fis_lib_vid/lib/async_vid/reader.dart

import 'dart:typed_data';

import 'package:flutter/foundation.dart';
import 'package:vid/us/vid_us_data_http_reader.dart';

typedef AsyncVidDataReaderBytesProxy = Uint8List Function();

abstract class AsyncVidDataReaderBase {
  Uint8List _chunkedData = Uint8List(0);
  int _bufferSize = 0;
  int _index = 0;
  bool _error = false;
  String _errorMsg = '';
  double _downloadProgress = 0;
  String url;

  DownloadCallback? downloadCallback;
  AsyncVidDataReaderBytesProxy? _bytesProxy;

  AsyncVidDataReaderBase(this.url, {this.downloadCallback}) {
    startDownload();
  }

  Uint8List get _underlyingData {
    if (_bytesProxy != null) {
      return _bytesProxy!.call();
    }
    return _chunkedData;
  }

  int get downloadedSize => _bufferSize;
  int get totalSize => _underlyingData.length;

  void startDownload();

  void initChunk(int size) {
    _chunkedData = Uint8List(size);
  }

  void appendChunk(Uint8List chunk) {
    _chunkedData.setAll(_bufferSize, chunk);
    setBufferSize(_bufferSize + chunk.length);
  }

  @protected
  void setBufferSize(int size) {
    _bufferSize = size;
  }

  void setError(bool hasErr, [String msg = '']) {
    _error = hasErr;
    _errorMsg = hasErr ? msg : '';
    if (_error) {
      downloadCallback?.call(_downloadProgress, DownloadErrorException(msg));
    }
  }

  void updateProgress(double progress, [DownloadErrorException? err]) {
    _downloadProgress = progress;
    downloadCallback?.call(_downloadProgress, err);
  }

  /// 通过代理从其他渠道读取字节数组
  ///
  /// 仅用于接入[VidUsDataHttpReader]
  @protected
  void setBytesProxy(AsyncVidDataReaderBytesProxy proxy) {
    _bytesProxy = proxy;
  }

  Uint8List toBytes() {
    return _underlyingData;
  }

  //Close the reader and its overhead.
  void close();

  ///Read int value from binary data(little endian),
  int readInt([int index = -1]) {
    if (_error) {
      throw DownloadErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_bufferSize - _index) < 4) {
        throw NotReadyException();
      }
      var intData = _underlyingData.buffer.asByteData(_index, 4);
      _index += 4;
      return intData.getInt32(0, Endian.little);
    } else {
      if ((_bufferSize - index) < 4) {
        throw NotReadyException();
      }
      var intData = _underlyingData.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 DownloadErrorException(_errorMsg);
    }
    int dataLength;
    if (index == -1) {
      dataLength = readInt();
      if ((_bufferSize - _index) < dataLength) {
        throw NotReadyException();
      }
    } else {
      dataLength = readInt(index);
      if ((_bufferSize - index) < dataLength) {
        throw NotReadyException();
      }
    }
    var stringData = _underlyingData.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 DownloadErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_bufferSize - _index) < 2) {
        throw NotReadyException();
      }
      var intData = _underlyingData.buffer.asByteData(_index, 2);
      _index += 2;
      return intData.getInt16(0, Endian.little);
    } else {
      if ((_bufferSize - index) < 2) {
        throw NotReadyException();
      }
      var intData = _underlyingData.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 DownloadErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_bufferSize - _index) < 8) {
        throw NotReadyException();
      }
      var intData = _underlyingData.buffer.asByteData(_index, 8);
      _index += 8;
      return intData.getInt64(0, Endian.little);
    } else {
      if ((_bufferSize - index) < 8) {
        throw NotReadyException();
      }
      var intData = _underlyingData.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 DownloadErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_bufferSize - _index) < 8) {
        throw NotReadyException();
      }
      int low = readInt();
      int high = readInt();
      int value = high >> 32;
      value |= low;
      return value;
    } else {
      if ((_bufferSize - 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 DownloadErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_bufferSize - _index) < 4) {
        throw NotReadyException();
      }
      var floatData = _underlyingData.buffer.asByteData(_index, 4);
      _index += 4;
      return floatData.getFloat32(0, Endian.little);
    } else {
      if ((_bufferSize - index) < 4) {
        throw NotReadyException();
      }
      var floatData = _underlyingData.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 DownloadErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_bufferSize - _index) < 8) {
        throw NotReadyException();
      }
      var floatData = _underlyingData.buffer.asByteData(_index, 8);
      _index += 8;
      return floatData.getFloat64(0, Endian.little);
    } else {
      if ((_bufferSize - index) < 8) {
        throw NotReadyException();
      }
      var floatData = _underlyingData.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 DownloadErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_bufferSize - _index) < 1) {
        throw NotReadyException();
      }
      var boolData = _underlyingData.buffer.asByteData(_index, 1);
      _index++;
      return boolData.getInt8(0) == 1;
    } else {
      if ((_bufferSize - index) < 1) {
        throw NotReadyException();
      }
      var boolData = _underlyingData.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 DownloadErrorException(_errorMsg);
    }
    if (index == -1) {
      if ((_bufferSize - _index) < 1) {
        throw NotReadyException();
      }
      var byteData = _underlyingData.buffer.asByteData(_index, 1);
      _index++;
      return byteData.getInt8(0);
    } else {
      if ((_bufferSize - index) < 1) {
        throw NotReadyException();
      }
      var byteData = _underlyingData.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 DownloadErrorException(_errorMsg);
    }
    var dataLength = readInt(index);
    if ((_bufferSize - _index) < dataLength) {
      throw NotReadyException();
    }
    var bytes = _underlyingData.buffer.asUint8List(_index, dataLength);
    _index += dataLength;
    return bytes;
  }
}