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[C++] Add Vector64 specialization for std::vector<bool> #8757

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Merged
aardappel merged 4 commits into from
Nov 17, 2025
Merged

[C++] Add Vector64 specialization for std::vector<bool> #8757

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1a59e8d
add vector64 specialization for vector<bool>
jtdavis777 Nov 5, 2025
b2bbebf
fix generated code
jtdavis777 Nov 5, 2025
aecf832
Merge branch 'master' into feature/vector64_of_bool
jtdavis777 Nov 5, 2025
e4b2ba1
Merge branch 'master' into feature/vector64_of_bool
aardappel Nov 17, 2025
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10 changes: 10 additions & 0 deletions include/flatbuffers/flatbuffer_builder.h
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Original file line number Diff line number Diff line change
Expand Up @@ -834,6 +834,16 @@ class FlatBufferBuilderImpl {
return Offset<Vector<uint8_t>>(EndVector(v.size()));
}

Offset64<Vector64<uint8_t>> CreateVector64(const std::vector<bool>& v) {
StartVector<uint8_t, Offset64, Vector64<uint8_t>::size_type>(v.size());
for (auto i = v.size(); i > 0;) {
PushElement(static_cast<uint8_t>(v[--i]));
}
return Offset64<Vector64<uint8_t>>(
EndVector<Vector64<uint8_t>::size_type,
Offset64<Vector64<uint8_t>>::offset_type>(v.size()));
}

/// @brief Serialize values returned by a function into a FlatBuffer `vector`.
/// This is a convenience function that takes care of iteration for you.
/// @tparam T The data type of the `std::vector` elements.
Expand Down
24 changes: 15 additions & 9 deletions tests/64bit/offset64_test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,9 @@ void Offset64Test() {
far_data[0] = 4;
far_data[far_vector_size - 1] = 2;

std::vector<bool> big_bool_data = {true, false, true, true,
false, false, true};

std::vector<uint8_t> big_data;
big_data.resize(big_vector_size);
big_data[0] = 8;
Expand All @@ -49,15 +52,18 @@ void Offset64Test() {
const Offset64<Vector64<uint8_t>> big_vector_offset =
builder.CreateVector64(big_data);

const Offset64<Vector64<uint8_t>> big_bool_vector_offset =
builder.CreateVector64(big_bool_data);

// Now that we are done with the 64-bit fields, we can create and add the
// normal fields.
const Offset<String> near_string_offset =
builder.CreateString("some near string");

// Finish by building the root table by passing in all the offsets.
const Offset<RootTable> root_table_offset =
CreateRootTable(builder, far_vector_offset, 0, far_string_offset,
big_vector_offset, near_string_offset);
const Offset<RootTable> root_table_offset = CreateRootTable(
builder, far_vector_offset, 0, far_string_offset,
big_bool_vector_offset, big_vector_offset, near_string_offset);

// Finish the buffer.
builder.Finish(root_table_offset);
Expand Down Expand Up @@ -118,7 +124,7 @@ void Offset64NestedFlatBuffer() {

// Finish by building the root table by passing in all the offsets.
const Offset<RootTable> root_table_offset =
CreateRootTable(fbb, 0, 0, 0, 0, near_string_offset, 0);
CreateRootTable(fbb, 0, 0, 0, 0, 0, near_string_offset, 0);

// Finish the buffer.
fbb.Finish(root_table_offset);
Expand All @@ -145,7 +151,7 @@ void Offset64NestedFlatBuffer() {

// Finish by building the root table by passing in all the offsets.
const Offset<RootTable> root_table_offset = CreateRootTable(
fbb, 0, 0, 0, 0, near_string_offset, nested_flatbuffer_offset);
fbb, 0, 0, 0, 0, 0, near_string_offset, nested_flatbuffer_offset);

// Finish the buffer.
fbb.Finish(root_table_offset);
Expand Down Expand Up @@ -184,7 +190,7 @@ void Offset64CreateDirect() {
// Call the "Direct" creation method to ensure that things are added to the
// buffer in the correct order, Offset64 first followed by any Offsets.
const Offset<RootTable> root_table_offset = CreateRootTableDirect(
fbb, &data, 0, "some far string", &data, "some near string");
fbb, &data, 0, "some far string", nullptr, &data, "some near string");

