Problem: need atomic reference counting in several projects

Solution: as libzmq already provides this across all platforms,
expose an atomic counter API. I've not wrapped atomic pointers,
though someone who needs this may want to do so.

.gitignore

@@ -98,6 +98,9 @@ test_capabilities
 test_hwm_pubsub
 test_router_mandatory_hwm
 test_xpub_nodrop
+test_xpub_manual
+test_xpub_welcome_msg
+test_atomics
 tests/test*.log
 tests/test*.trs
 src/platform.hpp*

Makefile.am

@@ -330,7 +330,8 @@ test_apps = \
 	tests/test_capabilities \
 	tests/test_xpub_nodrop \
 	tests/test_xpub_manual \
-	tests/test_xpub_welcome_msg
+	tests/test_xpub_welcome_msg \
+	tests/test_atomics
 
 tests_test_system_SOURCES = tests/test_system.cpp
 tests_test_system_LDADD = src/libzmq.la
@@ -502,6 +503,9 @@ tests_test_xpub_manual_LDADD = src/libzmq.la
 tests_test_xpub_welcome_msg_SOURCES = tests/test_xpub_welcome_msg.cpp
 tests_test_xpub_welcome_msg_LDADD = src/libzmq.la
 
+tests_test_atomics_SOURCES = tests/test_atomics.cpp
+tests_test_atomics_LDADD = src/libzmq.la
+
 if !ON_MINGW
 test_apps += \
 	tests/test_shutdown_stress \

doc/Makefile.am

@@ -13,7 +13,11 @@ MAN3 = zmq_bind.3 zmq_unbind.3 zmq_connect.3 zmq_disconnect.3 zmq_close.3 \
     zmq_errno.3 zmq_strerror.3 zmq_version.3 \
     zmq_sendmsg.3 zmq_recvmsg.3 \
     zmq_proxy.3 zmq_proxy_steerable.3 \
-    zmq_z85_encode.3 zmq_z85_decode.3 zmq_curve_keypair.3 zmq_has.3
+    zmq_z85_encode.3 zmq_z85_decode.3 zmq_curve_keypair.3 \
+    zmq_has.3 \
+    zmq_atomic_counter_new.3 zmq_atomic_counter_set.3 \
+    zmq_atomic_counter_inc.3 zmq_atomic_counter_dec.3 \
+    zmq_atomic_counter_value.3 zmq_atomic_counter_destroy.3
 
 MAN7 = zmq.7 zmq_tcp.7 zmq_pgm.7 zmq_inproc.7 zmq_ipc.7 \
     zmq_null.7 zmq_plain.7 zmq_curve.7 zmq_tipc.7

doc/zmq.txt

@@ -132,7 +132,7 @@ Sending and receiving messages::
     linkzmq:zmq_recv[3]
     linkzmq:zmq_send_const[3]
 
-Monitoring socket events:
+Monitoring socket events::
     linkzmq:zmq_socket_monitor[3]
 
 .Input/output multiplexing
@@ -187,13 +187,11 @@ Plain-text authentication using username and password::
 Elliptic curve authentication and encryption::
     linkzmq:zmq_curve[7]
 
-Generate a CURVE keypair in armored text format:
+Generate a CURVE keypair in armored text format::
     linkzmq:zmq_curve_keypair[3]
 
-Convert an armored key into a 32-byte binary key:
+Converting keys to/from armoured text strings::
     linkzmq:zmq_z85_decode[3]
-
-Convert a 32-byte binary CURVE key to an armored text string:
     linkzmq:zmq_z85_encode[3]
 
 
@@ -213,6 +211,19 @@ The _zmq_strerror()_ function is provided to translate 0MQ-specific error codes
 into error message strings; for details refer to linkzmq:zmq_strerror[3].
 
