Question

我想知道是否有人可以解释一个让我疯狂的问题：

我正在编写一个压缩解压缩测试类。为了测试它，我将数据集序列化为内存流，压缩它，解压缩并比较结果。

压缩很好，但是压缩是打击污垢的地方。这是解压缩功能：

    public static Stream GetUncompressedStreamCopy(Stream inStream)
    {
      Stream outStream = new MemoryStream();

      inStream.Position = 0;

      DeflateStream uncompressStream = new DeflateStream(inStream, 
        CompressionMode.Decompress, true);

      byte[] buffer = new byte[65536];

      int totalread = 0;
      int bytesread = 0;


      do {
        bytesread = uncompressStream.Read(buffer, 0, buffer.Length);
        totalread += bytesread;
        outStream.Write(buffer, 0, bytesread);
        Console.WriteLine("bytesRead: [{0}]\t outStream.Length [{1}]",
        bytesread, outStream.Length);
      } while (bytesread > 0);


      Console.WriteLine("total bytes read [{0}]", totalread);
      outStream.Flush();
      return outStream;
}

对于大小为65536的缓冲区，解压缩的流总是返回比未压缩的小一个字节。

现在这让我想到了我正在与之抗争的第二个问题。对于某些缓冲区大小，uncompressStream.Read返回0，即使仍有压缩数据要提取。

对于这些情况，deflateStream.Read（s）只在do {}循环中返回一次，然后返回一个等于buffersize的未压缩流，如果你将buffersize增加一个字节，那么一切都很好（除了丢失的字节）

缓冲区大小为65536的输出:(原始未压缩数据为207833）

bytesRead: [65536]       outStream.Length [65536]
bytesRead: [65536]       outStream.Length [131072]
bytesRead: [58472]       outStream.Length [189544]
bytesRead: [18288]       outStream.Length [207832]
bytesRead: [0]           outStream.Length [207832]
total bytes read [207832]

1589544的缓冲区（代码槽中的一些神奇数字）

bytesRead: [189544]      outStream.Length [189544]
bytesRead: [0]           outStream.Length [189544]
total bytes read [189544]
Unompressed stream size 189544

另请注意第三次读取buffersize 65536 ex：bytesRead：[58472]显然这也应该是65536，因为缓冲区上还有数据？

任何想法都将非常赞赏。

TIA

雅科

Answer 1

您应该始终在压缩流上调用Close（）。请注意，Flush（）不够。我怀疑因此，deflate流缺少数据。

Answer 2

我的通灵能力告诉我，你确实有一个有效的解压缩实现，但忘记了之前刷新压缩流。

Answer 3

好吧，我无法发现您的问题，但请遵循我之前为ICSharpCode.SharpZipLib撰写的一些代码;

byte[] compressedData;
using(MemoryStream ms = new MemoryStream())
{
    Deflater deflater = new Deflater(Deflater.BEST_COMPRESSION, true);
    Stream s = new DeflaterOutputStream(ms, deflater);
    s.Write(sendData, 0, sendData.Length);
    s.Close();
    compressedData = (byte[])ms.ToArray();
}

// ...

MemoryStream inflated = new MemoryStream();
using (Stream inflater = new InflaterInputStream(
    inputStream, new Inflater(true)))
{
    int count = 0;
    byte[] deflated = new byte[4096];
    while ((count = inflater.Read(deflated, 0, deflated.Length)) != 0)
    {
        inflated.Write(deflated, 0, count);
    }
    inflated.Seek(0, SeekOrigin.Begin);
}
byte[] content = new byte[inflated.Length];
inflated.Read(content, 0, content.Length);

令人费解.Net C＃DeflateStream问题

3 个答案: