTILINE_CPP_IS_BRIEF = NO
# documentation from any documented member that it re-implements.
# The default value is: YES.
INHERIT_DOCS = NO
INHERIT_DOCS = YES
# If the SEPARATE_MEMBER_PAGES tag is set to YES, then doxygen will produce a
# new page for each member. If set to NO, the documentation of a member will be
@@ -216,7 +216,7 @@ SEPARATE_MEMBER_PAGES = NO
# uses this value to replace tabs by spaces in code fragments.
# Minimum value: 1, maximum value: 16, default value: 4.
TAB_SIZE = 1
TAB_SIZE = 2
# This tag can be used to specify a number of aliases that act as commands in
# the documentation. An alias has the form:
@@ -296,7 +296,9 @@ MARKDOWN_SUPPORT = YES
# or globally by setting AUTOLINK_SUPPORT to NO.
# The default value is: YES.
AUTOLINK_SUPPORT = YES
AUTOLINK_SUPPORT = NO # Due to the multiple languages included in the API
# reference for FlatBuffers, the Auto-links were
# wrong more often than not.
# If you use STL classes (i.e. std::string, std::vector, etc.) but do not want
# to include (a tag file for) the STL sources as input, then you should set this
@@ -347,7 +349,7 @@ DISTRIBUTE_GROUP_DOC = NO
# \nosubgrouping command.
# The default value is: YES.
SUBGROUPING = NO
SUBGROUPING = YES
# When the INLINE_GROUPED_CLASSES tag is set to YES, classes, structs and unions
# are shown inside the group in which they are included (e.g. using \ingroup)
@@ -424,7 +426,7 @@ EXTRACT_PACKAGE = NO
# included in the documentation.
# The default value is: NO.
EXTRACT_STATIC = NO
EXTRACT_STATIC = YES
# If the EXTRACT_LOCAL_CLASSES tag is set to YES classes (and structs) defined
# locally in source files will be included in the documentation. If set to NO
@@ -508,7 +510,7 @@ HIDE_SCOPE_NAMES = NO
# the files that are included by a file in the documentation of that file.
# The default value is: YES.
SHOW_INCLUDE_FILES = NO
SHOW_INCLUDE_FILES = YES
# If the FORCE_LOCAL_INCLUDES tag is set to YES then doxygen will list include
# files with double quotes in the documentation rather than with sharp brackets.
@@ -520,21 +522,21 @@ FORCE_LOCAL_INCLUDES = NO
# documentation for inline members.
# The default value is: YES.
INLINE_INFO = NO
INLINE_INFO = YES
# If the SORT_MEMBER_DOCS tag is set to YES then doxygen will sort the
# (detailed) documentation of file and class members alphabetically by member
# name. If set to NO the members will appear in declaration order.
# The default value is: YES.
SORT_MEMBER_DOCS = NO
SORT_MEMBER_DOCS = YES
# If the SORT_BRIEF_DOCS tag is set to YES then doxygen will sort the brief
# descriptions of file, namespace and class members alphabetically by member
# name. If set to NO the members will appear in declaration order.
# The default value is: NO.
SORT_BRIEF_DOCS = NO
SORT_BRIEF_DOCS = YES
# If the SORT_MEMBERS_CTORS_1ST tag is set to YES then doxygen will sort the
# (brief and detailed) documentation of class members so that constructors and
@@ -600,7 +602,7 @@ GENERATE_BUGLIST = NO
# the documentation.
# The default value is: YES.
GENERATE_DEPRECATEDLIST= NO
GENERATE_DEPRECATEDLIST= YES
# The ENABLED_SECTIONS tag can be used to enable conditional documentation
# sections, marked by \if <section_label> ... \endif and \cond <section_label>
@@ -624,21 +626,21 @@ MAX_INITIALIZER_LINES = 30
# will mention the files that were used to generate the documentation.
# The default value is: YES.
SHOW_USED_FILES = NO
