[PATCH 1/6] core: add simple message interface

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This patch adds a new feature to the core which allows to send
messages to objects. An object can register/unregister a message
handler with pa_core_message_handler_{register, unregister}() while
a message can be sent to the handler using the pa_core_send_message()
function. A message has 4 arguments (apart from passing the core):

recipient: The name of the message handler that will receive the message
message: message command
message_parameters: A string containing additional parameters
response: Pointer to a response string that will be filled by the
          message handler. The caller is responsible to free the string.

The patch is a precondition for the following patches that allow clients
to send messages to pulseaudio objects.

There is no restriction on object names, except that a handler name
always starts with a "/". The intention is to use a path-like syntax,
for example /core/sink_1 for a sink or /name/instances/index for modules.
The exact naming convention still needs to be agreed.
---
 src/Makefile.am               |   1 +
 src/pulsecore/core-messages.c | 118 ++++++++++++++++++++++++++++++++++++++++++
 src/pulsecore/core-messages.h |  51 ++++++++++++++++++
 src/pulsecore/core.c          |   4 ++
 src/pulsecore/core.h          |   2 +-
 5 files changed, 175 insertions(+), 1 deletion(-)
 create mode 100644 src/pulsecore/core-messages.c
 create mode 100644 src/pulsecore/core-messages.h

diff --git a/src/Makefile.am b/src/Makefile.am
index 3ff1139f..7355cf03 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -957,6 +957,7 @@ libpulsecore_ at PA_MAJORMINOR@_la_SOURCES = \
 		pulsecore/core-scache.c pulsecore/core-scache.h \
 		pulsecore/core-subscribe.c pulsecore/core-subscribe.h \
 		pulsecore/core.c pulsecore/core.h \
+		pulsecore/core-messages.c pulsecore/core-messages.h \
 		pulsecore/hook-list.c pulsecore/hook-list.h \
 		pulsecore/ltdl-helper.c pulsecore/ltdl-helper.h \
 		pulsecore/modargs.c pulsecore/modargs.h \
diff --git a/src/pulsecore/core-messages.c b/src/pulsecore/core-messages.c
new file mode 100644
index 00000000..69055786
--- /dev/null
+++ b/src/pulsecore/core-messages.c
@@ -0,0 +1,118 @@
+/***
+  This file is part of PulseAudio.
+
+  Copyright 2004-2006 Lennart Poettering
+  Copyright 2006 Pierre Ossman <ossman at cendio.se> for Cendio AB
+
+  PulseAudio 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 2.1 of the License,
+  or (at your option) any later version.
+
+  PulseAudio 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
+  General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include <pulse/xmalloc.h>
+
+#include <pulsecore/core.h>
+#include <pulsecore/core-util.h>
+#include <pulsecore/log.h>
+#include <pulsecore/macro.h>
+
+#include "core-messages.h"
+
+struct pa_core_message_handler {
+    char *recipient;
+    char *description;
+    pa_core_message_handler_cb_t callback;
+    void *userdata;
+};
+
+/* Message handler functions */
+
+/* Register message handler. recipient_name must be a unique name starting with "/". */
+void pa_core_message_handler_register(pa_core *c, const char *recipient_name, const char *description, pa_core_message_handler_cb_t cb, void *userdata) {
+    struct pa_core_message_handler *handler;
+
+    pa_assert(c);
+    pa_assert(recipient_name);
+    pa_assert(cb);
+    pa_assert(userdata);
+
+    /* Ensure that the recipient name is not empty and starts with "/". */
+    pa_assert(recipient_name[0] == '/');
+
+    /* Name must not be in use. */
+    pa_assert(!pa_hashmap_get(c->message_handlers, recipient_name));
+
+    handler = pa_xnew0(struct pa_core_message_handler, 1);
+    handler->userdata = userdata;
+    handler->callback = cb;
+    handler->recipient = pa_xstrdup(recipient_name);
+    handler->description = pa_xstrdup(description);
+
+    pa_assert_se(pa_hashmap_put(c->message_handlers, handler->recipient, (void *) handler) == 0);
+}
+
+/* Unregister a message handler */
+void pa_core_message_handler_unregister(pa_core *c, const char *recipient_name) {
+    struct pa_core_message_handler *handler;
+
+    pa_assert(c);
+    pa_assert(recipient_name);
+
+    pa_assert_se(handler = pa_hashmap_remove(c->message_handlers, recipient_name));
+
+    pa_xfree(handler->recipient);
+    pa_xfree(handler->description);
+    pa_xfree(handler);
+}
+
+/* Send a message to a recipient or recipient group */
+int pa_core_send_message(pa_core *c, const char *recipient_name, const char *message, const char *message_parameters, char **response) {
+    struct pa_core_message_handler *handler;
+
+    pa_assert(c);
+    pa_assert(recipient_name);
+    pa_assert(message);
+    pa_assert(response);
+
+    *response = NULL;
+
+    if (!(handler = pa_hashmap_get(c->message_handlers, recipient_name)))
+        return PA_CORE_SEND_NO_RECIPIENT;
+
+    if (handler->callback(handler->recipient, message, message_parameters, response, handler->userdata) < 0)
+        return PA_CORE_SEND_FAILURE;
+
+    return PA_CORE_SEND_OK;
+}
+
+/* Set handler description */
+int pa_core_message_handler_set_description(pa_core *c, const char *recipient_name, const char *description) {
+    struct pa_core_message_handler *handler;
+
+    pa_assert(c);
+    pa_assert(recipient_name);
+
+    if (!(handler = pa_hashmap_get(c->message_handlers, recipient_name)))
+        return -1;
+
+    pa_xfree(handler->description);
+    handler->description = pa_xstrdup(description);
+
+    return 0;
+}
diff --git a/src/pulsecore/core-messages.h b/src/pulsecore/core-messages.h
new file mode 100644
index 00000000..d34e304e
--- /dev/null
+++ b/src/pulsecore/core-messages.h
@@ -0,0 +1,51 @@
+#ifndef foocoremessageshfoo
+#define foocoremessageshfoo
+
+/***
+  This file is part of PulseAudio.
+
+  Copyright 2004-2006 Lennart Poettering
+
+  PulseAudio 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 2.1 of the License,
+  or (at your option) any later version.
+
+  PulseAudio 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
+  General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <pulsecore/core.h>
+
+/* Message handler types and functions */
+
+/* Values returned by pa_core_send_message() */
+enum {
+    PA_CORE_SEND_OK,
+    PA_CORE_SEND_NO_RECIPIENT,
+    PA_CORE_SEND_FAILURE
+};
+
+/* Prototype for message callback */
+typedef int (*pa_core_message_handler_cb_t)(
+        const char *recipient,
+        const char *message,
+        const char *message_parameters,
+        char **response,
+        void *userdata);
+
+/* Handler registration */
+void pa_core_message_handler_register(pa_core *c, const char *recipient_name, const char *description, pa_core_message_handler_cb_t cb, void *userdata);
+void pa_core_message_handler_unregister(pa_core *c, const char *recipient_name);
+
+/* Send message to recipient */
+int pa_core_send_message(pa_core *c, const char *recipient_name, const char *message, const char *message_parameters, char **response);
+
+/* Set handler properties */
+int pa_core_message_handler_set_description(pa_core *c, const char *recipient_name, const char *description);
+#endif
diff --git a/src/pulsecore/core.c b/src/pulsecore/core.c
index e01677d5..3145caaf 100644
--- a/src/pulsecore/core.c
+++ b/src/pulsecore/core.c
@@ -103,6 +103,7 @@ pa_core* pa_core_new(pa_mainloop_api *m, bool shared, bool enable_memfd, size_t
 
