Use Libcurl to download files for small cases

Libcurl is a powerful open source network processing library that supports HTTP, HTTPS, FTP ... A range of network protocols. Using it for HTTP get\post or download files is a piece of cake, the chrome kernel has used it, this article mainly on a use Curl download file of the small example.

The first is to download the latest Curl source code, and then compile into a dynamic library or a static library, and then put the head files and library files to join our own project, the reference statement:

" curl.h "   #ifdef _DEBUG  #pragma comment (lib, ". /debug/libcurld ")  #else  #pragma comment (lib,". /release/libcurl ")  #endif  

Deliberately added some comments on the original code, hoping to better understand the code:

<pre name="Code" class="CPP">//UseLibCurl.cpp: Defines the entry point of the console application. //  #include"stdafx.h"#include<Windows.h>#include<CommCtrl.h>#include"resource.h"#include"curl.h"#ifdef _DEBUG#pragmaComment (lib, "... /debug/libcurld ")#else  #pragmaComment (lib, "... /release/libcurl ")#endif      //This is the window handle to Save the dialog box, because the window handle must be known after the message is sent to the windowHWND G_hdlgwnd =NULL; //provides a function to curl download progress callback for saving downloaded data to a fileStaticsize_t Downloadcallback (void* pbuffer, size_t nSize, size_t nmembyte,void*pparam); //a function for curl download progress callback to calculate the download Progress notification interfaceStatic intProgresscallback (void*CLIENTP,DoubleDltotal,DoubleDlnow,DoubleUltotalDoubleUlnow); //This is the message loop of the dialog box, creating a GUI in the console program, just to better show the download callback functionint_ptr CALLBACK DialogProc (HWND hwnd, UINT umsg, WPARAM WPARAM, LPARAM LPARAM); //This is the download of the thread function, in order not to put the main interface of the dialog box to die, must be a self-threading downloadDWORD WINAPI downloadthread (LPVOID lpparam); int_tmain (intARGC, _tchar*argv[]) {      //Pop-up dialog box, knowing that the dialog closes before execution exitsdialogbox (NULL, Makeintresource (IDD_DIALOG1), NULL, DIALOGPROC); return 0; }    Staticsize_t Downloadcallback (void* pbuffer, size_t nSize, size_t nmembyte,void*pparam) {      //append the downloaded data to the file (must have a, otherwise the previously written content will be overwritten)file* fp =NULL; Fopen_s (&AMP;FP,"c:\\test.apk","ab+"); size_t Nwrite=fwrite (pbuffer, NSize, Nmembyte, FP);      Fclose (FP); returnNwrite; }    Static intProgresscallback (void*CLIENTP,DoubleDltotal,DoubleDlnow,DoubleUltotalDoubleUlnow) {      if(Dltotal >-0.1&& Dltotal <0.1 )          return 0; intNPos = (int) ((dlnow/dltotal) * - ); //Notification progress bar update download Progress::P ostmessage (G_hdlgwnd, Wm_user + the, NPos,0); //:: Sleep (10);     return 0; } INT_PTR CALLBACK DialogProc (HWND hwnd, UINT umsg, WPARAM WPARAM, LPARAM LPARAM) {Switch(umsg) { Casewm_initdialog: {g_hdlgwnd=hWnd; HWND hprogress=GetDlgItem (hWnd, IDC_PROGRESS1); SendMessage (Hprogress, Pbm_setrange32, (WPARAM)0, (LPARAM) -); //Create a download thread when the dialog box is initializedHANDLE hthread = CreateThread (NULL,0, Downloadthread,0,0, NULL);              CloseHandle (Hthread); :: SetWindowText (hWnd, L"examples of downloading files using curl:"); returnTRUE; }       Casewm_command: {WORD msg=HiWord (WParam); WORD ID=LoWord (WParam); if(id = = IDOK | | id = =IDCANCEL)              EndDialog (hWnd, id);  Break; }       CaseWM_ERASEBKGND:returnTRUE;  Casewm_ctlcolorstatic:return( int_ptr) (hbrush):: Getstockobject (White_brush);  CaseWm_user + the:          {//receive message to set progressHWND hprogress =GetDlgItem (hWnd, IDC_PROGRESS1); HWND Hstatus=GetDlgItem (hWnd, idc_status); if(hprogress) SendMessage (hprogress, Pbm_setpos, WParam,0L); if(hstatus) {WCHAR szbuffer[ -] = {0}; if(wparam< -) swprintf (szbuffer, L"downloading file, progress:%d%%", WParam); Elseswprintf (szbuffer, L"File Download complete! ");              :: SetWindowText (Hstatus, szbuffer); }              return 0; }      default:           Break; }      returnDefWindowProc (hWnd, umsg, WParam, LParam); } DWORD WINAPI Downloadthread (lpvoid lpparam) {//Initialize curl, this is a must.curl* Curl =Curl_easy_init (); Curl_easy_setopt (Curl, Curlopt_url,"http://android.shoujids.com/software/download?id=154103"); //set callback to receive datacurl_easy_setopt (Curl, curlopt_writefunction, downloadcallback); //curl_easy_setopt (Curl, curlopt_infilesize, lfilesize); //curl_easy_setopt (Curl, Curlopt_header, 1); //curl_easy_setopt (Curl, curlopt_nobody, 1); //curl_easy_setopt (Curl, curlopt_nosignal, 1); //to set the maximum number of redirectsCurl_easy_setopt (Curl, Curlopt_maxredirs,5); //set 301, 302 jump following locationCurl_easy_setopt (Curl, Curlopt_followlocation,1); Curl_easy_setopt (Curl, curlopt_noprogress,0); //set the progress callback functioncurl_easy_setopt (Curl, curlopt_progressfunction, progresscallback); //curl_easy_getinfo (Curl, Curlinfo_content_length_download, &lfilesize); //curl_easy_setopt (Curl, Curlopt_progressdata, G_hdlgwnd); //Start Execution RequestCurlcode Retccode =curl_easy_perform (Curl); //See if there is an error message    Const Char* Perror =Curl_easy_strerror (Retccode); //clean curl, and match the previous initializationcurl_easy_cleanup (Curl); return 0; }  

Original link: Use libcurl download File Small example

Use Libcurl to download files for small cases