libcurl下载文件并实现进度条

昨天使用了windows api实现了下载文件以及显示下载进度&＃xff1a;

Windows客户端开发–URLDownloadToFile下载文件进度条

今天就来说一使用libcurl实现http下载&＃xff0c;并实现进度条。

简单介绍libcurl:
官网&＃xff1a;
https://curl.haxx.se/
libcurl主要功能就是用不同的协议连接和沟通不同的服务器~也就是相当封装了的sockPHP 支持libcurl&＃xff08;允许你用不同的协议连接和沟通不同的服务器&＃xff09;。, libcurl当前支持http, https, ftp, gopher, telnet, dict, file, 和ldap 协议。libcurl同样支持HTTPS证书授权&＃xff0c;HTTP POST, HTTP PUT, FTP 上传&＃xff08;当然你也可以使用PHP的ftp扩展&＃xff09;, HTTP基本表单上传&＃xff0c;代理&＃xff0c;COOKIEs,和用户认证。

使用libcurl:

文档&＃xff1a;
https://curl.haxx.se/libcurl/c/libcurl-tutorial.html

For historical and traditional reasons, libcurl has a built-in progress meter that can be switched on and then makes it present a progress meter in your terminal.

Switch on the progress meter by, oddly enough, setting CURLOPT_NOPROGRESS to zero. This option is set to 1 by default.

For most applications however, the built-in progress meter is useless and what instead is interesting is the ability to specify a progress callback. The function pointer you pass to libcurl will then be called on irregular intervals with information about the current transfer.

Set the progress callback by using CURLOPT_PROGRESSFUNCTION. And pass a pointer to a function that matches this prototype:

int progress_callback(void *clientp,double dltotal,double dlnow,double ultotal,double ulnow);


If any of the input arguments is unknown, a 0 will be passed. The first argument, the ‘clientp’ is the pointer you pass to libcurl with CURLOPT_PROGRESSDATA. libcurl won’t touch it.

开始&＃xff1a;
根据上面的文档&＃xff0c;实现我们自己的progress_func&＃xff1a;

int progress_func(void* ptr, double TotalToDownload, double NowDownloaded, double TotalToUpload, double NowUploaded)
{int totaldotz&＃61;40;double fractiondownloaded &＃61; NowDownloaded / TotalToDownload;int dotz &＃61; round(fractiondownloaded * totaldotz);int ii&＃61;0;printf("%3.0f%% [",fractiondownloaded*100);for ( ; ii printf("&＃61;");}for ( ; ii printf(" ");}printf("]\r");fflush(stdout);
}

同样根据文档&＃xff1a;
setting CURLOPT_NOPROGRESS to zero
Set the progress callback by using CURLOPT_PROGRESSFUNCTION

FILE *file_param;
file_param &＃61; fopen("download_to_path", "wb");curl_easy_setopt(curl, CURLOPT_WRITEDATA, file_param); curl_easy_setopt(curl, CURLOPT_NOPROGRESS, FALSE);curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, progress_func)

最后看一个完整的官方例子&＃xff1a;
https://curl.haxx.se/libcurl/c/progressfunc.html
不同的版本&＃xff0c;不同的处理&＃xff1a;

#include
#include #define STOP_DOWNLOAD_AFTER_THIS_MANY_BYTES 6000
#define MINIMAL_PROGRESS_FUNCTIONALITY_INTERVAL 3struct myprogress {double lastruntime;CURL *curl;
};static int xferinfo(void *p,curl_off_t dltotal, curl_off_t dlnow,curl_off_t ultotal, curl_off_t ulnow)
{struct myprogress *myp &＃61; (struct myprogress *)p;CURL *curl &＃61; myp->curl;double curtime &＃61; 0;curl_easy_getinfo(curl, CURLINFO_TOTAL_TIME, &curtime);if((curtime - myp->lastruntime) >&＃61; MINIMAL_PROGRESS_FUNCTIONALITY_INTERVAL) {myp->lastruntime &＃61; curtime;fprintf(stderr, "TOTAL TIME: %f \r\n", curtime);}fprintf(stderr, "UP: %" CURL_FORMAT_CURL_OFF_T " of %" CURL_FORMAT_CURL_OFF_T" DOWN: %" CURL_FORMAT_CURL_OFF_T " of %" CURL_FORMAT_CURL_OFF_T"\r\n",ulnow, ultotal, dlnow, dltotal);if(dlnow > STOP_DOWNLOAD_AFTER_THIS_MANY_BYTES)
return 1;
return 0;
}/* for libcurl older than 7.32.0 (CURLOPT_PROGRESSFUNCTION) */
static int older_progress(void *p,double dltotal, double dlnow,double ultotal, double ulnow)
{
return xferinfo(p,(curl_off_t)dltotal,(curl_off_t)dlnow,(curl_off_t)ultotal,(curl_off_t)ulnow);
}int main(void)
{CURL *curl;CURLcode res &＃61; CURLE_OK;struct myprogress prog;curl &＃61; curl_easy_init();if(curl) {prog.lastruntime &＃61; 0;prog.curl &＃61; curl;curl_easy_setopt(curl, CURLOPT_URL, "http://example.com/");curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, older_progress);/* pass the struct pointer into the progress function */ curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, &prog);#if LIBCURL_VERSION_NUM >&＃61; 0x072000/* xferinfo was introduced in 7.32.0, no earlier libcurl versions willcompile as they won&＃39;t have the symbols around.If built with a newer libcurl, but running with an older libcurl:curl_easy_setopt() will fail in run-time trying to set the newcallback, making the older callback get used.New libcurls will prefer the new callback and instead use that one evenif both callbacks are set. */ curl_easy_setopt(curl, CURLOPT_XFERINFOFUNCTION, xferinfo);/* pass the struct pointer into the xferinfo function, note that this isan alias to CURLOPT_PROGRESSDATA */ curl_easy_setopt(curl, CURLOPT_XFERINFODATA, &prog);
#endifcurl_easy_setopt(curl, CURLOPT_NOPROGRESS, 0L);res &＃61; curl_easy_perform(curl);if(res !&＃61; CURLE_OK)fprintf(stderr, "%s\n", curl_easy_strerror(res));/* always cleanup */ curl_easy_cleanup(curl);}
return (int)res;
}