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      1 /*	$NetBSD: once.h,v 1.9 2023/09/09 00:15:09 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c)2005 YAMAMOTO Takashi,
      5  * Copyright (c)2008 Antti Kantee,
      6  * All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     27  * SUCH DAMAGE.
     28  */
     29 
     30 #ifndef _SYS_ONCE_H_
     31 #define	_SYS_ONCE_H_
     32 
     33 typedef struct {
     34 	int o_error;
     35 	uint16_t o_refcnt;
     36 	uint16_t o_status;
     37 #define	ONCE_VIRGIN	0
     38 #define	ONCE_RUNNING	1
     39 #define	ONCE_DONE	2
     40 } once_t;
     41 
     42 void once_init(void);
     43 int _init_once(once_t *, int (*)(void));
     44 void _fini_once(once_t *, void (*)(void));
     45 
     46 #define	ONCE_DECL(o) \
     47 	once_t (o) = { \
     48 		.o_status = 0, \
     49 		.o_refcnt = 0, \
     50 	};
     51 
     52 #define	RUN_ONCE(o, fn) \
     53     (__predict_true((o)->o_status == ONCE_DONE) ? \
     54       ((o)->o_error) : _init_once((o), (fn)))
     55 
     56 #define	INIT_ONCE(o, fn)	_init_once((o), (fn))
     57 #define	FINI_ONCE(o, fn)	_fini_once((o), (fn))
     58 
     59 #endif /* _SYS_ONCE_H_ */
     60