openrc/src/rc-plugin.c

/*
   librc-plugin.c 
   Simple plugin handler
   Copyright 2007 Gentoo Foundation
   Released under the GPLv2
   */

#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "einfo.h"
#include "rc.h"
#include "rc-misc.h"
#include "rc-plugin.h"
#include "strlist.h"

typedef struct plugin
{
	char *name;
	void *handle;
	int (*hook) (rc_hook_t hook, const char *name);
	struct plugin *next;
} plugin_t;

static plugin_t *plugins = NULL;

void rc_plugin_load (void)
{
	char **files;
	char *file;
	int i;
	plugin_t *plugin = plugins;

	/* Ensure some sanity here */
	rc_plugin_unload ();

	if (! rc_exists (RC_PLUGINDIR))
		return;

	files = rc_ls_dir (NULL, RC_PLUGINDIR, 0);
	STRLIST_FOREACH (files, file, i) {
		char *p = rc_strcatpaths (RC_PLUGINDIR, file, NULL);
		/*
		 * We load the use RTLD_NOW so that we know it works
		 * as if we have any unknown symbols when we run then the
		 * program bails out in rc_plugin_run which is very very bad.
		 */
		void *h = dlopen (p, RTLD_NOW);
		char *func;
		void *f;
		int len;

		if (! h) {
			eerror ("dlopen: %s", dlerror ());
			free (p);
			continue;
		}

		func = file;
		file = strsep (&func, ".");
		len = strlen (file) + 7;
		func = rc_xmalloc (sizeof (char *) * len);
		snprintf (func, len, "_%s_hook", file);

		f = dlsym (h, func);
		if (! f) {
			eerror ("`%s' does not expose the symbol `%s'", p, func);
			dlclose (h);
		} else {
			if (plugin) {
				plugin->next = rc_xmalloc (sizeof (plugin_t));
				plugin = plugin->next;
			} else
				plugin = plugins = rc_xmalloc (sizeof (plugin_t));

			memset (plugin, 0, sizeof (plugin_t));
			plugin->name = strdup (file);
			plugin->handle = h;
			plugin->hook = f;
		}

		free (func);
		free (p);
	}

	rc_strlist_free (files);
}

void rc_plugin_run (rc_hook_t hook, const char *value)
{
	plugin_t *plugin = plugins;

	while (plugin) {
		if (plugin->hook)
			plugin->hook (hook, value);

		plugin = plugin->next;
	}
}

void rc_plugin_unload (void)
{
	plugin_t *plugin = plugins;
	plugin_t *next;

	while (plugin) {
		next = plugin->next;
		dlclose (plugin->handle);
		free (plugin->name);
		free (plugin);
		plugin = next;
	}
	plugins = NULL;
}