// CheckByteLayout verifies the bytes of a Builder in various scenarios.
func CheckByteLayout(fail func(string, ...interface{})) {
var b *flatbuffers.Builder
var i int
check := func(want []byte) {
i++
got := b.Bytes[b.Head():]
if !bytes.Equal(want, got) {
fail("case %d: want\n%v\nbut got\n%v\n", i, want, got)
}
}
// test 1: numbers
b = flatbuffers.NewBuilder(0)
check([]byte{})
b.PrependBool(true)
check([]byte{1})
b.PrependInt8(-127)
check([]byte{129, 1})
b.PrependUint8(255)
check([]byte{255, 129, 1})
b.PrependInt16(-32222)
check([]byte{0x22, 0x82, 0, 255, 129, 1}) // first pad
b.PrependUint16(0xFEEE)
check([]byte{0xEE, 0xFE, 0x22, 0x82, 0, 255, 129, 1}) // no pad this time
b.PrependInt32(-53687092)
check([]byte{204, 204, 204, 252, 0xEE, 0xFE, 0x22, 0x82, 0, 255, 129, 1})
b.PrependUint32(0x98765432)
check([]byte{0x32, 0x54, 0x76, 0x98, 204, 204, 204, 252, 0xEE, 0xFE, 0x22, 0x82, 0, 255, 129, 1})
// test 1b: numbers 2
b = flatbuffers.NewBuilder(0)
b.PrependUint64(0x1122334455667788)
check([]byte{0x88, 0x77, 0x66, 0x55, 0x44, 0x33, 0x22, 0x11})
// test 2: 1xbyte vector
b = flatbuffers.NewBuilder(0)
check([]byte{})
b.StartVector(flatbuffers.SizeByte, 1, 1)
check([]byte{0, 0, 0}) // align to 4bytes
b.PrependByte(1)
check([]byte{1, 0, 0, 0})
b.EndVector(1)
check([]byte{1, 0, 0, 0, 1, 0, 0, 0}) // padding
// test 3: 2xbyte vector
b = flatbuffers.NewBuilder(0)
b.StartVector(flatbuffers.SizeByte, 2, 1)
check([]byte{0, 0}) // align to 4bytes
b.PrependByte(1)
check([]byte{1, 0, 0})
b.PrependByte(2)
check([]byte{2, 1, 0, 0})
b.EndVector(2)
check([]byte{2, 0, 0, 0, 2, 1, 0, 0}) // padding
// test 3b: 11xbyte vector matches builder size
b = flatbuffers.NewBuilder(12)
b.StartVector(flatbuffers.SizeByte, 8, 1)
start := []byte{}
check(start)
for i := 1; i < 12; i++ {
b.PrependByte(byte(i))
start = append([]byte{byte(i)}, start...)
check(start)
}
b.EndVector(8)
check(append([]byte{8, 0, 0, 0}, start...))
