deflatefilter.cs

C#的zip的源代码

using System;
using System.IO;

using ICSharpCode.SharpZipLib.Zip.Compression;
using ICSharpCode.SharpZipLib.Zip.Compression.Streams;

namespace blowery.Web.HttpModules {
  /// <summary>
  /// Summary description for DeflateFilter.
  /// </summary>
  public class DeflateFilter : HttpCompressingFilter {

    /// <summary>
    /// compression stream member
    /// has to be a member as we can only have one instance of the
    /// actual filter class
    /// </summary>
    private DeflaterOutputStream m_stream = null;

    /// <summary>
    /// Basic constructor that uses the Normal compression level
    /// </summary>
    /// <param name="baseStream">The stream to wrap up with the deflate algorithm</param>
    public DeflateFilter(Stream baseStream) : this(baseStream, CompressionLevels.Normal) { }

    /// <summary>
    /// Full constructor that allows you to set the wrapped stream and the level of compression
    /// </summary>
    /// <param name="baseStream">The stream to wrap up with the deflate algorithm</param>
    /// <param name="compressionLevel">The level of compression to use</param>
    public DeflateFilter(Stream baseStream, CompressionLevels compressionLevel) : base(baseStream, compressionLevel) { }

    /// <summary>
    /// Write out bytes to the underlying stream after compressing them using deflate
    /// </summary>
    /// <param name="buffer">The array of bytes to write</param>
    /// <param name="offset">The offset into the supplied buffer to start</param>
    /// <param name="count">The number of bytes to write</param>
    public override void Write(byte[] buffer, int offset, int count) {
      
      if (m_stream == null) {
        Deflater deflater;
      
        switch(CompressionLevel) {
          case CompressionLevels.High:
            deflater = new Deflater(Deflater.BEST_COMPRESSION, true);
            break;
          case CompressionLevels.Low:
            deflater = new Deflater(Deflater.BEST_SPEED, true);
            break;
          case CompressionLevels.Normal:
          default:
            deflater = new Deflater(Deflater.DEFAULT_COMPRESSION, true);
            break;
        }
        m_stream = new DeflaterOutputStream(BaseStream, deflater);
      }
      m_stream.Write(buffer, offset, count);
    }

    /// <summary>
    /// Return the Http name for this encoding.  Here, deflate.
    /// </summary>
    public override string NameOfContentEncoding {
      get { return "deflate"; }
    }

    /// <summary>
    /// Closes this Filter and calls the base class implementation.
    /// </summary>
    public override void Close() {
      if (m_stream != null)
        m_stream.Finish();
      base.Close();
    }
  }
}