mirror of
https://github.com/google/flatbuffers.git
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108 lines
4.1 KiB
Java
108 lines
4.1 KiB
Java
/*
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* Copyright 2014 Google Inc. All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.flatbuffers;
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import static com.google.flatbuffers.Constants.*;
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import java.nio.ByteBuffer;
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import java.nio.ByteOrder;
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// All tables in the generated code derive from this class, and add their own accessors.
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public class Table {
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protected int bb_pos;
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protected ByteBuffer bb;
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public ByteBuffer getByteBuffer() { return bb; }
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// Look up a field in the vtable, return an offset into the object, or 0 if the field is not
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// present.
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protected int __offset(int vtable_offset) {
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int vtable = bb_pos - bb.getInt(bb_pos);
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return vtable_offset < bb.getShort(vtable) ? bb.getShort(vtable + vtable_offset) : 0;
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}
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// Retrieve the relative offset stored at "offset"
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protected int __indirect(int offset) {
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return offset + bb.getInt(offset);
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}
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// Create a java String from UTF-8 data stored inside the flatbuffer.
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// This allocates a new string and converts to wide chars upon each access,
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// which is not very efficient. Instead, each FlatBuffer string also comes with an
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// accessor based on __vector_as_bytebuffer below, which is much more efficient,
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// assuming your Java program can handle UTF-8 data directly.
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protected String __string(int offset) {
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offset += bb.getInt(offset);
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if (bb.hasArray()) {
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return new String(bb.array(), bb.arrayOffset() + offset + SIZEOF_INT, bb.getInt(offset), FlatBufferBuilder.utf8charset);
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} else {
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// We can't access .array(), since the ByteBuffer is read-only,
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// off-heap or a memory map
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ByteBuffer bb = this.bb.duplicate().order(ByteOrder.LITTLE_ENDIAN);
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// We're forced to make an extra copy:
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byte[] copy = new byte[bb.getInt(offset)];
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bb.position(offset + SIZEOF_INT);
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bb.get(copy);
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return new String(copy, 0, copy.length, FlatBufferBuilder.utf8charset);
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}
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}
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// Get the length of a vector whose offset is stored at "offset" in this object.
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protected int __vector_len(int offset) {
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offset += bb_pos;
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offset += bb.getInt(offset);
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return bb.getInt(offset);
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}
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// Get the start of data of a vector whose offset is stored at "offset" in this object.
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protected int __vector(int offset) {
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offset += bb_pos;
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return offset + bb.getInt(offset) + SIZEOF_INT; // data starts after the length
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}
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// Get a whole vector as a ByteBuffer. This is efficient, since it only allocates a new
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// bytebuffer object, but does not actually copy the data, it still refers to the same
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// bytes as the original ByteBuffer.
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// Also useful with nested FlatBuffers etc.
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protected ByteBuffer __vector_as_bytebuffer(int vector_offset, int elem_size) {
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int o = __offset(vector_offset);
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if (o == 0) return null;
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ByteBuffer bb = this.bb.duplicate().order(ByteOrder.LITTLE_ENDIAN);
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int vectorstart = __vector(o);
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bb.position(vectorstart);
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bb.limit(vectorstart + __vector_len(o) * elem_size);
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return bb;
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}
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// Initialize any Table-derived type to point to the union at the given offset.
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protected Table __union(Table t, int offset) {
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offset += bb_pos;
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t.bb_pos = offset + bb.getInt(offset);
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t.bb = bb;
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return t;
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}
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protected static boolean __has_identifier(ByteBuffer bb, String ident) {
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if (ident.length() != FILE_IDENTIFIER_LENGTH)
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throw new AssertionError("FlatBuffers: file identifier must be length " +
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FILE_IDENTIFIER_LENGTH);
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for (int i = 0; i < FILE_IDENTIFIER_LENGTH; i++) {
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if (ident.charAt(i) != (char)bb.get(bb.position() + SIZEOF_INT + i)) return false;
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}
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return true;
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}
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}
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