关键部分代码如下：

    1. #include "curl.h"
    3. #pragma comment(lib, "libcurl.lib")
    7. size_t CROS_DownloadDlg::getContentLengthFunc(void * ptr, size_t size, size_t nmemb, void * stream)
    8. {
    9.     LONGLONG len = 0;
    10.     int r = sscanf((const char *)ptr, "Content-Length:%I64d\n",&len);
    11.     if(r)
    12.         *((LONGLONG *) stream) = len;
    14.     return size * nmemb;
    15. }
    18. //根据URL获取下载文件大小
    19. LONGLONG CROS_DownloadDlg::getDownloadFileSize(const char*  url)
    20. {
    21.     double lensize = 0.0;
    22.     for(int iTry = 0 ; iTry < 3 ; iTry ++)//由于curl_easy_perform可能会有偶发性的    CURLE_WRITE_ERROR错误，所以添加重试机制
    23.     {
    24.         CURL *handle = curl_easy_init();
    25.         curl_easy_setopt(handle, CURLOPT_URL, url);
    26.         curl_easy_setopt(handle, CURLOPT_HEADER, 1);
    27.         curl_easy_setopt(handle, CURLOPT_FOLLOWLOCATION, 1);
    28.         curl_easy_setopt(handle, CURLOPT_NOBODY, 1);
    29.         CURLcode res = curl_easy_perform(handle), resGetInfo = CURLE_OK;
    30.         if (res == CURLE_OK) {
    31.             resGetInfo = curl_easy_getinfo(handle, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &lensize);
    32.             if(CURLE_OK == resGetInfo){
    33.                 curl_easy_cleanup(handle);
    34.                 return (LONGLONG)lensize;
    35.             }
    36.         }
    37.         curl_easy_cleanup(handle);
    38.         Sleep(200);
    39.     }
    40. return 0;
    41. }
    44. size_t CROS_DownloadDlg::downLoadPackage(void *ptr, size_t size, size_t nmemb, void *userdata)
    45. {
    46.     if(!ptr || !userdata)
    47.         return 0;
    49.     return fwrite(ptr, size, nmemb, (FILE *)userdata);
    50. }
    53. int CROS_DownloadDlg::assetsManagerProgressFunc(void *ptr, double totalToDownload, double nowDownloaded, double totalToUpLoad, double nowUpLoaded)
    54. {
    55.     if(m_bStop)
    56.         return -1;
    58.     if(totalToDownload > 0.0)
    59.     {
    60.         CROS_DownloadDlg* pDlg = (CROS_DownloadDlg*)ptr;
    61.         pDlg->m_lProcessSize = (LONGLONG)nowDownloaded;
    62.         pDlg->SendMessage(WM_DOWNLOADPROC_MSG, 1, 0);
    63.     }
    65.     return 0;
    66. }
    69. /*
    70. 0 设置总大小
    71. 1 设置当前下载
    72. 2 下载完成
    73. 3 用户停止下载，其他异常终止下载
    74. 4 网络问题引发的下载异常
    75. 5 设备断开连接
    76. 6 磁盘剩余空间不足
    77. */
    78. UINT CROS_DownloadDlg::DownloadProc(LPVOID lpParam)
    79. {
    81. //////////////////////////////////////////////////////////////////////////使用CURL实现下载
    82.     string sURL = CStringConverter::Unicode2Ansi(strURL.GetString()), sSavePath =         CStringConverter::Unicode2Ansi(strSavePath.GetString());
    85.     LONGLONG local_file_len = GetFileSize(strSavePath);
    86.     pDlg->m_lLocalFileCurSize = local_file_len;
    87.     curl_global_init(CURL_GLOBAL_DEFAULT);
    88.     LONGLONG remote_file_len = getDownloadFileSize(sURL.c_str());
    90.     if(!remote_file_len)
    91.     {
    92.         pDlg->SendMessage(WM_DOWNLOADPROC_MSG, 4, 0);//网络问题获取失败
    93.         return 0;
    94.     }
    96.     pDlg->m_lTotalSize = remote_file_len;
