1  /*-
 2   * Copyright (c) 1983, 1993
 3   *	The Regents of the University of California.  All rights reserved.
 4   *
 5   * Redistribution and use in source and binary forms, with or without
 6   * modification, are permitted provided that the following conditions
 7   * are met:
 8   * 1. Redistributions of source code must retain the above copyright
 9   *    notice, this list of conditions and the following disclaimer.
10   * 2. Redistributions in binary form must reproduce the above copyright
11   *    notice, this list of conditions and the following disclaimer in the
12   *    documentation and/or other materials provided with the distribution.
13   * 3. All advertising materials mentioning features or use of this software
14   *    must display the following acknowledgement:
15   *	This product includes software developed by the University of
16   *	California, Berkeley and its contributors.
17   * 4. Neither the name of the University nor the names of its contributors
18   *    may be used to endorse or promote products derived from this software
19   *    without specific prior written permission.
20   *
21   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31   * SUCH DAMAGE.
32   *
33   *	@(#)struct.h	8.1 (Berkeley) 6/2/93
34   */
35  
36  #ifndef _STRUCT_H_
37  #define	_STRUCT_H_
38  
39  /* Offset of the field in the structure. */
40  #define	fldoff(name, field) \
41  	((int)&(((struct name *)0)->field))
42  
43  /* Size of the field in the structure. */
44  #define	fldsiz(name, field) \
45  	(sizeof(((struct name *)0)->field))
46  
47  /* Address of the structure from a field. */
48  #define	strbase(name, addr, field) \
49  	((struct name *)((char *)(addr) - fldoff(name, field)))
50  
51  /*
52   * countof() cannot be safely used in a _Static_assert statement, so we provide
53   * an unsafe variant that does not verify the input array is statically-defined.
54   */
55  #define countof_unsafe(arr) \
56  	(sizeof(arr) / sizeof(arr[0]))
57  
58  /* Number of elements in a statically-defined array */
59  #if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L && __GNUC__
60  #define countof(arr) ({ \
61  	_Static_assert( \
62  			!__builtin_types_compatible_p(typeof(arr), typeof(&(arr)[0])), \
63  			"array must be statically defined"); \
64  	(sizeof(arr) / sizeof(arr[0])); \
65  })
66  #else
67  #define countof(arr) \
68  	countof_unsafe(arr)
69  #endif
70  
71  /* Length of a statically-defined string (does not include null terminator) */
72  #define lenof(str) \
73  	(sizeof(str) - 1)
74  
75  /* Last index of a statically-defined array */
76  #define lastof(arr) \
77  	(countof(arr) - 1)
78  
79  #endif /* !_STRUCT_H_ */