libctf/swap.h

   1 /* Interface to byteswapping functions.
   2    Copyright (C) 2006-2021 Free Software Foundation, Inc.
   3
   4    This file is part of libctf.
   5
   6    libctf is free software; you can redistribute it and/or modify it under
   7    the terms of the GNU General Public License as published by the Free
   8    Software Foundation; either version 3, or (at your option) any later
   9    version.
  10
  11    This program is distributed in the hope that it will be useful, but
  12    WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  14    See the GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; see the file COPYING.  If not see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef _CTF_SWAP_H
  21 #define _CTF_SWAP_H
  22
  23 #include "config.h"
  24 #include <stdint.h>
  25 #include <assert.h>
  26
  27 #ifdef HAVE_BYTESWAP_H
  28 #include <byteswap.h>
  29 #endif /* defined(HAVE_BYTESWAP_H) */
  30
  31 /* Provide our own versions of the byteswap functions.  */
  32
  33 #if !HAVE_DECL_BSWAP_16
  34 static inline uint16_t
  35 bswap_16 (uint16_t v)
  36 {
  37   return ((v >> 8) & 0xff) | ((v & 0xff) << 8);
  38 }
  39 #endif /* !HAVE_DECL_BSWAP16 */
  40
  41 #if !HAVE_DECL_BSWAP_32
  42 static inline uint32_t
  43 bswap_32 (uint32_t v)
  44 {
  45   return (  ((v & 0xff000000) >> 24)
  46           | ((v & 0x00ff0000) >>  8)
  47           | ((v & 0x0000ff00) <<  8)
  48           | ((v & 0x000000ff) << 24));
  49 }
  50 #endif /* !HAVE_DECL_BSWAP32 */
  51
  52 #if !HAVE_DECL_BSWAP_64
  53 static inline uint64_t
  54 bswap_64 (uint64_t v)
  55 {
  56   return (  ((v & 0xff00000000000000ULL) >> 56)
  57           | ((v & 0x00ff000000000000ULL) >> 40)
  58           | ((v & 0x0000ff0000000000ULL) >> 24)
  59           | ((v & 0x000000ff00000000ULL) >>  8)
  60           | ((v & 0x00000000ff000000ULL) <<  8)
  61           | ((v & 0x0000000000ff0000ULL) << 24)
  62           | ((v & 0x000000000000ff00ULL) << 40)
  63           | ((v & 0x00000000000000ffULL) << 56));
  64 }
  65 #endif /* !HAVE_DECL_BSWAP64 */
  66
  67 /* < C11? define away static assertions.  */
  68
  69 #if !defined (__STDC_VERSION__) || __STDC_VERSION__ < 201112L
  70 #define _Static_assert(cond, err)
  71 #endif
  72
  73 /* Swap the endianness of something.  */
  74
  75 #define swap_thing(x)                                                   \
  76   do {                                                                  \
  77     _Static_assert (sizeof (x) == 1 || (sizeof (x) % 2 == 0             \
  78                                         && sizeof (x) <= 8),            \
  79                     "Invalid size, update endianness code");            \
  80     switch (sizeof (x)) {                                               \
  81     case 2: x = bswap_16 (x); break;                                    \
  82     case 4: x = bswap_32 (x); break;                                    \
  83     case 8: x = bswap_64 (x); break;                                    \
  84     case 1: /* Nothing needs doing */                                   \
  85       break;                                                            \
  86     }                                                                   \
  87   } while (0);
  88
  89
  90 #endif /* !defined(_CTF_SWAP_H) */