 
+UTILITY
+-------
+The following utility functions are provided:
+
+Working with atomic counters::
+    linkzmq:zmq_atomic_counter_new[3]
+    linkzmq:zmq_atomic_counter_set[3]
+    linkzmq:zmq_atomic_counter_inc[3]
+    linkzmq:zmq_atomic_counter_dec[3]
+    linkzmq:zmq_atomic_counter_value[3]
+    linkzmq:zmq_atomic_counter_destroy[3]
+
+
 MISCELLANEOUS
 -------------
 The following miscellaneous functions are provided:

doc/zmq_atomic_counter_dec.txt

+zmq_atomic_counter_dec(3)
+=========================
+
+
+NAME
+----
+zmq_atomic_counter_dec - decrement an atomic counter
+
+
+SYNOPSIS
+--------
+*bool zmq_atomic_counter_dec (void *counter);*
+
+
+DESCRIPTION
+-----------
+The _zmq_atomic_counter_dec_ function decrements an atomic counter in
+a threadsafe fashion. This function uses platform specific atomic
+operations.
+
+
+RETURN VALUE
+------------
+The _zmq_atomic_counter_dec()_ function returns true if the counter is
+greater than zero after decrementing, or false if the counter reached
+zero.
+
+
+EXAMPLE
+-------
+.Test code for atomic counters
+----
+void *counter = zmq_atomic_counter_new ();
+assert (zmq_atomic_counter_value (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 1);
+assert (zmq_atomic_counter_inc (counter) == 2);
+assert (zmq_atomic_counter_value (counter) == 3);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_set (counter, 2);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_destroy (&counter);
+----
+
+
+SEE ALSO
+--------
+linkzmq:zmq_atomic_counter_new[3]
+linkzmq:zmq_atomic_counter_set[3]
+linkzmq:zmq_atomic_counter_inc[3]
+linkzmq:zmq_atomic_counter_value[3]
+linkzmq:zmq_atomic_counter_destroy[3]
+
+
+AUTHORS
+-------
+This page was written by the 0MQ community. To make a change please
+read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>.

doc/zmq_atomic_counter_destroy.txt

+zmq_atomic_counter_destroy(3)
+=============================
+
+
+NAME
+----
+zmq_atomic_counter_destroy - destroy an atomic counter
+
+
+SYNOPSIS
+--------
+*void zmq_atomic_counter_destroy (void **counter_p);*
+
+
+DESCRIPTION
+-----------
+The _zmq_atomic_counter_destroy_ function destroys an atomic counter and
+nullifies its reference. Pass the address of an atomic counter (void **)
+rather than the counter itself. You must destroy all counters that you
+create, to avoid memory leakage. This function uses platform specific
+atomic operations.
+
+
+RETURN VALUE
+------------
+The _zmq_atomic_counter_destroy()_ function has no return value.
+
+
+EXAMPLE
+-------
+.Test code for atomic counters
+----
+void *counter = zmq_atomic_counter_new ();
+assert (zmq_atomic_counter_value (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 1);
+assert (zmq_atomic_counter_inc (counter) == 2);
+assert (zmq_atomic_counter_value (counter) == 3);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_set (counter, 2);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_destroy (&counter);
+----
+
+
+SEE ALSO
+--------
+linkzmq:zmq_atomic_counter_new[3]
+linkzmq:zmq_atomic_counter_set[3]
+linkzmq:zmq_atomic_counter_inc[3]
+linkzmq:zmq_atomic_counter_dec[3]
+linkzmq:zmq_atomic_counter_value[3]
+
+
+AUTHORS
+-------
+This page was written by the 0MQ community. To make a change please
+read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>.

doc/zmq_atomic_counter_inc.txt

+zmq_atomic_counter_inc(3)
+=========================
+
+
+NAME
+----
+zmq_atomic_counter_inc - increment an atomic counter
+
+
+SYNOPSIS
+--------
+*int zmq_atomic_counter_inc (void *counter);*
+
+
+DESCRIPTION
+-----------
+The _zmq_atomic_counter_inc_ function increments an atomic counter in a
+threadsafe fashion. This function uses platform specific atomic
+operations.
+
+
+RETURN VALUE
+------------
+The _zmq_atomic_counter_inc()_ function returns the old value of the
+counter, before incrementing.
+
+
+EXAMPLE
+-------
+.Test code for atomic counters
+----
+void *counter = zmq_atomic_counter_new ();
+assert (zmq_atomic_counter_value (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 1);
+assert (zmq_atomic_counter_inc (counter) == 2);
+assert (zmq_atomic_counter_value (counter) == 3);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_set (counter, 2);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_destroy (&counter);
+----
+
+
+SEE ALSO
+--------
+linkzmq:zmq_atomic_counter_new[3]
+linkzmq:zmq_atomic_counter_set[3]
+linkzmq:zmq_atomic_counter_dec[3]
+linkzmq:zmq_atomic_counter_value[3]
+linkzmq:zmq_atomic_counter_destroy[3]
+
+
+AUTHORS
+-------
+This page was written by the 0MQ community. To make a change please
+read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>.