// test 4: 1xuint16 vector
b = flatbuffers.NewBuilder(0)
b.StartVector(flatbuffers.SizeUint16, 1, 1)
check([]byte{0, 0}) // align to 4bytes
b.PrependUint16(1)
check([]byte{1, 0, 0, 0})
b.EndVector(1)
check([]byte{1, 0, 0, 0, 1, 0, 0, 0}) // padding
// test 5: 2xuint16 vector
b = flatbuffers.NewBuilder(0)
b.StartVector(flatbuffers.SizeUint16, 2, 1)
check([]byte{}) // align to 4bytes
b.PrependUint16(0xABCD)
check([]byte{0xCD, 0xAB})
b.PrependUint16(0xDCBA)
check([]byte{0xBA, 0xDC, 0xCD, 0xAB})
b.EndVector(2)
check([]byte{2, 0, 0, 0, 0xBA, 0xDC, 0xCD, 0xAB})
// test 6: CreateString
b = flatbuffers.NewBuilder(0)
b.CreateString("foo")
check([]byte{3, 0, 0, 0, 'f', 'o', 'o', 0}) // 0-terminated, no pad
b.CreateString("moop")
check([]byte{4, 0, 0, 0, 'm', 'o', 'o', 'p', 0, 0, 0, 0, // 0-terminated, 3-byte pad
3, 0, 0, 0, 'f', 'o', 'o', 0})
// test 6b: CreateString unicode
b = flatbuffers.NewBuilder(0)
// These characters are chinese from blog.golang.org/strings
// We use escape codes here so that editors without unicode support
// aren't bothered:
uni_str := "\u65e5\u672c\u8a9e"
b.CreateString(uni_str)
check([]byte{9, 0, 0, 0, 230, 151, 165, 230, 156, 172, 232, 170, 158, 0, // null-terminated, 2-byte pad
0, 0})
// test 6c: CreateByteString
b = flatbuffers.NewBuilder(0)
b.CreateByteString([]byte("foo"))
check([]byte{3, 0, 0, 0, 'f', 'o', 'o', 0}) // 0-terminated, no pad
b.CreateByteString([]byte("moop"))
check([]byte{4, 0, 0, 0, 'm', 'o', 'o', 'p', 0, 0, 0, 0, // 0-terminated, 3-byte pad
3, 0, 0, 0, 'f', 'o', 'o', 0})
// test 7: empty vtable
b = flatbuffers.NewBuilder(0)
b.StartObject(0)
check([]byte{})
b.EndObject()
check([]byte{4, 0, 4, 0, 4, 0, 0, 0})
// test 8: vtable with one true bool
b = flatbuffers.NewBuilder(0)
check([]byte{})
b.StartObject(1)
check([]byte{})
b.PrependBoolSlot(0, true, false)
b.EndObject()
check([]byte{
6, 0, // vtable bytes
8, 0, // length of object including vtable offset
7, 0, // start of bool value
6, 0, 0, 0, // offset for start of vtable (int32)
0, 0, 0, // padded to 4 bytes
1, // bool value
})
// test 9: vtable with one default bool
b = flatbuffers.NewBuilder(0)
check([]byte{})
b.StartObject(1)
check([]byte{})
b.PrependBoolSlot(0, false, false)
b.EndObject()
check([]byte{
6, 0, // vtable bytes
4, 0, // end of object from here
0, 0, // entry 1 is zero
6, 0, 0, 0, // offset for start of vtable (int32)
})
// test 10: vtable with one int16
b = flatbuffers.NewBuilder(0)
b.StartObject(1)
b.PrependInt16Slot(0, 0x789A, 0)
b.EndObject()
check([]byte{
6, 0, // vtable bytes
8, 0, // end of object from here
6, 0, // offset to value
6, 0, 0, 0, // offset for start of vtable (int32)
0, 0, // padding to 4 bytes
0x9A, 0x78,
})
// test 11: vtable with two int16
b = flatbuffers.NewBuilder(0)
b.StartObject(2)
b.PrependInt16Slot(0, 0x3456, 0)
b.PrependInt16Slot(1, 0x789A, 0)
b.EndObject()
check([]byte{
8, 0, // vtable bytes
8, 0, // end of object from here
6, 0, // offset to value 0
4, 0, // offset to value 1
8, 0, 0, 0, // offset for start of vtable (int32)
0x9A, 0x78, // value 1