// Finish the buffer.
fbb.Finish(root_table_offset);
Expand Down Expand Up @@ -306,7 +312,7 @@ void Offset64VectorOfStructs() {
// Add the two vectors of leaf structs.
const Offset<RootTable> root_table_offset =
CreateRootTableDirect(builder, nullptr, 0, nullptr, nullptr, nullptr,
nullptr, &far_leaves, &big_leaves);
nullptr, nullptr, &far_leaves, &big_leaves);

// Finish the buffer.
builder.Finish(root_table_offset);
Expand Down Expand Up @@ -346,7 +352,7 @@ void Offset64SizePrefix() {

// Finish by building the root table by passing in all the offsets.
const Offset<RootTable> root_table_offset =
CreateRootTable(builder, 0, 0, 0, 0, near_string_offset, 0);
CreateRootTable(builder, 0, 0, 0, 0, 0, near_string_offset, 0);

// Finish the buffer.
FinishSizePrefixedRootTableBuffer(builder, root_table_offset);
Expand Down Expand Up @@ -448,7 +454,7 @@ void Offset64ForceAlign() {
// Use the CreateDirect which calls the ForceVectorAlign
const auto root_table_offset =
CreateRootTableDirect(builder, nullptr, 0, nullptr, nullptr, nullptr,
nullptr, nullptr, nullptr, nullptr, &data);
nullptr, nullptr, nullptr, nullptr, nullptr, &data);

// Finish the buffer.
FinishRootTableBuffer(builder, root_table_offset);
Expand Down
118 changes: 67 additions & 51 deletions tests/64bit/test_64bit.afb
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Original file line number Diff line number Diff line change
@@ -1,74 +1,90 @@
// Annotated Flatbuffer Binary
//
// Schema file: tests/64bit/test_64bit.fbs
// Schema file: tests/64bit/test_64bit.bfbs
// Binary file: tests/64bit/test_64bit.bin

header:
+0x00 | 1C 00 00 00 | UOffset32 | 0x0000001C (28) Loc: 0x1C | offset to root table `RootTable`
+0x0000 | 1C 00 00 00 | UOffset32 | 0x0000001C (28) Loc: 0x001C | offset to root table `RootTable`

padding:
+0x04 | 00 00 00 00 | uint8_t[4] | .... | padding
+0x0004 | 00 00 | uint8_t[2] | .. | padding

vtable (RootTable):
+0x08 | 14 00 | uint16_t | 0x0014 (20) | size of this vtable
+0x0A | 34 00 | uint16_t | 0x0034 (52) | size of referring table
+0x0C | 04 00 | VOffset16 | 0x0004 (4) | offset to field `far_vector` (id: 0)
+0x0E | 10 00 | VOffset16 | 0x0010 (16) | offset to field `a` (id: 1)
+0x10 | 14 00 | VOffset16 | 0x0014 (20) | offset to field `far_string` (id: 2)
+0x12 | 24 00 | VOffset16 | 0x0024 (36) | offset to field `big_vector` (id: 3)
+0x14 | 20 00 | VOffset16 | 0x0020 (32) | offset to field `near_string` (id: 4)
+0x16 | 00 00 | VOffset16 | 0x0000 (0) | offset to field `nested_root` (id: 5) <null> (Vector64)
+0x18 | 00 00 | VOffset16 | 0x0000 (0) | offset to field `far_struct_vector` (id: 6) <null> (Vector)
+0x1A | 2C 00 | VOffset16 | 0x002C (44) | offset to field `big_struct_vector` (id: 7)
+0x0006 | 16 00 | uint16_t | 0x0016 (22) | size of this vtable
+0x0008 | 3C 00 | uint16_t | 0x003C (60) | size of referring table
+0x000A | 04 00 | VOffset16 | 0x0004 (4) | offset to field `far_vector` (id: 0)
+0x000C | 10 00 | VOffset16 | 0x0010 (16) | offset to field `a` (id: 1)
+0x000E | 14 00 | VOffset16 | 0x0014 (20) | offset to field `far_string` (id: 2)
+0x0010 | 24 00 | VOffset16 | 0x0024 (36) | offset to field `big_bool_vector` (id: 3)
+0x0012 | 2C 00 | VOffset16 | 0x002C (44) | offset to field `big_vector` (id: 4)
+0x0014 | 20 00 | VOffset16 | 0x0020 (32) | offset to field `near_string` (id: 5)
+0x0016 | 00 00 | VOffset16 | 0x0000 (0) | offset to field `nested_root` (id: 6) <null> (Vector64)
+0x0018 | 00 00 | VOffset16 | 0x0000 (0) | offset to field `far_struct_vector` (id: 7) <null> (Vector)
+0x001A | 34 00 | VOffset16 | 0x0034 (52) | offset to field `big_struct_vector` (id: 8)

