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 should catch all modern GCCs and Clang */
  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(__LITTLE_ENDIAN__) && __LITTLE_ENDIAN__ == 1) || \
  58       (defined(_LITTLE_ENDIAN) && _LITTLE_ENDIAN == 1) || \
  59       defined(_M_IX86) || defined(_M_AMD64) /* MSVC */
  60 # ifdef ENDIANNESS_DEBUG
  61 #  warning "Detected Little Endian target CPU"
  62 # endif
  63 # define ENDIANNESS_LE 1
  64 # define ENDIANNESS_BE 0
  65 #elif defined(__MIPSEB) || defined(_MIPSEB) || defined(MIPSEB) || \
  66       defined(__MICROBLAZEEB__) || defined(__ARMEB__) || \
  67       (defined(__BIG_ENDIAN__) && __BIG_ENDIAN__ == 1) || \
  68       (defined(_BIG_ENDIAN) && _BIG_ENDIAN == 1)
  69 # ifdef ENDIANNESS_DEBUG
  70 #  warning "Detected Big Endian target CPU"
  71 # endif
  72 # define ENDIANNESS_LE 0
  73 # define ENDIANNESS_BE 1
  74 /* Try to get it from a header */
  75 #else
  76 # if defined(__linux)
  77 #  ifdef ENDIANNESS_DEBUG
  78 #   warning "Taking endiannes from endian.h"
  79 #  endif
  80 #  include <endian.h>
  81 # else
  82 #  ifdef ENDIANNESS_DEBUG
  83 #   warning "Taking endiannes from machine/endian.h"
  84 #  endif
  85 #  include <machine/endian.h>
  86 # endif
  87 #endif
  88
  89 #ifndef ENDIANNESS_LE
  90 # undef ENDIANNESS_BE
  91 # if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN)
  92 #  if __BYTE_ORDER == __LITTLE_ENDIAN
  93 #   define ENDIANNESS_LE 1
  94 #   define ENDIANNESS_BE 0
  95 #  elif __BYTE_ORDER == __BIG_ENDIAN
  96 #   define ENDIANNESS_LE 0
  97 #   define ENDIANNESS_BE 1
  98 #  endif
  99 # elif 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 # endif
 108 #endif
 109
 110 /* In case the user passed one of -DENDIANNESS_LE or BE in CPPFLAS,
 111    set the second one too */
 112 #if defined(ENDIANNESS_LE) && !(defined(ENDIANNESS_BE))
 113 # if ENDIANNESS_LE == 0
 114 #  define ENDIANNESS_BE 1
 115 # else
 116 #  define ENDIANNESS_BE 0
 117 # endif
 118 #elif defined(ENDIANNESS_BE) && !(defined(ENDIANNESS_LE))
 119 # if ENDIANNESS_BE == 0
 120 #  define ENDIANNESS_LE 1
 121 # else
 122 #  define ENDIANNESS_LE 0
 123 # endif
 124 #endif
 125
 126 #if !(defined(ENDIANNESS_LE)) && !(defined(ENDIANNESS_PORTABLE_CONVERSION))
 127 # 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!"
 128 #endif
 129
 130 #ifdef ENDIANNESS_DEBUG
 131 # if ENDIANNESS_LE == 1
 132 #  warning "Detected Little Endian target CPU"
 133 # endif
 134 # if ENDIANNESS_BE == 1
 135 #  warning "Detected BIG Endian target CPU"
 136 # endif
 137 #endif
 138
 139 #include <stdint.h>
 140 #include <limits.h>
 141
 142 static __inline uint16_t end_bswap16(uint16_t __x)
 143 {
 144         return (__x<<8) | (__x>>8);
 145 }
 146
 147 static __inline uint32_t end_bswap32(uint32_t __x)
 148 {
 149         return (__x>>24) | (__x>>8&0xff00) | (__x<<8&0xff0000) | (__x<<24);
 150 }
 151
 152 static __inline uint64_t end_bswap64(uint64_t __x)
 153 {
 154         return ((end_bswap32(__x)+0ULL)<<32) | (end_bswap32(__x>>32));
 155 }
 156
 157 static __inline uint16_t end_net2host16(uint16_t net_number)
 158 {
 159         uint16_t result = 0;
 160         int i;
 161         for (i = 0; i < (int)sizeof(result); i++) {
 162                 result <<= CHAR_BIT;
 163                 result += (((unsigned char *)&net_number)[i] & UCHAR_MAX);
 164         }
 165         return result;
 166 }
 167
 168 static __inline uint16_t end_host2net16(uint16_t native_number)
 169 {
 170         uint16_t result = 0;
 171         int i;
 172         for (i = (int)sizeof(result) - 1; i >= 0; i--) {
 173                 ((unsigned char *)&result)[i] = native_number & UCHAR_MAX;
