121 lines
3.2 KiB
Markdown
121 lines
3.2 KiB
Markdown
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---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_XFERINFOFUNCTION
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_NOPROGRESS (3)
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- CURLOPT_XFERINFODATA (3)
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---
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# NAME
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CURLOPT_XFERINFOFUNCTION - progress meter callback
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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int progress_callback(void *clientp,
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curl_off_t dltotal,
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curl_off_t dlnow,
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curl_off_t ultotal,
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curl_off_t ulnow);
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_XFERINFOFUNCTION,
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progress_callback);
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~~~
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# DESCRIPTION
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Pass a pointer to your callback function, which should match the prototype
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shown above.
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This function gets called by libcurl instead of its internal equivalent with a
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frequent interval. While data is being transferred it gets called frequently,
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and during slow periods like when nothing is being transferred it can slow
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down to about one call per second.
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*clientp* is the pointer set with CURLOPT_XFERINFODATA(3), it is not
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used by libcurl but is only passed along from the application to the callback.
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The callback gets told how much data libcurl is about to transfer and has
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already transferred, in number of bytes. *dltotal* is the total number of
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bytes libcurl expects to download in this transfer. *dlnow* is the number
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of bytes downloaded so far. *ultotal* is the total number of bytes libcurl
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expects to upload in this transfer. *ulnow* is the number of bytes
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uploaded so far.
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Unknown/unused argument values passed to the callback are set to zero (like if
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you only download data, the upload size remains 0). Many times the callback is
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called one or more times first, before it knows the data sizes so a program
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must be made to handle that.
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If your callback function returns CURL_PROGRESSFUNC_CONTINUE it makes libcurl
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to continue executing the default progress function.
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Returning any other non-zero value from this callback makes libcurl abort the
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transfer and return *CURLE_ABORTED_BY_CALLBACK*.
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If you transfer data with the multi interface, this function is not called
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during periods of idleness unless you call the appropriate libcurl function
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that performs transfers.
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CURLOPT_NOPROGRESS(3) must be set to 0 to make this function actually
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get called.
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# DEFAULT
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By default, libcurl has an internal progress meter. That is rarely wanted by
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users.
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# PROTOCOLS
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All
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# EXAMPLE
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~~~c
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struct progress {
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char *private;
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size_t size;
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};
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static size_t progress_callback(void *clientp,
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curl_off_t dltotal,
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curl_off_t dlnow,
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curl_off_t ultotal,
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curl_off_t ulnow)
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{
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struct progress *memory = clientp;
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printf("my ptr: %p\n", memory->private);
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/* use the values */
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return 0; /* all is good */
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}
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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struct progress data;
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/* pass struct to callback */
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curl_easy_setopt(curl, CURLOPT_XFERINFODATA, &data);
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curl_easy_setopt(curl, CURLOPT_XFERINFOFUNCTION, progress_callback);
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}
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}
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~~~
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# AVAILABILITY
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Added in 7.32.0. This callback replaces CURLOPT_PROGRESSFUNCTION(3)
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# RETURN VALUE
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Returns CURLE_OK.
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