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dart Builder - expose finished buffer size (#6403)

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This commit is contained in:
Ivan Dlugos
2021-01-22 01:06:11 +01:00
committed by GitHub
parent 52e2177069
commit ad3a729f96
2 changed files with 9 additions and 6 deletions
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14
dart/lib/flat_buffers.dart
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@@ -149,6 +149,9 @@ class Builder {
reset(); reset();
} }
/// Calculate the finished buffer size (aligned).
int size() => _tail + ((-_tail) % _maxAlign);
/// Add the [field] with the given boolean [value]. The field is not added if /// Add the [field] with the given boolean [value]. The field is not added if
/// the [value] is equal to [def]. Booleans are stored as 8-bit fields with /// the [value] is equal to [def]. Booleans are stored as 8-bit fields with
/// `0` for `false` and `1` for `true`. /// `0` for `false` and `1` for `true`.
@@ -335,8 +338,7 @@ class Builder {
/// ///
/// Most clients should prefer calling [finish]. /// Most clients should prefer calling [finish].
Uint8List lowFinish() { Uint8List lowFinish() {
int alignedTail = _tail + ((-_tail) % _maxAlign); return _buf.buffer.asUint8List(_buf.lengthInBytes - size());
return _buf.buffer.asUint8List(_buf.lengthInBytes - alignedTail);
} }
/// Finish off the creation of the buffer. The given [offset] is used as the /// Finish off the creation of the buffer. The given [offset] is used as the
@@ -346,15 +348,15 @@ class Builder {
/// bytes 4-7 of the file. /// bytes 4-7 of the file.
Uint8List finish(int offset, [String fileIdentifier]) { Uint8List finish(int offset, [String fileIdentifier]) {
_prepare(max(_sizeofUint32, _maxAlign), fileIdentifier == null ? 1 : 2); _prepare(max(_sizeofUint32, _maxAlign), fileIdentifier == null ? 1 : 2);
int alignedTail = _tail + ((-_tail) % _maxAlign); final finishedSize = size();
_setUint32AtTail(_buf, alignedTail, alignedTail - offset); _setUint32AtTail(_buf, finishedSize, finishedSize - offset);
if (fileIdentifier != null) { if (fileIdentifier != null) {
for (int i = 0; i < 4; i++) { for (int i = 0; i < 4; i++) {
_setUint8AtTail(_buf, alignedTail - _sizeofUint32 - i, _setUint8AtTail(_buf, finishedSize - _sizeofUint32 - i,
fileIdentifier.codeUnitAt(i)); fileIdentifier.codeUnitAt(i));
} }
} }
return _buf.buffer.asUint8List(_buf.lengthInBytes - alignedTail); return _buf.buffer.asUint8List(_buf.lengthInBytes - finishedSize);
} }
/// Writes a Float64 to the tail of the buffer after preparing space for it. /// Writes a Float64 to the tail of the buffer after preparing space for it.

1
dart/test/flat_buffers_test.dart
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@@ -265,6 +265,7 @@ class BuilderTest {
builder.addInt32(1, 20, 10); builder.addInt32(1, 20, 10);
int offset = builder.endTable(); int offset = builder.endTable();
byteList = builder.finish(offset); byteList = builder.finish(offset);
expect(builder.size(), byteList.length);
} }
// read and verify // read and verify
BufferContext buffer = new BufferContext.fromBytes(byteList); BufferContext buffer = new BufferContext.fromBytes(byteList);