ZMQII-26: Use zero-copy for large messages

src/encoder.hpp

@@ -24,6 +24,8 @@
 #include <string.h>
 #include <algorithm>
 
+#include <stdio.h>
+
 namespace zmq
 {
 
@@ -44,17 +46,31 @@ namespace zmq
         //  NULL, it is filled by offset of the first message in the batch.
         //  If there's no beginning of a message in the batch, offset is
         //  set to -1.
-        inline size_t read (unsigned char *data_, size_t size_,
+        inline void read (unsigned char **data_, size_t *size_,
             int *offset_ = NULL)
         {
             int offset = -1;
             size_t pos = 0;
 
-            while (pos < size_) {
+            while (pos < *size_) {
+
+                //  If we are able to fill whole buffer in a single go, let's
+                //  use zero-copy. There's no disadvantage to it as we cannot
+                //  stuck multiple messages into the buffer anyway.
+                if (pos == 0 && to_write >= *size_) {
+                    *data_ = write_pos;
+                    write_pos += *size_;
+                    to_write -= *size_;
+
+                    //  TODO: manage beginning & offset here.
+
+                    return;
+                }
+
                 if (to_write) {
 
-                    size_t to_copy = std::min (to_write, size_ - pos);
+                    size_t to_copy = std::min (to_write, *size_ - pos);
-                    memcpy (data_ + pos, write_pos, to_copy);
+                    memcpy (*data_ + pos, write_pos, to_copy);
                     pos += to_copy;
                     write_pos += to_copy;
                     to_write -= to_copy;
@@ -70,10 +86,12 @@ namespace zmq
                 }
             }
 
+            //  Return offset of the first message in the buffer.
             if (offset_)
                 *offset_ = offset;
 
-            return pos;
+            //  Return the size of the filled-in portion of the buffer.
+            *size_ = pos;
         }
     protected:
 

src/zmq_engine.cpp

@@ -26,17 +26,19 @@
 
 zmq::zmq_engine_t::zmq_engine_t (io_thread_t *parent_, fd_t fd_) :
     io_object_t (parent_),
+    inbuf (NULL),
     insize (0),
     inpos (0),
+    outbuf (NULL),
     outsize (0),
     outpos (0),
     inout (NULL)
 {
     //  Allocate read & write buffer.
-    inbuf = (unsigned char*) malloc (in_batch_size);
+    inbuf_storage = (unsigned char*) malloc (in_batch_size);
-    zmq_assert (inbuf);
+    zmq_assert (inbuf_storage);
-    outbuf = (unsigned char*) malloc (out_batch_size);
+    outbuf_storage = (unsigned char*) malloc (out_batch_size);
-    zmq_assert (outbuf);
+    zmq_assert (outbuf_storage);
 
     //  Initialise the underlying socket.
     int rc = tcp_socket.open (fd_);
@@ -45,8 +47,8 @@ zmq::zmq_engine_t::zmq_engine_t (io_thread_t *parent_, fd_t fd_) :
 
 zmq::zmq_engine_t::~zmq_engine_t ()
 {
-    free (outbuf);
+    free (outbuf_storage);
-    free (inbuf);
+    free (inbuf_storage);
 }
 
 void zmq::zmq_engine_t::plug (i_inout *inout_)
@@ -80,11 +82,12 @@ void zmq::zmq_engine_t::in_event ()
     if (inpos == insize) {
 
         //  Read as much data as possible to the read buffer.
+        inbuf = inbuf_storage;
         insize = tcp_socket.read (inbuf, in_batch_size);
         inpos = 0;
 
         //  Check whether the peer has closed the connection.
-        if (insize == -1) {
+        if (insize == (size_t) -1) {
             insize = 0;
             error ();
             return;
@@ -111,7 +114,9 @@ void zmq::zmq_engine_t::out_event ()
     //  If write buffer is empty, try to read new data from the encoder.
     if (outpos == outsize) {
 
-        outsize = encoder.read (outbuf, out_batch_size);
+        outbuf = outbuf_storage;
+        outsize = out_batch_size;
+        encoder.read (&outbuf, &outsize);
         outpos = 0;
 
         //  If there is no data to send, stop polling for output.

src/zmq_engine.hpp

@@ -20,6 +20,8 @@
 #ifndef __ZMQ_ZMQ_ENGINE_HPP_INCLUDED__
 #define __ZMQ_ZMQ_ENGINE_HPP_INCLUDED__
 
+#include <stddef.h>
+
 #include "i_engine.hpp"
 #include "io_object.hpp"
 #include "tcp_socket.hpp"
@@ -54,13 +56,15 @@ namespace zmq
         tcp_socket_t tcp_socket;
         handle_t handle;
 
+        unsigned char *inbuf_storage;
         unsigned char *inbuf;
-        int insize;
+        size_t insize;
-        int inpos;
+        size_t inpos;
 
+        unsigned char *outbuf_storage;
         unsigned char *outbuf;
-        int outsize;
+        size_t outsize;
-        int outpos;
+        size_t outpos;
 
         i_inout *inout;