使用libcurl下载文件小例

#include "curl.h" ?#ifdef _DEBUG ?#pragma comment(lib, "../Debug/libcurld") ?#else ?#pragma comment(lib, "../Release/libcurl") ?#endif ?

<pre name="code" class="cpp">// UseLibCurl.cpp : 定义控制台应用程序的入口点。 ?// ???#include "stdafx.h" ?#include <Windows.h> ?#include <CommCtrl.h> ?#include "resource.h" ?#include "curl.h" ?#ifdef _DEBUG ?#pragma comment(lib, "../Debug/libcurld") ?#else ?#pragma comment(lib, "../Release/libcurl") ?#endif ?????//这个用来保存对话框的窗口句柄，因为后面要向这个窗口发消息，必须知道其窗口句柄 ?HWND ???g_hDlgWnd = NULL; ?//提供给CURL下载进度回调的函数，用于保存下载的数据到文件 ?static size_t ??DownloadCallback(void* pBuffer, size_t nSize, size_t nMemByte, void* pParam); ?//提供给CURL下载进度回调的函数，用于计算下载进度通知界面 ?static int ProgressCallback(void *clientp, double dltotal, double dlnow, double ultotal, double ulnow); ?//这是对话框的消息循环，在控制台程序里面创建GUI，仅仅是为了更好地展现下载回调这个功能 ?INT_PTR CALLBACK DialogProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam); ?//这个是下载的线程函数，为了不把对话框主界面卡死，肯定是要自己开线程来下载的了 ?DWORD WINAPI DownloadThread(LPVOID lpParam); ???int _tmain(int argc, _TCHAR* argv[]) ?{ ?????//弹出对话框，知道对话框关闭才会执行退出 ?????DialogBox(NULL, MAKEINTRESOURCE(IDD_DIALOG1), NULL, DialogProc ); ?????return 0; ?} ???static size_t DownloadCallback(void* pBuffer, size_t nSize, size_t nMemByte, void* pParam) ?{ ?????//把下载到的数据以追加的方式写入文件(一定要有a，否则前面写入的内容就会被覆盖了) ?????FILE* fp = NULL; ?????fopen_s(&fp, "c:\\test.apk", "ab+"); ?????size_t nWrite = fwrite(pBuffer, nSize, nMemByte, fp); ?????fclose(fp); ?????return nWrite; ?} ???static int ProgressCallback(void *clientp, double dltotal, double dlnow, double ultotal, double ulnow) ?{ ?????if ( dltotal > -0.1 && dltotal < 0.1 ) ?????????return 0; ?????int nPos = (int) ( (dlnow/dltotal)*100 ); ?????//通知进度条更新下载进度 ?????::PostMessage(g_hDlgWnd, WM_USER + 110, nPos, 0); ?????//::Sleep(10); ?????return 0; ?} ???INT_PTR CALLBACK DialogProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) ?{ ?????switch( uMsg ) ?????{ ?????case WM_INITDIALOG: ?????????{ ?????????????g_hDlgWnd = hWnd; ?????????????HWND hProgress = GetDlgItem(hWnd, IDC_PROGRESS1); ?????????????SendMessage(hProgress, PBM_SETRANGE32, (WPARAM) 0, (LPARAM) 100); ?????????????//对话框初始化时创建下载线程 ?????????????HANDLE hThread = CreateThread(NULL, 0, DownloadThread, 0, 0, NULL); ?????????????CloseHandle(hThread); ?????????????::SetWindowText(hWnd, L"使用CURL下载文件示例："); ?????????????return TRUE; ?????????} ?????case WM_COMMAND: ?????????{ ?????????????WORD ?msg = HIWORD(wParam); ?????????????WORD ?id ?= LOWORD(wParam); ?????????????if ( id == IDOK || id == IDCANCEL ) ?????????????????EndDialog(hWnd, id); ?????????????break; ?????????} ?????case WM_ERASEBKGND: ?????????return TRUE; ?????case WM_CTLCOLORSTATIC: ?????????return (INT_PTR)(HBRUSH)::GetStockObject(WHITE_BRUSH); ?????case WM_USER + 110: ?????????{//接收到设置进度的消息 ?????????????HWND ???hProgress ??= GetDlgItem(hWnd, IDC_PROGRESS1); ?????????????HWND ???hStatus ????= GetDlgItem(hWnd, IDC_STATUS); ?????????????if ( hProgress ) ?????????????????SendMessage(hProgress, PBM_SETPOS, wParam, 0L); ?????????????if ( hStatus ) ?????????????{ ?????????????????WCHAR szBuffer[100] = {0}; ?????????????????if ( wParam<100 ) ?????????????????????swprintf(szBuffer, L"正在下载文件，进度：%d%%", wParam); ?????????????????else ?????????????????????swprintf(szBuffer, L"文件下载完毕！"); ?????????????????::SetWindowText(hStatus, szBuffer); ?????????????} ?????????????return 0; ?????????} ?????default: ?????????break; ?????} ?????return DefWindowProc(hWnd, uMsg, wParam, lParam); ?} ???DWORD WINAPI DownloadThread(LPVOID lpParam) ?{ ?????//初始化curl，这个是必须的 ?????CURL* curl = curl_easy_init(); ?????curl_easy_setopt(curl, CURLOPT_URL, "http://android.shoujids.com/software/download?id=154103"); ?????//设置接收数据的回调 ?????curl_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); ?????// 设置重定向的最大次数 ?????curl_easy_setopt(curl, CURLOPT_MAXREDIRS, 5); ?????// 设置301、302跳转跟随location ?????curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1); ?????curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 0); ?????//设置进度回调函数 ?????curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, ProgressCallback); ?????//curl_easy_getinfo(curl, ?CURLINFO_CONTENT_LENGTH_DOWNLOAD, &lFileSize); ?????//curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, g_hDlgWnd); ?????//开始执行请求 ?????CURLcode retcCode = curl_easy_perform(curl); ?????//查看是否有出错信息 ?????const char* pError = curl_easy_strerror(retcCode); ?????//清理curl，和前面的初始化匹配 ?????curl_easy_cleanup(curl); ?????return 0; ?} ?