root_table (RootTable):
+0x1C | 14 00 00 00 | SOffset32 | 0x00000014 (20) Loc: 0x08 | offset to vtable
+0x20 | D0 00 00 00 00 00 00 00 | UOffset64 | 0x00000000000000D0 (208) Loc: 0xF0 | offset to field `far_vector` (vector)
+0x28 | 00 00 00 00 | uint8_t[4] | .... | padding
+0x2C | D2 04 00 00 | uint32_t | 0x000004D2 (1234) | table field `a` (Int)
+0x30 | 8C 00 00 00 00 00 00 00 | UOffset64 | 0x000000000000008C (140) Loc: 0xBC | offset to field `far_string` (string)
+0x38 | 00 00 00 00 | uint8_t[4] | .... | padding
+0x3C | 40 00 00 00 | UOffset32 | 0x00000040 (64) Loc: 0x7C | offset to field `near_string` (string)
+0x40 | 70 00 00 00 00 00 00 00 | UOffset64 | 0x0000000000000070 (112) Loc: 0xB0 | offset to field `big_vector` (vector64)
+0x48 | 08 00 00 00 00 00 00 00 | UOffset64 | 0x0000000000000008 (8) Loc: 0x50 | offset to field `big_struct_vector` (vector64)
+0x001C | 16 00 00 00 | SOffset32 | 0x00000016 (22) Loc: 0x0006 | offset to vtable
+0x0020 | E8 00 00 00 00 00 00 00 | UOffset64 | 0x00000000000000E8 (232) Loc: 0x0108 | offset to field `far_vector` (vector)
+0x0028 | 00 00 00 00 | uint8_t[4] | .... | padding
+0x002C | D2 04 00 00 | uint32_t | 0x000004D2 (1234) | table field `a` (Int)
+0x0030 | A4 00 00 00 00 00 00 00 | UOffset64 | 0x00000000000000A4 (164) Loc: 0x00D4 | offset to field `far_string` (string)
+0x0038 | 00 00 00 00 | uint8_t[4] | .... | padding
+0x003C | 48 00 00 00 | UOffset32 | 0x00000048 (72) Loc: 0x0084 | offset to field `near_string` (string)
+0x0040 | 78 00 00 00 00 00 00 00 | UOffset64 | 0x0000000000000078 (120) Loc: 0x00B8 | offset to field `big_bool_vector` (vector64)
+0x0048 | 80 00 00 00 00 00 00 00 | UOffset64 | 0x0000000000000080 (128) Loc: 0x00C8 | offset to field `big_vector` (vector64)
+0x0050 | 08 00 00 00 00 00 00 00 | UOffset64 | 0x0000000000000008 (8) Loc: 0x0058 | offset to field `big_struct_vector` (vector64)

