如何使用 7z SDK 压缩和解压文件 [英] How to use the 7z SDK to compress and decompress a file

问题描述

根据此链接 如何创建 7-Zip使用 .NET 存档?，WOPR 告诉我们如何使用 7z SDK(http://www.7-zip.org/sdk.html )

According to this link How do I create 7-Zip archives with .NET? , WOPR tell us how to compress a file with LMZA (7z compression algorithm) using 7z SDK ( http://www.7-zip.org/sdk.html )

using SevenZip.Compression.LZMA;
private static void CompressFileLZMA(string inFile, string outFile)
{
   SevenZip.Compression.LZMA.Encoder coder = new SevenZip.Compression.LZMA.Encoder();

   using (FileStream input = new FileStream(inFile, FileMode.Open))
   {
      using (FileStream output = new FileStream(outFile, FileMode.Create))
      {
          coder.Code(input, output, -1, -1, null);
          output.Flush();
      }
   }
}

但是如何解压呢?

我试试:

private static void DecompressFileLZMA(string inFile, string outFile)
        {
            SevenZip.Compression.LZMA.Decoder coder = new SevenZip.Compression.LZMA.Decoder();
            using (FileStream input = new FileStream(inFile, FileMode.Open))
            {
                using (FileStream output = new FileStream(outFile, FileMode.Create))
                {
                    coder.Code(input, output, input.Length, -1, null);
                    output.Flush();
                }
            }
        }

但没有成功.

你有一个可行的例子吗?

Do you have a working example?

谢谢

附注:根据其他代码 http://www.koders.com/csharp/fid43E85EE5AE7BB255C69D18ECC3288285AD67A4A4.aspx?s=zip+encoder#L5 ，看来解码器需要一个header，文件开头的字典才能工作.Koders 生成的这个文件不是 7z 存档.

PS: According to an other code http://www.koders.com/csharp/fid43E85EE5AE7BB255C69D18ECC3288285AD67A4A4.aspx?s=zip+encoder#L5 , it seems that the decoder needs a header, a dictionary at the beginning of the file to work. This file generated by Koders is not a 7z archive.

   public static void Decompress(Stream inStream, Stream outStream)
    {
        byte[] properties = new byte[5];
        inStream.Read(properties, 0, 5);
        SevenZip.Compression.LZMA.Decoder decoder = new SevenZip.Compression.LZMA.Decoder();
        decoder.SetDecoderProperties(properties);
        long outSize = 0;
        for (int i = 0; i < 8; i++)
        {
            int v = inStream.ReadByte();
            outSize |= ((long)(byte)v) << (8 * i);
        }
        long compressedSize = inStream.Length - inStream.Position;
        decoder.Code(inStream, outStream, compressedSize, outSize, null);
    }

outSize 的计算方式与其 Compress 方法相同.但否则如何计算输出大小?

The outSize is computed the same way than their Compress method. But how to compute the output size otherwise?

推荐答案

这个问题有点老了，但谷歌未能提供令人满意的答案，所以这适合像我这样仍在寻找它的人.如果您查看 SDK 的 LMZAAlone 文件夹，就会有压缩和解压缩文件的代码.以它为例，您似乎需要编写和读取编码器属性并将文件大小解压缩到输出文件中:

This question is a little old, but google fails to provide a satisfactory answer so this is for those like me still seeking it out. If you look into the LMZAAlone folder of the SDK there is code that compresses and decompresses files. Using it as an example it would seem you need to write and read the encoder properties and decompresses file size to your output file:

private static void CompressFileLZMA(string inFile, string outFile)
    {
        SevenZip.Compression.LZMA.Encoder coder = new SevenZip.Compression.LZMA.Encoder();
        FileStream input = new FileStream(inFile, FileMode.Open);
        FileStream output = new FileStream(outFile, FileMode.Create);

        // Write the encoder properties
        coder.WriteCoderProperties(output);

        // Write the decompressed file size.
        output.Write(BitConverter.GetBytes(input.Length), 0, 8);

        // Encode the file.
        coder.Code(input, output, input.Length, -1, null);
        output.Flush();
        output.Close();
    }

    private static void DecompressFileLZMA(string inFile, string outFile)
    {
        SevenZip.Compression.LZMA.Decoder coder = new SevenZip.Compression.LZMA.Decoder();
        FileStream input = new FileStream(inFile, FileMode.Open);
        FileStream output = new FileStream(outFile, FileMode.Create);

        // Read the decoder properties
        byte[] properties = new byte[5];
        input.Read(properties, 0, 5);

        // Read in the decompress file size.
        byte [] fileLengthBytes = new byte[8];
        input.Read(fileLengthBytes, 0, 8);
        long fileLength = BitConverter.ToInt64(fileLengthBytes, 0);

        coder.SetDecoderProperties(properties);
        coder.Code(input, output, input.Length, fileLength, null);
        output.Flush();
        output.Close();
    }

请注意，以这种方式创建的文件也可以由 7zip 程序提取，但不会保留其文件名或任何其他元数据.

Note that the files created this way can be extracted by the 7zip program as well but will not retain their filename or any other metadata.

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