attempt to repro pausing problem with multi_socket API

pause.c

#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))
#else
#define _Unused
#endif

#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;
      __case(CURLM_BAD_SOCKET);
      fprintf(MSG_OUT, "ERROR: %s returns %s\n", where, s);
      /* ignore this error */
      return;
    }
    fprintf(MSG_OUT, "ERROR: %s returns %s\n", where, s);
    exit(code);
  }
}


/* 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);

  /* TODO
   *
   * 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_del(&g->timer_event);
  else
    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);
      free(conn->url);
      curl_easy_cleanup(easy);
      free(conn->buffer.mem);
      event_del(&conn->periodic);
      free(conn);
    }
  }
}



/* 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) |
    (kind & EV_WRITE ? CURL_CSELECT_OUT : 0);

  rc = curl_multi_socket_action(g->multi, fd, action, &g->still_running);
  mcode_or_die("event_cb: curl_multi_socket_action", rc);

  check_multi_info(g);
  if(g->still_running <= 0) {
    fprintf(MSG_OUT, "last transfer done, kill timeout\n");
    if(evtimer_pending(&g->timer_event, NULL)) {
      evtimer_del(&g->timer_event);
    }
  }
}



/* 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);
  check_multi_info(g);
}

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,
          conn->paused?"[PAUSED]":"");

  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) {
    event_del(&f->ev);
    free(f);
  }
}



/* Assign information to a SockInfo structure */
static void setsock(SockInfo *f, curl_socket_t s, CURL *e, int act,
                    GlobalInfo *g)
{
  int kind =
     (act&CURL_POLL_IN?EV_READ:0)|(act&CURL_POLL_OUT?EV_WRITE:0)|EV_PERSIST;

  f->sockfd = s;
  f->action = act;
  f->easy = e;
  event_del(&f->ev);
  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);
}

/* CURLMOPT_SOCKETFUNCTION */
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" };

  fprintf(MSG_OUT,
          "socket callback: s=%d e=%p what=%s ", s, e, whatstr[what]);
  if(what == CURL_POLL_REMOVE) {
    fprintf(MSG_OUT, "\n");
    remsock(fdp);
  }
  else {
    if(!fdp) {
      fprintf(MSG_OUT, "Adding data: %s\n", whatstr[what]);
      addsock(s, e, what, g);
    }
    else {
      fprintf(MSG_OUT,
              "Changing action from %s to %s\n",
              whatstr[fdp->action], whatstr[what]);
      setsock(fdp, s, e, what, g);
    }
  }
  return 0;
}

/* CURLOPT_WRITEFUNCTION */
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;
    return CURL_WRITEFUNC_PAUSE;
  }

  fprintf(MSG_OUT, "write_cb: called %d\n", pausecounter);
  return realsize;
}


/* CURLOPT_PROGRESSFUNCTION */
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->error[0]='\0';

  conn->easy = curl_easy_init();
  if(!conn->easy) {
    fprintf(MSG_OUT, "curl_easy_init() failed, exiting!\n");
    exit(2);
  }
  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);
  fprintf(MSG_OUT,
          "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);

  event_base_dispatch(g.evbase);

  /* 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. */
  event_del(&g.timer_event);
  event_base_free(g.evbase);
  curl_multi_cleanup(g.multi);
  return 0;
}