Implemented zmq_send_const

doc/zmq_send.txt

@@ -90,6 +90,7 @@ assert (rc == 2);
 
 SEE ALSO
 --------
+linkzmq:zmq_send_const[3]
 linkzmq:zmq_recv[3]
 linkzmq:zmq_socket[7]
 linkzmq:zmq[7]

doc/zmq_send_const.txt

+zmq_send_const(3)
+===========
+
+
+NAME
+----
+zmq_send_const - send a constant-memory message part on a socket
+
+
+SYNOPSIS
+--------
+*int zmq_send_const (void '*socket', void '*buf', size_t 'len', int 'flags');*
+
+
+DESCRIPTION
+-----------
+The _zmq_send_const()_ function shall queue a message created from the buffer
+referenced by the 'buf' and 'len' arguments. The message buffer is assumed
+to be constant-memory and will therefore not be copied or deallocated
+in any way. The 'flags' argument is a combination of the flags defined below:
+
+*ZMQ_DONTWAIT*::
+For socket types (DEALER, PUSH) that block when there are no available peers 
+(or all peers have full high-water mark), specifies that the operation should 
+be performed in non-blocking mode. If the message cannot be queued on the 
+'socket', the _zmq_send_const()_ function shall fail with 'errno' set to EAGAIN.
+
+*ZMQ_SNDMORE*::
+Specifies that the message being sent is a multi-part message, and that further
+message parts are to follow. Refer to the section regarding multi-part messages
+below for a detailed description.
+
+NOTE: A successful invocation of _zmq_send_const()_ does not indicate that the
+message has been transmitted to the network, only that it has been queued on
+the 'socket' and 0MQ has assumed responsibility for the message.
+
+
+Multi-part messages
+~~~~~~~~~~~~~~~~~~~
+A 0MQ message is composed of 1 or more message parts. 0MQ ensures atomic
+delivery of messages: peers shall receive either all _message parts_ of a
+message or none at all. The total number of message parts is unlimited except
+by available memory.
+
+An application that sends multi-part messages must use the _ZMQ_SNDMORE_ flag
+when sending each message part except the final one.
+
+
+RETURN VALUE
+------------
+The _zmq_send_const()_ function shall return number of bytes in the message
+if successful. Otherwise it shall return `-1` and set 'errno' to one of the
+values defined below.
+
+
+ERRORS
+------
+*EAGAIN*::
+Non-blocking mode was requested and the message cannot be sent at the moment.
+*ENOTSUP*::
+The _zmq_send_send()_ operation is not supported by this socket type.
+*EFSM*::
+The _zmq_send_send()_ operation cannot be performed on this socket at the moment
+due to the socket not being in the appropriate state.  This error may occur with
+socket types that switch between several states, such as ZMQ_REP.  See the
+_messaging patterns_ section of linkzmq:zmq_socket[3] for more information.
+*ETERM*::
+The 0MQ 'context' associated with the specified 'socket' was terminated.
+*ENOTSOCK*::
+The provided 'socket' was invalid.
+*EINTR*::
+The operation was interrupted by delivery of a signal before the message was
+sent.
+*EHOSTUNREACH*::
+The message cannot be routed.
+
+
+EXAMPLE
+-------
+.Sending a multi-part message
+----
+/* Send a multi-part message consisting of three parts to socket */
+rc = zmq_send_const (socket, "ABC", 3, ZMQ_SNDMORE);
+assert (rc == 3);
+rc = zmq_send_send (socket, "DEFGH", 5, ZMQ_SNDMORE);
+assert (rc == 5);
+/* Final part; no more parts to follow */
+rc = zmq_send_const (socket, "JK", 2, 0);
+assert (rc == 2);
+----
+
+SEE ALSO
+--------
+linkzmq:zmq_send[3]
+linkzmq:zmq_recv[3]
+linkzmq:zmq_socket[7]
+linkzmq:zmq[7]
+
+
+AUTHORS
+-------
+This page was written by the 0MQ community. To make a change please
+read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>.

include/zmq.h

@@ -342,6 +342,7 @@ ZMQ_EXPORT int zmq_connect (void *s, const char *addr);
 ZMQ_EXPORT int zmq_unbind (void *s, const char *addr);
 ZMQ_EXPORT int zmq_disconnect (void *s, const char *addr);
 ZMQ_EXPORT int zmq_send (void *s, const void *buf, size_t len, int flags);
+ZMQ_EXPORT int zmq_send_const (void *s, const void *buf, size_t len, int flags);
 ZMQ_EXPORT int zmq_recv (void *s, void *buf, size_t len, int flags);
 ZMQ_EXPORT int zmq_socket_monitor (void *s, const char *addr, int events);
 

src/zmq.cpp

@@ -376,6 +376,32 @@ int zmq_send (void *s_, const void *buf_, size_t len_, int flags_)
     return rc;
 }
 
+int zmq_send_const (void *s_, const void *buf_, size_t len_, int flags_)
+{
+    if (!s_ || !((zmq::socket_base_t*) s_)->check_tag ()) {
+        errno = ENOTSOCK;
+        return -1;
+    }
+    zmq_msg_t msg;
+    int rc = zmq_msg_init_data (&msg, (void*)buf_, len_, NULL, NULL);
+    if (rc != 0)
+        return -1;
+
+    zmq::socket_base_t *s = (zmq::socket_base_t *) s_;
+    rc = s_sendmsg (s, &msg, flags_);
+    if (unlikely (rc < 0)) {
+        int err = errno;
+        int rc2 = zmq_msg_close (&msg);
+        errno_assert (rc2 == 0);
+        errno = err;
+        return -1;
+    }
+    
+    //  Note the optimisation here. We don't close the msg object as it is
+    //  empty anyway. This may change when implementation of zmq_msg_t changes.
+    return rc;
+}
+
 
 // Send multiple messages.
 // TODO: this function has no man page