1 /* $NetBSD: magic.h,v 1.6 2023/01/25 21:43:31 christos Exp $ */ 2 3 /* 4 * Copyright (C) Internet Systems Consortium, Inc. ("ISC") 5 * 6 * SPDX-License-Identifier: MPL-2.0 7 * 8 * This Source Code Form is subject to the terms of the Mozilla Public 9 * License, v. 2.0. If a copy of the MPL was not distributed with this 10 * file, you can obtain one at https://mozilla.org/MPL/2.0/. 11 * 12 * See the COPYRIGHT file distributed with this work for additional 13 * information regarding copyright ownership. 14 */ 15 16 #ifndef ISC_MAGIC_H 17 #define ISC_MAGIC_H 1 18 19 #include <isc/likely.h> 20 21 /*! \file isc/magic.h */ 22 23 typedef struct { 24 unsigned int magic; 25 } isc__magic_t; 26 27 /*% 28 * To use this macro the magic number MUST be the first thing in the 29 * structure, and MUST be of type "unsigned int". 30 * The intent of this is to allow magic numbers to be checked even though 31 * the object is otherwise opaque. 32 */ 33 static __inline int 34 checkmagic(const void *_p, unsigned int _m) 35 { 36 const isc__magic_t *s = _p; 37 return s->magic == _m; 38 } 39 40 #define ISC_MAGIC_VALID(a, b) \ 41 (ISC_LIKELY((a) != NULL) && ISC_LIKELY(checkmagic(a, b))) \ 42 43 #define ISC_MAGIC(a, b, c, d) ((a) << 24 | (b) << 16 | (c) << 8 | (d)) 44 45 #endif /* ISC_MAGIC_H */ 46