include/struct.h

   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_ */