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docs: added multi-event.c example

Similar to multi-uv.c but using libevent 2. This is a simpler libevent
integration example then hiperfifo.c.

Closes #4471
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Andrei Valeriu BICA authored and bagder committed Oct 7, 2019
1 parent 8bb3a95 commit b905e26b0573e0b98c36e958c901480ac249350c
Showing with 241 additions and 1 deletion.
  1. +1 −1 docs/examples/Makefile.inc
  2. +240 −0 docs/examples/multi-event.c
@@ -45,4 +45,4 @@ COMPLICATED_EXAMPLES = curlgtk.c curlx.c htmltitle.cpp cacertinmem.c \
sampleconv.c synctime.c threaded-ssl.c evhiperfifo.c \
smooth-gtk-thread.c version-check.pl href_extractor.c asiohiper.cpp \
multi-uv.c xmlstream.c usercertinmem.c sessioninfo.c \
threaded-shared-conn.c crawler.c ephiperfifo.c
threaded-shared-conn.c crawler.c ephiperfifo.c multi-event.c
@@ -0,0 +1,240 @@
/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at https://curl.haxx.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
***************************************************************************/

/* <DESC>
* multi_socket API using libevent
* </DESC>
*/

#include <stdio.h>
#include <stdlib.h>
#include <event2/event.h>
#include <curl/curl.h>

struct event_base *base;
CURLM *curl_handle;
struct event *timeout;

typedef struct curl_context_s {
struct event *event;
curl_socket_t sockfd;
} curl_context_t;

static void curl_perform(int fd, short event, void *arg);

static curl_context_t* create_curl_context(curl_socket_t sockfd)
{
curl_context_t *context;

context = (curl_context_t *) malloc(sizeof(*context));

context->sockfd = sockfd;

context->event = event_new(base, sockfd, 0, curl_perform, context);

return context;
}

static void destroy_curl_context(curl_context_t *context)
{
event_del(context->event);
event_free(context->event);
free(context);
}

static void add_download(const char *url, int num)
{
char filename[50];
FILE *file;
CURL *handle;

snprintf(filename, 50, "%d.download", num);

file = fopen(filename, "wb");
if(!file) {
fprintf(stderr, "Error opening %s\n", filename);
return;
}

handle = curl_easy_init();
curl_easy_setopt(handle, CURLOPT_WRITEDATA, file);
curl_easy_setopt(handle, CURLOPT_PRIVATE, file);
curl_easy_setopt(handle, CURLOPT_URL, url);
curl_multi_add_handle(curl_handle, handle);
fprintf(stderr, "Added download %s -> %s\n", url, filename);
}

static void check_multi_info(void)
{
char *done_url;
CURLMsg *message;
int pending;
CURL *easy_handle;
FILE *file;

while((message = curl_multi_info_read(curl_handle, &pending))) {
switch(message->msg) {
case CURLMSG_DONE:
/* Do not use message data after calling curl_multi_remove_handle() and
curl_easy_cleanup(). As per curl_multi_info_read() docs:
"WARNING: The data the returned pointer points to will not survive
calling curl_multi_cleanup, curl_multi_remove_handle or
curl_easy_cleanup." */
easy_handle = message->easy_handle;

curl_easy_getinfo(easy_handle, CURLINFO_EFFECTIVE_URL, &done_url);
curl_easy_getinfo(easy_handle, CURLINFO_PRIVATE, &file);
printf("%s DONE\n", done_url);

curl_multi_remove_handle(curl_handle, easy_handle);
curl_easy_cleanup(easy_handle);
if(file) {
fclose(file);
}
break;

default:
fprintf(stderr, "CURLMSG default\n");
break;
}
}
}

static void curl_perform(int fd, short event, void *arg)
{
int running_handles;
int flags = 0;
curl_context_t *context;

if(event & EV_READ)
flags |= CURL_CSELECT_IN;
if(event & EV_WRITE)
flags |= CURL_CSELECT_OUT;

context = (curl_context_t *) arg;

curl_multi_socket_action(curl_handle, context->sockfd, flags,
&running_handles);

check_multi_info();
}

static void on_timeout(evutil_socket_t fd, short events, void *arg)
{
int running_handles;
curl_multi_socket_action(curl_handle, CURL_SOCKET_TIMEOUT, 0,
&running_handles);
check_multi_info();
}

static int start_timeout(CURLM *multi, long timeout_ms, void *userp)
{
if(timeout_ms < 0) {
evtimer_del(timeout);
}
else {
if(timeout_ms == 0)
timeout_ms = 1; /* 0 means directly call socket_action, but we'll do it
in a bit */
struct timeval tv;
tv.tv_sec = timeout_ms / 1000;
tv.tv_usec = (timeout_ms % 1000) * 1000;
evtimer_del(timeout);
evtimer_add(timeout, &tv);
}
return 0;
}

static int handle_socket(CURL *easy, curl_socket_t s, int action, void *userp,
void *socketp)
{
curl_context_t *curl_context;
int events = 0;

switch(action) {
case CURL_POLL_IN:
case CURL_POLL_OUT:
case CURL_POLL_INOUT:
curl_context = socketp ?
(curl_context_t *) socketp : create_curl_context(s);

curl_multi_assign(curl_handle, s, (void *) curl_context);

if(action != CURL_POLL_IN)
events |= EV_WRITE;
if(action != CURL_POLL_OUT)
events |= EV_READ;

events |= EV_PERSIST;

event_del(curl_context->event);
event_assign(curl_context->event, base, curl_context->sockfd, events,
curl_perform, curl_context);
event_add(curl_context->event, NULL);

break;
case CURL_POLL_REMOVE:
if(socketp) {
event_del(((curl_context_t*) socketp)->event);
destroy_curl_context((curl_context_t*) socketp);
curl_multi_assign(curl_handle, s, NULL);
}
break;
default:
abort();
}

return 0;
}

int main(int argc, char **argv)
{
if(argc <= 1)
return 0;

if(curl_global_init(CURL_GLOBAL_ALL)) {
fprintf(stderr, "Could not init curl\n");
return 1;
}

base = event_base_new();
timeout = evtimer_new(base, on_timeout, NULL);

curl_handle = curl_multi_init();
curl_multi_setopt(curl_handle, CURLMOPT_SOCKETFUNCTION, handle_socket);
curl_multi_setopt(curl_handle, CURLMOPT_TIMERFUNCTION, start_timeout);

while(argc-- > 1) {
add_download(argv[argc], argc);
}

event_base_dispatch(base);

curl_multi_cleanup(curl_handle);
event_free(timeout);
event_base_free(base);

libevent_global_shutdown();
curl_global_cleanup();

return 0;
}

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