From 046534480bd9973eb124ad3b4c88175521865106 Mon Sep 17 00:00:00 2001
From: jean-airoldie <25088801+jean-airoldie@users.noreply.github.com>
Date: Sat, 27 Apr 2019 20:36:24 -0400
Subject: [PATCH] Problem: Cannot get thread safe socket fd

Solution: Add a method to get the zmq_poller's signaler fd. Then we can
associate a poller instance with every thread safe socket and use its
fd.
---
 include/zmq.h         |  1 +
 src/socket_poller.cpp | 11 +++++++++++
 src/socket_poller.hpp |  2 ++
 src/zmq.cpp           |  5 +++++
 src/zmq_draft.h       |  1 +
 5 files changed, 20 insertions(+)

diff --git a/include/zmq.h b/include/zmq.h
index 2b3a5ec7..780dfc6c 100644
--- a/include/zmq.h
+++ b/include/zmq.h
@@ -709,6 +709,7 @@ ZMQ_EXPORT int zmq_poller_wait_all (void *poller,
                                     zmq_poller_event_t *events,
                                     int n_events,
                                     long timeout);
+ZMQ_EXPORT int zmq_poller_fd (void *poller);
 
 #if defined _WIN32
 ZMQ_EXPORT int
diff --git a/src/socket_poller.cpp b/src/socket_poller.cpp
index 57360bbc..9aaf4607 100644
--- a/src/socket_poller.cpp
+++ b/src/socket_poller.cpp
@@ -86,6 +86,17 @@ bool zmq::socket_poller_t::check_tag ()
     return _tag == 0xCAFEBABE;
 }
 
+int zmq::socket_poller_t::signaler_fd ()
+{
+    if (_signaler) {
+        return _signaler->get_fd ();
+    } else {
+        // Only thread-safe socket types are guaranteed to have a signaler.
+        errno = EINVAL;
+        return -1;
+    }
+}
+
 int zmq::socket_poller_t::add (socket_base_t *socket_,
                                void *user_data_,
                                short events_)
diff --git a/src/socket_poller.hpp b/src/socket_poller.hpp
index 916d98a7..336832d2 100644
--- a/src/socket_poller.hpp
+++ b/src/socket_poller.hpp
@@ -75,6 +75,8 @@ class socket_poller_t
     int add_fd (fd_t fd_, void *user_data_, short events_);
     int modify_fd (fd_t fd_, short events_);
     int remove_fd (fd_t fd_);
+    // Returns the signaler's fd if there is one, otherwise errors.
+    int signaler_fd ();
 
     int wait (event_t *event_, int n_events_, long timeout_);
 
diff --git a/src/zmq.cpp b/src/zmq.cpp
index 5d186283..521d9939 100644
--- a/src/zmq.cpp
+++ b/src/zmq.cpp
@@ -1278,6 +1278,11 @@ int zmq_poller_wait_all (void *poller_,
     return rc;
 }
 
+int zmq_poller_fd (void *poller_)
+{
+    return static_cast<zmq::socket_poller_t *> (poller_)->signaler_fd ();
+}
+
 //  Peer-specific state
 
 int zmq_socket_get_peer_state (void *s_,
diff --git a/src/zmq_draft.h b/src/zmq_draft.h
index c8934d45..2bba4133 100644
--- a/src/zmq_draft.h
+++ b/src/zmq_draft.h
@@ -105,6 +105,7 @@ int zmq_poller_wait_all (void *poller_,
                          zmq_poller_event_t *events_,
                          int n_events_,
                          long timeout_);
+int zmq_poller_fd (void *poller_);
 
 #if defined _WIN32
 int zmq_poller_add_fd (void *poller_,