Uint8List _decode()

in lib/src/chunked_coding/decoder.dart [75:147]
60 lines of code
15 McCabe index (conditional complexity)

  Uint8List _decode(List<int> bytes, int start, int end) {
    /// Throws a [FormatException] if `bytes[start] != $char`. Uses [name] to
    /// describe the character in the exception text.
    void assertCurrentChar(int char, String name) {
      if (bytes[start] != char) {
        throw FormatException('Expected $name.', bytes, start);
      }
    }

    final buffer = Uint8Buffer();
    while (start != end) {
      switch (_state) {
        case _State.boundary:
          _size = _digitForByte(bytes, start);
          _state = _State.size;
          start++;
          break;

        case _State.size:
          if (bytes[start] == $cr) {
            _state = _State.sizeBeforeLF;
          } else {
            // Shift four bits left since a single hex digit contains four bits
            // of information.
            _size = (_size << 4) + _digitForByte(bytes, start);
          }
          start++;
          break;

        case _State.sizeBeforeLF:
          assertCurrentChar($lf, 'LF');
          _state = _size == 0 ? _State.endBeforeCR : _State.body;
          start++;
          break;

        case _State.body:
          final chunkEnd = math.min(end, start + _size);
          buffer.addAll(bytes, start, chunkEnd);
          _size -= chunkEnd - start;
          start = chunkEnd;
          if (_size == 0) _state = _State.bodyBeforeCR;
          break;

        case _State.bodyBeforeCR:
          assertCurrentChar($cr, 'CR');
          _state = _State.bodyBeforeLF;
          start++;
          break;

        case _State.bodyBeforeLF:
          assertCurrentChar($lf, 'LF');
          _state = _State.boundary;
          start++;
          break;

        case _State.endBeforeCR:
          assertCurrentChar($cr, 'CR');
          _state = _State.endBeforeLF;
          start++;
          break;

        case _State.endBeforeLF:
          assertCurrentChar($lf, 'LF');
          _state = _State.end;
          start++;
          break;

        case _State.end:
          throw FormatException('Expected no more data.', bytes, start);
      }
    }
    return buffer.buffer.asUint8List(0, buffer.length);
  }