7zip compress network stream

问题:

I will like to compress a file before sending it through the network. I think the best approach is 7zip because it is free and open source.

How I use 7zip with .net?

I know that 7zip is free and that they have the source code in c# but for some reason it is very slow on c# so I rather call the dll 7z.dll that comes when installing 7zip for performance reasons. So the way I am able to eassily marshal and call the methods in 7z.dll is with the help of the library called sevenzipsharp . For example adding that dll to my project will enable me to do:

        // if you installed 7zip 64bit version then make sure you change plataform target
        // like on the picture I showed above!
        SevenZip.SevenZipCompressor.SetLibraryPath(@"C:\Program Files\7-Zip\7z.dll");

        var stream = System.IO.File.OpenRead(@"SomeFileToCompress.txt");
        var outputStream = System.IO.File.Create("Output.7z");

        SevenZip.SevenZipCompressor compressor = new SevenZip.SevenZipCompressor();
        compressor.CompressionMethod = SevenZip.CompressionMethod.Lzma2;
        compressor.CompressionLevel = SevenZip.CompressionLevel.Ultra;
        compressor.CompressStream(stream, outputStream);

that's how I use 7zip within c#.

Now my question is:

I will like to send a compressed file over the network. I know I could compress it first then send it. The file is 4GB so I will have to wait a long time for it to compress. I will be wasting a lot of space on hard drive. then I will finally be able to send it. I think that is to complicated. I was wondering how it will be possible to send the file meanwhile it is being compressed.

---

It seems to be a problem with SevenZipSharp:

回答1:

Have you considered an alternate library - one that doesn't even require 7-Zip to be installed / available?

From the description posted at http://dotnetzip.codeplex.com/ :

creating zip files from stream content, saving to a stream, extracting to a stream, reading from a stream

Unlike 7-Zip, DotNetZip is designed to work with C# / .Net.

Plenty of examples - including streaming, are available at http://dotnetzip.codeplex.com/wikipage?title=CS-Examples&referringTitle=Examples .

Another option is to use the 7-Zip Command Line Version (7z.exe), and write to/read from standard in/out. This would allow you to use the 7-Zip file format, while also keeping all of the core work in native code (though there likely won't be much of a significant difference).

Looking back at SevenZipSharp:

Since the 0.29 release, streaming is supported.

Looking at http://sevenzipsharp.codeplex.com/SourceControl/changeset/view/59007#364711 :

it seems you'd want this method:

public void CompressStream(Stream inStream, Stream outStream)

Thank you for considering performance here! I think way too many people would do exactly what you're trying to avoid: compress to a temp file, then do something with the temp file.

回答2:

CompressStream threw an exception. My code is as follows:

    public void TestCompress()
    {
        string fileToCompress = @"C:\Users\gary\Downloads\BD01.DAT";
        byte[] inputBytes = File.ReadAllBytes(fileToCompress);
        var inputStream = new MemoryStream(inputBytes);

        byte[] zipBytes = new byte[38000000];   // this memory size is large enough.
        MemoryStream outStream = new MemoryStream(zipBytes);

        string compressorEnginePath = @"C:\Engine\7z.dll";
        SevenZipCompressor.SetLibraryPath(compressorEnginePath);

        compressor = new SevenZip.SevenZipCompressor();
        compressor.CompressionLevel = CompressionLevel.Fast;
        compressor.CompressionMethod = CompressionMethod.Lzma2;
        compressor.CompressStream(inputStream, outputStream);

        inputStream.Close();
        outputStream.Close();

The exception messages: Message: Test method Test7zip.UnitTest1.TestCompress threw exception: SevenZip.SevenZipException: The execution has failed due to the bug in the SevenZipSharp. Please report about it to http://sevenzipsharp.codeplex.com/WorkItem/List.aspx, post the release number and attach the archive