    97.     pDlg->SendMessage(WM_DOWNLOADPROC_MSG, 0, 0);
    98.     if(local_file_len == remote_file_len)
    99.     {
    100.         pDlg->SendMessage(WM_DOWNLOADPROC_MSG, 2, 0);
    101.         return 0;
    102.     }
    104. //得到准确大小后应判断strSavePath空间是否足够先
    105.     if(remote_file_len >= (pDlg->m_ulDiskSpaceMax))
    106.     {
    107.         pDlg->SendMessage(WM_DOWNLOADPROC_MSG, 6, 0);
    108.         return 0;
    109.     }
    111.     FILE *fp = fopen(sSavePath.c_str(), "ab+");
    112.     if(!fp)
    113.     {
    114.         pDlg->SendMessage(WM_DOWNLOADPROC_MSG, 3, 0);
    115.         return 0;
    116.     }
    118.     LONGLONG filesize = 0;
    119.     m_pCurl = curl_easy_init();//curl初始化
    120.     CURLcode res;
    121.     curl_easy_setopt(m_pCurl, CURLOPT_URL, sURL.c_str());//设定curl的链接
    122.     curl_easy_setopt(m_pCurl, CURLOPT_CONNECTTIMEOUT,5);//设置连接超时，单位秒
    123.     curl_easy_setopt(m_pCurl, CURLOPT_HEADERFUNCTION,getContentLengthFunc);
    124.     curl_easy_setopt(m_pCurl, CURLOPT_HEADERDATA, &filesize);
    125.     curl_easy_setopt(m_pCurl, CURLOPT_RESUME_FROM_LARGE, local_file_len);//断点下载设置
    126.     curl_easy_setopt(m_pCurl, CURLOPT_WRITEFUNCTION, downLoadPackage);
    127.     curl_easy_setopt(m_pCurl, CURLOPT_WRITEDATA, fp);//设置将data写入到文件流fp中
    128.     curl_easy_setopt(m_pCurl, CURLOPT_FOLLOWLOCATION, 1L);//设置重定位URL，使用自动跳转，返回的头部中有Location(一般直接请求的url没找到)，则继续请求Location对应的数据
    129.     curl_easy_setopt(m_pCurl, CURLOPT_MAXREDIRS,5);//查找次数，防止查找太深
    130.     curl_easy_setopt(m_pCurl, CURLOPT_NOPROGRESS, false);//设为false 下面才能设置进度响应函数
    131.     curl_easy_setopt(m_pCurl, CURLOPT_PROGRESSFUNCTION, assetsManagerProgressFunc);//进度响应函数
    132.     curl_easy_setopt(m_pCurl, CURLOPT_PROGRESSDATA, pDlg);//数据传输的对象
    133.     curl_easy_setopt(m_pCurl, CURLOPT_VERBOSE,1L);
    134.     res = curl_easy_perform(m_pCurl);
    135.     curl_easy_cleanup(m_pCurl);
    136.     curl_global_cleanup();
    137.     m_pCurl = NULL;
    139.     if (res != CURLE_OK)
    140.     {
    141.         fclose(fp);
    142.         if(res == CURLE_ABORTED_BY_CALLBACK)//点击停止下载
    143.             pDlg->SendMessage(WM_DOWNLOADPROC_MSG, 3, 0);
    144.         else if(res == CURLE_RECV_ERROR)//断网     /* 56 - failure in receiving network data */
    145.             pDlg->SendMessage(WM_DOWNLOADPROC_MSG, 4, 0);
    146.         else
    147.             pDlg->SendMessage(WM_DOWNLOADPROC_MSG, 3, 0);
    149.         return 0;
    150.     }
    152.     fclose(fp);
    153.     pDlg->SendMessage(WM_DOWNLOADPROC_MSG, 2, 0);
    154.     return 0;
    156. }
    162. void CROS_DownloadDlg::OnClickBtnStop()
    163. {
    164.     if(m_pCurl){
    165.         curl_easy_pause(m_pCurl, CURLPAUSE_RECV);
    167.         if(IDYES == ShowMessage(IDS_DEF_ROS_SURE_TO_STOP, CiPhoneUtil::GetApplicationName(), SM_ICON_QUESTION|SM_YES_AND_NO)){
    168.             m_btnStop.EnableWindow(FALSE);
    169.             m_bStop = true;
    170.             return;
    171.         }
    172.         curl_easy_pause(m_pCurl, CURLPAUSE_RECV_CONT);
    173.     }
    174. }

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