SHOW_USED_FILES = YES
# Set the SHOW_FILES tag to NO to disable the generation of the Files page. This
# will remove the Files entry from the Quick Index and from the Folder Tree View
# (if specified).
# The default value is: YES.
SHOW_FILES = NO
SHOW_FILES = YES
# Set the SHOW_NAMESPACES tag to NO to disable the generation of the Namespaces
# page. This will remove the Namespaces entry from the Quick Index and from the
# Folder Tree View (if specified).
# The default value is: YES.
SHOW_NAMESPACES = NO
SHOW_NAMESPACES = YES
# The FILE_VERSION_FILTER tag can be used to specify a program or script that
# doxygen should invoke to get the current version for each file (typically from
@@ -661,7 +663,7 @@ FILE_VERSION_FILTER =
# DoxygenLayout.xml, doxygen will parse it automatically even if the LAYOUT_FILE
# tag is left empty.
LAYOUT_FILE =
LAYOUT_FILE = doxygen_layout.xml
# The CITE_BIB_FILES tag can be used to specify one or more bib files containing
# the reference definitions. This must be a list of .bib files. The .bib
@@ -692,14 +694,14 @@ QUIET = NO
# Tip: Turn warnings on while writing the documentation.
# The default value is: YES.
WARNINGS = NO
WARNINGS = YES
# If the WARN_IF_UNDOCUMENTED tag is set to YES, then doxygen will generate
# warnings for undocumented members. If EXTRACT_ALL is set to YES then this flag
# will automatically be disabled.
# The default value is: YES.
WARN_IF_UNDOCUMENTED = NO
WARN_IF_UNDOCUMENTED = YES
# If the WARN_IF_DOC_ERROR tag is set to YES, doxygen will generate warnings for
# potential errors in the documentation, such as not documenting some parameters
@@ -748,14 +750,28 @@ INPUT = "FlatBuffers.md" \
"Compiler.md" \
"Schemas.md" \
"CppUsage.md" \
"CUsage.md" \
"GoUsage.md" \
"JavaUsage.md" \
"JavaCsharpUsage.md" \
"JavaScriptUsage.md" \
"PHPUsage.md" \
"PythonUsage.md" \
"Support.md" \
"Benchmarks.md" \
"WhitePaper.md" \
"Internals.md" \
"Grammar.md"
"Grammar.md" \
"CONTRIBUTING.md" \
"Tutorial.md" \
"GoApi.md" \
"groups" \
"../../java/com/google/flatbuffers" \
"../../python/flatbuffers/builder.py" \
"../../js/flatbuffers.js" \
"../../php/FlatbufferBuilder.php" \
"../../net/FlatBuffers/FlatBufferBuilder.cs" \
"../../include/flatbuffers/flatbuffers.h" \
"../../go/builder.go"
# This tag can be used to specify the character encoding of the source files
# that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses
@@ -816,13 +832,14 @@ FILE_PATTERNS = *.c \
*.ucf \
*.qsf \
*.as \
*.js
*.js \
*.go
# The RECURSIVE tag can be used to specify whether or not subdirectories should
# be searched for input files as well.
# The default value is: NO.
RECURSIVE = NO
RECURSIVE = YES
# The EXCLUDE tag can be used to specify files and/or directories that should be
# excluded from the INPUT source files. This way you can easily exclude a
@@ -847,7 +864,8 @@ EXCLUDE_SYMLINKS = NO
# Note that the wildcards are matched against the file with absolute path, so to
# exclude all test directories for example use the pattern */test/*
EXCLUDE_PATTERNS =
EXCLUDE_PATTERNS = *_test.py |
__init__.py
# The EXCLUDE_SYMBOLS tag can be used to specify one or more symbol names
# (namespaces, classes, functions, etc.) that should be excluded from the
@@ -864,7 +882,7 @@ EXCLUDE_SYMBOLS =
# that contain example code fragments that are included (see the \include
# command).
EXAMPLE_PATH =
EXAMPLE_PATH = "GoApi_generated.txt"
