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@bagder bagder/pause.c
Created Mar 16, 2018

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attempt to repro pausing problem with multi_socket API
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>
#include <sys/poll.h>
#include <curl/curl.h>
#include <event2/event.h>
#include <event2/event_struct.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
#include <sys/cdefs.h>
#ifdef __GNUC__
#define _Unused __attribute__((unused))
#define _Unused
#define MSG_OUT stdout /* Send info to stdout, change to stderr if you want */
/* Global information, common to all connections */
typedef struct _GlobalInfo
struct event_base *evbase;
struct event timer_event;
CURLM *multi;
int still_running;
FILE *input;
} GlobalInfo;
/* Information associated with a specific easy handle */
typedef struct _ConnInfo
CURL *easy;
char *url;
GlobalInfo *global;
char error[CURL_ERROR_SIZE];
struct event periodic;
struct {
char *mem;
unsigned size;
unsigned base;
unsigned avail;
} buffer;
int paused;
} ConnInfo;
/* Information associated with a specific socket */
typedef struct _SockInfo
curl_socket_t sockfd;
CURL *easy;
int action;
long timeout;
struct event ev;
GlobalInfo *global;
} SockInfo;
#define BUFFER_SIZE 2097152
#define __case(code) \
case code: s = __STRING(code)
/* Die if we get a bad CURLMcode somewhere */
static void mcode_or_die(const char *where, CURLMcode code)
if(CURLM_OK != code) {
const char *s;
switch(code) {
__case(CURLM_BAD_HANDLE); break;
__case(CURLM_BAD_EASY_HANDLE); break;
__case(CURLM_OUT_OF_MEMORY); break;
__case(CURLM_INTERNAL_ERROR); break;
__case(CURLM_UNKNOWN_OPTION); break;
__case(CURLM_LAST); break;
default: s = "CURLM_unknown"; break;
fprintf(MSG_OUT, "ERROR: %s returns %s\n", where, s);
/* ignore this error */
fprintf(MSG_OUT, "ERROR: %s returns %s\n", where, s);
/* Update the event timer after curl_multi library calls */
static int multi_timer_cb(CURLM *multi _Unused, long timeout_ms, GlobalInfo *g)
struct timeval timeout;
CURLMcode rc;
timeout.tv_sec = timeout_ms/1000;
timeout.tv_usec = (timeout_ms%1000)*1000;
fprintf(MSG_OUT, "multi_timer_cb: Setting timeout to %ld ms\n", timeout_ms);
* if timeout_ms is 0, call curl_multi_socket_action() at once!
* if timeout_ms is -1, just delete the timer
* for all other values of timeout_ms, this should set or *update*
* the timer to the new value
if (timeout_ms == 0) {
rc = curl_multi_socket_action(g->multi,
CURL_SOCKET_TIMEOUT, 0, &g->still_running);
mcode_or_die("multi_timer_cb: curl_multi_socket_action", rc);
} else if (timeout_ms == -1)
evtimer_add(&g->timer_event, &timeout);
return 0;
/* Check for completed transfers, and remove their easy handles */
static void check_multi_info(GlobalInfo *g)
char *eff_url;
CURLMsg *msg;
int msgs_left;
ConnInfo *conn;
CURL *easy;
CURLcode res;
fprintf(MSG_OUT, "REMAINING: %d\n", g->still_running);
while((msg = curl_multi_info_read(g->multi, &msgs_left))) {
if(msg->msg == CURLMSG_DONE) {
easy = msg->easy_handle;
res = msg->data.result;
curl_easy_getinfo(easy, CURLINFO_PRIVATE, &conn);
curl_easy_getinfo(easy, CURLINFO_EFFECTIVE_URL, &eff_url);
fprintf(MSG_OUT, "DONE: %s => (%d) %s\n", eff_url, res, conn->error);
curl_multi_remove_handle(g->multi, easy);
/* Called by libevent when we get action on a multi socket */
static void event_cb(int fd, short kind, void *userp)
GlobalInfo *g = (GlobalInfo*) userp;
CURLMcode rc;
int action =
(kind & EV_READ ? CURL_CSELECT_IN : 0) |
rc = curl_multi_socket_action(g->multi, fd, action, &g->still_running);
mcode_or_die("event_cb: curl_multi_socket_action", rc);
if(g->still_running <= 0) {
fprintf(MSG_OUT, "last transfer done, kill timeout\n");
if(evtimer_pending(&g->timer_event, NULL)) {
/* Called by libevent when our timeout expires */
static void timer_cb(int fd _Unused, short kind _Unused, void *userp)
GlobalInfo *g = (GlobalInfo *)userp;
CURLMcode rc;
rc = curl_multi_socket_action(g->multi,
CURL_SOCKET_TIMEOUT, 0, &g->still_running);
mcode_or_die("timer_cb: curl_multi_socket_action", rc);
static int pausecounter = 0;
/* Called by libevent for our periodic timers */
static void periodic_cb(int fd _Unused, short kind _Unused, void *userp)
