socket_poller::wait returns only triggered events

Return value is the number of events found. This also propagates to the return value of zmq_poller_wait_all.

zmq_poller_wait was only returning events on the first-registered socket.

src/socket_poller.cpp

@@ -412,7 +412,6 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
     uint64_t end = 0;
 
     bool first_pass = true;
-    bool found = false;
 
     while (true) {
         //  Compute the timeout for the subsequent poll.
@@ -440,13 +439,13 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
             signaler.recv ();
 
         //  Check for the events.
-        int i = 0;
-        for (items_t::iterator it = items.begin (); it != items.end () && i < n_events_; ++i, ++it) {
+        int found = 0;
+        for (items_t::iterator it = items.begin (); it != items.end () && found < n_events_; ++it) {
 
-            events_[i].socket = NULL;
-            events_[i].fd = 0;
-            events_[i].user_data = NULL;
-            events_[i].events = 0;
+            events_[found].socket = NULL;
+            events_[found].fd = 0;
+            events_[found].user_data = NULL;
+            events_[found].events = 0;
 
             //  The poll item is a 0MQ socket. Retrieve pending events
             //  using the ZMQ_EVENTS socket option.
@@ -458,10 +457,10 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
                 }
 
                 if (it->events & events) {
-                    events_[i].socket = it->socket;
-                    events_[i].user_data = it->user_data;
-                    events_[i].events = it->events & events;
-                    found = true;
+                    events_[found].socket = it->socket;
+                    events_[found].user_data = it->user_data;
+                    events_[found].events = it->events & events;
+                    ++found;
                 }
             }
             //  Else, the poll item is a raw file descriptor, simply convert
@@ -480,16 +479,22 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
                     events |= ZMQ_POLLERR;
 
                 if (events) {
-                    events_[i].socket = NULL;
-                    events_[i].user_data = it->user_data;
-                    events_[i].fd = it->fd;
-                    events_[i].events = events;
-                    found = true;
+                    events_[found].socket = NULL;
+                    events_[found].user_data = it->user_data;
+                    events_[found].fd = it->fd;
+                    events_[found].events = events;
+                    ++found;
                 }
             }
         }
         if (found) {
-            return 0;
+            for (int i = found; i < n_events_; ++i) {
+                events_[i].socket = NULL;
+                events_[i].fd = 0;
+                events_[i].user_data = NULL;
+                events_[i].events = 0;
+            }
+            return found;
         }
 
         //  If timeout is zero, exit immediately whether there are events or not.
@@ -548,7 +553,6 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
     uint64_t end = 0;
 
     bool first_pass = true;
-    bool found = false;
     fd_set inset, outset, errset;
 
     while (true) {
@@ -596,8 +600,8 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
             signaler.recv ();
 
         //  Check for the events.
-        int i = 0;
-        for (items_t::iterator it = items.begin (); it != items.end () && i < n_events_; ++i, ++it) {
+        int found = 0;
+        for (items_t::iterator it = items.begin (); it != items.end () && found < n_events_; ++it) {
 
             //  The poll item is a 0MQ socket. Retrieve pending events
             //  using the ZMQ_EVENTS socket option.
@@ -608,10 +612,10 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
                     return -1;
 
                 if (it->events & events) {
-                    events_[i].socket = it->socket;
-                    events_[i].user_data = it->user_data;
-                    events_[i].events = it->events & events;
-                    found = true;
+                    events_[found].socket = it->socket;
+                    events_[found].user_data = it->user_data;
+                    events_[found].events = it->events & events;
+                    ++found;
                 }
             }
             //  Else, the poll item is a raw file descriptor, simply convert
@@ -627,16 +631,23 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
                     events |= ZMQ_POLLERR;
 
                 if (events) {
-                    events_[i].socket = NULL;
-                    events_[i].user_data = it->user_data;
-                    events_[i].fd = it->fd;
-                    events_[i].events = events;
-                    found = true;
+                    events_[found].socket = NULL;
+                    events_[found].user_data = it->user_data;
+                    events_[found].fd = it->fd;
+                    events_[found].events = events;
+                    ++found;
                 }
             }
         }
         if (found) {
-            return 0;
+            // zero-out remaining events
+            for (int i = found; i < n_events_; ++i) {
+                events_[i].socket = NULL;
+                events_[i].fd = 0;
+                events_[i].user_data = NULL;
+                events_[i].events = 0;
+            }
+            return found;
         }
 
         //  If timeout is zero, exit immediately whether there are events or not.

src/zmq.cpp

@@ -755,6 +755,7 @@ inline int zmq_poller_poll (zmq_pollitem_t *items_, int nitems_, long timeout_)
 
     //  Register sockets with poller
     for (int i = 0; i < nitems_; i++) {
+        items_[i].revents = 0;
         if (items_[i].socket) {
             //  Poll item is a 0MQ socket.
             rc = zmq_poller_add (poller, items_[i].socket, NULL, items_[i].events);
@@ -782,9 +783,19 @@ inline int zmq_poller_poll (zmq_pollitem_t *items_, int nitems_, long timeout_)
         return rc;
     }
 
-    //  Put the event information where zmq_poll expects it to go.
-    for (int i = 0; i < nitems_; i++) {
-        items_[i].revents = events[i].events;
+    //  Transform poller events into zmq_pollitem events
+    //  items_ contains all items, while events only contains fired events.
+    //  The two are still co-ordered, so the step through items
+    //  Checking for matches only on the first event
+    int found_events = rc;
+    for (int i = 0, j = 0; i < nitems_ && j < found_events; i++) {
+        if (
+            (items_[i].socket && items_[i].socket == events[j].socket) ||
+            (items_[i].fd && items_[i].fd == events[j].fd)
+        ) {
+            items_[i].revents = events[j].events;
+            j++;
+        }
     }
 
     //  Cleanup
@@ -1284,8 +1295,8 @@ int zmq_poller_wait (void *poller_, zmq_poller_event_t *event, long timeout_)
     if (rc < 0) {
         memset (event, 0, sizeof(zmq_poller_event_t));
     }
-
-    return rc;
+    // wait_all returns number of events, but we return 0 for any success
+    return rc >= 0 ? 0 : rc;
 }
 
 int zmq_poller_wait_all (void *poller_, zmq_poller_event_t *events, int n_events, long timeout_)