0x56, 0x34, // value 0
})
// test 12: vtable with int16 and bool
b = flatbuffers.NewBuilder(0)
b.StartObject(2)
b.PrependInt16Slot(0, 0x3456, 0)
b.PrependBoolSlot(1, true, false)
b.EndObject()
check([]byte{
8, 0, // vtable bytes
8, 0, // end of object from here
6, 0, // offset to value 0
5, 0, // offset to value 1
8, 0, 0, 0, // offset for start of vtable (int32)
0, // padding
1, // value 1
0x56, 0x34, // value 0
})
// test 12: vtable with empty vector
b = flatbuffers.NewBuilder(0)
b.StartVector(flatbuffers.SizeByte, 0, 1)
vecend := b.EndVector(0)
b.StartObject(1)
b.PrependUOffsetTSlot(0, vecend, 0)
b.EndObject()
check([]byte{
6, 0, // vtable bytes
8, 0,
4, 0, // offset to vector offset
6, 0, 0, 0, // offset for start of vtable (int32)
4, 0, 0, 0,
0, 0, 0, 0, // length of vector (not in struct)
})
// test 12b: vtable with empty vector of byte and some scalars
b = flatbuffers.NewBuilder(0)
b.StartVector(flatbuffers.SizeByte, 0, 1)
vecend = b.EndVector(0)
b.StartObject(2)
b.PrependInt16Slot(0, 55, 0)
b.PrependUOffsetTSlot(1, vecend, 0)
b.EndObject()
check([]byte{
8, 0, // vtable bytes
12, 0,
10, 0, // offset to value 0
4, 0, // offset to vector offset
8, 0, 0, 0, // vtable loc
8, 0, 0, 0, // value 1
0, 0, 55, 0, // value 0
0, 0, 0, 0, // length of vector (not in struct)
})
// test 13: vtable with 1 int16 and 2-vector of int16
b = flatbuffers.NewBuilder(0)
b.StartVector(flatbuffers.SizeInt16, 2, 1)
b.PrependInt16(0x1234)
b.PrependInt16(0x5678)
vecend = b.EndVector(2)
b.StartObject(2)
b.PrependUOffsetTSlot(1, vecend, 0)
b.PrependInt16Slot(0, 55, 0)
b.EndObject()
check([]byte{
8, 0, // vtable bytes
12, 0, // length of object
6, 0, // start of value 0 from end of vtable
8, 0, // start of value 1 from end of buffer
8, 0, 0, 0, // offset for start of vtable (int32)
0, 0, // padding
55, 0, // value 0
4, 0, 0, 0, // vector position from here
2, 0, 0, 0, // length of vector (uint32)
0x78, 0x56, // vector value 1
0x34, 0x12, // vector value 0
})
// test 14: vtable with 1 struct of 1 int8, 1 int16, 1 int32
b = flatbuffers.NewBuilder(0)
b.StartObject(1)
b.Prep(4+4+4, 0)
b.PrependInt8(55)
b.Pad(3)
b.PrependInt16(0x1234)
b.Pad(2)
b.PrependInt32(0x12345678)
structStart := b.Offset()
b.PrependStructSlot(0, structStart, 0)
b.EndObject()
check([]byte{
6, 0, // vtable bytes
16, 0, // end of object from here
4, 0, // start of struct from here
6, 0, 0, 0, // offset for start of vtable (int32)
0x78, 0x56, 0x34, 0x12, // value 2
0, 0, // padding
0x34, 0x12, // value 1
0, 0, 0, // padding
55, // value 0
})
// test 15: vtable with 1 vector of 2 struct of 2 int8
b = flatbuffers.NewBuilder(0)
b.StartVector(flatbuffers.SizeInt8*2, 2, 1)
b.PrependInt8(33)
b.PrependInt8(44)
b.PrependInt8(55)
b.PrependInt8(66)
vecend = b.EndVector(2)
b.StartObject(1)
b.PrependUOffsetTSlot(0, vecend, 0)
b.EndObject()
check([]byte{
6, 0, // vtable bytes
8, 0,
4, 0, // offset of vector offset
6, 0, 0, 0, // offset for start of vtable (int32)
4, 0, 0, 0, // vector start offset
2, 0, 0, 0, // vector length
66, // vector value 1,1
55, // vector value 1,0