doc/zmq_atomic_counter_new.txt

+zmq_atomic_counter_new(3)
+=========================
+
+
+NAME
+----
+zmq_atomic_counter_new - create a new atomic counter
+
+
+SYNOPSIS
+--------
+*void *zmq_atomic_counter_new (void);*
+
+
+DESCRIPTION
+-----------
+The _zmq_atomic_counter_new_ function creates a new atomic counter. You
+can use this in multithreaded applications to do, for example, reference
+counting of shared objects. The atomic counter is at least 32 bits large.
+This function uses platform specific atomic operations.
+
+
+RETURN VALUE
+------------
+The _zmq_atomic_counter_new()_ function returns the new atomic counter
+if successful. Otherwise it returns NULL.
+
+
+EXAMPLE
+-------
+.Test code for atomic counters
+----
+void *counter = zmq_atomic_counter_new ();
+assert (zmq_atomic_counter_value (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 1);
+assert (zmq_atomic_counter_inc (counter) == 2);
+assert (zmq_atomic_counter_value (counter) == 3);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_set (counter, 2);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_destroy (&counter);
+----
+
+
+SEE ALSO
+--------
+linkzmq:zmq_atomic_counter_set[3]
+linkzmq:zmq_atomic_counter_inc[3]
+linkzmq:zmq_atomic_counter_dec[3]
+linkzmq:zmq_atomic_counter_value[3]
+linkzmq:zmq_atomic_counter_destroy[3]
+
+
+AUTHORS
+-------
+This page was written by the 0MQ community. To make a change please
+read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>.

doc/zmq_atomic_counter_set.txt

+zmq_atomic_counter_set(3)
+=========================
+
+
+NAME
+----
+zmq_atomic_counter_set - set atomic counter to new value
+
+
+SYNOPSIS
+--------
+*void zmq_atomic_counter_set (void *counter, int value);*
+
+
+DESCRIPTION
+-----------
+The _zmq_atomic_counter_set_ function sets the counter to a new value,
+in a threadsafe fashion. The largest value that is guaranteed to work
+across all platforms is 2^31-1. This function uses platform specific
+atomic operations.
+
+
+RETURN VALUE
+------------
+The _zmq_atomic_counter_set()_ function has no return value.
+
+
+EXAMPLE
+-------
+.Test code for atomic counters
+----
+void *counter = zmq_atomic_counter_new ();
+assert (zmq_atomic_counter_value (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 1);
+assert (zmq_atomic_counter_inc (counter) == 2);
+assert (zmq_atomic_counter_value (counter) == 3);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_set (counter, 2);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_destroy (&counter);
+----
+
+
+SEE ALSO
+--------
+linkzmq:zmq_atomic_counter_new[3]
+linkzmq:zmq_atomic_counter_inc[3]
+linkzmq:zmq_atomic_counter_dec[3]
+linkzmq:zmq_atomic_counter_value[3]
+linkzmq:zmq_atomic_counter_destroy[3]
+
+
+AUTHORS
+-------
+This page was written by the 0MQ community. To make a change please
+read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>.

doc/zmq_atomic_counter_value.txt

+zmq_atomic_counter_value(3)
+===========================
+
+
+NAME
+----
+zmq_atomic_counter_value - return value of atomic counter
+
+
+SYNOPSIS
+--------
+*int zmq_atomic_counter_value (void *counter);*
+
+
+DESCRIPTION
+-----------
+The _zmq_atomic_counter_value_ function returns the value of an atomic
+counter. This function uses platform specific atomic operations.
+
+
+RETURN VALUE
+------------
+The _zmq_atomic_counter_value()_ function returns the new atomic counter
+if successful. Otherwise it returns NULL.
+
+
+EXAMPLE
+-------
+.Test code for atomic counters
+----
+void *counter = zmq_atomic_counter_new ();
+assert (zmq_atomic_counter_value (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 0);
+assert (zmq_atomic_counter_inc (counter) == 1);
+assert (zmq_atomic_counter_inc (counter) == 2);
+assert (zmq_atomic_counter_value (counter) == 3);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_set (counter, 2);
+assert (zmq_atomic_counter_dec (counter) == true);
+assert (zmq_atomic_counter_dec (counter) == false);
+zmq_atomic_counter_destroy (&counter);
+----
+
+
+SEE ALSO
+--------
+linkzmq:zmq_atomic_counter_new[3]
+linkzmq:zmq_atomic_counter_set[3]
+linkzmq:zmq_atomic_counter_inc[3]
+linkzmq:zmq_atomic_counter_dec[3]
+linkzmq:zmq_atomic_counter_destroy[3]
+
+
+AUTHORS
+-------
+This page was written by the 0MQ community. To make a change please
+read the 0MQ Contribution Policy at <http://www.zeromq.org/docs:contributing>.

