Expose the ability to have zero allocation sends.

Makefile.am

@@ -1067,7 +1067,8 @@ test_apps += tests/test_poller \
 	tests/test_hiccup_msg \
 	tests/test_zmq_ppoll_fd \
 	tests/test_xsub_verbose \
-	tests/test_pubsub_topics_count
+	tests/test_pubsub_topics_count \
+	tests/test_msg_ffn_external_storage
 
 tests_test_poller_SOURCES = tests/test_poller.cpp
 tests_test_poller_LDADD = ${TESTUTIL_LIBS} src/libzmq.la
@@ -1149,6 +1150,10 @@ tests_test_pubsub_topics_count_SOURCES = tests/test_pubsub_topics_count.cpp
 tests_test_pubsub_topics_count_LDADD = ${TESTUTIL_LIBS} src/libzmq.la
 tests_test_pubsub_topics_count_CPPFLAGS = ${TESTUTIL_CPPFLAGS}
 
+tests_test_msg_ffn_external_storage_SOURCES = tests/test_msg_ffn_external_storage.cpp
+tests_test_msg_ffn_external_storage_LDADD = ${TESTUTIL_LIBS} src/libzmq.la
+tests_test_msg_ffn_external_storage_CPPFLAGS = ${TESTUTIL_CPPFLAGS}
+
 if HAVE_FORK
 test_apps += tests/test_zmq_ppoll_signals
 

builds/gyp/project-tests.gypi

@@ -132,6 +132,17 @@
         'libzmq'
       ],
     },
+    {
+      'target_name': 'test_msg_ffn_external_storage',
+      'type': 'executable',
+      'sources': [
+        '../../tests/test_msg_ffn_external_storage.cpp',
+        '../../tests/testutil.hpp'
+      ],
+      'dependencies': [
+        'libzmq'
+      ],
+    },
     {
       'target_name': 'test_msg_init',
       'type': 'executable',

builds/gyp/project-tests.xml

@@ -11,6 +11,7 @@
     <test name = "test_invalid_rep" />
     <test name = "test_msg_flags" />
     <test name = "test_msg_ffn" />
+    <test name = "test_msg_ffn_external_storage" />
     <test name = "test_msg_init" />
     <test name = "test_connect_resolve" />
     <test name = "test_immediate" />

include/zmq.h

@@ -701,6 +701,30 @@ ZMQ_EXPORT const char *zmq_msg_group (zmq_msg_t *msg);
 ZMQ_EXPORT int
 zmq_msg_init_buffer (zmq_msg_t *msg_, const void *buf_, size_t size_);
 
+/*  Draft Msg control block type for init_external_storage.                   */
+typedef struct zmq_msg_content_t
+{
+#if defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
+    __declspec (align (8)) unsigned char _[64];
+#elif defined(_MSC_VER)                                                        \
+  && (defined(_M_IX86) || defined(_M_ARM_ARMV7VE) || defined(_M_ARM))
+    __declspec (align (4)) unsigned char _[64];
+#elif defined(__GNUC__) || defined(__INTEL_COMPILER)                           \
+  || (defined(__SUNPRO_C) && __SUNPRO_C >= 0x590)                              \
+  || (defined(__SUNPRO_CC) && __SUNPRO_CC >= 0x590)
+    unsigned char _[64] __attribute__ ((aligned (sizeof (void *))));
+#else
+    unsigned char _[64];
+#endif
+} zmq_msg_content_t;
+
+ZMQ_EXPORT int zmq_msg_init_external_storage (zmq_msg_t *msg_,
+                                              zmq_msg_content_t *content_,
+                                              void *data_,
+                                              size_t size_,
+                                              zmq_free_fn *ffn_,
+                                              void *hint_);
+
 /*  DRAFT Msg property names.                                                 */
 #define ZMQ_MSG_PROPERTY_ROUTING_ID "Routing-Id"
 #define ZMQ_MSG_PROPERTY_SOCKET_TYPE "Socket-Type"

src/zmq.cpp

@@ -84,6 +84,10 @@ struct iovec
 typedef char
   check_msg_t_size[sizeof (zmq::msg_t) == sizeof (zmq_msg_t) ? 1 : -1];
 
+// Compile time check whether msg_t::content_t fits into zmq_msg_content_t.
+// It is expected to be larger.
+typedef char check_msg_content_size
+  [sizeof (zmq::msg_t::content_t) <= sizeof (zmq_msg_content_t) ? 1 : -1];
 
 void zmq_version (int *major_, int *minor_, int *patch_)
 {
@@ -606,6 +610,20 @@ int zmq_msg_init_data (
       ->init_data (data_, size_, ffn_, hint_);
 }
 
+int zmq_msg_init_external_storage (zmq_msg_t *msg_,
+                                   zmq_msg_content_t *content_,
+                                   void *data_,
+                                   size_t size_,
+                                   zmq_free_fn *ffn_,
+                                   void *hint_)
+{
+    return (reinterpret_cast<zmq::msg_t *> (msg_))
+      ->init_external_storage (
+        reinterpret_cast<zmq::msg_t::content_t *> (content_), data_, size_,
+        ffn_, hint_);
+}
+
+
 int zmq_msg_send (zmq_msg_t *msg_, void *s_, int flags_)
 {
     zmq::socket_base_t *s = as_socket_base_t (s_);

src/zmq_draft.h

@@ -91,6 +91,30 @@ int zmq_msg_set_group (zmq_msg_t *msg_, const char *group_);
 const char *zmq_msg_group (zmq_msg_t *msg_);
 int zmq_msg_init_buffer (zmq_msg_t *msg_, const void *buf_, size_t size_);
 
