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https://gitlab.freedesktop.org/wayland/weston
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![Pekka Paalanen](/assets/img/avatar_default.png)
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>
157 lines
4.7 KiB
C
157 lines
4.7 KiB
C
/*
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* Copyright (C) 2016 DENSO CORPORATION
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice (including the
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* next paragraph) shall be included in all copies or substantial
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* portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include "config.h"
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#include <assert.h>
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#include <string.h>
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#include <stdlib.h>
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#include "compositor.h"
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#include "plugin-registry.h"
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struct weston_plugin_api {
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struct wl_list link; /**< in weston_compositor::plugin_api_list */
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char *api_name; /**< The search key */
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const void *vtable; /**< The function table */
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size_t vtable_size; /**< Size of the function table in bytes */
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};
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/** Register an implementation of an API
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*
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* \param compositor The compositor instance.
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* \param api_name The API name which other plugins use to find the
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* implementation.
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* \param vtable Pointer to the function table of the API.
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* \param vtable_size Size of the function table in bytes.
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* \return 0 on success, -1 on error, -2 if api_name already registered
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*
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* This call makes the given vtable to be reachable via
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* weston_plugin_api_get(). Calls through the vtable may start happening
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* as soon as the caller returns after success. Argument vtable must not be
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* NULL. Argument api_name must be non-NULL and non-zero length.
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*
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* You can increase the function table size without breaking the ABI.
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* To cater for ABI breaks, it is recommended to have api_name include a
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* version number.
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*
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* A registered API cannot be unregistered. However, calls through a
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* registered API must not be made from the compositor destroy signal handlers.
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*/
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WL_EXPORT int
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weston_plugin_api_register(struct weston_compositor *compositor,
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const char *api_name,
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const void *vtable,
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size_t vtable_size)
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{
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struct weston_plugin_api *wpa;
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assert(api_name);
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assert(strlen(api_name) > 0);
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assert(vtable);
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if (!api_name || !vtable || strlen(api_name) == 0)
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return -1;
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wl_list_for_each(wpa, &compositor->plugin_api_list, link)
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if (strcmp(wpa->api_name, api_name) == 0)
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return -2;
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wpa = zalloc(sizeof(*wpa));
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if (!wpa)
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return -1;
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wpa->api_name = strdup(api_name);
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wpa->vtable = vtable;
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wpa->vtable_size = vtable_size;
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if (!wpa->api_name) {
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free(wpa);
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return -1;
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}
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wl_list_insert(&compositor->plugin_api_list, &wpa->link);
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weston_log("Registered plugin API '%s' of size %zd\n",
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wpa->api_name, wpa->vtable_size);
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return 0;
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}
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/** Internal function to free registered APIs
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*
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* \param compositor The compositor instance.
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*/
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void
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weston_plugin_api_destroy_list(struct weston_compositor *compositor)
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{
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struct weston_plugin_api *wpa, *tmp;
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wl_list_for_each_safe(wpa, tmp, &compositor->plugin_api_list, link) {
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free(wpa->api_name);
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wl_list_remove(&wpa->link);
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free(wpa);
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}
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}
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/** Fetch the implementation of an API
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*
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* \param compositor The compositor instance.
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* \param api_name The name of the API to search for.
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* \param vtable_size The expected function table size in bytes.
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* \return Pointer to the function table, or NULL on error.
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*
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* Find the function table corresponding to api_name. The vtable_size here
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* must be less or equal to the vtable_size given in the corresponding
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* weston_plugin_api_register() call made by the implementing plugin.
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*
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* Calls can be made through the function table immediately. However, calls
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* must not be made from or after the compositor destroy signal handler.
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*/
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WL_EXPORT const void *
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weston_plugin_api_get(struct weston_compositor *compositor,
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const char *api_name,
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size_t vtable_size)
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{
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struct weston_plugin_api *wpa;
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assert(api_name);
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if (!api_name)
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return NULL;
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wl_list_for_each(wpa, &compositor->plugin_api_list, link) {
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if (strcmp(wpa->api_name, api_name) != 0)
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continue;
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if (vtable_size <= wpa->vtable_size)
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return wpa->vtable;
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return NULL;
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}
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return NULL;
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}
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