flutter_vid/lib/us/vid_us_data_stream_reader.dart

import 'dart:typed_data';

//Raised when data is not ready.
class NotReadyException implements Exception {}

class StreamErrorException implements Exception {
  String _msg;

  StreamErrorException(this._msg);

  @override
  String toString() {
    return _msg;
  }
}

class VidUsDataStreamReader {
  late final List<int> _data = [];
  late int _index;
  late ByteBuffer _buffer;
  late bool _error;
  late String _errorMsg;

  VidUsDataStreamReader(Stream<Uint8List> stream, [int offset = 0]) {
    _buffer = Uint8List.fromList(_data).buffer;
    stream.listen(onDataArrived, onError: onStreamError, onDone: onStreamDone);
    _index = offset;
  }

  void onDataArrived(Uint8List data) {
    _data.addAll(data);
    _buffer = Uint8List.fromList(_data).buffer;
  }

  void onStreamError(String msg) {
    _error = true;
    _errorMsg = msg;
  }

  void onStreamDone() {
    //Update the last data into the buffer.
    _buffer = Uint8List.fromList(_data).buffer;
  }

  ///Read int value from binary data(little endian),
  int readInt([int index = -1]) {
    if (_error) {
      throw StreamErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_buffer.lengthInBytes - _index) < 4) {
        throw NotReadyException();
      }
      var intData = _buffer.asByteData(_index, 4);
      _index += 4;
      return intData.getInt32(0, Endian.little);
    } else {
      if ((_buffer.lengthInBytes - index) < 4) {
        throw NotReadyException();
      }
      var intData = _buffer.asByteData(index, 4);
      _index = index + 4;
      return intData.getInt32(0, Endian.little);
    }
  }

  ///Read string from the binary data, the string format is utf-16, which is unicode in C#
  String readString([int index = -1]) {
    if (_error) {
      throw StreamErrorException(_errorMsg);
    }
    int dataLength;
    if (index == -1) {
      dataLength = readInt();
      if ((_buffer.lengthInBytes - _index) < dataLength) {
        throw NotReadyException();
      }
    } else {
      dataLength = readInt(index);
      if ((_buffer.lengthInBytes - index) < dataLength) {
        throw NotReadyException();
      }
    }
    var stringData = _buffer.asUint8List(_index, dataLength);
    _index += dataLength;
    var unicodeStringData = Uint8List.fromList(stringData.toList()).buffer.asUint16List();
    return String.fromCharCodes(unicodeStringData);
  }

  ///Read int16 value from binary data(little endian)
  int readInt16([int index = -1]) {
    if (_error) {
      throw StreamErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_buffer.lengthInBytes - _index) < 2) {
        throw NotReadyException();
      }
      var intData = _buffer.asByteData(_index, 2);
      _index += 2;
      return intData.getInt16(0, Endian.little);
    } else {
      if ((_buffer.lengthInBytes - index) < 2) {
        throw NotReadyException();
      }
      var intData = _buffer.asByteData(index, 2);
      _index = index + 2;
      return intData.getInt16(0, Endian.little);
    }
  }

  ///Read int64 value from binary data(little endian)
  ///this method is not support in web platform use readInt64V2 instead.
  int readInt64([int index = -1]) {
    if (_error) {
      throw StreamErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_buffer.lengthInBytes - _index) < 8) {
        throw NotReadyException();
      }
      var intData = _buffer.asByteData(_index, 8);
      _index += 8;
      return intData.getInt64(0, Endian.little);
    } else {
      if ((_buffer.lengthInBytes - index) < 8) {
        throw NotReadyException();
      }
      var intData = _buffer.asByteData(index, 8);
      _index = index + 8;
      return intData.getInt64(0, Endian.little);
    }
  }

  ///Read int64 value from binary data(little endian)
  ///this method use two int32 to support read int64 on web platform
  int readInt64V2([int index = -1]) {
    if (_error) {
      throw StreamErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_buffer.lengthInBytes - _index) < 8) {
        throw NotReadyException();
      }
      int low = readInt();
      int high = readInt();
      int value = high >> 32;
      value |= low;
      return value;
    } else {
      if ((_buffer.lengthInBytes - index) < 8) {
        throw NotReadyException();
      }
      int low = readInt(index);
      //Read the next int.
      int high = readInt();
      int value = high >> 32;
      value |= low;
      return value;
    }
  }

  ///Read float value from binary data(little endian)
  double readFloat([int index = -1]) {
    if (_error) {
      throw StreamErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_buffer.lengthInBytes - _index) < 4) {
        throw NotReadyException();
      }
      var floatData = _buffer.asByteData(_index, 4);
      _index += 4;
      return floatData.getFloat32(0, Endian.little);
    } else {
      if ((_buffer.lengthInBytes - index) < 4) {
        throw NotReadyException();
      }
      var floatData = _buffer.asByteData(index, 4);
      _index = index + 4;
      return floatData.getFloat32(0, Endian.little);
    }
  }

  ///Read double value from binary data(little endian)
  double readDouble([int index = -1]) {
    if (_error) {
      throw StreamErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_buffer.lengthInBytes - _index) < 8) {
        throw NotReadyException();
      }
      var floatData = _buffer.asByteData(_index, 8);
      _index += 8;
      return floatData.getFloat64(0, Endian.little);
    } else {
      if ((_buffer.lengthInBytes - index) < 8) {
        throw NotReadyException();
      }
      var floatData = _buffer.asByteData(index, 8);
      _index = index + 8;
      return floatData.getFloat64(0, Endian.little);
    }
  }

  ///Read bool value from binary data
  bool readBool([int index = -1]) {
    if (_error) {
      throw StreamErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_buffer.lengthInBytes - _index) < 1) {
        throw NotReadyException();
      }
      var boolData = _buffer.asByteData(_index, 1);
      _index++;
      return boolData.getInt8(0) == 1;
    } else {
      if ((_buffer.lengthInBytes - index) < 1) {
        throw NotReadyException();
      }
      var boolData = _buffer.asByteData(index, 1);
      _index = index + 1;
      return boolData.getInt8(0) == 1;
    }
  }

  ///Read byte value from binary data
  int readByte([int index = -1]) {
    if (_error) {
      throw StreamErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_buffer.lengthInBytes - _index) < 1) {
        throw NotReadyException();
      }
      var byteData = _buffer.asByteData(_index, 1);
      _index++;
      return byteData.getInt8(0);
    } else {
      if ((_buffer.lengthInBytes - index) < 1) {
        throw NotReadyException();
      }
      var byteData = _buffer.asByteData(index, 1);
      _index = index + 1;
      return byteData.getInt8(0);
    }
  }

  ///Read bytes from the binary data.
  Uint8List readBytes([int index = -1]) {
    if (_error) {
      throw StreamErrorException(_errorMsg);
    }
    var dataLength = readInt(index);
    if ((_buffer.lengthInBytes - _index) < dataLength) {
      throw NotReadyException();
    }
    var bytes = _buffer.asUint8List(_index, dataLength);
    _index += dataLength;
    return bytes;
  }
}