/**

 * $Id: hook.h 662 2008-03-02 11:38:08Z nkeynes $

 *

 * This file defines some useful generic macros for hooks

 *

 * Copyright (c) 2008 Nathan Keynes.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 */

#ifndef lxdream_hook_H

#define lxdream_hook_H 1

#include <assert.h>

/**

 * Hook functions are generally useful, so we'd let to limit the overhead (and 

 * opportunity for stupid bugs) by minimizing the amount of code involved. Glib

 * has GHook (and of course signals), but they don't actually simplify anything

 * at this level.

 * 

 * Hence, the gratuitous macro abuse here.

 * 

 * Usage:

 * 

 * In header file:

 * 

 * DECLARE_HOOK( hook_name, hook_fn_type );

 * 

 * In implementation file:

 * 

 * DEFINE_HOOK( hook_name, hook_fn_type );

 *

 */

#define DECLARE_HOOK( name, fn_type ) \

    void register_##name( fn_type fn, void *user_data ); \

    void unregister_##name( fn_type fn, void *user_data );

#define FOREACH_HOOK( h, name ) struct name##_hook_struct *h; for( h = name##_hook_list; h != NULL; h = h->next )

#define CALL_HOOKS( name, args... ) FOREACH_HOOK(h, name) { h->fn(args, h->user_data); } 

#define DEFINE_HOOK( name, fn_type ) \

    struct name##_hook_struct { \

        fn_type fn; \

        void *user_data; \

        struct name##_hook_struct *next; \

    } *name##_hook_list = NULL; \

    void register_##name( fn_type fn, void *user_data ) { \

        struct name##_hook_struct *h = malloc(sizeof(struct name##_hook_struct)); \

        assert(h != NULL); \

        h->fn = fn; \

        h->user_data = user_data; \

        h->next = name##_hook_list; \

        name##_hook_list = h; \

    } \

    void unregister_##name( fn_type fn, void *user_data ) { \

        struct name##_hook_struct *last = NULL, *h = name##_hook_list; \

        while( h != NULL )  { \

            if( h->fn == fn && h->user_data == user_data ) { \

                if( last == NULL ) { \

                    name##_hook_list = h->next; \

                } else { \

                    last->next = h->next; \

                } \

                free( h ); \

            } \

            last = h; \

            h = h->next; \

        }\

    }

#endif /* !lxdream_hook_H */