1/*
2 * Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License").  You may not use
5 * this file except in compliance with the License.  You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10#ifndef OSSL_INTERNAL_ENDIAN_H
11# define OSSL_INTERNAL_ENDIAN_H
12# pragma once
13
14/*
15 * IS_LITTLE_ENDIAN and IS_BIG_ENDIAN can be used to detect the endiannes
16 * at compile time. To use it, DECLARE_IS_ENDIAN must be used to declare
17 * a variable.
18 *
19 * L_ENDIAN and B_ENDIAN can be used at preprocessor time. They can be set
20 * in the configarion using the lib_cppflags variable. If neither is
21 * set, it will fall back to code works with either endianness.
22 */
23
24# if defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__)
25#  define DECLARE_IS_ENDIAN const int ossl_is_little_endian = __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
26#  define IS_LITTLE_ENDIAN (ossl_is_little_endian)
27#  define IS_BIG_ENDIAN (!ossl_is_little_endian)
28#  if defined(L_ENDIAN) && (__BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__)
29#   error "L_ENDIAN defined on a big endian machine"
30#  endif
31#  if defined(B_ENDIAN) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
32#   error "B_ENDIAN defined on a little endian machine"
33#  endif
34#  if !defined(L_ENDIAN) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
35#   define L_ENDIAN
36#  endif
37#  if !defined(B_ENDIAN) && (__BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__)
38#   define B_ENDIAN
39#  endif
40# else
41#  define DECLARE_IS_ENDIAN \
42    const union { \
43        long one; \
44        char little; \
45    } ossl_is_endian = { 1 }
46
47#  define IS_LITTLE_ENDIAN (ossl_is_endian.little != 0)
48#  define IS_BIG_ENDIAN    (ossl_is_endian.little == 0)
49# endif
50
51#endif
52