vector64 (RootTable.big_struct_vector):
+0x50 | 02 00 00 00 00 00 00 00 | uint64_t | 0x0000000000000002 (2) | length of vector (# items)
+0x58 | 0C 00 00 00 | uint32_t | 0x0000000C (12) | struct field `[0].a` of 'LeafStruct' (Int)
<4 regions omitted>
+0x70 | 33 33 33 33 33 33 22 40 | double | 0x4022333333333333 (9.1) | struct field `[1].b` of 'LeafStruct' (Double)
+0x0058 | 02 00 00 00 00 00 00 00 | uint64_t | 0x0000000000000002 (2) | length of vector (# items)
+0x0060 | 0C 00 00 00 | uint32_t | 0x0000000C (12) | struct field `[0].a` of 'LeafStruct' (Int)
+0x0064 | 00 00 00 00 | uint8_t[4] | .... | padding
+0x0068 | D9 CE F7 53 E3 A5 0B 40 | double | 0x400BA5E353F7CED9 (3.456) | struct field `[0].b` of 'LeafStruct' (Double)
+0x0070 | 4E 00 00 00 | uint32_t | 0x0000004E (78) | struct field `[1].a` of 'LeafStruct' (Int)
+0x0074 | 00 00 00 00 | uint8_t[4] | .... | padding
+0x0078 | 33 33 33 33 33 33 22 40 | double | 0x4022333333333333 (9.1) | struct field `[1].b` of 'LeafStruct' (Double)

padding:
+0x78 | 00 00 00 00 | uint8_t[4] | .... | padding
+0x0080 | 00 00 00 00 | uint8_t[4] | .... | padding

string (RootTable.near_string):
+0x7C | 2F 00 00 00 | uint32_t | 0x0000002F (47) | length of string
+0x80 | 74 68 69 73 20 69 73 20 | char[47] | this is | string literal
+0x88 | 61 20 6E 65 61 72 20 73 | | a near s
+0x90 | 74 72 69 6E 67 20 77 68 | | tring wh
+0x98 | 69 63 68 20 68 61 73 20 | | ich has
+0xA0 | 61 20 33 32 2D 62 69 74 | | a 32-bit
+0xA8 | 20 6F 66 66 73 65 74 | | offset
+0xAF | 00 | char | 0x00 (0) | string terminator
+0x0084 | 2F 00 00 00 | uint32_t | 0x0000002F (47) | length of string
+0x0088 | 74 68 69 73 20 69 73 20 | char[47] | this is | string literal
+0x0090 | 61 20 6E 65 61 72 20 73 | | a near s
+0x0098 | 74 72 69 6E 67 20 77 68 | | tring wh
+0x00A0 | 69 63 68 20 68 61 73 20 | | ich has
+0x00A8 | 61 20 33 32 2D 62 69 74 | | a 32-bit
+0x00B0 | 20 6F 66 66 73 65 74 | | offset
+0x00B7 | 00 | char | 0x00 (0) | string terminator

vector64 (RootTable.big_bool_vector):
+0x00B8 | 07 00 00 00 00 00 00 00 | uint64_t | 0x0000000000000007 (7) | length of vector (# items)
+0x00C0 | 01 | uint8_t | 0x01 (1) | value[0]
+0x00C1 | 00 | uint8_t | 0x00 (0) | value[1]
+0x00C2 | 01 | uint8_t | 0x01 (1) | value[2]
+0x00C3 | 01 | uint8_t | 0x01 (1) | value[3]
+0x00C4 | 00 | uint8_t | 0x00 (0) | value[4]
+0x00C5 | 00 | uint8_t | 0x00 (0) | value[5]
+0x00C6 | 01 | uint8_t | 0x01 (1) | value[6]

vector64 (RootTable.big_vector):
+0xB0 | 04 00 00 00 00 00 00 00 | uint64_t | 0x0000000000000004 (4) | length of vector (# items)
+0xB8 | 05 | uint8_t | 0x05 (5) | value[0]
<2 regions omitted>
+0xBB | 08 | uint8_t | 0x08 (8) | value[3]
+0x00C8 | 04 00 00 00 00 00 00 00 | uint64_t | 0x0000000000000004 (4) | length of vector (# items)
+0x00D0 | 05 | uint8_t | 0x05 (5) | value[0]
+0x00D1 | 06 | uint8_t | 0x06 (6) | value[1]
+0x00D2 | 07 | uint8_t | 0x07 (7) | value[2]
+0x00D3 | 08 | uint8_t | 0x08 (8) | value[3]