44, // vector value 0,1
33, // vector value 0,0
})
// test 16: table with some elements
b = flatbuffers.NewBuilder(0)
b.StartObject(2)
b.PrependInt8Slot(0, 33, 0)
b.PrependInt16Slot(1, 66, 0)
off := b.EndObject()
b.Finish(off)
check([]byte{
12, 0, 0, 0, // root of table: points to vtable offset
8, 0, // vtable bytes
8, 0, // end of object from here
7, 0, // start of value 0
4, 0, // start of value 1
8, 0, 0, 0, // offset for start of vtable (int32)
66, 0, // value 1
0, // padding
33, // value 0
})
// test 17: one unfinished table and one finished table
b = flatbuffers.NewBuilder(0)
b.StartObject(2)
b.PrependInt8Slot(0, 33, 0)
b.PrependInt8Slot(1, 44, 0)
off = b.EndObject()
b.Finish(off)
b.StartObject(3)
b.PrependInt8Slot(0, 55, 0)
b.PrependInt8Slot(1, 66, 0)
b.PrependInt8Slot(2, 77, 0)
off = b.EndObject()
b.Finish(off)
check([]byte{
16, 0, 0, 0, // root of table: points to object
0, 0, // padding
10, 0, // vtable bytes
8, 0, // size of object
7, 0, // start of value 0
6, 0, // start of value 1
5, 0, // start of value 2
10, 0, 0, 0, // offset for start of vtable (int32)
0, // padding
77, // value 2
66, // value 1
55, // value 0
12, 0, 0, 0, // root of table: points to object
8, 0, // vtable bytes
8, 0, // size of object
7, 0, // start of value 0
6, 0, // start of value 1
8, 0, 0, 0, // offset for start of vtable (int32)
0, 0, // padding
44, // value 1
33, // value 0
})
// test 18: a bunch of bools
b = flatbuffers.NewBuilder(0)
b.StartObject(8)
b.PrependBoolSlot(0, true, false)
b.PrependBoolSlot(1, true, false)
b.PrependBoolSlot(2, true, false)
b.PrependBoolSlot(3, true, false)
b.PrependBoolSlot(4, true, false)
b.PrependBoolSlot(5, true, false)
b.PrependBoolSlot(6, true, false)
b.PrependBoolSlot(7, true, false)
off = b.EndObject()
b.Finish(off)
check([]byte{
24, 0, 0, 0, // root of table: points to vtable offset
20, 0, // vtable bytes
12, 0, // size of object
11, 0, // start of value 0
10, 0, // start of value 1
9, 0, // start of value 2
8, 0, // start of value 3
7, 0, // start of value 4
6, 0, // start of value 5
5, 0, // start of value 6
4, 0, // start of value 7
20, 0, 0, 0, // vtable offset
1, // value 7
1, // value 6
1, // value 5
1, // value 4
1, // value 3
1, // value 2
1, // value 1
1, // value 0
})
// test 19: three bools
b = flatbuffers.NewBuilder(0)
b.StartObject(3)
b.PrependBoolSlot(0, true, false)
b.PrependBoolSlot(1, true, false)
b.PrependBoolSlot(2, true, false)
off = b.EndObject()
b.Finish(off)
check([]byte{
16, 0, 0, 0, // root of table: points to vtable offset
0, 0, // padding
10, 0, // vtable bytes
8, 0, // size of object
7, 0, // start of value 0
6, 0, // start of value 1
5, 0, // start of value 2
10, 0, 0, 0, // vtable offset from here
0, // padding
1, // value 2
1, // value 1
1, // value 0
})
// test 20: some floats
b = flatbuffers.NewBuilder(0)
b.StartObject(1)
b.PrependFloat32Slot(0, 1.0, 0.0)
off = b.EndObject()
check([]byte{
6, 0, // vtable bytes
8, 0, // size of object
4, 0, // start of value 0
6, 0, 0, 0, // vtable offset
0, 0, 128, 63, // value 0
})
}