read method
Implementation
@override
Future<int> read(int offset, Uint8List buffer) => _serialize(() async {
if (offset < 0) throw RangeError.value(offset, 'offset');
final image = _image;
if (image != null) {
if (offset >= image.length) return 0;
final count = buffer.length < image.length - offset
? buffer.length
: image.length - offset;
buffer.setRange(0, count, image, offset);
return count;
}
await _file.setPosition(offset);
return _file.readInto(buffer);
});