string (RootTable.far_string):
+0xBC | 2E 00 00 00 | uint32_t | 0x0000002E (46) | length of string
+0xC0 | 74 68 69 73 20 69 73 20 | char[46] | this is | string literal
+0xC8 | 61 20 66 61 72 20 73 74 | | a far st
+0xD0 | 72 69 6E 67 20 77 68 69 | | ring whi
+0xD8 | 63 68 20 68 61 73 20 61 | | ch has a
+0xE0 | 20 36 34 2D 62 69 74 20 | | 64-bit
+0xE8 | 6F 66 66 73 65 74 | | offset
+0xEE | 00 | char | 0x00 (0) | string terminator
+0x00D4 | 2E 00 00 00 | uint32_t | 0x0000002E (46) | length of string
+0x00D8 | 74 68 69 73 20 69 73 20 | char[46] | this is | string literal
+0x00E0 | 61 20 66 61 72 20 73 74 | | a far st
+0x00E8 | 72 69 6E 67 20 77 68 69 | | ring whi
+0x00F0 | 63 68 20 68 61 73 20 61 | | ch has a
+0x00F8 | 20 36 34 2D 62 69 74 20 | | 64-bit
+0x0100 | 6F 66 66 73 65 74 | | offset
+0x0106 | 00 | char | 0x00 (0) | string terminator

vector (RootTable.far_vector):
+0xF0 | 03 00 00 00 | uint32_t | 0x00000003 (3) | length of vector (# items)
+0xF4 | 01 | uint8_t | 0x01 (1) | value[0]
+0xF5 | 02 | uint8_t | 0x02 (2) | value[1]
+0xF6 | 03 | uint8_t | 0x03 (3) | value[2]
+0x0108 | 03 00 00 00 | uint32_t | 0x00000003 (3) | length of vector (# items)
+0x010C | 01 | uint8_t | 0x01 (1) | value[0]
+0x010D | 02 | uint8_t | 0x02 (2) | value[1]
+0x010E | 03 | uint8_t | 0x03 (3) | value[2]
Binary file modified tests/64bit/test_64bit.bfbs
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Binary file modified tests/64bit/test_64bit.bin
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14 changes: 9 additions & 5 deletions tests/64bit/test_64bit.fbs
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Expand Up @@ -18,6 +18,10 @@ table RootTable {
// A normal 32-bit sized string, that could be very far away (64-bit address).
far_string:string (offset64);

// a big vector of bool, that could be very far away (64-bit address).
// tests vector<bool> specialization with 64-bit offsets.
big_bool_vector:[ubyte] (vector64);

// A big 64-bit sized vector, that could be very far away (64-bit address).
big_vector:[ubyte] (vector64);

Expand All @@ -27,19 +31,19 @@ table RootTable {
// A big 64-bit sized vector that is a nested flatbuffers (64-bit address).
nested_root:[ubyte] (vector64, nested_flatbuffer: "RootTable");

// A normal 32-bit size vector of structs, that could be very far away
// A normal 32-bit size vector of structs, that could be very far away
// (64-bit address)
far_struct_vector:[LeafStruct] (offset64);

// A big 64-bit size vector of structs that could be very far away
// A big 64-bit size vector of structs that could be very far away
// (64-bit address)
big_struct_vector:[LeafStruct] (vector64);

// A normal 32-bit size vector of tables. Currently 64-bit vectors don't
// A normal 32-bit size vector of tables. Currently 64-bit vectors don't
// support tables as it would require serializing a table (32-bit) before the
// vector (64-bit), which is not allowed.
//
// This demonstrates how you could have many vectors in the buffer, by
// This demonstrates how you could have many vectors in the buffer, by
// effectively having a vector of 64-bit vectors. The IDL doesn't support
// nested vecotrs (e.g.: [[type]] ), so going through a wrapper table allows
// this.
Expand All @@ -50,4 +54,4 @@ table RootTable {
forced_aligned_vector:[ubyte] (vector64, force_align:32);
}

root_type RootTable;
root_type RootTable;
11 changes: 10 additions & 1 deletion tests/64bit/test_64bit.json
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Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,22 @@
"a": 1234,
"far_string": "this is a far string which has a 64-bit offset",
"big_vector": [5, 6, 7, 8],
"big_bool_vector": [
1,
0,
1,
1,
0,
0,
1
],
"near_string": "this is a near string which has a 32-bit offset",
"big_struct_vector": [
{
"a": 12,
"b": 3.456
},
{
{
"a": 78,
"b": 9.10
}
Expand Down
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