# If the value of the EXAMPLE_PATH tag contains directories, you can use the
# EXAMPLE_PATTERNS tag to specify one or more wildcard pattern (like *.cpp and
@@ -910,7 +928,7 @@ INPUT_FILTER =
# filters are used. If the FILTER_PATTERNS tag is empty or if none of the
# patterns match the file name, INPUT_FILTER is applied.
FILTER_PATTERNS =
FILTER_PATTERNS = *.py=py_filter
# If the FILTER_SOURCE_FILES tag is set to YES, the input filter (if set using
# INPUT_FILTER ) will also be used to filter the input files that are used for
@@ -978,7 +996,7 @@ REFERENCES_RELATION = NO
# link to the documentation.
# The default value is: YES.
REFERENCES_LINK_SOURCE = NO
REFERENCES_LINK_SOURCE = YES
# If SOURCE_TOOLTIPS is enabled (the default) then hovering a hyperlink in the
# source code will show a tooltip with additional information such as prototype,
@@ -1018,26 +1036,7 @@ USE_HTAGS = NO
# See also: Section \class.
# The default value is: YES.
VERBATIM_HEADERS = NO
# If the CLANG_ASSISTED_PARSING tag is set to YES, then doxygen will use the
# clang parser (see: http://clang.llvm.org/) for more acurate parsing at the
# cost of reduced performance. This can be particularly helpful with template
# rich C++ code for which doxygen's built-in parser lacks the necessary type
# information.
# Note: The availability of this option depends on whether or not doxygen was
# compiled with the --with-libclang option.
# The default value is: NO.
CLANG_ASSISTED_PARSING = NO
# If clang assisted parsing is enabled you can provide the compiler with command
# line options that you would normally use when invoking the compiler. Note that
# the include paths will already be set by doxygen for the files and directories
# specified with INPUT and INCLUDE_PATH.
# This tag requires that the tag CLANG_ASSISTED_PARSING is set to YES.
CLANG_OPTIONS =
VERBATIM_HEADERS = YES
#---------------------------------------------------------------------------
# Configuration options related to the alphabetical class index
@@ -1048,7 +1047,7 @@ CLANG_OPTIONS =
# classes, structs, unions or interfaces.
# The default value is: YES.
ALPHABETICAL_INDEX = NO
ALPHABETICAL_INDEX = YES
# The COLS_IN_ALPHA_INDEX tag can be used to specify the number of columns in
# which the alphabetical index list will be split.
@@ -1129,7 +1128,7 @@ HTML_FOOTER = ../footer.html
# obsolete.
# This tag requires that the tag GENERATE_HTML is set to YES.
HTML_STYLESHEET = style.css
HTML_STYLESHEET =
# The HTML_EXTRA_STYLESHEET tag can be used to specify an additional user-
# defined cascading style sheet that is included after the standard style sheets
@@ -1140,7 +1139,7 @@ HTML_STYLESHEET = style.css
# see the documentation.
# This tag requires that the tag GENERATE_HTML is set to YES.
HTML_EXTRA_STYLESHEET =
HTML_EXTRA_STYLESHEET = style.css
# The HTML_EXTRA_FILES tag can be used to specify one or more extra images or
# other source files which should be copied to the HTML output directory. Note
@@ -1150,7 +1149,9 @@ HTML_EXTRA_STYLESHEET =
# files will be copied as-is; there are no commands or markers available.
# This tag requires that the tag GENERATE_HTML is set to YES.
HTML_EXTRA_FILES = ../images/fpl_logo_small.png ../images/ftv2mnode.png ../images/ftv2pnode.png
HTML_EXTRA_FILES = "../images/fpl_logo_small.png" \
"../images/ftv2mnode.png" \
"../images/ftv2pnode.png"
