From 5815b768b9b6075d8743fe32947006af853fa9e8 Mon Sep 17 00:00:00 2001
From: Olaf Mandel <o.mandel@menlosystems.com>
Date: Thu, 13 Feb 2014 15:54:06 +0100
Subject: [PATCH] Add ZMQ_MAX_SOCKETS_MAX to zmq_ctx_get()

The new options allows querying the maximum allowed number of sockets.
This is system dependent and cannot be encoded in the include file as a
preprocessor macro: for ZMQ_USE_SELECT, this depends on the FD_SETSIZE
macro at time of library compilation, not at time of include file use.
---
 doc/zmq_ctx_get.txt        | 5 +++++
 doc/zmq_ctx_set.txt        | 3 ++-
 include/zmq.h              | 1 +
 src/ctx.cpp                | 4 ++++
 tests/test_ctx_options.cpp | 8 ++++++++
 5 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/doc/zmq_ctx_get.txt b/doc/zmq_ctx_get.txt
index 980a2a90..5361453d 100644
--- a/doc/zmq_ctx_get.txt
+++ b/doc/zmq_ctx_get.txt
@@ -31,6 +31,11 @@ ZMQ_MAX_SOCKETS: Get maximum number of sockets
 The 'ZMQ_MAX_SOCKETS' argument returns the maximum number of sockets
 allowed for this context.
 
+ZMQ_MAX_SOCKETS_MAX: Get largest configurable number of sockets
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The 'ZMQ_MAX_SOCKETS_MAX' argument returns the largest number of sockets
+that linkzmq:zmq_ctx_set[3] will accept.
+
 ZMQ_IPV6: Set IPv6 option
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 The 'ZMQ_IPV6' argument returns the IPv6 option for the context.
diff --git a/doc/zmq_ctx_set.txt b/doc/zmq_ctx_set.txt
index 461444bc..0049dff2 100644
--- a/doc/zmq_ctx_set.txt
+++ b/doc/zmq_ctx_set.txt
@@ -35,7 +35,8 @@ Default value:: 1
 ZMQ_MAX_SOCKETS: Set maximum number of sockets
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 The 'ZMQ_MAX_SOCKETS' argument sets the maximum number of sockets allowed
-on the context.
+on the context. You can query the maximal allowed value with
+linkzmq:zmq_ctx_get[3] using 'option_name' set to 'ZMQ_MAX_SOCKETS_MAX'.
 
 [horizontal]
 Default value:: 1024
diff --git a/include/zmq.h b/include/zmq.h
index 961c2836..9a1a413c 100644
--- a/include/zmq.h
+++ b/include/zmq.h
@@ -178,6 +178,7 @@ ZMQ_EXPORT void zmq_version (int *major, int *minor, int *patch);
 /*  Context options                                                           */
 #define ZMQ_IO_THREADS  1
 #define ZMQ_MAX_SOCKETS 2
+#define ZMQ_MAX_SOCKETS_MAX 3
 
 /*  Default for new contexts                                                  */
 #define ZMQ_IO_THREADS_DFLT  1
diff --git a/src/ctx.cpp b/src/ctx.cpp
index b11c5a3e..b69c7143 100644
--- a/src/ctx.cpp
+++ b/src/ctx.cpp
@@ -24,6 +24,7 @@
 #include <unistd.h>
 #endif
 
+#include <limits>
 #include <new>
 #include <string.h>
 
@@ -204,6 +205,9 @@ int zmq::ctx_t::get (int option_)
     if (option_ == ZMQ_MAX_SOCKETS)
         rc = max_sockets;
     else
+    if (option_ == ZMQ_MAX_SOCKETS_MAX)
+        rc = clipped_maxsocket (std::numeric_limits<int>::max());
+    else
     if (option_ == ZMQ_IO_THREADS)
         rc = io_thread_count;
     else
diff --git a/tests/test_ctx_options.cpp b/tests/test_ctx_options.cpp
index 1e598386..c01d42aa 100644
--- a/tests/test_ctx_options.cpp
+++ b/tests/test_ctx_options.cpp
@@ -17,6 +17,7 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <limits>
 #include "testutil.hpp"
 
 int main (void)
@@ -29,6 +30,13 @@ int main (void)
     assert (ctx);
     
     assert (zmq_ctx_get (ctx, ZMQ_MAX_SOCKETS) == ZMQ_MAX_SOCKETS_DFLT);
+#if defined(ZMQ_USE_SELECT)
+    assert (zmq_ctx_get (ctx, ZMQ_MAX_SOCKETS_MAX) == ZMQ_MAX_SOCKETS_DFLT);
+#elif    defined(ZMQ_USE_POLL) || defined(ZMQ_USE_EPOLL)     \
+      || defined(ZMQ_USE_DEVPOLL) || defined(ZMQ_USE_KQUEUE)
+    assert (zmq_ctx_get (ctx, ZMQ_MAX_SOCKETS_MAX)
+                              == std::numeric_limits<int>::max());
+#endif
     assert (zmq_ctx_get (ctx, ZMQ_IO_THREADS) == ZMQ_IO_THREADS_DFLT);
     assert (zmq_ctx_get (ctx, ZMQ_IPV6) == 0);