ConnInfo *conn = (ConnInfo *)userp;
fprintf(stderr, "tick: counter %d %s\n", pausecounter,
if (conn->paused) {
if (!--pausecounter) {
fprintf(stderr, "tick: resuming stream\n");
conn->paused = 0;
curl_easy_pause(conn->easy, CURLPAUSE_CONT);
/* Clean up the SockInfo structure */
static void remsock(SockInfo *f)
if(f) {
/* Assign information to a SockInfo structure */
static void setsock(SockInfo *f, curl_socket_t s, CURL *e, int act,
GlobalInfo *g)
int kind =
f->sockfd = s;
f->action = act;
f->easy = e;
event_assign(&f->ev, g->evbase, f->sockfd, kind, event_cb, g);
event_add(&f->ev, NULL);
/* Initialize a new SockInfo structure */
static void addsock(curl_socket_t s, CURL *easy, int action, GlobalInfo *g)
SockInfo *fdp = calloc(sizeof(SockInfo), 1);
fdp->global = g;
setsock(fdp, s, easy, action, g);
curl_multi_assign(g->multi, s, fdp);
static int sock_cb(CURL *e, curl_socket_t s, int what, void *cbp, void *sockp)
GlobalInfo *g = (GlobalInfo*) cbp;
SockInfo *fdp = (SockInfo*) sockp;
const char *whatstr[]={ "none", "IN", "OUT", "INOUT", "REMOVE" };
"socket callback: s=%d e=%p what=%s ", s, e, whatstr[what]);
if(what == CURL_POLL_REMOVE) {
fprintf(MSG_OUT, "\n");
else {
if(!fdp) {
fprintf(MSG_OUT, "Adding data: %s\n", whatstr[what]);
addsock(s, e, what, g);
else {
"Changing action from %s to %s\n",
whatstr[fdp->action], whatstr[what]);
setsock(fdp, s, e, what, g);
return 0;
static size_t write_cb(void *ptr _Unused, size_t size, size_t nmemb, void *data)
size_t realsize = size * nmemb;
ConnInfo *conn _Unused = (ConnInfo*) data;
if (++pausecounter > 10) {
fprintf(MSG_OUT, "write_cb: PAUSE!\n");
conn->paused = 1;
fprintf(MSG_OUT, "write_cb: called %d\n", pausecounter);
return realsize;
static int prog_cb(void *p, double dltotal, double dlnow, double ult _Unused,
double uln _Unused)
ConnInfo *conn _Unused = (ConnInfo *)p;
// fprintf(MSG_OUT, "Progress: %s (%g/%g)\n", conn->url, dlnow, dltotal);
return 0;
/* Create a new easy handle, and add it to the global curl_multi */
static void new_conn(char *url, GlobalInfo *g)
ConnInfo *conn;
CURLMcode rc;
struct timeval tv = (struct timeval) { 0, 100000 };
conn = calloc(1, sizeof(ConnInfo));
memset(conn, 0, sizeof(ConnInfo));
conn->easy = curl_easy_init();
if(!conn->easy) {
fprintf(MSG_OUT, "curl_easy_init() failed, exiting!\n");
conn->global = g;
conn->url = strdup(url);
curl_easy_setopt(conn->easy, CURLOPT_URL, conn->url);
curl_easy_setopt(conn->easy, CURLOPT_WRITEFUNCTION, write_cb);
curl_easy_setopt(conn->easy, CURLOPT_WRITEDATA, conn);
curl_easy_setopt(conn->easy, CURLOPT_VERBOSE, 1L);
curl_easy_setopt(conn->easy, CURLOPT_ERRORBUFFER, conn->error);
curl_easy_setopt(conn->easy, CURLOPT_PRIVATE, conn);
curl_easy_setopt(conn->easy, CURLOPT_NOPROGRESS, 0L);
curl_easy_setopt(conn->easy, CURLOPT_PROGRESSFUNCTION, prog_cb);
curl_easy_setopt(conn->easy, CURLOPT_PROGRESSDATA, conn);
curl_easy_setopt(conn->easy, CURLOPT_FOLLOWLOCATION, 1L);
"Adding easy %p to multi %p (%s)\n", conn->easy, g->multi, url);
rc = curl_multi_add_handle(g->multi, conn->easy);
mcode_or_die("new_conn: curl_multi_add_handle", rc);
/* note that the add_handle() will set a time-out to trigger very soon so
that the necessary socket_action() call will be called by this app */
event_assign(&conn->periodic, g->evbase, -1, EV_TIMEOUT | EV_PERSIST, periodic_cb, conn);
event_add(&conn->periodic, &tv);
conn->buffer.mem = malloc(BUFFER_SIZE);
conn->buffer.size = BUFFER_SIZE;
// conn->buffer.base = conn->buffer.avail = 0;
int main(int argc, char **argv)
GlobalInfo g;
int n;
memset(&g, 0, sizeof(GlobalInfo));
g.evbase = event_base_new();
g.multi = curl_multi_init();
evtimer_assign(&g.timer_event, g.evbase, timer_cb, &g);
/* setup the generic multi interface options we want */
curl_multi_setopt(g.multi, CURLMOPT_SOCKETFUNCTION, sock_cb);
curl_multi_setopt(g.multi, CURLMOPT_SOCKETDATA, &g);
curl_multi_setopt(g.multi, CURLMOPT_TIMERFUNCTION, multi_timer_cb);
curl_multi_setopt(g.multi, CURLMOPT_TIMERDATA, &g);
for (n = 1; n < argc; ++n)
new_conn(argv[n], &g);
/* this, of course, won't get called since only way to stop this program is
via ctrl-C, but it is here to show how cleanup /would/ be done. */
return 0;
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