using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace FengBan
{


    /// 
    /// 多執行緒下載、斷點下載的管理類
    /// 
    class DFGManager : IDisposable
    {
        private string dfgFilename;
        private int size;
        private FileStream writer;
        private SortedSet rset = new SortedSet(new RangeCompare());

        /// 
        /// 多執行緒下載、斷點下載的管理類
        /// 
        /// 
        internal DFGManager(string dfgFilename)
        {
            this.dfgFilename = dfgFilename;
            if (File.Exists(dfgFilename))
            {
                ReadDFGFile();
                File.Delete(dfgFilename);
            }

            writer = new FileStream(dfgFilename, FileMode.OpenOrCreate);
            WriteDFGFile();

        }

        /// 
        /// 獲取或設定要下載的檔案大小
        /// 
        public int Size
        {
            get { return size; }
            set
            {
                size = value;
                byte[] head = new byte[16];
                byte[] bsize = BitConverter.GetBytes(size);
                int i;
                for (i = 0; i < bsize.Count(); i++)
                {
                    head[i] = bsize[i];
                }
                writer.Seek(0, SeekOrigin.Begin);
                writer.Write(head, 0, 16);
                writer.Flush();
            }
        }

        /// 
        /// 釋放檔案段，該段已經下載完成
        /// 
        /// 
        public void Free(Range range)
        {
            lock (rset)
            {
                var find = from r in rset
                           where r.left == range.left && r.status == 1
                           select r;
                if (find.Count() == 1)
                {
                    var ele = find.First();
                    ele.status = 2;
                    range.status = 2;
                    if (ele.right < range.right)
                    {
                        ele.right = range.right;
                    }
                    else
                    {
                        range.right = ele.right;
                    }
                    MergeRange();
                    writer.Write(BitConverter.GetBytes(range.left), 0, 4);
                    writer.Write(BitConverter.GetBytes(range.right), 0, 4);
                    writer.Flush();
                }
                else if (find.Count() == 0)
                {
                    throw new Exception("找不到釋放的塊");
                }
                else
                {
                    throw new Exception("多個符合條件的塊");
                }
            }
        }

        /// 
        /// 分配檔案段
        /// 
        /// 期望分配的大小
        /// 實際分配的大小
        public Range Alloc(int expectSize = 102400)
        {
            lock (rset)
            {
                Range range = new Range();
                if (rset.Count == 0)
                {
                    range.left = 0;
                    range.right = Math.Min(expectSize, this.size);
                    range.status = 1;
                    rset.Add(range);
                }
                else if (rset.Count == 1)
                {
                    if (rset.First().left > 0)
                    {
                        range.left = 0;
                        range.right = rset.First().left;
                        range.status = 1;
                        rset.Add(range);
                    }
                    else if (rset.Last().right < size)
                    {
                        range.left = rset.Last().right;
                        range.right = Math.Min(size, range.left + expectSize);
                        range.status = 1;
                        rset.Add(range);
                    }
                    else
                    {
                        range = null;
                    }
                }
                else
                {
                    if (rset.First().left > 0)
                    {
                        range.left = 0;
                        range.right = rset.First().left;
                        range.status = 1;
                        rset.Add(range);
                    }
                    else if (rset.Last().right < size)
                    {
                        range.left = rset.Last().right;
                        range.right = Math.Min(size, range.left + expectSize);
                        range.status = 1;
                        rset.Add(range);
                    }
                    else
                    {
                        for (int i = 1; i < rset.Count; i++)
                        {
                            Range l = rset.ElementAt(i - 1);
                            Range r = rset.ElementAt(i);
                            if (l.right < r.left)
                            {
                                range.left = l.right;
                                range.right = r.left;
                                range.status = 1;
                                rset.Add(range);
                                return range;
                            }
                        }
                        range = null;
                    }
                }
                return range;
            }
            
        }

        private void ReadDFGFile()
        {

            StreamReader reader = new StreamReader(dfgFilename);
            byte[] head = new byte[16];/*head佔4個int*/
            reader.BaseStream.Read(head, 0, 16);

            size = BitConverter.ToInt32(head, 0);

            byte[] buff = new byte[8];
            int rd = 0;
            do
            {
                rd = reader.BaseStream.Read(buff, 0, 8);
                if (rd == 0)
                {
                    break;
                }

