Add basic support for dynamically loadable plugins

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

plugin.c

@@ -0,0 +1,120 @@
+/* Test of dlopen() for a plugin based services architecture for finit
+ *
+ * Copyright (c) 2012  Joachim Nilsson <troglobit@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <errno.h>
+#include <dlfcn.h>		/* dlopen() et al */
+#include <dirent.h>		/* readdir() et al */
+#include <stdio.h>
+#include <string.h>
+#include <sys/queue.h>		/* BSD sys/queue.h API */
+
+#include "plugin.h"
+
+static LIST_HEAD(, plugin) plugins = LIST_HEAD_INITIALIZER();
+
+int plugin_register(plugin_t *plugin)
+{
+	if (!plugin) {
+		errno = EINVAL;
+		return 1;
+	}
+
+	if (!plugin->name) {
+		Dl_info info;
+
+		if (!dladdr(plugin, &info) || !info.dli_fname)
+			plugin->name = "unknown";
+		else
+			plugin->name = info.dli_fname;
+	}
+	LIST_INSERT_HEAD(&plugins, plugin, link);
+
+	return 0;
+}
+
+int plugin_unregister(plugin_t *plugin)
+{
+	LIST_REMOVE(plugin, link);
+
+	return 0;
+}
+
+void run_hooks(hook_point_t no)
+{
+	plugin_t *p;
+
+	PLUGIN_ITERATOR(p) {
+		if (p->hook[no].cb) {
+			printf("Calling %s hook n:o %d from runloop...\n", p->name, no);
+			p->hook[no].cb(p->hook[no].arg);
+		}
+	}
+}
+
+void run_services(void)
+{
+	plugin_t *p;
+
+	PLUGIN_ITERATOR(p) {
+		if (p->svc.cb) {
+			printf("Calling svc %s from runloop...\n", p->name);
+			p->svc.cb(p->svc.arg);
+		}
+	}
+}
+
+int load_plugins(void)
+{
+	DIR *dp = opendir(PLUGIN_PATH);
+	struct dirent *entry;
+
+	if (!dp) {
+		fprintf(stderr, "Failed, cannot open plugin directory %s: %s\n",
+			PLUGIN_PATH, strerror(errno));
+		return 1;
+	}
+
+	while ((entry = readdir(dp))) {
+		char *ext = entry->d_name + strlen(entry->d_name) - 3;
+
+		if (!strcmp(ext, ".so")) {
+			void *handle;
+			char filename[1024];
+
+			snprintf(filename, sizeof(filename), "%s/%s", PLUGIN_PATH, entry->d_name);
+			printf("Loading plugin %s ...\n", filename);
+			handle = dlopen(filename, RTLD_LAZY);
+			if (!handle) {
+				fprintf(stderr,
+					"Failed loading plugin %s: %s\n", filename, dlerror());
+				return 1;
+			}
+		}
+	}
+
+	closedir(dp);
+
+	return 0;
+}
+
+/**
+ * Local Variables:
+ *  version-control: t
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */