read method

@override Future<Uint8List> read(ByteRange range)

Reads exactly the bytes covered by range.

Implementation

@override
Future<Uint8List> read(ByteRange range) async {
  if (!_bounds.containsRange(range)) {
    throw ByteRangeOutOfBoundsException(range, _bounds);
  }

  final result = Uint8List(range.length);
  var sourceOffset = range.start;
  var destinationOffset = 0;
  while (sourceOffset < range.end) {
    final remaining = range.end - sourceOffset;
    final count = remaining < chunkSize ? remaining : chunkSize;
    final end = sourceOffset + count;
    Uint8List bytes;
    try {
      final buffer = await _blob
          .slice(sourceOffset, end)
          .arrayBuffer()
          .toDart;
      bytes = buffer.toDart.asUint8List();
    } catch (error) {
      throw ByteSourceIoException(operation: 'read Blob bytes', cause: error);
    }
    if (bytes.length != count) {
      throw TruncatedReadException(
        range: ByteRange(sourceOffset, end),
        expectedLength: count,
        actualLength: bytes.length,
      );
    }
    result.setRange(destinationOffset, destinationOffset + count, bytes);
    sourceOffset = end;
    destinationOffset += count;
  }
  return result;
}