/// <summary>
/// 将若干压缩缩的字节读入指定的字节数组。
/// </summary>
/// <param name="buffer">用于存储压缩缩的字节的数组。</param>
/// <param name="offset">数组中开始读取的位置。</param>
/// <param name="count">读取的压缩缩字节数。</param>
/// <returns>压缩缩到字节数组中的字节数。</returns>
/// <remarks>
/// <para>
/// 如果需要使用 <c>DeflateStream</c> 在读取时同步解压， 可以设置解压模式到 <c>CompressionMode.Compress</c>。然后使用 Read() 方法读取并解压。
/// 如果需要使用 <c>DeflateStream</c> 在读取时同步压缩， 可以设置解压模式到 <c>CompressionMode.DeCompress</c>。然后使用 Read() 方法读取并解压。
/// </para>
/// <para>
/// 一个 <c>DeflateStream</c> 只能用于 <c>Read()</c> 或 <c>Write()</c>, 但不能同时读写。
/// </para>
/// </remarks>
/// <exception cref="ZlibException">已经执行过 Write() 。</exception>
/// <exception cref="T:System.ArgumentException">
/// <paramref name="offset"/> 与 <paramref name="count"/> 的和大于缓冲区长度。</exception>
/// <exception cref="T:System.ArgumentNullException">
/// <paramref name="buffer"/> 为 null。</exception>
/// <exception cref="T:System.ArgumentOutOfRangeException">
/// <paramref name="offset"/> 或 <paramref name="count"/> 为负。</exception>
/// <exception cref="T:System.IO.IOException">发生 I/O 错误。</exception>
/// <exception cref="T:System.NotSupportedException">流不支持读取。</exception>
/// <exception cref="T:System.ObjectDisposedException">在流关闭后调用方法。</exception>
public override int Read(byte[] buffer, int offset, int count)
{
// According to MS documentation, any implementation of the IO.Stream.Read function must:
// (a) throw an exception if offset & count reference an invalid part of the buffer,
// or if count < 0, or if buffer is null
// (b) return 0 only upon EOF, or if count = 0
// (c) if not EOF, then return at least 1 byte, up to <count> bytes
Thrower.CheckArgumentException(buffer, offset, count);
Thrower.ThrowObjectDisposedExceptionIf(IsDisposed, TypeName);
if (_streamMode == StreamMode.Undefined)
{
Thrower.ThrowNotSupportedExceptionIf(!_stream.CanRead, "流不支持读取。");
_streamMode = StreamMode.Reader;
ZlibCodec.AvailableBytesIn = 0;
}
ValidStreamMode(StreamMode.Reader);
if (count == 0)
{
return(0);
}
if (_noMore && WantCompress)
{
return(0);
}
Thrower.ThrowArgumentNullExceptionIf(buffer, "buffer");
Thrower.ThrowArgumentOutOfRangeExceptionIf(count <0 || (offset + count)> buffer.GetLength(0), "count");
Thrower.ThrowArgumentOutOfRangeExceptionIf(offset < buffer.GetLowerBound(0), "offset");
ZlibState rc;
// set up the output of the deflate/inflate codec:
_z.OutputBuffer = buffer;
_z.NextOut = offset;
_z.AvailableBytesOut = count;
// This is necessary in case _workingBuffer has been resized. (new byte[])
// (The first reference to _workingBuffer goes through the private accessor which
// may initialize it.)
_z.InputBuffer = WorkingBuffer;
do
{
// need data in _workingBuffer in order to deflate/inflate. Here, we check if we have any.
if ((_z.AvailableBytesIn == 0) && (!_noMore))
{
// No data available, so try to Read data from the captive stream.
_z.NextIn = 0;
_z.AvailableBytesIn = _stream.Read(_workingBuffer, 0, _workingBuffer.Length);
if (_z.AvailableBytesIn == 0)
{
_noMore = true;
}
}
// we have data in InputBuffer; now compress or decompress as appropriate
rc = (WantCompress)
? _z.Deflate(_flushMode)
: _z.Inflate(_flushMode);
if (_noMore && (rc == ZlibState.BufferError))
{
return(0);
}
if (rc != ZlibState.Success && rc != ZlibState.StreamEnd)
{
throw new ZlibException(Py.Core.Str.FormatX("{0}: 结果={1} 信息={2}", (WantCompress ? "压缩" : "解压"), rc, _z.Message));
}
if ((_noMore || rc == ZlibState.StreamEnd) && (_z.AvailableBytesOut == count))
{
break; // nothing more to read
}
} while (_z.AvailableBytesOut > 0 && !_noMore && rc == ZlibState.Success);
// workitem 8557
// is there more room in output?
if (_z.AvailableBytesOut > 0)
{
if (rc == ZlibState.Success && _z.AvailableBytesIn == 0)
{
// deferred
}
// are we completely done reading?
if (_noMore)
{
// and in compression?
if (WantCompress)
{
// no more input data available; therefore we flush to
// try to complete the read
rc = _z.Deflate(FlushType.Finish);
if (rc != ZlibState.Success && rc != ZlibState.StreamEnd)
{
throw new ZlibException(String.Format("压缩: 状态={0} 消息={1}", rc, _z.Message));
}
}
}
}
return(count - _z.AvailableBytesOut);
}
