[pulseaudio-discuss] [PATCH 1/3] core: add generic message interface
Georg Chini
georg at chini.tk
Fri Aug 4 13:37:27 UTC 2017
This patch adds a new feature to the core which allows to exchange
messages between objects. An object can register/unregister a message
handler with pa_core_message_handler_{register, unregister}() while
any other object can send a message to the handler using the
pa_core_send_message() function. A message has 5 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
message_data: void pointer to some parameter structure, can be used
as alternative to message_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 also allow
clients to send messages to pulseaudio objects.
Because not every message handler should be visible to clients, a flag
was added to the handler structure which allows to mark a handler as
public or private.
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.
Message groups are also implemented, so that a handler can subscribe
to a message group using pa_core_message_handler_group_[un]subscribe()
to receive messages sent to the group. To distinguish group and handler
names, group names lack the leading "/". Some of the code used to
implement the message groups was adapted from hook-list.c. Message
groups are created/deleted implicitely on subscription/unsubscription.
The messaging interface can serve as a full replacement for the current
hook system with several advantages:
- no need to change header files when a new handler/group is implemented
- slightly simpler registration interface
- multi-purpose message handlers that can handle multiple events
- mesage handlers may also be accessible from the client side
---
src/Makefile.am | 2 +
src/pulsecore/core-messages.c | 420 ++++++++++++++++++++++++++++++++++++++++++
src/pulsecore/core-messages.h | 67 +++++++
src/pulsecore/core.c | 4 +
src/pulsecore/core.h | 2 +-
5 files changed, 494 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..42047823 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -676,6 +676,7 @@ libpulsecommon_ at PA_MAJORMINOR@_la_SOURCES = \
pulsecore/core-format.c pulsecore/core-format.h \
pulsecore/core-rtclock.c pulsecore/core-rtclock.h \
pulsecore/core-util.c pulsecore/core-util.h \
+ pulsecore/core-messages.c pulsecore/core-messages.h \
pulsecore/creds.h \
pulsecore/dynarray.c pulsecore/dynarray.h \
pulsecore/endianmacros.h \
@@ -957,6 +958,7 @@ 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..9ebaab24
--- /dev/null
+++ b/src/pulsecore/core-messages.c
@@ -0,0 +1,420 @@
+/***
+ 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;
+ bool is_private;
+ pa_idxset *groups;
+ pa_core_message_handler_cb_t callback;
+ void *userdata;
+};
+
+struct pa_handler_group_member {
+ char *name;
+ int priority;
+ bool dead;
+ PA_LLIST_FIELDS(struct pa_handler_group_member);
+};
+
+struct pa_handler_group {
+ int n_dead;
+ int n_sending;
+ pa_core *core;
+ PA_LLIST_HEAD(struct pa_handler_group_member, handler_list);
+};
+
+/* Message handler functions */
+
+/* Find a message handler for a given name or group */
+static int find_message_handler(pa_core *c, const char *search_string, struct pa_core_message_handler **handler) {
+ pa_assert(c);
+ pa_assert(search_string);
+
+ *handler = NULL;
+
+ /* Check if the search string exactly matches a handler name */
+ if (search_string[0] == '/')
+ *handler = pa_hashmap_get(c->message_handlers, search_string);
+
+ else {
+ /* Check for group name */
+ char *name = pa_sprintf_malloc("/groups/%s", search_string);
+ *handler = pa_hashmap_get(c->message_handlers, name);
+ pa_xfree(name);
+ }
+
+ /* Nothing found, return failure */
+ if (!*handler)
+ return -1;
+
+ return 0;
+}
+
+/* Compares the left most characters of a to b */
+static bool str_starts_with(const char *a, const char *b) {
+ uint32_t i, l;
+
+ if (!a) {
+ if (!b)
+ return true;
+ return false;
+ }
+
+ l = strlen(b);
+
+ /* a must contain at least as many characters as b */
+ if (strlen(a) < l)
+ return false;
+
+ for (i = 0; i < l; i++) {
+ if (a[i] != b[i])
+ return false;
+ }
+
+ return true;
+}
+
+/* Test existence and scope of a handler */
+int pa_core_message_handler_test(pa_core *c, const char *search_string) {
+ int ret;
+ struct pa_core_message_handler *handler;
+
+ if ((ret = find_message_handler(c, search_string, &handler)) < 0)
+ return PA_CORE_HANDLER_NONE;
+ if (handler->is_private)
+ return PA_CORE_HANDLER_PRIVATE;
+ return PA_CORE_HANDLER_PUBLIC;
+}
+
+/* Register message handler. recipient_name must be a unique name starting with "/". */
+static void handler_register(pa_core *c, const char *recipient_name, const char *description, bool is_private, pa_core_message_handler_cb_t cb, void *userdata) {
