+ if(!event_count) {
+ Sleep(timeout_ms);
+ continue;
+ }
+
+ /*
+ For some reason, Microsoft decided to make the FD_WRITE event edge-triggered instead of level-triggered,
+ which is the opposite of what select() does. In practice, that means that if a FD_WRITE event triggers,
+ it will never trigger again until a send() returns EWOULDBLOCK. Since the semantics of this event loop
+ is that write events are level-triggered (i.e. they continue firing until the socket is full), we need
+ to emulate these semantics by making sure we fire each IO_WRITE that is still writeable.
+
+ Note that technically FD_CLOSE has the same problem, but it's okay because user code does not rely on
+ this event being fired again if ignored.
+ */
+ io_t *writeable_io = NULL;
+
+ for splay_each(io_t, io, &io_tree)
+ if(io->flags & IO_WRITE && send(io->fd, NULL, 0, 0) == 0) {
+ writeable_io = io;
+ break;
+ }
+
+ if(writeable_io) {
+ writeable_io->cb(writeable_io->data, IO_WRITE);
+ continue;
+ }
+
+ WSAEVENT *events = xmalloc(event_count * sizeof(*events));
+ DWORD event_index = 0;
+
+ for splay_each(io_t, io, &io_tree) {
+ events[event_index] = io->event;
+ event_index++;
+ }
+
+ DWORD result = WSAWaitForMultipleEvents(event_count, events, FALSE, timeout_ms, FALSE);
+
+ WSAEVENT event;
+
+ if(result >= WSA_WAIT_EVENT_0 && result < WSA_WAIT_EVENT_0 + event_count) {
+ event = events[result - WSA_WAIT_EVENT_0];
+ }
+
+ free(events);
+
+ if(result == WSA_WAIT_TIMEOUT) {
+ continue;
+ }
+
+ if(result < WSA_WAIT_EVENT_0 || result >= WSA_WAIT_EVENT_0 + event_count) {
+ return false;
+ }
+
+ io_t *io = splay_search(&io_tree, &((io_t) {
+ .event = event
+ }));
+
+ if(!io) {
+ abort();
+ }
+
+ if(io->fd == -1) {
+ io->cb(io->data, 0);
+ } else {
+ WSANETWORKEVENTS network_events;
+
+ if(WSAEnumNetworkEvents(io->fd, io->event, &network_events) != 0) {
+ return false;
+ }
+
+ if(network_events.lNetworkEvents & READ_EVENTS) {
+ io->cb(io->data, IO_READ);
+ }
+
+ /*
+ The fd might be available for write too. However, if we already fired the read callback, that
+ callback might have deleted the io (e.g. through terminate_connection()), so we can't fire the
+ write callback here. Instead, we loop back and let the writable io loop above handle it.
+ */
+ }
+ }
+
+#endif
+
+ return true;