endianness.h

   1 #ifndef ENDIANNESS_H
   2 #define ENDIANNESS_H
   3
   4 /* Public domain implementation for endianness detection and byte ordering on
   5    several platforms. In case the concept of public domain does not exist
   6    under your jurisdiction, you can consider it to be dual licensed
   7    under the MIT, Apache and WTFPL licenses.
   8
   9    Grab it and drop it into your project, include it and use
  10    the following macros to determine endianness:
  11
  12    ENDIANNESS_LE, ENDIANNESS_BE
  13
  14    e.g. #if ENDIANNESS_LE ...
  15
  16    or, even nicer without littering your code with #ifdefs:
  17
  18    if (ENDIANNESS_BE) { big_endian_code(); } else { little_endian_code(); }
  19
  20    ... since the compiler can optimize away unused branches, this makes your
  21    code easier to read while not loosing any of the advantage of using
  22    conditional compilation, plus you get a free compile-time check of the
  23    unused code path (rarely used conditonally compiled code paths often get
  24    defunct over time if nobody checks them all the time).
  25
  26    To debug this header yourself, you can define ENDIANNESS_DEBUG to see
  27    warnings from where we take the defs for the specific target.
  28
  29    If you need only the conversion functions from big to little endian
  30    and vice versa, you may want to #define ENDIANNESS_PORTABLE_CONVERSION
  31    prior to including this header. That way, when the endiannes can't be
  32    determined at compile time, the code will fallback to a slower,
  33    but portable version of those functions.
  34    However, if using it, it's not guaranteed that ENDIANNESS_LE/BE
  35    will be defined.
  36    Most people however need only the conversion functions in their code,
  37    so if you stick to them you can safely turn the portable conversion on.
  38 */
  39
  40 /* This catches all modern GCCs (>= 4.6) and Clang (>=3.2) */
  41 #if (defined __BYTE_ORDER__) && (defined __ORDER_LITTLE_ENDIAN__)
  42 # ifdef ENDIANNESS_DEBUG
  43 #  warning "Taking endiannes from built-in __BYTE_ORDER__"
  44 # endif
  45 # if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
  46 #  define ENDIANNESS_LE 1
  47 #  define ENDIANNESS_BE 0
  48 # elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
  49 #  define ENDIANNESS_LE 0
  50 #  define ENDIANNESS_BE 1
  51 # endif
  52 /* Try to derive from arch/compiler-specific macros */
  53 #elif defined(_X86_) || defined(__x86_64__) || defined(__i386__) || \
  54       defined(__i486__) || defined(__i586__) || defined(__i686__) || \
  55       defined(__MIPSEL) || defined(_MIPSEL) || defined(MIPSEL) || \
  56       defined(__ARMEL__) || \
  57       defined(__MSP430__) || \
  58       (defined(__LITTLE_ENDIAN__) && __LITTLE_ENDIAN__ == 1) || \