                Range range = new Range();
                range.left = BitConverter.ToInt32(buff, 0);
                range.right = BitConverter.ToInt32(buff, 4);
                range.status = 2;

                rset.Add(range);

            }
            while (true);

            reader.Close();

            MergeRange();
        }

        private void WriteDFGFile()
        {
            
            
            byte[] head = new byte[16];
            byte[] bsize = BitConverter.GetBytes(size);
            int i;
            for (i = 0; i < bsize.Count(); i++)
            {
                head[i] = bsize[i];
            }
            writer.Write(head, 0, 16);
            for (i = 0; i < rset.Count; i++)
            {
                Range r = rset.ElementAt(i);
                if (r.status == 2)
                {
                    writer.Write(BitConverter.GetBytes(r.left), 0, 4);
                    writer.Write(BitConverter.GetBytes(r.right), 0, 4);
                }
            }
            writer.Flush();
        }

        private void MergeRange()
        {
            int i;
            if (rset.Count >= 2)
            {
                Range last = rset.First();
                for (i = 1; i < rset.Count && rset.Count >= 2; i++)
                {
                    Range cur = rset.ElementAt(i);
                    if (cur.left <= last.right && cur.status == 2 && last.status == 2)
                    {
                        last.right = cur.right;
                        rset.Remove(cur);
                        i--;
                    }
                    else
                    {
                        last = cur;
                    }
                }
            }

        }

        /// 
        /// 釋放資源
        /// 
        public void Dispose()
        {
            if (writer != null)
            {
                writer.Close();
                writer = null;
            }
        }

        ~DFGManager()
        {
            Dispose();
        }

    }

    class Range
    {
        public int left;
        public int right;
        public int status;
    }

    class RangeCompare : IComparer
    {

        public int Compare(Range x, Range y)
        {
            return (x.left - y.left);
        }
    }

}
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Text.RegularExpressions;

namespace FengBan
{
    class Program
    {
        static void Main()
        {
            MultiThreadDownload downloader = new MultiThreadDownload();
            
            downloader.Download("http://dlsw.baidu.com/sw-search-sp/soft/3a/12350/QQ_V7.0.14275.0_setup.1426647314.exe", "qq.exe");
        }
    }

    /// 
    /// 多執行緒下載類
    /// 
    class MultiThreadDownload
    {
        /*dfg檔案記錄下載好的檔案段*/
        private const string suffix = ".dfg";

        private string site;/*檔案下載地址*/
        private string outname;/*下載的檔名稱*/

        private DFGManager dfgManager;/*檔案分段下載管理物件*/
        private FileStream writer;/*多個下載子執行緒共用一個輸出流*/

        /*通過currentDownload和lastDownload來實現限速*/
        private int currentDownload;
        private int lastDownload;
        private int shouldSleep;/*限速時應該休眠的時長，單位毫秒*/
        private System.Timers.Timer timer;/*限速計時器*/

        /*上網代理*/
        public string ProxyAddressAndPort { get; set; }
        public string ProxyUserName { get; set; }
        public string ProxyPassword { get; set; }

        public MultiThreadDownload(int ThreadCount = 5)
        {
            this.ThreadCount = ThreadCount;

            timer = new System.Timers.Timer(1000);
            timer.Elapsed += CheckDownloadSpeed;
            timer.AutoReset = true;
        }

        /// 
        /// 下載檔案的函式，僅支援http協議下載
        /// 
        /// 檔案下載地址
        /// 輸出檔名
        public void Download(string site, string outname)
        {
            string realname = outname;
            outname += ".down";
            this.site = site;
            this.outname = outname;

            try
            {
                /*根據需要設定代理*/
                if (ProxyEnable)
                {
                    ICredentials cred = new NetworkCredential(ProxyUserName, ProxyPassword);
                    WebProxy p = new WebProxy(ProxyAddressAndPort, true, null, cred);
                    WebRequest.DefaultWebProxy = p;
                }

                /*獲取要下載的檔案的資訊,主要是獲取檔案大小*/
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(site);
                request.UserAgent = "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.101 Safari/537.36";

                WebResponse response = request.GetResponse();
                Stream responseStream = response.GetResponseStream();
                long contentLength = response.ContentLength;
                Console.WriteLine("要下載的檔案大小:{0}", contentLength);

                responseStream.Close();
                response.Close();

