compositor: add plugin-registry
Implement a simple register and lookup for function tables. This is
intended for plugins to expose APIs to other plugins.
It has been very hard to arrange a plugin to be able to call into
another plugin without modifying Weston core to explicitly support each
case. This patch fixes that.
The tests all pass.
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Signed-off-by: Giulio Camuffo <giuliocamuffo@gmail.com>
diff --git a/libweston/plugin-registry.c b/libweston/plugin-registry.c
new file mode 100644
index 0000000..48c4220
--- /dev/null
+++ b/libweston/plugin-registry.c
@@ -0,0 +1,156 @@
+/*
+ * Copyright (C) 2016 DENSO CORPORATION
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "config.h"
+
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include "compositor.h"
+#include "plugin-registry.h"
+
+struct weston_plugin_api {
+ struct wl_list link; /**< in weston_compositor::plugin_api_list */
+
+ char *api_name; /**< The search key */
+ const void *vtable; /**< The function table */
+ size_t vtable_size; /**< Size of the function table in bytes */
+};
+
+/** Register an implementation of an API
+ *
+ * \param compositor The compositor instance.
+ * \param api_name The API name which other plugins use to find the
+ * implementation.
+ * \param vtable Pointer to the function table of the API.
+ * \param vtable_size Size of the function table in bytes.
+ * \return 0 on success, -1 on error, -2 if api_name already registered
+ *
+ * This call makes the given vtable to be reachable via
+ * weston_plugin_api_get(). Calls through the vtable may start happening
+ * as soon as the caller returns after success. Argument vtable must not be
+ * NULL. Argument api_name must be non-NULL and non-zero length.
+ *
+ * You can increase the function table size without breaking the ABI.
+ * To cater for ABI breaks, it is recommended to have api_name include a
+ * version number.
+ *
+ * A registered API cannot be unregistered. However, calls through a
+ * registered API must not be made from the compositor destroy signal handlers.
+ */
+WL_EXPORT int
+weston_plugin_api_register(struct weston_compositor *compositor,
+ const char *api_name,
+ const void *vtable,
+ size_t vtable_size)
+{
+ struct weston_plugin_api *wpa;
+
+ assert(api_name);
+ assert(strlen(api_name) > 0);
+ assert(vtable);
+
+ if (!api_name || !vtable || strlen(api_name) == 0)
+ return -1;
+
+ wl_list_for_each(wpa, &compositor->plugin_api_list, link)
+ if (strcmp(wpa->api_name, api_name) == 0)
+ return -2;
+
+ wpa = zalloc(sizeof(*wpa));
+ if (!wpa)
+ return -1;
+
+ wpa->api_name = strdup(api_name);
+ wpa->vtable = vtable;
+ wpa->vtable_size = vtable_size;
+
+ if (!wpa->api_name) {
+ free(wpa);
+
+ return -1;
+ }
+
+ wl_list_insert(&compositor->plugin_api_list, &wpa->link);
+ weston_log("Registered plugin API '%s' of size %zd\n",
+ wpa->api_name, wpa->vtable_size);
+
+ return 0;
+}
+
+/** Internal function to free registered APIs
+ *
+ * \param compositor The compositor instance.
+ */
+void
+weston_plugin_api_destroy_list(struct weston_compositor *compositor)
+{
+ struct weston_plugin_api *wpa, *tmp;
+
+ wl_list_for_each_safe(wpa, tmp, &compositor->plugin_api_list, link) {
+ free(wpa->api_name);
+ wl_list_remove(&wpa->link);
+ free(wpa);
+ }
+}
+
+/** Fetch the implementation of an API
+ *
+ * \param compositor The compositor instance.
+ * \param api_name The name of the API to search for.
+ * \param vtable_size The expected function table size in bytes.
+ * \return Pointer to the function table, or NULL on error.
+ *
+ * Find the function table corresponding to api_name. The vtable_size here
+ * must be less or equal to the vtable_size given in the corresponding
+ * weston_plugin_api_register() call made by the implementing plugin.
+ *
+ * Calls can be made through the function table immediately. However, calls
+ * must not be made from or after the compositor destroy signal handler.
+ */
+WL_EXPORT const void *
+weston_plugin_api_get(struct weston_compositor *compositor,
+ const char *api_name,
+ size_t vtable_size)
+{
+ struct weston_plugin_api *wpa;
+
+ assert(api_name);
+ if (!api_name)
+ return NULL;
+
+ wl_list_for_each(wpa, &compositor->plugin_api_list, link) {
+ if (strcmp(wpa->api_name, api_name) != 0)
+ continue;
+
+ if (vtable_size <= wpa->vtable_size)
+ return wpa->vtable;
+
+ return NULL;
+ }
+
+ return NULL;
+}