using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.IO;

using System.Threading;

namespace ProjectWenDangManage.Framework

{

    /// <summary>

    /// HTTP文件下载辅助类

    /// </summary>

    public class HttpDownLoadHelper

    {

        /// <summary>

        /// 文件下载

        /// </summary>

        /// <param name="_Request"></param>

        /// <param name="_Response"></param>

        /// <param name="_fileName">下载文件时的短文件名称</param>

        /// <param name="_fullPath">待下载文件的绝对路径</param>

        /// <param name="_speed">下载速度</param>

        /// <returns></returns>

        public static bool ResponseFile(HttpRequest _Request, HttpResponse _Response, string _fileName, string _fullPath, long _speed)

        {

            try

            {

                FileStream myFile = new FileStream(_fullPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);

                BinaryReader br = new BinaryReader(myFile);

                try

                {

                    _Response.AddHeader("Accept-Ranges", "bytes");

                    _Response.Buffer = false;

                    long fileLength = myFile.Length;

                    long startBytes = ;

                    double pack = ; //10K bytes

                    //int sleep = 200;   //每秒5次   即5*10K bytes每秒

                    int sleep = (int)Math.Floor( * pack / _speed) + ;

                    if (_Request.Headers["Range"] != null)

                    {

                        _Response.StatusCode = ;

                        string[] range = _Request.Headers["Range"].Split(new char[] { '=', '-' });

                        startBytes = Convert.ToInt64(range[]);

                    }

                    _Response.AddHeader("Content-Length", (fileLength - startBytes).ToString());

                    if (startBytes != )

                    {

                        //Response.AddHeader("Content-Range", string.Format(" bytes {0}-{1}/{2}", startBytes, fileLength-1, fileLength));

                    }

                    _Response.AddHeader("Connection", "Keep-Alive");

                    _Response.ContentType = "application/octet-stream";

                    _Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(_fileName, System.Text.Encoding.UTF8));

                    br.BaseStream.Seek(startBytes, SeekOrigin.Begin);

                    int maxCount = (int)Math.Floor((fileLength - startBytes) / pack) + ;

                    for (int i = ; i < maxCount; i++)

                    {

                        if (_Response.IsClientConnected)

                        {

                            _Response.BinaryWrite(br.ReadBytes(int.Parse(pack.ToString())));

                            Thread.Sleep(sleep);

                        }

                        else

                        {

                            i = maxCount;

                        }

                    }

                    return true;

                }

                catch

                {

                    return false;

                }

                finally

                {

                    br.Close();

                    myFile.Close();

                }

            }

            catch

            {

                return false;

            }

        }

    }

}