     c->namereg = pa_hashmap_new(pa_idxset_string_hash_func, pa_idxset_string_compare_func);
     c->shared = pa_hashmap_new(pa_idxset_string_hash_func, pa_idxset_string_compare_func);
+    c->message_handlers = pa_hashmap_new(pa_idxset_string_hash_func, pa_idxset_string_compare_func);
 
     c->default_source = NULL;
     c->default_sink = NULL;
@@ -204,6 +205,9 @@ static void core_free(pa_object *o) {
     pa_assert(pa_hashmap_isempty(c->shared));
     pa_hashmap_free(c->shared);
 
+    pa_assert(pa_hashmap_isempty(c->message_handlers));
+    pa_hashmap_free(c->message_handlers);
+
     pa_assert(pa_hashmap_isempty(c->modules_pending_unload));
     pa_hashmap_free(c->modules_pending_unload);
 
diff --git a/src/pulsecore/core.h b/src/pulsecore/core.h
index 79a095d2..bc8a371e 100644
--- a/src/pulsecore/core.h
+++ b/src/pulsecore/core.h
@@ -160,7 +160,7 @@ struct pa_core {
     pa_idxset *clients, *cards, *sinks, *sources, *sink_inputs, *source_outputs, *modules, *scache;
 
     /* Some hashmaps for all sorts of entities */
-    pa_hashmap *namereg, *shared;
+    pa_hashmap *namereg, *shared, *message_handlers;
 
     /* The default sink/source as configured by the user. If the user hasn't
      * explicitly configured anything, these are set to NULL. These are strings
-- 
2.11.0



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