using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;
using System.IO.Compression;
/// <summary>
/// GzipDeflate 的摘要说明
/// </summary>
public class GzipDeflate:IHttpModule
{
  public GzipDeflate()
  {
    //
    // TODO: 在此处添加构造函数逻辑
    //
  }
  public void Init(HttpApplication app)
  {
    app.BeginRequest += new EventHandler(app_BeginRequest);
  }
  void app_BeginRequest(object sender, EventArgs e)
  {
    //HTTP头域可分为四类：通用头、请求头、响应头、实体头。
    HttpApplication app=(HttpApplication)sender;
    string acceptEncoding = app.Request.Headers["Accept-Encoding"];
    //客户端支持的解码方式。属于请求头。
    Stream requestStream = app.Response.Filter;
    acceptEncoding = acceptEncoding.ToLower();
    if(acceptEncoding.Contains("gzip"))
    {
      app.Response.Filter = new GZipStream(requestStream, CompressionMode.Compress);
      app.Response.AppendHeader("Content-Encoding", "gzip");
    }
    else if(acceptEncoding.Contains("deflate"))
    {
      app.Response.Filter = new DeflateStream(requestStream, CompressionMode.Compress);
      app.Response.AppendHeader("Content-Encoding", "deflate");
      //属于实体头。
    }
  }
  public void Dispose()
  {
  }
}