FlatBuffers 64 for C++ (#7935)

* First working hack of adding 64-bit. Don't judge :)

* Made vector_downward work on 64 bit types

* vector_downward uses size_t, added offset64 to reflection

* cleaned up adding offset64 in parser

* Add C++ testing skeleton for 64-bit

* working test for CreateVector64

* working >2 GiB buffers

* support for large strings

* simplified CreateString<> to just provide the offset type

* generalize CreateVector template

* update test_64.afb due to upstream format change

* Added Vector64 type, which is just an alias for vector ATM

* Switch to Offset64 for Vector64

* Update for reflection bfbs output change

* Starting to add support for vector64 type in C++

* made a generic CreateVector that can handle different offsets and vector types

* Support for 32-vector with 64-addressing

* Vector64 basic builder + tests working

* basic support for json vector64 support

* renamed fields in test_64bit.fbs to better reflect their use

* working C++ vector64 builder

* Apply --annotate-sparse-vector to 64-bit tests

* Enable Vector64 for --annotate-sparse-vectors

* Merged from upstream

* Add `near_string` field for testing 32-bit offsets alongside

* keep track of where the 32-bit and 64-bit regions are for flatbufferbuilder

* move template<> outside class body for GCC

* update run.sh to build and run tests

* basic assertion for adding 64-bit offset at the wrong time

* started to separate `FlatBufferBuilder` into two classes, 1 64-bit aware, the other not

* add test for nested flatbuffer vector64, fix bug in alignment of big vectors

* fixed CreateDirect method by iterating by Offset64 first

* internal refactoring of flatbufferbuilder

* block not supported languages in the parser from using 64-bit

* evolution tests for adding a vector64 field

* conformity tests for adding/removing offset64 attributes

* ensure test is for a big buffer

* add parser error tests for `offset64` and `vector64` attributes

* add missing static that GCC only complains about

* remove stdint-uintn.h header that gets automatically added

* move 64-bit CalculateOffset internal

* fixed return size of EndVector

* various fixes on windows

* add SizeT to vector_downward

* minimze range of size changes in vector and builder

* reworked how tracking if 64-offsets are added

* Add ReturnT to EndVector

* small cleanups

* remove need for second Array definition

* combine IndirectHelpers into one definition

* started support for vector of struct

* Support for 32/64-vectors of structs + Offset64

* small cleanups

* add verification for vector64

* add sized prefix for 64-bit buffers

* add fuzzer for 64-bit

* add example of adding many vectors using a wrapper table

* run the new -bfbs-gen-embed logic on the 64-bit tests

* remove run.sh and fix cmakelist issue

* fixed bazel rules

* fixed some PR comments

* add 64-bit tests to cmakelist

src/binary_annotator.h

@@ -48,6 +48,7 @@ enum class BinaryRegionType {
   Float = 15,
   Double = 16,
   UType = 17,
+  UOffset64 = 18,
 };
 
 template<typename T>
@@ -179,6 +180,7 @@ enum class BinarySectionType {
   Vector = 7,
   Union = 8,
   Padding = 9,
+  Vector64 = 10,
 };
 
 // A section of the binary that is grouped together in some logical manner, and
@@ -216,6 +218,7 @@ inline static BinaryRegionType GetRegionType(reflection::BaseType base_type) {
 inline static std::string ToString(const BinaryRegionType type) {
   switch (type) {
     case BinaryRegionType::UOffset: return "UOffset32";
+    case BinaryRegionType::UOffset64: return "UOffset64";
     case BinaryRegionType::SOffset: return "SOffset32";
     case BinaryRegionType::VOffset: return "VOffset16";
     case BinaryRegionType::Bool: return "bool";
@@ -242,12 +245,14 @@ class BinaryAnnotator {
   explicit BinaryAnnotator(const uint8_t *const bfbs,
                            const uint64_t bfbs_length,
                            const uint8_t *const binary,
-                           const uint64_t binary_length)
+                           const uint64_t binary_length,
+                           const bool is_size_prefixed)
       : bfbs_(bfbs),
         bfbs_length_(bfbs_length),
         schema_(reflection::GetSchema(bfbs)),
         binary_(binary),
-        binary_length_(binary_length) {}
+        binary_length_(binary_length),
+        is_size_prefixed_(is_size_prefixed) {}
 
   std::map<uint64_t, BinarySection> Annotate();
 
@@ -387,6 +392,7 @@ class BinaryAnnotator {
   // The binary data itself.
   const uint8_t *binary_;
   const uint64_t binary_length_;
+  const bool is_size_prefixed_;
 
   // Map of binary offset to vtables, to dedupe vtables.
   std::map<uint64_t, std::list<VTable>> vtables_;