include/zmq.h

@@ -433,6 +433,17 @@ ZMQ_EXPORT uint8_t *zmq_z85_decode (uint8_t *dest, const char *string);
 /*  Returns 0 on success.                                                     */
 ZMQ_EXPORT int zmq_curve_keypair (char *z85_public_key, char *z85_secret_key);
 
+/******************************************************************************/
+/*  Atomic utility methods                                                    */
+/******************************************************************************/
+
+ZMQ_EXPORT void *zmq_atomic_counter_new (void);
+ZMQ_EXPORT void zmq_atomic_counter_set (void *counter, int value);
+ZMQ_EXPORT int zmq_atomic_counter_inc (void *counter);
+ZMQ_EXPORT bool zmq_atomic_counter_dec (void *counter);
+ZMQ_EXPORT int zmq_atomic_counter_value (void *counter);
+ZMQ_EXPORT void zmq_atomic_counter_destroy (void **counter_p);
+
 
 /******************************************************************************/
 /*  These functions are not documented by man pages -- use at your own risk.  */

src/zmq_utils.cpp

@@ -22,6 +22,8 @@
 #include "clock.hpp"
 #include "err.hpp"
 #include "thread.hpp"
+#include "atomic_counter.hpp"
+#include "atomic_ptr.hpp"
 #include <assert.h>
 #include "../include/zmq_utils.h"
 
@@ -204,3 +206,50 @@ int zmq_curve_keypair (char *z85_public_key, char *z85_secret_key)
     return -1;
 #endif
 }
+
+
+//  --------------------------------------------------------------------------
+//  Initialize a new atomic counter, which is set to zero
+
+void *zmq_atomic_counter_new (void)
+{
+    zmq::atomic_counter_t *counter = new zmq::atomic_counter_t;
+    alloc_assert (counter);
+    return counter;
+}
+
+//  Se the value of the atomic counter
+
+void zmq_atomic_counter_set (void *counter_, int value_)
+{
+    ((zmq::atomic_counter_t *) counter_)->set (value_);
+}
+
+//  Increment the atomic counter, and return the old value
+
+int zmq_atomic_counter_inc (void *counter_)
+{
+    return ((zmq::atomic_counter_t *) counter_)->add (1);
+}
+
+//  Decrement the atomic counter and return true if still > zero
+
+bool zmq_atomic_counter_dec (void *counter_)
+{
+    return ((zmq::atomic_counter_t *) counter_)->sub (1);
+}
+
+//  Return actual value of atomic counter
+
+int zmq_atomic_counter_value (void *counter_)
+{
+    return ((zmq::atomic_counter_t *) counter_)->get ();
+}
+
+//  Destroy atomic counter, and set reference to NULL
+
+void zmq_atomic_counter_destroy (void **counter_p_)
+{
+    delete ((zmq::atomic_counter_t *) *counter_p_);
+    *counter_p_ = NULL;
+}

tests/test_atomics.cpp

+/*
+    Copyright (c) 2007-2014 Contributors as noted in the AUTHORS file
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "testutil.hpp"
+
+int main (void)
+{
+    void *counter = zmq_atomic_counter_new ();
+    assert (zmq_atomic_counter_value (counter) == 0);
+    assert (zmq_atomic_counter_inc (counter) == 0);
+    assert (zmq_atomic_counter_inc (counter) == 1);
+    assert (zmq_atomic_counter_inc (counter) == 2);
+    assert (zmq_atomic_counter_value (counter) == 3);
+    assert (zmq_atomic_counter_dec (counter) == true);
+    assert (zmq_atomic_counter_dec (counter) == true);
+    assert (zmq_atomic_counter_dec (counter) == false);
+    zmq_atomic_counter_set (counter, 2);
+    assert (zmq_atomic_counter_dec (counter) == true);
+    assert (zmq_atomic_counter_dec (counter) == false);
+    zmq_atomic_counter_destroy (&counter);
+    return 0;
+}