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/tests/plugin-registry-test.c b/tests/plugin-registry-test.c
new file mode 100644
index 0000000..7fc88f3
--- /dev/null
+++ b/tests/plugin-registry-test.c
@@ -0,0 +1,101 @@
+/*
+ * 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 "compositor.h"
+#include "plugin-registry.h"
+
+static void
+dummy_func(void)
+{
+}
+
+static const struct my_api {
+	void (*func1)(void);
+	void (*func2)(void);
+	void (*func3)(void);
+} my_test_api = {
+	dummy_func,
+	dummy_func,
+	dummy_func,
+};
+
+#define MY_API_NAME "test_my_api_v1"
+
+static void
+init_tests(struct weston_compositor *compositor)
+{
+	assert(weston_plugin_api_get(compositor, MY_API_NAME,
+				     sizeof(my_test_api)) == NULL);
+
+	assert(weston_plugin_api_register(compositor, MY_API_NAME, &my_test_api,
+					  sizeof(my_test_api)) == 0);
+
+	assert(weston_plugin_api_register(compositor, MY_API_NAME, &my_test_api,
+					  sizeof(my_test_api)) == -2);
+
+	assert(weston_plugin_api_get(compositor, MY_API_NAME,
+				     sizeof(my_test_api)) == &my_test_api);
+
+	assert(weston_plugin_api_register(compositor, "another", &my_test_api,
+					  sizeof(my_test_api)) == 0);
+}
+
+static void
+runtime_tests(void *data)
+{
+	struct weston_compositor *compositor = data;
+	const struct my_api *api;
+	size_t sz = sizeof(struct my_api);
+
+	assert(weston_plugin_api_get(compositor, MY_API_NAME, sz) ==
+				     &my_test_api);
+
+	assert(weston_plugin_api_get(compositor, MY_API_NAME, sz - 4) ==
+				     &my_test_api);
+
+	assert(weston_plugin_api_get(compositor, MY_API_NAME, sz + 4) == NULL);
+
+	api = weston_plugin_api_get(compositor, MY_API_NAME, sz);
+	assert(api && api->func2 == dummy_func);
+
+	wl_display_terminate(compositor->wl_display);
+}
+
+WL_EXPORT int
+module_init(struct weston_compositor *compositor, int *argc, char *argv[])
+{
+	struct wl_event_loop *loop;
+
+	init_tests(compositor);
+
+	loop = wl_display_get_event_loop(compositor->wl_display);
+	wl_event_loop_add_idle(loop, runtime_tests, compositor);
+
+	return 0;
+}