# The HTML_COLORSTYLE_HUE tag controls the color of the HTML output. Doxygen
# will adjust the colors in the stylesheet and background images according to
@@ -1407,7 +1408,7 @@ ECLIPSE_DOC_ID = org.doxygen.Project
# The default value is: NO.
# This tag requires that the tag GENERATE_HTML is set to YES.
DISABLE_INDEX = YES
DISABLE_INDEX = NO
# The GENERATE_TREEVIEW tag is used to specify whether a tree-like index
# structure should be generated to display hierarchical information. If the tag
@@ -1538,7 +1539,7 @@ MATHJAX_CODEFILE =
# The default value is: YES.
# This tag requires that the tag GENERATE_HTML is set to YES.
SEARCHENGINE = NO
SEARCHENGINE = YES
# When the SERVER_BASED_SEARCH tag is enabled the search engine will be
# implemented using a web server instead of a web client using Javascript. There
@@ -2071,7 +2072,7 @@ EXTERNAL_GROUPS = NO
# be listed.
# The default value is: YES.
EXTERNAL_PAGES = NO
EXTERNAL_PAGES = YES
# The PERL_PATH should be the absolute path and name of the perl script
# interpreter (i.e. the result of 'which perl').

View File

@@ -0,0 +1,232 @@
<!-- Copyright 2015 Google Inc. All rights reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<doxygenlayout version="1.0">
<navindex>
<tab type="mainpage" visible="no" title=""/>
<tab type="usergroup" url="" title="Programmer's Guide">
<tab type="user" url="@ref flatbuffers_guide_building"
title="Building"/>
<tab type="user" url="@ref flatbuffers_guide_tutorial" title="Tutorial"/>
<tab type="user" url="@ref flatbuffers_guide_using_schema_compiler"
title="Using the schema compiler"/>
<tab type="user" url="@ref flatbuffers_guide_writing_schema"
title="Writing a schema"/>
<tab type="user" url="@ref flatbuffers_guide_use_cpp"
title="Use in C++"/>
<tab type="user" url="@ref flatbuffers_guide_use_c"
title="Use in C"/>
<tab type="user" url="@ref flatbuffers_guide_use_go"
title="Use in Go"/>
<tab type="user" url="@ref flatbuffers_guide_use_java_c-sharp"
title="Use in Java/C#"/>
<tab type="user" url="@ref flatbuffers_guide_use_javascript"
title="Use in JavaScript"/>
<tab type="user" url="@ref flatbuffers_guide_use_php"
title="Use in PHP"/>
<tab type="user" url="@ref flatbuffers_guide_use_python"
title="Use in Python"/>
</tab>
<tab type="user" url="@ref flatbuffers_support"
title="Platform / Language / Feature support"/>
<tab type="user" url="@ref flatbuffers_benchmarks"
title="Benchmarks"/>
<tab type="user" url="@ref flatbuffers_white_paper"
title="FlatBuffers white paper"/>
<tab type="user" url="@ref flatbuffers_internals"
title="FlatBuffers internals"/>
<tab type="user" url="@ref flatbuffers_grammar"
title="Grammar of the schema language"/>
<tab type="usergroup" url="" title="API Reference">
<tab type="modules" visible="yes" title="APIs" intro=""/>
<tab type="classes" visible="yes" title="">
<tab type="classlist" visible="yes" title="" intro=""/>
<tab type="classindex" visible="$ALPHABETICAL_INDEX" title=""/>
<tab type="hierarchy" visible="yes" title="" intro=""/>
<tab type="classmembers" visible="yes" title="" intro=""/>
</tab>
</tab>
<tab type="user" url="@ref contributing" title="Contributing"/>
</navindex>
<!-- Layout definition for a class page -->
<class>
<briefdescription visible="yes"/>
<includes visible="$SHOW_INCLUDE_FILES"/>
<inheritancegraph visible="$CLASS_GRAPH"/>
<collaborationgraph visible="$COLLABORATION_GRAPH"/>
<detaileddescription title=""/>
<memberdecl>
<nestedclasses visible="yes" title=""/>
<publictypes title=""/>
<services title=""/>
<interfaces title=""/>
<publicslots title=""/>
<signals title=""/>
<publicmethods title=""/>
<publicstaticmethods title=""/>
<publicattributes title=""/>
<publicstaticattributes title=""/>
<protectedtypes title=""/>
<protectedslots title=""/>
<protectedmethods title=""/>
<protectedstaticmethods title=""/>
<protectedattributes title=""/>
<protectedstaticattributes title=""/>
<packagetypes title=""/>
<packagemethods title=""/>
<packagestaticmethods title=""/>
<packageattributes title=""/>
<packagestaticattributes title=""/>
<properties title=""/>
<events title=""/>
<privatetypes title=""/>
<privateslots title=""/>
<privatemethods title=""/>
<privatestaticmethods title=""/>
<privateattributes title=""/>
<privatestaticattributes title=""/>
<friends title=""/>
<related title="" subtitle=""/>
<membergroups visible="yes"/>