+ struct pa_core_message_handler *handler;
+
+ /* Name must not be in use. */
+ pa_assert(find_message_handler(c, recipient_name, &handler) < 0);
+
+ 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);
+ handler->groups = NULL;
+ handler->is_private = is_private;
+
+ pa_assert_se(pa_hashmap_put(c->message_handlers, handler->recipient, (void *) handler) == 0);
+}
+
+void pa_core_message_handler_register(pa_core *c, const char *recipient_name, const char *description, bool is_private, pa_core_message_handler_cb_t cb, void *userdata) {
+
+ 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] == '/');
+
+ /* Prefix /groups/ is reserved for message groups */
+ pa_assert(!str_starts_with(recipient_name, "/groups/"));
+
+ return handler_register(c, recipient_name, description, is_private, cb, userdata);
+}
+
+/* Unregister a message handler */
+static void 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_get(c->message_handlers, recipient_name));
+
+ /* Unsubscribe from groups */
+ if (handler->groups) {
+ char *group, *tmp_group;
+ uint32_t idx;
+
+ PA_IDXSET_FOREACH(group, handler->groups, idx) {
+ /* group will be destroyed when the group is removed from
+ * the idxset in pa_core_message_handler_group_unsubscribe(),
+ * therefore we need to copy the string before passing it
+ * to the function. */
+ tmp_group = pa_xstrdup(group);
+
+ pa_core_message_handler_group_unsubscribe(c, handler->recipient, tmp_group);
+ pa_xfree(tmp_group);
+ }
+
+ pa_assert(pa_idxset_isempty(handler->groups));
+ pa_idxset_free(handler->groups, NULL);
+ }
+
+ pa_assert_se(handler = pa_hashmap_remove(c->message_handlers, recipient_name));
+
+ pa_xfree(handler->recipient);
+ pa_xfree(handler->description);
+ pa_xfree(handler);
+}
+
+void pa_core_message_handler_unregister(pa_core *c, const char *recipient_name) {
+
+ /* Message groups are unregistered implicitely. */
+ pa_assert(!str_starts_with(recipient_name, "/groups/"));
+
+ handler_unregister(c, recipient_name);
+}
+
+/* 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, void *message_data, char **response) {
+ struct pa_core_message_handler *handler;
+
+ pa_assert(c);
+ pa_assert(recipient_name);
+ pa_assert(message);
+ pa_assert(response);
+
+ *response = NULL;
+
+ if (find_message_handler(c, recipient_name, &handler) < 0)
+ return PA_CORE_SEND_NO_RECIPIENT;
+
+ if (handler->callback(handler->recipient, message, message_parameters, message_data, 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 (find_message_handler(c, recipient_name, &handler) < 0)
+ return -1;
+
+ pa_xfree(handler->description);
+ handler->description = pa_xstrdup(description);
+
+ return 0;
+}
+
+/* Set handler private flag, mainly useful to change group visibility because
+ * groups are always created private. */
+int pa_core_message_handler_set_private(pa_core *c, const char *recipient_name, bool is_private) {
+ struct pa_core_message_handler *handler;
+
+ pa_assert(c);
+ pa_assert(recipient_name);
+
+ if (find_message_handler(c, recipient_name, &handler) < 0)
+ return -1;
+
+ handler->is_private = is_private;
+
+ return 0;
+}
+
+/* Callback for message groups. Mostly stolen from hook-list.c. */
+static int handler_group_callback(const char *recipient, const char *message, const char *message_parameters, void *message_data, char **response, void *userdata) {
+ struct pa_handler_group_member *gm, *next;
+ struct pa_handler_group *g = (struct pa_handler_group *) userdata;
+ int n_errors = 0;
+ int ret;
+
+ g->n_sending ++;
+
+ PA_LLIST_FOREACH(gm, g->handler_list) {
+ if (gm->dead)
+ continue;
+
+ ret = pa_core_send_message(g->core, gm->name, message, message_parameters, message_data, response);
+ if (ret == PA_CORE_SEND_NO_RECIPIENT) {
+ gm->dead = true;
+ g->n_dead++;
+ } else if (ret != PA_CORE_SEND_OK)
+ n_errors++;
+
+ /* Ignore return string */
+ pa_xfree(*response);
+ }
+
+ g->n_sending --;
+ pa_assert(g->n_sending >= 0);
+
+ if (g->n_sending == 0) {
+ for (gm = g->handler_list; g->n_dead > 0 && gm; gm = next) {
+ next = gm->next;
+
+ if (gm->dead) {
+ PA_LLIST_REMOVE(struct pa_handler_group_member, g->handler_list, gm);
+ pa_xfree(gm->name);
+ pa_xfree(gm);
+ g->n_dead--;
+ }
+ }
+
+ pa_assert(g->n_dead == 0);
+ }
+
+ *response = pa_xstrdup("OK");
+ return -n_errors;
+
+}
+
+int pa_core_message_handler_group_subscribe(pa_core *c, const char *recipient_name, const char *group_name, int priority) {
+ struct pa_core_message_handler *handler, *recipient;
+ struct pa_handler_group *g;
+ struct pa_handler_group_member *gm, *insert_after, *current;
+
+ pa_assert(c);
