On Wed, 20 Nov 2002, Juan Ignacio Hervás wrote:

> I am very interesting in the new feature introduced in the 7.10 version
> related with the use of bandwidth limit. I think that this new option (
> --limit-rate <speed> ) has been introduced in the curl command line tool
> but, can it be used with the libcurl in a Visual C++ project? In that case,
> how to do it? is there any new CURLOPT_ option?

Yes, there was a new CURLOPT added (which is used when this feature is use
for downloads). CURLOPT_BUFFERSIZE sets the "prefered" read buffer size to
libcurl, and by doing that we can get a callback more often.

The read callback in curl is then making sure that it doesn't return control
back to libcurl too fast, like this:

  if(config->recvpersecond) {
    /*
     * We know when we received data the previous time. We know how much data
     * we get now. Make sure that this is not faster than we are told to run.
     * If we're faster, sleep a while *before* doing the fwrite() here.
     */

    time_t timediff;
    time_t now;

    now = time(NULL);
    timediff = now - config->lastrecvtime;
    if( size*nmemb > config->recvpersecond*timediff) {
      /* figure out how many milliseconds to rest */
      go_sleep ( (size*nmemb)*1000/config->recvpersecond - timediff*1000 );
      now = time(NULL);
    }
    config->lastrecvtime = now;
  }

  /* make fwrite() here */

(go_sleep() is present in src/main.c and is a portable function for
ms-resolution sleeps.)

-- 
 Daniel Stenberg -- curl, cURL, Curl, CURL. Groks URLs.
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