                /*建立管理物件，負責給每一個執行緒分配下載的檔案段*/
                dfgManager = new DFGManager(outname + suffix);
                dfgManager.Size = Convert.ToInt32(contentLength);

                currentDownload = 0;
                lastDownload = 0;
                writer = new FileStream(outname, FileMode.OpenOrCreate);
                ManualResetEvent[] _ManualEvents = new ManualResetEvent[ThreadCount];
                //開啟執行緒池下載
                for (int i = 0; i < ThreadCount; i++)
                {
                    _ManualEvents[i] = new ManualResetEvent(false);
                    ThreadPool.QueueUserWorkItem(new WaitCallback(SDown), _ManualEvents[i]);
                }
                WaitHandle.WaitAll(_ManualEvents);/*等待子執行緒下載結束*/
                Console.WriteLine("全部下載子執行緒結束");

                //下載完成，釋放資源
                writer.Close();
                dfgManager.Dispose();

                /*收尾*/
                if (File.Exists(realname))
                {
                    File.Delete(realname);
                }
                File.Move(outname, realname);
                File.Delete(outname + suffix);
            }
            finally
            {
                
            }
        }



        private void CheckDownloadSpeed(object sender, System.Timers.ElapsedEventArgs e)
        {
            int curSpeed = (currentDownload - lastDownload);
            Console.WriteLine("當前速度 {0:f} kb/s", ((double)curSpeed) / 1000);
            lastDownload = currentDownload;
            
            //如果當前速度超過設定的速度，則應該執行限速動作
            
            //未實現
        }

        /// 
        /// 設定代理
        /// 
        /// 代理伺服器地址和埠
        /// 代理伺服器使用者名稱
        /// 代理伺服器密碼
        public void SetProxy(string ProxyAddressAndPort, string Username, string Password)
        {
            this.ProxyAddressAndPort = ProxyAddressAndPort;
            this.ProxyUserName = Username;
            this.ProxyPassword = Password;
            this.ProxyEnable = true;
        }
        
        /*是否使用代理*/
        public bool ProxyEnable
        {
            get;
            set;
        }

        /// 
        /// 設定或獲取多執行緒下載的數量
        /// 
        public int ThreadCount
        {
            set;
            get;
        }

        /*多執行緒下載的執行緒函式*/
        private void SDown(object param)
        {

            Range range;
            byte[] buff = null;

            /*從dfgManager中獲取要下載的檔案段*/
            while ((range = dfgManager.Alloc()) != null)
            {
               
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(site);
                request.AddRange(range.left, range.right);
                request.UserAgent = "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.101 Safari/537.36";

                WebResponse response = request.GetResponse();
                int contentLength = (int)response.ContentLength;

                //分配下載的快取空間
                if (buff == null || buff.Count() < contentLength)
                {
                    buff = new byte[contentLength];
                }

                //使用while迴圈讀取全部位元組到buff中
                int count = 0;
                while (count < contentLength)
                {
                    count += response.GetResponseStream().Read(buff, count, (int)contentLength - count);
                }

                //真正從伺服器下載下來的檔案段
                Range realRange = new Range();
                realRange.left = range.left;
                realRange.right = Math.Min(range.left + count, range.right);
                dfgManager.Free(realRange);

                response.Close();

                //將buff寫入檔案           
                writer.Seek(realRange.left, SeekOrigin.Begin);
                writer.Write(buff, 0, realRange.right - realRange.left);
                writer.Flush();

                int realDown = realRange.right - realRange.left;
                currentDownload += realDown;
                Console.WriteLine("本次分段下載大小{0}", realDown);

                if (LimitSpeed > 0 && shouldSleep > 10)
                {
                    Console.WriteLine("休眠{0}", shouldSleep);
                    Thread.Sleep(shouldSleep);
                }
            }

            Console.WriteLine("執行緒執行結束");
            /*通知主執行緒執行完成*/
            ManualResetEvent e = (ManualResetEvent)param;
            e.Set();
        }

        private int xiansu;
        /// 
        /// 表示是否限速,0表示不限速,單位 b/s
        /// 
        public int LimitSpeed 
        {
            get 
            {
                return xiansu;
            }
            set
            {
                xiansu = value;
                if (value > 0)
                {
                    timer.Enabled = true;
                }
            }
        }
    }
}