 174                 native_number >>= CHAR_BIT;
 175         }
 176         return result;
 177 }
 178
 179 static __inline uint32_t end_net2host32(uint32_t net_number)
 180 {
 181         uint32_t result = 0;
 182         int i;
 183         for (i = 0; i < (int)sizeof(result); i++) {
 184                 result <<= CHAR_BIT;
 185                 result += (((unsigned char *)&net_number)[i] & UCHAR_MAX);
 186         }
 187         return result;
 188 }
 189
 190 static __inline uint32_t end_host2net32(uint32_t native_number)
 191 {
 192         uint32_t result = 0;
 193         int i;
 194         for (i = (int)sizeof(result) - 1; i >= 0; i--) {
 195                 ((unsigned char *)&result)[i] = native_number & UCHAR_MAX;
 196                 native_number >>= CHAR_BIT;
 197         }
 198         return result;
 199 }
 200
 201 static __inline uint64_t end_net2host64(uint64_t net_number)
 202 {
 203         uint64_t result = 0;
 204         int i;
 205         for (i = 0; i < (int)sizeof(result); i++) {
 206                 result <<= CHAR_BIT;
 207                 result += (((unsigned char *)&net_number)[i] & UCHAR_MAX);
 208         }
 209         return result;
 210 }
 211
 212 static __inline uint64_t end_host2net64(uint64_t native_number)
 213 {
 214         uint64_t result = 0;
 215         int i;
 216         for (i = (int)sizeof(result) - 1; i >= 0; i--) {
 217                 ((unsigned char *)&result)[i] = native_number & UCHAR_MAX;
 218                 native_number >>= CHAR_BIT;
 219         }
 220         return result;
 221 }
 222
 223 #if ENDIANNESS_LE+0 == 1
 224 # define end_htobe16(x) end_bswap16(x)
 225 # define end_be16toh(x) end_bswap16(x)
 226 # define end_htobe32(x) end_bswap32(x)
 227 # define end_be32toh(x) end_bswap32(x)
 228 # define end_htobe64(x) end_bswap64(x)
 229 # define end_be64toh(x) end_bswap64(x)
 230 # define end_htole16(x) (uint16_t)(x)
 231 # define end_le16toh(x) (uint16_t)(x)
 232 # define end_htole32(x) (uint32_t)(x)
 233 # define end_le32toh(x) (uint32_t)(x)
 234 # define end_htole64(x) (uint64_t)(x)
 235 # define end_le64toh(x) (uint64_t)(x)
 236 #elif ENDIANNESS_BE+0 == 1
 237 # define end_htobe16(x) (uint16_t)(x)
 238 # define end_be16toh(x) (uint16_t)(x)
 239 # define end_htobe32(x) (uint32_t)(x)
 240 # define end_be32toh(x) (uint32_t)(x)
 241 # define end_htobe64(x) (uint64_t)(x)
 242 # define end_be64toh(x) (uint64_t)(x)
 243 # define end_htole16(x) end_bswap16(x)
 244 # define end_le16toh(x) end_bswap16(x)
 245 # define end_htole32(x) end_bswap32(x)
 246 # define end_le32toh(x) end_bswap32(x)
 247 # define end_htole64(x) end_bswap64(x)
 248 # define end_le64toh(x) end_bswap64(x)
 249 #else
 250 /* Resort to slower, but neutral code */
 251 # define end_htobe16(x)  end_host2net16(x)
 252 # define end_be16toh(x)  end_net2host16(x)
 253 # define end_htobe32(x)  end_host2net32(x)
 254 # define end_be32toh(x)  end_net2host32(x)
 255 # define end_htobe64(x)  end_host2net64(x)
 256 # define end_be64toh(x)  end_net2host64(x)
 257 # define end_htole16(x)  end_bswap_16(end_host2net16(x))
 258 # define end_le16toh(x)  end_bswap_16(end_host2net16(x))
 259 # define end_htole32(x)  end_bswap_32(end_host2net32(x))
 260 # define end_le32toh(x)  end_bswap_32(end_host2net32(x))
 261 # define end_htole64(x)  end_bswap_64(end_host2net64(x))
 262 # define end_le64toh(x)  end_bswap_64(end_host2net64(x))
 263 #endif
 264
 265 #define end_ntoh16(x)  end_be16toh(x)
 266 #define end_hton16(x)  end_htobe16(x)
 267 #define end_ntoh32(x)  end_be32toh(x)
 268 #define end_hton32(x)  end_htobe32(x)
 269 #define end_ntoh64(x)  end_be64toh(x)
 270 #define end_hton64(x)  end_htobe64(x)
 271
 272 #endif