From 06d7a447378c8e9f0805c219deaf8e7e7ef1eeb0 Mon Sep 17 00:00:00 2001
From: Martin Hurton <hurtonm@gmail.com>
Date: Tue, 2 Mar 2010 10:48:30 +0100
Subject: Implement flow control for ZMQ_PUB sockets

---
 src/pub.cpp | 34 ++++++++++++++++++++++++++--------
 src/pub.hpp |  7 +++++++
 2 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/src/pub.cpp b/src/pub.cpp
index b6802fd..2971e5c 100644
--- a/src/pub.cpp
+++ b/src/pub.cpp
@@ -25,7 +25,8 @@
 #include "pipe.hpp"
 
 zmq::pub_t::pub_t (class app_thread_t *parent_) :
-    socket_base_t (parent_)
+    socket_base_t (parent_),
+    stalled_pipe (NULL)
 {
     options.requires_in = false;
     options.requires_out = true;
@@ -53,6 +54,8 @@ void zmq::pub_t::xdetach_inpipe (class reader_t *pipe_)
 void zmq::pub_t::xdetach_outpipe (class writer_t *pipe_)
 {
     out_pipes.erase (pipe_);
+    if (pipe_ == stalled_pipe)
+        stalled_pipe = NULL;
 }
 
 void zmq::pub_t::xkill (class reader_t *pipe_)
@@ -67,7 +70,8 @@ void zmq::pub_t::xrevive (class reader_t *pipe_)
 
 void zmq::pub_t::xrevive (class writer_t *pipe_)
 {
-    zmq_not_implemented ();
+    zmq_assert (stalled_pipe = pipe_);
+    stalled_pipe = NULL;
 }
 
 int zmq::pub_t::xsetsockopt (int option_, const void *optval_,
@@ -91,11 +95,10 @@ int zmq::pub_t::xsend (zmq_msg_t *msg_, int flags_)
     }
 
     //  First check whether all pipes are available for writing.
-    for (out_pipes_t::size_type i = 0; i != pipes_count; i++)
-        if (!out_pipes [i]->check_write ()) {
-            errno = EAGAIN;
-            return -1;
-        }
+    if (!check_write ()) {
+        errno = EAGAIN;
+        return -1;
+    }
 
     msg_content_t *content = (msg_content_t*) msg_->content;
 
@@ -171,7 +174,22 @@ bool zmq::pub_t::xhas_in ()
 
 bool zmq::pub_t::xhas_out ()
 {
-    //  TODO: Reimplement when queue limits are added.
+    return check_write ();
+}
+
+bool zmq::pub_t::check_write ()
+{
+    if (stalled_pipe != NULL)
+        return false;
+
+    out_pipes_t::size_type pipes_num = out_pipes.size ();
+    for (out_pipes_t::size_type i = 0; i < pipes_num; i++) {
+        if (!out_pipes [i]->check_write ()) {
+            stalled_pipe = out_pipes [i];
+            return false;
+        }
+    }
+
     return true;
 }
 
diff --git a/src/pub.hpp b/src/pub.hpp
index a85301f..3a4fe09 100644
--- a/src/pub.hpp
+++ b/src/pub.hpp
@@ -54,6 +54,13 @@ namespace zmq
         typedef yarray_t <class writer_t> out_pipes_t;
         out_pipes_t out_pipes;
 
+        //  Pointer to the pipe we are waiting for to became writable
+        //  again; NULL if tha last send operation was successful.
+        class writer_t *stalled_pipe;
+
+        //  Check whether we can write a message to all pipes.
+        bool check_write ();
+
         pub_t (const pub_t&);
         void operator = (const pub_t&);
     };
-- 
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