Add support for RADIO/DISH sockets if draft API is enabled

This commit introduces new socket_type enumeration values as well
as the following supporting functions:

socket_t::join()
socket_t::leave()
message_t::group()
message_t::set_group()

Author: Tulon

tests/message.cpp

@@ -126,4 +126,11 @@ TEST(message, routing_id_persists)
     msg.set_routing_id(123);
     ASSERT_EQ(123u, msg.routing_id());
 }
+
+TEST(message, group_persists)
+{
+    zmq::message_t msg;
+    msg.set_group("mygroup");
+    ASSERT_STREQ("mygroup", msg.group());
+}
 #endif

zmq.hpp

@@ -409,6 +409,18 @@ class message_t
         if (rc != 0)
             throw error_t();
     }
+
+    inline const char* group() const
+    {
+        return zmq_msg_group(const_cast<zmq_msg_t*>(&msg));
+    }
+
+    inline void set_group(const char* group)
+    {
+        int rc = zmq_msg_set_group(&msg, group);
+        if (rc != 0)
+            throw error_t();
+    }
 #endif
 
     /** Dump content to string. Ascii chars are readable, the rest is printed as hex.
@@ -546,9 +558,11 @@ enum class socket_type : int
     xsub = ZMQ_XSUB,
     push = ZMQ_PUSH,
     pull = ZMQ_PULL,
-#ifdef ZMQ_BUILD_DRAFT_API
+#if defined(ZMQ_BUILD_DRAFT_API) && ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 0)
     server = ZMQ_SERVER,
     client = ZMQ_CLIENT,
+    radio = ZMQ_RADIO,
+    dish = ZMQ_DISH,
 #endif
 #if ZMQ_VERSION_MAJOR >= 4
     stream = ZMQ_STREAM,
@@ -715,6 +729,22 @@ class socket_t
         throw error_t();
     }
 
+#if defined(ZMQ_BUILD_DRAFT_API) && ZMQ_VERSION >= ZMQ_MAKE_VERSION(4, 2, 0)
+    inline void join(const char* group)
+    {
+        int rc = zmq_join(ptr, group);
+        if (rc != 0)
+            throw error_t();
+    }
+
+    inline void leave(const char* group)
+    {
+        int rc = zmq_leave(ptr, group);
+        if (rc != 0)
+            throw error_t();
+    }
+#endif
+
   private:
     inline void init(context_t &context_, int type_)
     {