+ pa_assert(recipient_name);
+ pa_assert(group_name);
+
+ /* Group names must not start with "/". */
+ if (group_name[0] == '/')
+ return -1;
+
+ /* Handler must be already registered. */
+ if (!(recipient = pa_hashmap_get(c->message_handlers, recipient_name)))
+ return -1;
+
+ /* If the group does not exist, create it. */
+ if (find_message_handler(c, group_name, &handler) < 0) {
+ char *name;
+
+ g = pa_xnew0(struct pa_handler_group, 1);
+
+ name = pa_sprintf_malloc("/groups/%s", group_name);
+ handler_register(c, name, "Group callback", true, handler_group_callback, g);
+ pa_xfree(name);
+
+ pa_assert(find_message_handler(c, group_name, &handler) >= 0);
+ }
+
+ /* Add group to the group list of the handler. */
+ if (!recipient->groups)
+ recipient->groups = pa_idxset_new(pa_idxset_trivial_hash_func, pa_idxset_trivial_compare_func);
+ pa_idxset_put(recipient->groups, pa_xstrdup(group_name), NULL);
+
+ g = (struct pa_handler_group *) handler->userdata;
+ g->core = c;
+ gm = pa_xnew0(struct pa_handler_group_member, 1);
+ gm->name = pa_xstrdup(recipient_name);
+ gm->priority = priority;
+ gm->dead = false;
+
+ /* Add handler to the handler list of the group. */
+ insert_after = NULL;
+ for (current = g->handler_list; current; current = current->next) {
+ if (priority < current->priority)
+ break;
+ insert_after = current;
+ }
+
+ PA_LLIST_INSERT_AFTER(struct pa_handler_group_member, g->handler_list, insert_after, gm);
+
+ return 0;
+}
+
+int pa_core_message_handler_group_unsubscribe(pa_core *c, const char *recipient_name, const char *group_name) {
+ struct pa_core_message_handler *handler;
+ struct pa_handler_group *g;
+ struct pa_handler_group_member *gm, *next;
+ char *real_group_name;
+ pa_idxset *group_list;
+
+ pa_assert(c);
+ pa_assert(recipient_name);
+ pa_assert(group_name);
+
+ /* Handler must exist. */
+ if (!(handler = pa_hashmap_get(c->message_handlers, recipient_name)))
+ return -1;
+
+ group_list = handler->groups;
+ real_group_name = pa_sprintf_malloc("/groups/%s", group_name);
+
+ /* Group must exist. */
+ if (!(handler = pa_hashmap_get(c->message_handlers, real_group_name))) {
+ pa_xfree(real_group_name);
+ return -1;
+ }
+
+ /* Remove entry from the group list of the handler */
+ if (group_list) {
+ uint32_t idx;
+ char *group;
+
+ PA_IDXSET_FOREACH(group, group_list, idx) {
+ if (pa_streq(group, group_name)) {
+ pa_idxset_remove_by_index(group_list, idx);
+ pa_xfree(group);
+ }
+ }
+ }
+
+ /* Remove entry from the handler list of the group */
+ g = (struct pa_handler_group *) handler->userdata;
+ gm = g->handler_list;
+ while (gm) {
+ if (pa_streq(gm->name, recipient_name)) {
+ if (g->n_sending) {
+ g->n_dead++;
+ gm->dead = true;
+ gm = gm->next;
+ } else {
+ next = gm->next;
+ PA_LLIST_REMOVE(struct pa_handler_group_member, g->handler_list, gm);
+ pa_xfree(gm->name);
+ pa_xfree(gm);
+ gm = next;
+ }
+ } else
+ gm = gm->next;
+ }
+
+ /* If the last member was removed, also remove the group */
+ if (!g->handler_list) {
+ handler_unregister(c, real_group_name);
+ pa_xfree(g);
+ }
+
+ pa_xfree(real_group_name);
+ return 0;
+}
diff --git a/src/pulsecore/core-messages.h b/src/pulsecore/core-messages.h
new file mode 100644
index 00000000..d85f69f4
--- /dev/null
+++ b/src/pulsecore/core-messages.h
@@ -0,0 +1,67 @@
+#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_test_message_handler() */
+enum {
+ PA_CORE_HANDLER_NONE,
+ PA_CORE_HANDLER_PRIVATE,
+ PA_CORE_HANDLER_PUBLIC
+};
+
+/* 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,
+ void *message_data,
+ char **response,
+ void *userdata);
+
+/* Handler registration */
+void pa_core_message_handler_register(pa_core *c, const char *recipient_name, const char *description, bool is_private, pa_core_message_handler_cb_t cb, void *userdata);
+void pa_core_message_handler_unregister(pa_core *c, const char *recipient_name);
+
+/* Check availability and scope of handler */
+int pa_core_message_handler_test(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, void *message_data, char **response);
+
+/* Set handler properties */
+int pa_core_message_handler_set_description(pa_core *c, const char *recipient_name, const char *description);
+int pa_core_message_handler_set_private(pa_core *c, const char *recipient_name, bool is_private);
+
+/* Message group functions */
+int pa_core_message_handler_group_subscribe(pa_core *c, const char *recipient_name, const char *group_name, int priority);
+int pa_core_message_handler_group_unsubscribe(pa_core *c, const char *recipient_name, const char *group_name);
+#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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