external/bsd/ntp/dist/lib/isc/include/isc/magic.h

   1 /*      $NetBSD$        */
   2
   3 /*
   4  * Copyright (C) 2004-2007  Internet Systems Consortium, Inc. ("ISC")
   5  * Copyright (C) 1999-2001  Internet Software Consortium.
   6  *
   7  * Permission to use, copy, modify, and/or distribute this software for any
   8  * purpose with or without fee is hereby granted, provided that the above
   9  * copyright notice and this permission notice appear in all copies.
  10  *
  11  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
  12  * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  13  * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
  14  * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
  15  * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
  16  * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  17  * PERFORMANCE OF THIS SOFTWARE.
  18  */
  19
  20 /* Id: magic.h,v 1.18 2007/06/19 23:47:18 tbox Exp */
  21
  22 #ifndef ISC_MAGIC_H
  23 #define ISC_MAGIC_H 1
  24
  25 /*! \file isc/magic.h */
  26
  27 typedef struct {
  28         unsigned int magic;
  29 } isc__magic_t;
  30
  31
  32 /*%
  33  * To use this macro the magic number MUST be the first thing in the
  34  * structure, and MUST be of type "unsigned int".
  35  * The intent of this is to allow magic numbers to be checked even though
  36  * the object is otherwise opaque.
  37  */
  38 #define ISC_MAGIC_VALID(a,b)    (((a) != NULL) && \
  39                                  (((const isc__magic_t *)(a))->magic == (b)))
  40
  41 #define ISC_MAGIC(a, b, c, d)   ((a) << 24 | (b) << 16 | (c) << 8 | (d))
  42
  43 #endif /* ISC_MAGIC_H */