利用curl下载文件(进度条显示)

在项目中需要用到程序更新的功能,同事介绍说是curl中的开发库很不错,于是下载这个包测试了一下，确实不错。准备正式用到项目中，以下一个例子用于从互联网上抓取一个文件下载到本地，并加上进度条显示，做得挺简陋，不过功能差不多就这样了。 程序运行预览.   首先需要加入多线程的，因为程序一边在下载文件，一边在显示进度条，单线程的方式肯定不行，所以我用到了wxTimer来实现,在downloadMain.h 中定义了一个wxTimer，并做了事件申明. DECLARE_EVENT_TABLE()     /*************************************************************** * Name:            downloadMain.h * Purpose:     Defines Application Frame * Author:         () * Created:     2008-11-14 * Copyright:    () * License: **************************************************************/ #ifndef DOWNLOADMAIN_H #define DOWNLOADMAIN_H #include "downloadApp.h" #include #include "GUIDialog.h" class downloadDialog: public GUIDialog {         public:                 downloadDialog(wxDialog *dlg);                 ~downloadDialog();                 void .Timer(wxTimerEvent& event);         private:                 virtual void .Close(wxCloseEvent& event);                 virtual void .Quit(wxCommandEvent& event);                 virtual void .About(wxCommandEvent& event);                 void downloadfile();                 wxTimer* m_timerdown;                 DECLARE_EVENT_TABLE() }; #endif // DOWNLOADMAIN_H   下面是主程序的代码. /*************************************************************** * Name:            downloadMain.cpp * Purpose:     Code for Application Frame * Author:         (alan) * Created:     2008-11-14 * License: **************************************************************/ #ifdef WX_PRECOMP #include "wx_pch.h" #endif #ifdef __BORLANDC__ #pragma hdrstop #endif //__BORLANDC__ #include "downloadMain.h" #include #include #include #include "update.h" #include #include #define TIMER_ID 22222 //事件监听声明 BEGIN_EVENT_TABLE(downloadDialog, GUIDialog)         EVT_TIMER(TIMER_ID, downloadDialog::OnTimer) END_EVENT_TABLE() enum wxbuildinfoformat {         short_f, long_f }; wxString wxbuildinfo(wxbuildinfoformat format) {         wxString wxbuild(wxVERSION_STRING);         if (format == long_f )         { #if defined(__WXMSW__)                 wxbuild << _T("-Windows"); #elif defined(__WXMAC__)                 wxbuild << _T("-Mac"); #elif defined(__UNIX__)                 wxbuild << _T("-Linux"); #endif #if wxUSE_UNICODE                 wxbuild << _T("-Unicode build"); #else                 wxbuild << _T("-ANSI build"); #endif // wxUSE_UNICODE         }         return wxbuild; } //声明一个文件结构体 struct FtpFile {         char *filename;         FILE *stream; }; downloadDialog::downloadDialog(wxDialog *dlg)                 : GUIDialog(dlg) {         //创建一个定时器,制定TIMER_ID         m_timerdown = new wxTimer(this, TIMER_ID);         //定时器开始运行,这里会自动执行OnTimer函数         m_timerdown->Start(100); } downloadDialog::~downloadDialog() { } //定时器操作 void downloadDialog::OnTimer(wxTimerEvent &event) {         downloadfile(); } //文件写入流 int my_fwrite(void *buffer, size_t size, size_t nmemb, void *stream) {         struct FtpFile *out=(struct FtpFile *)stream;         if (out && !out->stream)         {                 out->stream=fopen(out->filename, "wb");                 if (!out->stream)                 {                         return -1;                 }         }         return fwrite(buffer, size, nmemb, out->stream); } //进度条显示函数 int wxcurldav_dl_progress_func(void* ptr, double rDlTotal, double rDlNow, double rUlTotal, double rUlNow) {                                 wxGauge* pGauge = (wxGauge*) ptr;                                 if(pGauge)                                 //设置进度条的值                                         pGauge->SetValue(100.0 * (rDlNow/rDlTotal));                                 return 0; } //下载文件函数 void downloadDialog::downloadfile() {         //创建curl对象         CURL *curl;         CURLcode res;         m_staticText2->SetLabel(wxT("请耐心等待程序下载更新包..."));         struct FtpFile ftpfile=         {                 //定义下载到本地的文件位置和路径                 "tmp.exe",NULL         };         curl_global_init(CURL_GLOBAL_DEFAULT);         //curl初始化         curl = curl_easy_init();         //curl对象存在的情况下执行操作         if (curl)         {                 //设置远端地址                 curl_easy_setopt(curl, CURLOPT_URL,"http://dl_dir.qq.com/minigamefile/QQGame2008ReleaseP2_web_setup.EXE");                 //执行写入文件流操作                 curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, my_fwrite);                 curl_easy_setopt(curl, CURLOPT_WRITEDATA, &ftpfile);                 //curl的进度条声明                 curl_easy_setopt(curl, CURLOPT_NOPROGRESS, FALSE);                 //回调进度条函数                 curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, wxcurldav_dl_progress_func);                 //设置进度条名称                 curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, m_gauge1);                 //进度条                 m_gauge1->SetValue(0);                 //写入文件                 res = curl_easy_perform(curl);                 m_gauge1->SetValue(100);                 //释放curl对象                 curl_easy_cleanup(curl);                 if (CURLE_OK != res)                         ;         }         if (ftpfile.stream)         {                 //关闭文件流                 fclose(ftpfile.stream);         }                 //释放全局curl对象                 curl_global_cleanup();                 //这一步很重要，停止定时器,不然程序会无休止的运行下去                 m_timerdown->Stop();                 //执行刚下载完毕的程序,进行程序更新                 int pid = ::wxExecute(_T("tmp.exe"));                 wxMessageBox(wxT("下载完毕，程序开始执行更新操作......")); } void downloadDialog::OnClose(wxCloseEvent &event) {         Destroy(); } void downloadDialog::OnQuit(wxCommandEvent &event) {         Destroy(); } void downloadDialog::OnAbout(wxCommandEvent &event) { }