</memberdecl>
<memberdef>
<inlineclasses title=""/>
<typedefs title=""/>
<enums title=""/>
<services title=""/>
<interfaces title=""/>
<constructors title=""/>
<functions title=""/>
<related title=""/>
<variables title=""/>
<properties title=""/>
<events title=""/>
</memberdef>
<allmemberslink visible="yes"/>
<usedfiles visible="$SHOW_USED_FILES"/>
<authorsection visible="yes"/>
</class>
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<namespace>
<briefdescription visible="yes"/>
<memberdecl>
<nestednamespaces visible="yes" title=""/>
<constantgroups visible="yes" title=""/>
<classes visible="yes" title=""/>
<typedefs title=""/>
<enums title=""/>
<functions title=""/>
<variables title=""/>
<membergroups visible="yes"/>
</memberdecl>
<detaileddescription title=""/>
<memberdef>
<inlineclasses title=""/>
<typedefs title=""/>
<enums title=""/>
<functions title=""/>
<variables title=""/>
</memberdef>
<authorsection visible="yes"/>
</namespace>
<!-- Layout definition for a file page -->
<file>
<briefdescription visible="yes"/>
<includes visible="$SHOW_INCLUDE_FILES"/>
<includegraph visible="$INCLUDE_GRAPH"/>
<includedbygraph visible="$INCLUDED_BY_GRAPH"/>
<sourcelink visible="yes"/>
<detaileddescription title=""/>
<memberdecl>
<classes visible="yes" title=""/>
<namespaces visible="yes" title=""/>
<constantgroups visible="yes" title=""/>
<defines title=""/>
<typedefs title=""/>
<enums title=""/>
<functions title=""/>
<variables title=""/>
<membergroups visible="yes"/>
</memberdecl>
<memberdef>
<inlineclasses title=""/>
<defines title=""/>
<typedefs title=""/>
<enums title=""/>
<functions title=""/>
<variables title=""/>
</memberdef>
<authorsection/>
</file>
<!-- Layout definition for a group page -->
<group>
<briefdescription visible="yes"/>
<groupgraph visible="$GROUP_GRAPHS"/>
<detaileddescription title=""/>
<memberdecl>
<nestedgroups visible="yes" title=""/>
<dirs visible="yes" title=""/>
<files visible="yes" title=""/>
<namespaces visible="yes" title=""/>
<classes visible="yes" title=""/>
<defines title=""/>
<typedefs title=""/>
<enums title=""/>
<enumvalues title=""/>
<functions title=""/>
<variables title=""/>
<signals title=""/>
<publicslots title=""/>
<protectedslots title=""/>
<privateslots title=""/>
<events title=""/>
<properties title=""/>
<friends title=""/>
<membergroups visible="yes"/>
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<memberdef>
<pagedocs/>
<inlineclasses title=""/>
<defines title=""/>
<typedefs title=""/>
<enums title=""/>
<enumvalues title=""/>
<functions title=""/>
<variables title=""/>
<signals title=""/>
<publicslots title=""/>
<protectedslots title=""/>
<privateslots title=""/>
<events title=""/>
<properties title=""/>
<friends title=""/>
</memberdef>
<authorsection visible="yes"/>
</group>
<!-- Layout definition for a directory page -->
<directory>
<briefdescription visible="yes"/>
<directorygraph visible="yes"/>
<memberdecl>
<dirs visible="yes"/>
<files visible="yes"/>
</memberdecl>
<detaileddescription title=""/>
</directory>
</doxygenlayout>

20
docs/source/groups Normal file
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@@ -0,0 +1,20 @@
/// @defgroup flatbuffers_cpp_api C++ API
/// @brief FlatBuffers API for C++
/// @defgroup flatbuffers_csharp_api C# API
/// @brief FlatBuffers API for C#
/// @defgroup flatbuffers_go_api Go API
/// @brief FlatBuffers API for Go
/// @defgroup flatbuffers_java_api Java API
/// @brief FlatBuffers API for Java
/// @defgroup flatbuffers_javascript_api JavaScript API
/// @brief FlatBuffers API for JavaScript
/// @defgroup flatbuffers_php_api PHP API
/// @brief FlatBuffers API for PHP
/// @defgroup flatbuffers_python_api Python API
/// @brief FlatBuffers API for Python

View File

@@ -366,7 +366,7 @@ div.line {
code, pre {
color: #455a64;
background: #f7f7f7;
font: 400 100%/1 Roboto Mono,monospace;
font: 400 100% Roboto Mono,monospace;
padding: 1px 4px;
}

View File

@@ -26,7 +26,8 @@ func (t *Table) Indirect(off UOffsetT) UOffsetT {
// String gets a string from data stored inside the flatbuffer.
func (t *Table) String(off UOffsetT) string {
return string(t.ByteVector(off))
b := t.ByteVector(off)
return byteSliceToString(b)
}
// ByteVector gets a byte slice from data stored inside the flatbuffer.

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