PGM: implement flow control

src/pgm_receiver.cpp

@@ -38,7 +38,9 @@ zmq::pgm_receiver_t::pgm_receiver_t (class io_thread_t *parent_,
     io_object_t (parent_),
     pgm_socket (true, options_),
     options (options_),
-    inout (NULL)
+    inout (NULL),
+    mru_decoder (NULL),
+    pending_bytes (0)
 {
 }
 
@@ -76,6 +78,9 @@ void zmq::pgm_receiver_t::unplug ()
     }
     peers.clear ();
 
+    mru_decoder = NULL;
+    pending_bytes = 0;
+
     //  Stop polling.
     rm_fd (socket_handle);
     rm_fd (pipe_handle);
@@ -90,7 +95,30 @@ void zmq::pgm_receiver_t::revive ()
 
 void zmq::pgm_receiver_t::resume_input ()
 {
-   zmq_not_implemented ();
+    //  It is possible that the most recently used decoder
+    //  processed the whole buffer but failed to write
+    //  the last message into the pipe.
+    if (pending_bytes == 0) {
+        if (mru_decoder != NULL)
+            mru_decoder->process_buffer (NULL, 0);
+        return;
+    }
+
+    zmq_assert (mru_decoder != NULL);
+    zmq_assert (pending_ptr != NULL);
+
+    //  Ask the decoder to process remaining data.
+    size_t n = mru_decoder->process_buffer (pending_ptr, pending_bytes);
+    pending_bytes -= n;
+
+    if (pending_bytes > 0)
+        return;
+
+    //  Resume polling.
+    set_pollin (pipe_handle);
+    set_pollin (socket_handle);
+
+    in_event ();
 }
 
 void zmq::pgm_receiver_t::add_prefix (const blob_t &identity_)
@@ -111,6 +139,8 @@ void zmq::pgm_receiver_t::in_event ()
     unsigned char *data = NULL;
     const pgm_tsi_t *tsi = NULL;
 
+    zmq_assert (pending_bytes == 0);
+
     //  TODO: This loop can effectively block other engines in the same I/O
     //  thread in the case of high load.
     while (true) {
@@ -130,6 +160,8 @@ void zmq::pgm_receiver_t::in_event ()
         if (received == -1) {
             zmq_assert (it != peers.end ());
             it->second.joined = false;
+            if (it->second.decoder == mru_decoder)
+                mru_decoder = NULL;
             if (it->second.decoder != NULL) {
                 delete it->second.decoder;
                 it->second.decoder = NULL;
@@ -172,10 +204,20 @@ void zmq::pgm_receiver_t::in_event ()
             it->second.decoder->set_inout (inout);
         }
 
+        mru_decoder = it->second.decoder;
+
         //  Push all the data to the decoder.
-        //  TODO: process_buffer may not process entire buffer!
         ssize_t processed = it->second.decoder->process_buffer (data, received);
-        zmq_assert (processed == received);
+        if (processed < received) {
+            //  Save some state so we can resume the decoding process later.
+            pending_bytes = received - processed;
+            pending_ptr = data + processed;
+            //  Stop polling.
+            reset_pollin (pipe_handle);
+            reset_pollin (socket_handle);
+
+            break;
+        }
     }
 
     //  Flush any messages decoder may have produced.

src/pgm_receiver.hpp

@@ -98,6 +98,15 @@ namespace zmq
         //  Parent session.
         i_inout *inout;
 
+        //  Most recently used decoder.
+        zmq_decoder_t *mru_decoder;
+
+        //  Number of bytes not consumed by the decoder due to pipe overflow.
+        size_t pending_bytes;
+
+        //  Pointer to data still waiting to be processed by the decoder.
+        unsigned char *pending_ptr;
+
         //  Poll handle associated with PGM socket.
         handle_t socket_handle;