  59       (defined(_LITTLE_ENDIAN) && _LITTLE_ENDIAN == 1) || \
  60       defined(_M_ARM) || defined(_M_ARM64) || \
  61       defined(_M_IX86) || defined(_M_AMD64) /* MSVC */
  62 # ifdef ENDIANNESS_DEBUG
  63 #  warning "Detected Little Endian target CPU"
  64 # endif
  65 # define ENDIANNESS_LE 1
  66 # define ENDIANNESS_BE 0
  67 #elif defined(__MIPSEB) || defined(_MIPSEB) || defined(MIPSEB) || \
  68       defined(__MICROBLAZEEB__) || defined(__ARMEB__) || \
  69       (defined(__BIG_ENDIAN__) && __BIG_ENDIAN__ == 1) || \
  70       (defined(_BIG_ENDIAN) && _BIG_ENDIAN == 1)
  71 # ifdef ENDIANNESS_DEBUG
  72 #  warning "Detected Big Endian target CPU"
  73 # endif
  74 # define ENDIANNESS_LE 0
  75 # define ENDIANNESS_BE 1
  76 /* Try to get it from a header */
  77 #else
  78 # if defined(__linux) || defined(__HAIKU__)
  79 #  ifdef ENDIANNESS_DEBUG
  80 #   warning "Taking endiannes from endian.h"
  81 #  endif
  82 #  include <endian.h>
  83 # elif defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || \
  84        defined(__DragonFly__)
  85 #  ifdef ENDIANNESS_DEBUG
  86 #   warning "Taking endiannes from sys/endian.h"
  87 #  endif
  88 #  include <sys/endian.h>
  89 # elif defined(__APPLE__)
  90 #  ifdef ENDIANNESS_DEBUG
  91 #   warning "Taking endiannes from machine/endian.h"
  92 #  endif
  93 #  include <machine/endian.h>
  94 # endif
  95 #endif
  96
  97 #ifndef ENDIANNESS_LE
  98 # undef ENDIANNESS_BE
  99 # if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN)
 100 #  if __BYTE_ORDER == __LITTLE_ENDIAN
 101 #   define ENDIANNESS_LE 1
 102 #   define ENDIANNESS_BE 0
 103 #  elif __BYTE_ORDER == __BIG_ENDIAN
 104 #   define ENDIANNESS_LE 0
 105 #   define ENDIANNESS_BE 1
 106 #  endif
 107 # elif defined(BYTE_ORDER) && defined(LITTLE_ENDIAN)
 108 #  if BYTE_ORDER == LITTLE_ENDIAN
 109 #   define ENDIANNESS_LE 1
 110 #   define ENDIANNESS_BE 0
 111 #  elif BYTE_ORDER == BIG_ENDIAN
 112 #   define ENDIANNESS_LE 0
 113 #   define ENDIANNESS_BE 1
 114 #  endif
 115 # endif
 116 #endif
 117
 118 /* In case the user passed one of -DENDIANNESS_LE or BE in CPPFLAS,
 119    set the second one too */
 120 #if defined(ENDIANNESS_LE) && !(defined(ENDIANNESS_BE))
 121 # if ENDIANNESS_LE == 0
 122 #  define ENDIANNESS_BE 1
 123 # else
 124 #  define ENDIANNESS_BE 0
 125 # endif
 126 #elif defined(ENDIANNESS_BE) && !(defined(ENDIANNESS_LE))
 127 # if ENDIANNESS_BE == 0
 128 #  define ENDIANNESS_LE 1
 129 # else
 130 #  define ENDIANNESS_LE 0
 131 # endif
 132 #endif
 133
 134 #if !(defined(ENDIANNESS_LE)) && !(defined(ENDIANNESS_PORTABLE_CONVERSION))
 135 # error "Sorry, we couldn't detect endiannes for your system! Please set -DENDIANNESS_LE=1 or 0 using your CPPFLAGS/CFLAGS and open an issue for your system on https://github.com/rofl0r/endianness.h - Thanks!"
