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93 lines
2.8 KiB
Groff
93 lines
2.8 KiB
Groff
.\" generated by cd2nroff 0.1 from curl_multi_waitfds.md
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.TH curl_multi_waitfds 3 "2024-06-01" libcurl
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.SH NAME
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curl_multi_waitfds \- extracts file descriptor information from a multi handle
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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#include <stdlib.h>
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CURLMcode curl_multi_waitfds(CURLM *multi,
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struct curl_waitfd *ufds,
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unsigned int size,
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unsigned int *fd_count);
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.fi
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.SH DESCRIPTION
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This function extracts \fIcurl_waitfd\fP structures which are similar to
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\fIpoll(2)\fP\(aqs \fIpollfd\fP structure from a given multi_handle.
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These structures can be used for polling on multi_handle file descriptors in a
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fashion similar to \fIcurl_multi_poll(3)\fP. The \fIcurl_multi_perform(3)\fP
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function should be called as soon as one of them is ready to be read from or
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written to.
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libcurl fills provided \fIufds\fP array up to the \fIsize\fP.
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If a number of descriptors used by the multi_handle is greater than the
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\fIsize\fP parameter then libcurl returns CURLM_OUT_OF_MEMORY error.
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If the \fIfd_count\fP argument is not a null pointer, it points to a variable
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that on returns specifies the number of descriptors used by the multi_handle to
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be checked for being ready to read or write.
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The client code can pass \fIsize\fP equal to zero just to get the number of the
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descriptors and allocate appropriate storage for them to be used in a
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subsequent function call.
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.SH PROTOCOLS
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All
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.SH EXAMPLE
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.nf
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int main(void)
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{
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CURLMcode mc;
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struct curl_waitfd *ufds;
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CURLM *multi = curl_multi_init();
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do {
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/* call curl_multi_perform() */
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/* get the count of file descriptors from the transfers */
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unsigned int fd_count = 0;
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mc = curl_multi_waitfds(multi, NULL, 0, &fd_count);
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if(mc != CURLM_OK) {
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fprintf(stderr, "curl_multi_waitfds() failed, code %d.\\n", mc);
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break;
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}
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if(!fd_count)
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continue; /* no descriptors yet */
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/* Allocate storage for our descriptors.
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* Note that a better approach can be used to minimize allocations and
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* deallocations, if needed, like pre-allocated or grow-only array.
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*/
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ufds = (struct curl_waitfd*)malloc(fd_count * sizeof(struct curl_waitfd));
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/* get wait descriptors from the transfers and put them into array. */
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mc = curl_multi_waitfds(multi, ufds, fd_count, NULL);
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if(mc != CURLM_OK) {
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fprintf(stderr, "curl_multi_waitfds() failed, code %d.\\n", mc);
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free(ufds);
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break;
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}
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/* Do polling on descriptors in ufds */
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free(ufds);
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} while (!mc);
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}
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.fi
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.SH AVAILABILITY
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Added in 8.8.0
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.SH RETURN VALUE
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\fBCURLMcode\fP type, general libcurl multi interface error code. See
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\fIlibcurl\-errors(3)\fP
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.SH SEE ALSO
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.BR curl_multi_fdset (3),
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.BR curl_multi_perform (3),
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.BR curl_multi_poll (3),
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.BR curl_multi_wait (3)
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