不支持写入压缩流.使用System.IO.GZipStream

Question

尝试使用.NET框架中包含的GZipStream类解压缩(.gz)文件时出现异常.我正在使用MSDN文档.这是例外:

不支持写入压缩流.

这是应用程序源:

 try
 {
     var infile = new FileStream(@"C:\TarDecomp\TarDecomp\TarDecomp\bin\Debug\nick_blah-2008.tar.gz", FileMode.Open, FileAccess.Read, FileShare.Read);
     byte[] buffer = new byte[infile.Length];
     // Read the file to ensure it is readable.
     int count = infile.Read(buffer, 0, buffer.Length);
     if (count != buffer.Length)
     {
         infile.Close();
         Console.WriteLine("Test Failed: Unable to read data from file");
         return;
     }
     infile.Close();
     MemoryStream ms = new MemoryStream();
     // Use the newly created memory stream for the compressed data.
     GZipStream compressedzipStream = new GZipStream(ms, CompressionMode.Decompress, true);
     Console.WriteLine("Decompression");
     compressedzipStream.Write(buffer, 0, buffer.Length); //<<Throws error here
     // Close the stream.
     compressedzipStream.Close();
     Console.WriteLine("Original size: {0}, Compressed size: {1}", buffer.Length, ms.Length);
} catch {...}

在compressedZipStream.write()中抛出异常.

有任何想法吗？什么是这个例外告诉我的？

Answer 1

它告诉你应该打电话Read而不是Write因为它是减压!内存流也应该用数据构造,或者你应该直接将文件流传递给GZipStream构造函数.

它应该如何完成的示例(尚未尝试编译):

Stream inFile = new FileStream(@"C:\TarDecomp\TarDecomp\TarDecomp\bin\Debug\nick_blah-2008.tar.gz", FileMode.Open, FileAccess.Read, FileShare.Read);
Stream decodedStream = new MemoryStream();
byte[] buffer = new byte[4096];

using (Stream inGzipStream = new GZipStream(inFile, CompressionMode.Decompress))
{
    int bytesRead;
    while ((bytesRead = inGzipStream.Read(buffer, 0, buffer.Length)) > 0)
        decodedStream.Write(buffer, 0, bytesRead);
}

// Now decodedStream contains the decoded data

Answer 2

压缩代码不像加密一样工作 - 您无法通过写入压缩数据从一个流解压缩到另一个流.您必须提供一个包含压缩数据的流,然后GZipStream从中读取.像这样的东西:

using (Stream file = File.OpenRead(filename))
using (Stream gzip = new GZipStream(file, CompressionMode.Decompress))
using (Stream memoryStream = new MemoryStream())
{
   CopyStream(gzip, memoryStream);
   return memoryStream.ToArray();
}

CopyStream是一种简单的实用方法,用于从一个流中读取并将所有数据复制到另一个流.像这样的东西:

static void CopyStream(Stream input, Stream output)
{
    byte[] buffer = new byte[8192];
    int bytesRead;
    while ((bytesRead = input.Read(buffer, 0, buffer.Length)) > 0)
    {
        output.Write(buffer, 0, bytesRead);
    }
}