Implement zmq_sendv.

Posix style send multiple messages using scatter/gather array.

src/zmq.cpp

@@ -50,6 +50,17 @@
 #include <unistd.h>
 #endif
 
+// XSI vector I/O
+#if ZMQ_HAVE_UIO
+#include <sys/uio.h>
+#else
+struct iovec 
+{
+    void *iov_base;
+    size_t iov_len;
+};
+#endif
+
 #include <string.h>
 #include <errno.h>
 #include <stdlib.h>
@@ -294,6 +305,10 @@ int zmq_sendmsg (void *s_, zmq_msg_t *msg_, int flags_)
 
 int zmq_send (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_size (&msg, len_);
     if (rc != 0)
@@ -317,6 +332,47 @@ int zmq_send (void *s_, const void *buf_, size_t len_, int flags_)
     return rc;
 }
 
+// Send multiple messages.
+//
+// If flag bit ZMQ_SNDMORE is set the vector is treated as
+// a single multi-part message, i.e. the last message has
+// ZMQ_SENDMORE bit switched off.
+//
+int zmq_sendv (void *s_, iovec *a_, size_t count_, int flags_)
+{
+    if (!s_ || !((zmq::socket_base_t*) s_)->check_tag ()) {
+        errno = ENOTSOCK;
+        return -1;
+    }
+    int rc = 0;
+    zmq_msg_t msg;
+    zmq::socket_base_t *s = (zmq::socket_base_t *) s_;
+    if(s->thread_safe()) s->lock();
+    for(size_t i = 0; i < count_; ++i)
+    {
+        rc = zmq_msg_init_size (&msg, a_[i].iov_len);
+        if (rc != 0)
+        {
+            rc = -1;
+            break;
+        }
+        memcpy (zmq_msg_data (&msg), a_[i].iov_base, a_[i].iov_len);
+
+        if (i == count_ - 1) flags_ = flags_ & ~ZMQ_SNDMORE;
+        rc = inner_sendmsg (s, &msg, flags_);
+        if (unlikely (rc < 0)) {
+           int err = errno;
+           int rc2 = zmq_msg_close (&msg);
+           errno_assert (rc2 == 0);
+           errno = err;
+           rc = -1;
+           break;
+        }
+    }
+    if(s->thread_safe()) s->unlock();
+    return rc; 
+}
+
 // Receiving functions.
 
 static int inner_recvmsg (zmq::socket_base_t *s_, zmq_msg_t *msg_, int flags_)