ZMQ_FILTER socket option added

This option is a performance tweak. In devices XSUB socket filters
the messages just to send them to XPUB socket which filters them
once more. Setting ZMQ_FILTER option to 0 allows to switch the
filtering in XSUB socket off.

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

3 files changed, 24 insertions, 2 deletions

diff --git a/src/options.cpp b/src/options.cpp
index 271ebdb..29cf023 100644
--- a/src/options.cpp
+++ b/src/options.cpp
@@ -38,6 +38,7 @@ zmq::options_t::options_t () :
     reconnect_ivl_max (0),
     backlog (100),
     maxmsgsize (-1),
+    filter (1),
     immediate_connect (true)
 {
 }
@@ -172,6 +173,15 @@ int zmq::options_t::setsockopt (int option_, const void *optval_,
         multicast_hops = *((int*) optval_);
         return 0;
 
+    case ZMQ_FILTER:
+        if (optvallen_ != sizeof (int) || (*((int*) optval_) != 0 &&
+                *((int*) optval_) != 1)) {
+            errno = EINVAL;
+            return -1;
+        }
+        filter = *((int*) optval_);
+        return 0;
+
     }
 
     errno = EINVAL;
@@ -317,6 +327,15 @@ int zmq::options_t::getsockopt (int option_, void *optval_, size_t *optvallen_)
         *optvallen_ = sizeof (int);
         return 0;
 
+    case ZMQ_FILTER:
+        if (*optvallen_ < sizeof (int)) {
+            errno = EINVAL;
+            return -1;
+        }
+        *((int*) optval_) = filter;
+        *optvallen_ = sizeof (int);
+        return 0;
+
     }
 
     errno = EINVAL;
diff --git a/src/options.hpp b/src/options.hpp
index fd39a74..e055919 100644
--- a/src/options.hpp
+++ b/src/options.hpp
@@ -75,6 +75,9 @@ namespace zmq
         //  Maximal size of message to handle.
         int64_t maxmsgsize;
 
+        //  If 1, (X)SUB socket should filter the messages. If 0, it should not.
+        int filter;
+
         //  If true, when connecting, pipes are created immediately without
         //  waiting for the connection to be established. That way the socket
         //  is not aware of the peer's identity, however, it is able to send
diff --git a/src/xsub.cpp b/src/xsub.cpp
index a847d7f..60ba598 100644
--- a/src/xsub.cpp
+++ b/src/xsub.cpp
@@ -133,7 +133,7 @@ int zmq::xsub_t::xrecv (msg_t *msg_, int flags_)
 
         //  Check whether the message matches at least one subscription.
         //  Non-initial parts of the message are passed 
-        if (more || match (msg_)) {
+        if (more || !options.filter || match (msg_)) {
             more = msg_->flags () & msg_t::more;
             return 0;
         }
@@ -173,7 +173,7 @@ bool zmq::xsub_t::xhas_in ()
         }
 
         //  Check whether the message matches at least one subscription.
-        if (match (&message)) {
+        if (!options.filter || match (&message)) {
             has_message = true;
             return true;
         }