Bug concerining identity in XREQ socket fixed (issue 280)

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

src/xreq.cpp

@@ -24,7 +24,8 @@
 #include "msg.hpp"
 
 zmq::xreq_t::xreq_t (class ctx_t *parent_, uint32_t tid_) :
-    socket_base_t (parent_, tid_)
+    socket_base_t (parent_, tid_),
+    prefetched (false)
 {
     options.type = ZMQ_XREQ;
 
@@ -36,10 +37,13 @@ zmq::xreq_t::xreq_t (class ctx_t *parent_, uint32_t tid_) :
 
     options.send_identity = true;
     options.recv_identity = true;
+
+    prefetched_msg.init ();
 }
 
 zmq::xreq_t::~xreq_t ()
 {
+    prefetched_msg.close ();
 }
 
 void zmq::xreq_t::xattach_pipe (pipe_t *pipe_)
@@ -56,6 +60,14 @@ int zmq::xreq_t::xsend (msg_t *msg_, int flags_)
 
 int zmq::xreq_t::xrecv (msg_t *msg_, int flags_)
 {
+    //  If there is a prefetched message, return it.
+    if (prefetched) {
+        int rc = msg_->move (prefetched_msg);
+        errno_assert (rc == 0);
+        prefetched = false;
+        return 0;
+    }
+
     //  XREQ socket doesn't use identities. We can safely drop it and 
     while (true) {
         int rc = fq.recv (msg_, flags_);
@@ -69,7 +81,17 @@ int zmq::xreq_t::xrecv (msg_t *msg_, int flags_)
 
 bool zmq::xreq_t::xhas_in ()
 {
-    return fq.has_in ();
+    //  We may already have a message pre-fetched.
+    if (prefetched)
+        return true;
+
+    //  Try to read the next message to the pre-fetch buffer.
+    int rc = xrecv (&prefetched_msg, ZMQ_DONTWAIT);
+    if (rc != 0 && errno == EAGAIN)
+        return false;
+    zmq_assert (rc == 0);
+    prefetched = true;
+    return true;
 }
 
 bool zmq::xreq_t::xhas_out ()

src/xreq.hpp

@@ -62,6 +62,12 @@ namespace zmq
         fq_t fq;
         lb_t lb;
 
+        //  Have we prefetched a message.
+        bool prefetched;
+
+        //  Holds the prefetched message.
+        msg_t prefetched_msg;
+
         xreq_t (const xreq_t&);
         const xreq_t &operator = (const xreq_t&);
     };