 136 #endif
 137
 138 #ifdef ENDIANNESS_DEBUG
 139 # if ENDIANNESS_LE == 1
 140 #  warning "Detected Little Endian target CPU"
 141 # endif
 142 # if ENDIANNESS_BE == 1
 143 #  warning "Detected BIG Endian target CPU"
 144 # endif
 145 #endif
 146
 147 #include <stdint.h>
 148
 149 static __inline uint16_t end_bswap16(uint16_t __x)
 150 {
 151         return (__x<<8) | (__x>>8);
 152 }
 153
 154 static __inline uint32_t end_bswap32(uint32_t __x)
 155 {
 156         return (__x>>24) | (__x>>8&0xff00) | (__x<<8&0xff0000) | (__x<<24);
 157 }
 158
 159 static __inline uint64_t end_bswap64(uint64_t __x)
 160 {
 161         return ((end_bswap32((uint32_t)__x)+0ULL)<<32) | (end_bswap32(__x>>32));
 162 }
 163
 164
 165 static __inline uint16_t end_htobe16_impl(uint16_t n)
 166 {
 167         union { int i; char c; } u = { 1 };
 168         return u.c ? end_bswap16(n) : n;
 169 }
 170
 171 static __inline uint16_t end_htole16_impl(uint16_t n)
 172 {
 173         union { int i; char c; } u = { 1 };
 174         return u.c ? n : end_bswap16(n);
 175 }
 176
 177 static __inline uint32_t end_htobe32_impl(uint32_t n)
 178 {
 179         union { int i; char c; } u = { 1 };
 180         return u.c ? end_bswap32(n) : n;
 181 }
 182
 183 static __inline uint32_t end_htole32_impl(uint32_t n)
 184 {
 185         union { int i; char c; } u = { 1 };
 186         return u.c ? n : end_bswap32(n);
 187 }
 188
 189 static __inline uint64_t end_htobe64_impl(uint64_t n)
 190 {
 191         union { int i; char c; } u = { 1 };
 192         return u.c ? end_bswap64(n) : n;
 193 }
 194
 195 static __inline uint64_t end_htole64_impl(uint64_t n)
 196 {
 197         union { int i; char c; } u = { 1 };
 198         return u.c ? n : end_bswap64(n);
 199 }
 200
 201 #if ENDIANNESS_LE+0 == 1
 202 # define end_htobe16(x) end_bswap16(x)
 203 # define end_be16toh(x) end_bswap16(x)
 204 # define end_htobe32(x) end_bswap32(x)
 205 # define end_be32toh(x) end_bswap32(x)
 206 # define end_htobe64(x) end_bswap64(x)
 207 # define end_be64toh(x) end_bswap64(x)
 208 # define end_htole16(x) (uint16_t)(x)
 209 # define end_le16toh(x) (uint16_t)(x)
 210 # define end_htole32(x) (uint32_t)(x)
 211 # define end_le32toh(x) (uint32_t)(x)
 212 # define end_htole64(x) (uint64_t)(x)
 213 # define end_le64toh(x) (uint64_t)(x)
 214 #elif ENDIANNESS_BE+0 == 1
 215 # define end_htobe16(x) (uint16_t)(x)
 216 # define end_be16toh(x) (uint16_t)(x)
 217 # define end_htobe32(x) (uint32_t)(x)
 218 # define end_be32toh(x) (uint32_t)(x)
 219 # define end_htobe64(x) (uint64_t)(x)
 220 # define end_be64toh(x) (uint64_t)(x)
 221 # define end_htole16(x) end_bswap16(x)
 222 # define end_le16toh(x) end_bswap16(x)
 223 # define end_htole32(x) end_bswap32(x)
 224 # define end_le32toh(x) end_bswap32(x)
 225 # define end_htole64(x) end_bswap64(x)
 226 # define end_le64toh(x) end_bswap64(x)
 227 #else
 228 /* Resort to slower, but neutral code */
 229 # define end_htobe16(x)  end_htobe16_impl(x)
 230 # define end_be16toh(x)  end_htobe16_impl(x)
 231 # define end_htobe32(x)  end_htobe32_impl(x)
 232 # define end_be32toh(x)  end_htobe32_impl(x)
 233 # define end_htobe64(x)  end_htobe64_impl(x)
 234 # define end_be64toh(x)  end_htobe64_impl(x)
 235 # define end_htole16(x)  end_htole16_impl(x)
 236 # define end_le16toh(x)  end_htole16_impl(x)
 237 # define end_htole32(x)  end_htole32_impl(x)
 238 # define end_le32toh(x)  end_htole32_impl(x)
 239 # define end_htole64(x)  end_htole64_impl(x)
 240 # define end_le64toh(x)  end_htole64_impl(x)
 241 #endif
 242
 243 #define end_ntoh16(x)  end_be16toh(x)
 244 #define end_hton16(x)  end_htobe16(x)
 245 #define end_ntoh32(x)  end_be32toh(x)
 246 #define end_hton32(x)  end_htobe32(x)
 247 #define end_ntoh64(x)  end_be64toh(x)
 248 #define end_hton64(x)  end_htobe64(x)
 249
 250 #endif