1--- 2c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 3SPDX-License-Identifier: curl 4Title: curl_multi_poll 5Section: 3 6Source: libcurl 7See-also: 8 - curl_multi_fdset (3) 9 - curl_multi_perform (3) 10 - curl_multi_wait (3) 11 - curl_multi_wakeup (3) 12Protocol: 13 - All 14Added-in: 7.66.0 15--- 16 17# NAME 18 19curl_multi_poll - poll on all easy handles in a multi handle 20 21# SYNOPSIS 22 23~~~c 24#include <curl/curl.h> 25 26CURLMcode curl_multi_poll(CURLM *multi_handle, 27 struct curl_waitfd extra_fds[], 28 unsigned int extra_nfds, 29 int timeout_ms, 30 int *numfds); 31~~~ 32 33# DESCRIPTION 34 35curl_multi_poll(3) polls all file descriptors used by the curl easy 36handles contained in the given multi handle set. It blocks until activity is 37detected on at least one of the handles or *timeout_ms* has passed. 38Alternatively, if the multi handle has a pending internal timeout that has a 39shorter expiry time than *timeout_ms*, that shorter time is used instead 40to make sure timeout accuracy is reasonably kept. 41 42The calling application may pass additional curl_waitfd structures which are 43similar to *poll(2)*'s *pollfd* structure to be waited on in the same 44call. 45 46On completion, if *numfds* is non-NULL, it gets populated with the total 47number of file descriptors on which interesting events occurred. This number 48can include both libcurl internal descriptors as well as descriptors provided 49in *extra_fds*. 50 51The curl_multi_wakeup(3) function can be used from another thread to 52wake up this function and return faster. This is one of the details 53that makes this function different than curl_multi_wait(3) which cannot 54be woken up this way. 55 56If no extra file descriptors are provided and libcurl has no file descriptor 57to offer to wait for, this function instead waits during *timeout_ms* 58milliseconds (or shorter if an internal timer indicates so). This is the other 59detail that makes this function different than curl_multi_wait(3). 60 61This function is encouraged to be used instead of select(3) when using the 62multi interface to allow applications to easier circumvent the common problem 63with 1024 maximum file descriptors. 64 65# curl_waitfd 66 67~~~c 68struct curl_waitfd { 69 curl_socket_t fd; 70 short events; 71 short revents; 72}; 73~~~ 74 75## CURL_WAIT_POLLIN 76 77Bit flag to curl_waitfd.events indicating the socket should poll on read 78events such as new data received. 79 80## CURL_WAIT_POLLPRI 81 82Bit flag to curl_waitfd.events indicating the socket should poll on high 83priority read events such as out of band data. 84 85## CURL_WAIT_POLLOUT 86 87Bit flag to curl_waitfd.events indicating the socket should poll on write 88events such as the socket being clear to write without blocking. 89 90# %PROTOCOLS% 91 92# EXAMPLE 93 94~~~c 95extern void handle_fd(int); 96 97int main(void) 98{ 99 CURL *easy_handle; 100 CURLM *multi_handle; 101 int still_running = 0; 102 int myfd; /* this is our own file descriptor */ 103 104 /* add the individual easy handle */ 105 curl_multi_add_handle(multi_handle, easy_handle); 106 107 do { 108 CURLMcode mc; 109 int numfds; 110 111 mc = curl_multi_perform(multi_handle, &still_running); 112 113 if(mc == CURLM_OK) { 114 struct curl_waitfd myown; 115 myown.fd = myfd; 116 myown.events = CURL_WAIT_POLLIN; /* wait for input */ 117 myown.revents = 0; /* clear it */ 118 119 /* wait for activity on curl's descriptors or on our own, 120 or timeout */ 121 mc = curl_multi_poll(multi_handle, &myown, 1, 1000, &numfds); 122 123 if(myown.revents) { 124 /* did our descriptor receive an event? */ 125 handle_fd(myfd); 126 } 127 } 128 129 if(mc != CURLM_OK) { 130 fprintf(stderr, "curl_multi failed, code %d.\n", mc); 131 break; 132 } 133 134 } while(still_running); 135 136 curl_multi_remove_handle(multi_handle, easy_handle); 137} 138~~~ 139 140# %AVAILABILITY% 141 142# RETURN VALUE 143 144CURLMcode type, general libcurl multi interface error code. See 145libcurl-errors(3) 146