+/*  Draft Msg control block type for init_external_storage.                   */
+typedef struct zmq_msg_content_t
+{
+#if defined(_MSC_VER) && (defined(_M_X64) || defined(_M_ARM64))
+    __declspec (align (8)) unsigned char _[64];
+#elif defined(_MSC_VER)                                                        \
+  && (defined(_M_IX86) || defined(_M_ARM_ARMV7VE) || defined(_M_ARM))
+    __declspec (align (4)) unsigned char _[64];
+#elif defined(__GNUC__) || defined(__INTEL_COMPILER)                           \
+  || (defined(__SUNPRO_C) && __SUNPRO_C >= 0x590)                              \
+  || (defined(__SUNPRO_CC) && __SUNPRO_CC >= 0x590)
+    unsigned char _[64] __attribute__ ((aligned (sizeof (void *))));
+#else
+    unsigned char _[64];
+#endif
+} zmq_msg_content_t;
+
+int zmq_msg_init_external_storage (zmq_msg_t *msg_,
+                                   zmq_msg_content_t *content_,
+                                   void *data_,
+                                   size_t size_,
+                                   zmq_free_fn *ffn_,
+                                   void *hint_);
+
 /*  DRAFT Msg property names.                                                 */
 #define ZMQ_MSG_PROPERTY_ROUTING_ID "Routing-Id"
 #define ZMQ_MSG_PROPERTY_SOCKET_TYPE "Socket-Type"

tests/CMakeLists.txt

@@ -175,6 +175,7 @@ if(ENABLE_DRAFTS)
     test_zmq_ppoll_fd
     test_xsub_verbose
     test_pubsub_topics_count
+    test_msg_ffn_external_storage
   )
 
   if(HAVE_FORK)

tests/test_msg_ffn_external_storage.cpp

@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: MPL-2.0 */
+
+#include "testutil.hpp"
+#include "testutil_unity.hpp"
+
+#include <string.h>
+
+SETUP_TEARDOWN_TESTCONTEXT
+
+void ffn (void *data_, void *hint_)
+{
+    // Signal that ffn has been called by writing "freed" to hint
+    (void) data_; //  Suppress 'unused' warnings at compile time
+    memcpy (hint_, (void *) "freed", 5);
+}
+
+void test_msg_init_ffn_external_storage ()
+{
+    //  Create the infrastructure
+    char my_endpoint[MAX_SOCKET_STRING];
+
+    void *router = test_context_socket (ZMQ_ROUTER);
+    bind_loopback_ipv4 (router, my_endpoint, sizeof my_endpoint);
+
+    void *dealer = test_context_socket (ZMQ_DEALER);
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_connect (dealer, my_endpoint));
+
+    // Test that creating and closing a message triggers ffn
+    zmq_msg_content_t *content = new zmq_msg_content_t;
+    zmq_msg_t msg;
+    char hint[5];
+    char data[255];
+    memset (data, 0, 255);
+    memcpy (data, (void *) "data", 4);
+    memcpy (hint, (void *) "hint", 4);
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_init_external_storage (
+      &msg, content, (void *) data, 255, ffn, (void *) hint));
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_close (&msg));
+
+    msleep (SETTLE_TIME);
+    TEST_ASSERT_EQUAL_STRING_LEN ("freed", hint, 5);
+    memcpy (hint, (void *) "hint", 4);
+
+    // Making and closing a copy triggers ffn
+    zmq_msg_t msg2;
+    zmq_msg_init (&msg2);
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_init_external_storage (
+      &msg, content, (void *) data, 255, ffn, (void *) hint));
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_copy (&msg2, &msg));
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_close (&msg2));
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_close (&msg));
+
+    msleep (SETTLE_TIME);
+    TEST_ASSERT_EQUAL_STRING_LEN ("freed", hint, 5);
+    memcpy (hint, (void *) "hint", 4);
+
+    // Test that sending a message triggers ffn
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_init_external_storage (
+      &msg, content, (void *) data, 255, ffn, (void *) hint));
+
+    zmq_msg_send (&msg, dealer, 0);
+    char buf[255];
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_recv (router, buf, 255, 0));
+    TEST_ASSERT_EQUAL_INT (255, zmq_recv (router, buf, 255, 0));
+    TEST_ASSERT_EQUAL_STRING_LEN (data, buf, 4);
+
+    msleep (SETTLE_TIME);
+    TEST_ASSERT_EQUAL_STRING_LEN ("freed", hint, 5);
+    memcpy (hint, (void *) "hint", 4);
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_close (&msg));
+
+    // Sending a copy of a message triggers ffn
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_init (&msg2));
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_init_external_storage (
+      &msg, content, (void *) data, 255, ffn, (void *) hint));
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_copy (&msg2, &msg));
+
+    zmq_msg_send (&msg, dealer, 0);
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_recv (router, buf, 255, 0));
+    TEST_ASSERT_EQUAL_INT (255, zmq_recv (router, buf, 255, 0));
+    TEST_ASSERT_EQUAL_STRING_LEN (data, buf, 4);
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_close (&msg2));
+    TEST_ASSERT_SUCCESS_ERRNO (zmq_msg_close (&msg));
+
+    msleep (SETTLE_TIME);
+    TEST_ASSERT_EQUAL_STRING_LEN ("freed", hint, 5);
+
+    //  Deallocate the infrastructure.
+    test_context_socket_close (router);
+    test_context_socket_close (dealer);
+
+    delete content;
+}
+
+int main (void)
+{
+    setup_test_environment ();
+
+    UNITY_BEGIN ();
+    RUN_TEST (test_msg_init_ffn_external_storage);
+    return UNITY_END ();
+}