xref: /curl/docs/examples/multi-event.c (revision 37fb50a8)
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8  * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
9  *
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21  * SPDX-License-Identifier: curl
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24 
25 /* <DESC>
26  * multi_socket API using libevent
27  * </DESC>
28  */
29 
30 #include <stdio.h>
31 #include <stdlib.h>
32 #include <event2/event.h>
33 #include <curl/curl.h>
34 
35 static struct event_base *base;
36 static CURLM *curl_handle;
37 static struct event *timeout;
38 
39 typedef struct curl_context_s {
40   struct event *event;
41   curl_socket_t sockfd;
42 } curl_context_t;
43 
44 static void curl_perform(int fd, short event, void *arg);
45 
create_curl_context(curl_socket_t sockfd)46 static curl_context_t *create_curl_context(curl_socket_t sockfd)
47 {
48   curl_context_t *context;
49 
50   context = (curl_context_t *) malloc(sizeof(*context));
51 
52   context->sockfd = sockfd;
53 
54   context->event = event_new(base, sockfd, 0, curl_perform, context);
55 
56   return context;
57 }
58 
destroy_curl_context(curl_context_t * context)59 static void destroy_curl_context(curl_context_t *context)
60 {
61   event_del(context->event);
62   event_free(context->event);
63   free(context);
64 }
65 
add_download(const char * url,int num)66 static void add_download(const char *url, int num)
67 {
68   char filename[50];
69   FILE *file;
70   CURL *handle;
71 
72   snprintf(filename, 50, "%d.download", num);
73 
74   file = fopen(filename, "wb");
75   if(!file) {
76     fprintf(stderr, "Error opening %s\n", filename);
77     return;
78   }
79 
80   handle = curl_easy_init();
81   curl_easy_setopt(handle, CURLOPT_WRITEDATA, file);
82   curl_easy_setopt(handle, CURLOPT_PRIVATE, file);
83   curl_easy_setopt(handle, CURLOPT_URL, url);
84   curl_multi_add_handle(curl_handle, handle);
85   fprintf(stderr, "Added download %s -> %s\n", url, filename);
86 }
87 
check_multi_info(void)88 static void check_multi_info(void)
89 {
90   char *done_url;
91   CURLMsg *message;
92   int pending;
93   CURL *easy_handle;
94   FILE *file;
95 
96   while((message = curl_multi_info_read(curl_handle, &pending))) {
97     switch(message->msg) {
98     case CURLMSG_DONE:
99       /* Do not use message data after calling curl_multi_remove_handle() and
100          curl_easy_cleanup(). As per curl_multi_info_read() docs:
101          "WARNING: The data the returned pointer points to does not survive
102          calling curl_multi_cleanup, curl_multi_remove_handle or
103          curl_easy_cleanup." */
104       easy_handle = message->easy_handle;
105 
106       curl_easy_getinfo(easy_handle, CURLINFO_EFFECTIVE_URL, &done_url);
107       curl_easy_getinfo(easy_handle, CURLINFO_PRIVATE, &file);
108       printf("%s DONE\n", done_url);
109 
110       curl_multi_remove_handle(curl_handle, easy_handle);
111       curl_easy_cleanup(easy_handle);
112       if(file) {
113         fclose(file);
114       }
115       break;
116 
117     default:
118       fprintf(stderr, "CURLMSG default\n");
119       break;
120     }
121   }
122 }
123 
curl_perform(int fd,short event,void * arg)124 static void curl_perform(int fd, short event, void *arg)
125 {
126   int running_handles;
127   int flags = 0;
128   curl_context_t *context;
129 
130   (void)fd;
131 
132   if(event & EV_READ)
133     flags |= CURL_CSELECT_IN;
134   if(event & EV_WRITE)
135     flags |= CURL_CSELECT_OUT;
136 
137   context = (curl_context_t *) arg;
138 
139   curl_multi_socket_action(curl_handle, context->sockfd, flags,
140                            &running_handles);
141 
142   check_multi_info();
143 }
144 
on_timeout(evutil_socket_t fd,short events,void * arg)145 static void on_timeout(evutil_socket_t fd, short events, void *arg)
146 {
147   int running_handles;
148   (void)fd;
149   (void)events;
150   (void)arg;
151   curl_multi_socket_action(curl_handle, CURL_SOCKET_TIMEOUT, 0,
152                            &running_handles);
153   check_multi_info();
154 }
155 
start_timeout(CURLM * multi,long timeout_ms,void * userp)156 static int start_timeout(CURLM *multi, long timeout_ms, void *userp)
157 {
158   (void)multi;
159   (void)userp;
160   if(timeout_ms < 0) {
161     evtimer_del(timeout);
162   }
163   else {
164     struct timeval tv;
165     if(timeout_ms == 0)
166       timeout_ms = 1; /* 0 means call socket_action asap */
167     tv.tv_sec = timeout_ms / 1000;
168     tv.tv_usec = (timeout_ms % 1000) * 1000;
169     evtimer_del(timeout);
170     evtimer_add(timeout, &tv);
171   }
172   return 0;
173 }
174 
handle_socket(CURL * easy,curl_socket_t s,int action,void * userp,void * socketp)175 static int handle_socket(CURL *easy, curl_socket_t s, int action, void *userp,
176                          void *socketp)
177 {
178   curl_context_t *curl_context;
179   int events = 0;
180 
181   (void)easy;
182   (void)userp;
183 
184   switch(action) {
185   case CURL_POLL_IN:
186   case CURL_POLL_OUT:
187   case CURL_POLL_INOUT:
188     curl_context = socketp ?
189       (curl_context_t *) socketp : create_curl_context(s);
190 
191     curl_multi_assign(curl_handle, s, (void *) curl_context);
192 
193     if(action != CURL_POLL_IN)
194       events |= EV_WRITE;
195     if(action != CURL_POLL_OUT)
196       events |= EV_READ;
197 
198     events |= EV_PERSIST;
199 
200     event_del(curl_context->event);
201     event_assign(curl_context->event, base, curl_context->sockfd,
202       (short)events, curl_perform, curl_context);
203     event_add(curl_context->event, NULL);
204 
205     break;
206   case CURL_POLL_REMOVE:
207     if(socketp) {
208       event_del(((curl_context_t*) socketp)->event);
209       destroy_curl_context((curl_context_t*) socketp);
210       curl_multi_assign(curl_handle, s, NULL);
211     }
212     break;
213   default:
214     abort();
215   }
216 
217   return 0;
218 }
219 
main(int argc,char ** argv)220 int main(int argc, char **argv)
221 {
222   if(argc <= 1)
223     return 0;
224 
225   if(curl_global_init(CURL_GLOBAL_ALL)) {
226     fprintf(stderr, "Could not init curl\n");
227     return 1;
228   }
229 
230   base = event_base_new();
231   timeout = evtimer_new(base, on_timeout, NULL);
232 
233   curl_handle = curl_multi_init();
234   curl_multi_setopt(curl_handle, CURLMOPT_SOCKETFUNCTION, handle_socket);
235   curl_multi_setopt(curl_handle, CURLMOPT_TIMERFUNCTION, start_timeout);
236 
237   while(argc-- > 1) {
238     add_download(argv[argc], argc);
239   }
240 
241   event_base_dispatch(base);
242 
243   curl_multi_cleanup(curl_handle);
244   event_free(timeout);
245   event_base_free(base);
246 
247   libevent_global_shutdown();
248   curl_global_cleanup();
249 
250   return 0;
251 }
252