Hello.
I'm sharing this just in case there is interest. The real bug in my code
was unrelated to this.
A small test case is attached to help me explain. It's not a real-world
use case.
The 2m file is created with dd:
dd if=/dev/urandom of=/tmp/2m bs=2M count=1
When running the test case on my laptop, I noticed the following:
1- All required data is read fast.
2- dlnow will report a completed transfer early on.
(It only represents the size of data received/read).
3- Not all data is flushed after writes
(unless you uncomment the fflush line).
4- libcurl will keep waiting until the speed limit is met on a now
long interval.
5- Finally, the remaining (unflushed) data is written.
I would have expected libcurl to:
1- not wait needlessly when there is no more data to receive/read.
2- not allow the size of data read, and the size written to be out of
sync for that long. Maybe flushing should be used after writes!
#include <stdio.h>
#include <curl/curl.h>
int simple_progress(void *start, double dltotal, double dlnow, double ultotal, double ulnow) {
//fflush(stdout);
//fprintf(stderr, "dur=%lu, dltotal=%f, dlnow=%f, ultotal=%f, ulnow=%f\n", time(NULL) - *(time_t *)start , dltotal, dlnow, ultotal, ulnow);
return 0;
}
int main(void)
{
CURL *curl;
CURLcode res;
time_t start = time(NULL);
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "file:///tmp/2m");
curl_easy_setopt(curl, CURLOPT_MAX_RECV_SPEED_LARGE, 4096);
curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 0l);
curl_easy_setopt(curl , CURLOPT_PROGRESSFUNCTION, &simple_progress);
curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, &start);
res = curl_easy_perform(curl);
if(res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
curl_easy_cleanup(curl);
}
return 0;
}
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