Question

I downloaded the SDK 7zip from here.

Then I used this code to compress a file to 7zip:

private static void CompressFileLZMA(string inFile, string outFile)
{
    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();
    }
}

I tried both the SDK versions 9.20 and 9.22 beta on the site.

The compression seems working to compress my file from: 1.6 MB to 239 KB.

However, if I use WinRar or 7zip to decompress. the archive file is not recognized by them, the error is like

“unknown archive file or damaged file”

Any idea for this?

Answer 1

You can try to use 7zSharp wrapper or at least analyze wrappers code how everything is done.

Code to compress file(taken from 7zSharp):

  public void EncodeSingleFile(string inFile, string outFile)
  {
     using (FileStream inStream = new FileStream(inFile, FileMode.Open, FileAccess.Read))
     {
        using (FileStream outStream = new FileStream(outFile, FileMode.OpenOrCreate, FileAccess.Write))
        {
           EncodeSingleFile(inStream, outStream);
        }
     }
  }

  public void EncodeSingleFile(FileStream inStream, FileStream outStream)
  {
     bool eos = false;
     Int32 dictionary = 1 << 21;
     Int32 posStateBits = 2;
     Int32 litContextBits = 3; // for normal files
     // UInt32 litContextBits = 0; // for 32-bit data
     Int32 litPosBits = 0;
     // UInt32 litPosBits = 2; // for 32-bit data
     Int32 algorithm = 2;
     Int32 numFastBytes = 128;
     string mf = "bt4";

     propIDs = new CoderPropID[]
        {
           CoderPropID.DictionarySize,
           CoderPropID.PosStateBits,
           CoderPropID.LitContextBits,
           CoderPropID.LitPosBits,
           CoderPropID.Algorithm,
           CoderPropID.NumFastBytes,
           CoderPropID.MatchFinder,
           CoderPropID.EndMarker
        };
     properties = new object[]
        {
           dictionary,
           posStateBits,
           litContextBits,
           litPosBits,
           algorithm,
           numFastBytes,
           mf,
           eos
        };

     Encoder encoder = new Encoder();
     encoder.SetCoderProperties(propIDs, properties);
     encoder.WriteCoderProperties(outStream);
     Int64 fileSize = inStream.Length;
     for (int i = 0; i < 8; i++)
     {
        outStream.WriteByte((Byte) (fileSize >> (8*i)));
     }
     encoder.Code(inStream, outStream, -1, -1, null);
  }