一个基于socket的资源共享平台的实现（二）

继续上次说的，其实任务调度宏观上普遍分为两种，实现上总的来说就是一个串行、一个并行，上次我们介绍的TCP传送服务我们是使用并行的实现的（任务池），这次我们再来一个串行的，这就简单多了，就是一个队列，FIFO，我们用它来实现下载任务（假设我们下载任务只能单独进行）。

我们用一个NS_Download_Pool类来封装对其的管理。

#ifndef NETSHARE_DOWNLOAD_POOL_H_ #define NETSHARE_DOWNLOAD_POOL_H_ #include "StdioFileEx/StdioFileEx.h" #include "NetShareIndexManager.h" #include "DownloadListDlg.h" #include <string> #include <vector> #include <algorithm> #include "cpplibbase.h" using namespace std; CString const DOWNLOAD_FILELIST_FILENAME("c://download_filelistfile"); //文件状态 enum FileStatus { Ready = 0, //未下载 Downloading, //下载中 Failed, //下载失败 Success, //完成 Paused //暂停 }; //下载文件信息类 struct DownloadFileInfoType { DownloadFileInfoType() : filename(_T("")) , size(_T("")) , ipaddr(_T("")) , status( Ready ) , percent( 0 ) , finish_size( 0 ) {} bool operator==( DownloadFileInfoType& opt ) { return ( filename == opt.filename && size == opt.size && ipaddr == opt.ipaddr && targetdir == opt.targetdir ); } CString filename;//文件名 CString size;//大小 CString ipaddr;//源IP CString targetdir;//保存地址 FileStatus status;//文件状态 double percent;//下载完成百分比 DWORD finish_size;//完成的字节数 }; namespace { bool IsComplete( DownloadFileInfoType const& unit ) { return ( unit.status == Success ); } } //下载池类 class NS_Download_Pool { public: NS_Download_Pool() : m_pDlg( NULL ) , m_pList( NULL ) { Load(); } ~NS_Download_Pool(){ Save(); } //增加 void Add( DownloadFileInfoType info ) { cpplib::resource::MutexLock MyMutex(FileListMutex); if( Exist( info ) ) return; else files_.push_back( info ); } void Save() { CStdioFileEx fp; fp.Open(DOWNLOAD_FILELIST_FILENAME,CFile::modeWrite|CFile::modeCreate); //|CFile::modeCreate for( size_t i=0;i<files_.size();++i) { DownloadFileInfoType& opt = files_[i]; fp.WriteString( opt.filename ); fp.WriteString(_T("/n")); fp.WriteString( opt.size ); fp.WriteString(_T("/n")); fp.WriteString( opt.ipaddr ); fp.WriteString(_T("/n")); fp.WriteString( opt.targetdir ); fp.WriteString(_T("/n")); CString write(""); write.Format(_T("%d"),opt.status); fp.WriteString( write ); fp.WriteString(_T("/n")); write.Format(_T("%.2lf"),opt.percent); fp.WriteString( write ); fp.WriteString(_T("/n")); write.Format(_T("%d"),opt.finish_size); fp.WriteString( write ); fp.WriteString(_T("/n")); } fp.Close(); } void Load() { CStdioFileEx fp; if(fp.Open(DOWNLOAD_FILELIST_FILENAME,CFile::modeRead)) { CString test; while( NULL!= fp.ReadString( test ) ) { if( test == "" ) break; DownloadFileInfoType tmp; tmp.filename = test; fp.ReadString( tmp.size ); fp.ReadString( tmp.ipaddr ); fp.ReadString( tmp.targetdir ); fp.ReadString( test ); char* p = NetShareIndexManager::UnicodeToAnsi(test.GetBuffer(0)); tmp.status = (FileStatus)(atoi( p )); delete p; fp.ReadString( test ); p = NetShareIndexManager::UnicodeToAnsi(test.GetBuffer(0)); tmp.percent = atof( p ); delete p; fp.ReadString( test ); p = NetShareIndexManager::UnicodeToAnsi(test.GetBuffer(0)); tmp.finish_size = atoi( p ); delete p; Add( tmp ); } fp.Close(); } else { Clear(); } } //删除 void Remove( DownloadFileInfoType& info ) { cpplib::resource::MutexLock MyMutex(FileListMutex); vector<DownloadFileInfoType>::iterator iter; for( iter = files_.begin(); iter != files_.end(); ++iter ) { if( *iter == info ) { files_.erase( iter ); return; } } Save(); } //删除容器src内指定序号的元素 template<class T> void Remove( vector<T>& src, vector<size_t> const& indexs ) { vector<T> result; int count = 0; for( vector<T>::iterator iter = src.begin(); iter != src.end(); ++iter ) { if( find( indexs.begin(), indexs.end(), count ) == indexs.end() ) { result.push_back( *iter ); } count++; } src = result; } //根据索引删除 void Remove( vector<size_t> delete_indexs ) { cpplib::resource::MutexLock MyMutex(FileListMutex); Remove( files_, delete_indexs ); Save(); } //移除所有已完成的下载 void RemoveAllCompleted() { cpplib::resource::MutexLock MyMutex(FileListMutex); files_.erase( remove_if( files_.begin(), files_.end(), IsComplete ), files_.end() ); Save(); Show(); } //清空 void Clear() { cpplib::resource::MutexLock MyMutex(FileListMutex); files_.clear(); } //弹出第一个元素 DownloadFileInfoType Pop() { for( vector<DownloadFileInfoType>::iterator iter = files_.begin(); iter != files_.end(); ++iter ) { //找未下的文件 if( iter->status == Ready ) { DownloadFileInfoType tmp = *iter; iter->status = Downloading; curr_iter_ = iter; return tmp; } } assert( TRUE );//不可能发生 DownloadFileInfoType tmp; return tmp; } //下载成功 void DownloadSuccess() { cpplib::resource::MutexLock MyMutex(FileListMutex); curr_iter_->status = Success; Save(); } //下载失败 void DownloadFailed( DWORD CompleteSize ) { cpplib::resource::MutexLock MyMutex(FileListMutex); curr_iter_->status = Failed; curr_iter_->finish_size = CompleteSize; Save(); } //设置当前下载已完成字节数 void CurrFinish( DWORD size ) { cpplib::resource::MutexLock MyMutex(FileListMutex); curr_iter_->finish_size = size; } //检测是否为空 bool Empty() { for( vector<DownloadFileInfoType>::iterator iter = files_.begin(); iter != files_.end(); ++iter ) { //找未下的文件 if( iter->status == Ready ) { return FALSE; } } return TRUE; } //检测是否存在 bool Exist( DownloadFileInfoType info ) { vector<DownloadFileInfoType>::iterator iter; for( iter = files_.begin(); iter != files_.end(); ++iter ) { if( *iter == info ) { return true; } } return false; } void SetDlgPtr( DownloadListDlg* p_dlg, CListCtrl* pList ) { m_pDlg = p_dlg; m_pList = pList; } //重置下载 void SetReady( vector<size_t> select_indexs ) { cpplib::resource::MutexLock MyMutex(FileListMutex); //若用户没有点选具体文件 if( select_indexs.size() == 0 ) { for( size_t i = 0; i < files_.size(); ++i ) if( files_[ i ].status != Success && files_[ i ].status != Downloading ) files_[ i ].status = Ready; return; } //对具体文件操作 for( size_t i = 0; i < select_indexs.size(); ++i ) { if( files_[ select_indexs[i]].status != Success && files_[ select_indexs[i]].status != Downloading ) files_[ select_indexs[i]].status = Ready; } } //停止 void StopAll() { cpplib::resource::MutexLock MyMutex(FileListMutex); for( vector<DownloadFileInfoType>::iterator iter = files_.begin(); iter != files_.end(); ++iter ) { //找未下的文件 if( iter->status != Success ) { iter->status = Paused; } } } //显示 void Show() { cpplib::resource::MutexLock MyMutex(FileListMutex); try { if( !m_pDlg || !m_pList ) return; /*if( ::IsWindowVisible( *m_pDlg ) == FALSE ) return;*/ int theItemCount = m_pList->GetItemCount(); vector<size_t> select_indexs; for( int i=0; i < theItemCount; i++ ) { if( m_pList->GetItemState(i, LVIS_SELECTED) == LVIS_SELECTED ) { select_indexs.push_back(i); } } UINT ListIndex = 0; wchar_t* pTmp; m_pList->DeleteAllItems(); vector<DownloadFileInfoType>::iterator iter; for( iter = files_.begin(); iter != files_.end(); ++iter ) { DownloadFileInfoType const& MyUnit = *iter; m_pList->InsertItem(ListIndex,MyUnit.filename);//文件名 m_pList->SetItemText(ListIndex,1,MyUnit.size);//文件大小 m_pList->SetItemText(ListIndex,2,MyUnit.ipaddr);//IP地址 m_pList->SetItemText(ListIndex,3,MyUnit.targetdir);//保存路径 CString status(""); switch( MyUnit.status ) { case Ready: status = "待下载"; break; case Downloading: status = "下载中"; break; case Failed: status = "停止"; break; case Success: status = "已完成"; break; case Paused: status = "暂停"; break; default: status = "格式错误"; break; } m_pList->SetItemText(ListIndex,4,status);//状态 if( Success == MyUnit.status ) { m_pList->SetItemText(ListIndex,5,CString("100.00"));//百分比 } else { CString process( "" ); CString tmp = MyUnit.size; char* p = NetShareIndexManager::UnicodeToAnsi( tmp ); double size = atof( p ); delete p; double percent = 0; if( size < 0.01 ) percent = 0; else percent = (double)MyUnit.finish_size * 100 / (double)(size * 1024 * 1024 ); process.Format(_T("%.2lf%%"),percent ); m_pList->SetItemText(ListIndex,5,process);//百分比 } ListIndex++; } for( size_t i=0; i < select_indexs.size(); i++ ) { m_pList->SetItemState(select_indexs[i], LVIS_SELECTED,LVIS_SELECTED ); } m_pDlg->UpdateData( FALSE ); }//try catch(...) {} } private: vector<DownloadFileInfoType> files_; vector<DownloadFileInfoType>::iterator curr_iter_; //当前下载的文件结构迭代器 cpplib::resource::Mutex FileListMutex; DownloadListDlg* m_pDlg; CListCtrl* m_pList; }; #endif

接下来我们针对资源传送过程中限速进行分析和实现。

如果需要将发送速度限制在一个值，我们可以这么理解，单位时间内最多允许发送数据为N，若超过之，就需要降低速度，若不足，则需要提高速度。

如何控制速度？这里我们采用最朴素的方法，sleep，只要将sleep的具体值控制好，我们是可以控制速度的。

1. 若超过限制的速度，则增加sleep的时间；

2. 若不足限制的速度，则减少sleep的时间；

那么sleep的变化值怎么考虑？我们希望速度变化越快趋近于预期值越好，这里我们采用 计算机网络里提到的网络带宽探测的模型。

假设刚开始速度为0，采用一个指数型计算公式提升速度，当发现有一点超速了，退回到上一个状态，采用直线逼近。

横坐标t为时间轴，纵坐标s为速度，1为起始位置，速度为0，2点之后探测到速度超过限制，退回到2点，然后采用直线逼近，直到逼近速度极限。

细心的用户能发现，使用迅雷等下载软件时，也是呈现类似于这种的现象，先速度猛增，然后在到一个值之后，回退一点，开始线性缓慢增长，直到问题。

未完待续……