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cross-platform / cross-compiler standalone endianness conversion
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/** | |
* @file endianness.h | |
* @brief Convert Endianness of shorts, longs, long longs, regardless of architecture/OS | |
* | |
* Defines (without pulling in platform-specific network include headers): | |
* bswap16, bswap32, bswap64, ntoh16, hton16, ntoh32 hton32, ntoh64, hton64 | |
* | |
* Should support linux / macos / solaris / windows. | |
* Supports GCC (on any platform, including embedded), MSVC2015, and clang, | |
* and should support intel, solaris, and ibm compilers as well. | |
* | |
* Released under MIT license | |
*/ | |
#ifndef _ENDIANNESS_H | |
#define _ENDIANNESS_H | |
#include <stdlib.h> | |
#include <stdint.h> | |
/* Detect platform endianness at compile time */ | |
// If boost were available on all platforms, could use this instead to detect endianness | |
// #include <boost/predef/endian.h> | |
// When available, these headers can improve platform endianness detection | |
#ifdef __has_include // C++17, supported as extension to C++11 in clang, GCC 5+, vs2015 | |
# if __has_include(<endian.h>) | |
# include <endian.h> // gnu libc normally provides, linux | |
# elif __has_include(<machine/endian.h>) | |
# include <machine/endian.h> //open bsd, macos | |
# elif __has_include(<sys/param.h>) | |
# include <sys/param.h> // mingw, some bsd (not open/macos) | |
# elif __has_include(<sys/isadefs.h>) | |
# include <sys/isadefs.h> // solaris | |
# endif | |
#endif | |
#if !defined(__LITTLE_ENDIAN__) && !defined(__BIG_ENDIAN__) | |
# if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ || \ | |
__BYTE_ORDER == __BIG_ENDIAN || _BYTE_ORDER == _BIG_ENDIAN || BYTE_ORDER == BIG_ENDIAN || \ | |
defined(_BIG_ENDIAN) || \ | |
defined(__ARMEB__) || defined(__THUMBEB__) || defined(__AARCH64EB__) || \ | |
defined(_MIBSEB) || defined(__MIBSEB) || defined(__MIBSEB__) || \ | |
defined(_M_PPC) | |
# define __BIG_ENDIAN__ | |
# elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ || /* gcc */\ | |
__BYTE_ORDER == __LITTLE_ENDIAN /* linux header */ || _BYTE_ORDER == _LITTLE_ENDIAN || BYTE_ORDER == LITTLE_ENDIAN /* mingw header */|| \ | |
defined(_LITTLE_ENDIAN) || /* solaris */ \ | |
defined(__ARMEL__) || defined(__THUMBEL__) || defined(__AARCH64EL__) || \ | |
defined(_MIPSEL) || defined(__MIPSEL) || defined(__MIPSEL__) || \ | |
defined(_M_IX86) || defined(_M_X64) || defined(_M_IA64) || /* msvc for intel processors */ \ | |
defined(_M_ARM) /* msvc code on arm executes in little endian mode */ | |
# define __LITTLE_ENDIAN__ | |
# endif | |
#endif | |
/* Define byte-swap functions, using fast processor-native built-ins where possible */ | |
#if defined(_MSC_VER) // needs to be first because msvc doesn't short-circuit after failing defined(__has_builtin) | |
# define bswap16(x) _byteswap_ushort((x)) | |
# define bswap32(x) _byteswap_ulong((x)) | |
# define bswap64(x) _byteswap_uint64((x)) | |
#elif (defined(__has_builtin) && __has_builtin(bswap16)) || /* for clang or future gcc */ \ | |
(__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8) | |
# define bswap16(x) __builtin_bswap16((x)) | |
# define bswap32(x) __builtin_bswap32((x)) | |
# define bswap64(x) __builtin_bswap64((x)) | |
#else | |
/* even in this case, compilers often optimize by using native instructions */ | |
static inline uint16_t bswap16(uint16_t x) { | |
return (( x >> 8 ) & 0xffu ) | (( x & 0xffu ) << 8 ); | |
} | |
static inline uint32_t bswap32(uint32_t x) { | |
return ((( x & 0xff000000u ) >> 24 ) | | |
(( x & 0x00ff0000u ) >> 8 ) | | |
(( x & 0x0000ff00u ) << 8 ) | | |
(( x & 0x000000ffu ) << 24 )); | |
} | |
static inline uint64_t bswap64(uint64_t x) { | |
return ((( x & 0xff00000000000000ull ) >> 56 ) | | |
(( x & 0x00ff000000000000ull ) >> 40 ) | | |
(( x & 0x0000ff0000000000ull ) >> 24 ) | | |
(( x & 0x000000ff00000000ull ) >> 8 ) | | |
(( x & 0x00000000ff000000ull ) << 8 ) | | |
(( x & 0x0000000000ff0000ull ) << 24 ) | | |
(( x & 0x000000000000ff00ull ) << 40 ) | | |
(( x & 0x00000000000000ffull ) << 56 )); | |
} | |
#endif | |
/* Defines network - host byte swaps as needed depending upon platform endianness */ | |
// note that network order is big endian) | |
#if defined(__LITTLE_ENDIAN__) | |
# define ntoh16(x) bswap16((x)) | |
# define hton16(x) bswap16((x)) | |
# define ntoh32(x) bswap32((x)) | |
# define hton32(x) bswap32((x)) | |
# define ntoh64(x) bswap64((x)) | |
# define hton64(x) bswap64((x)) | |
#elif defined(__BIG_ENDIAN__) | |
# define ntoh16(x) (x) | |
# define hton16(x) (x) | |
# define ntoh32(x) (x) | |
# define hton32(x) (x) | |
# define ntoh64(x) (x) | |
# define hton64(x) (x) | |
# else | |
# warning "UNKNOWN Platform / endianness; network / host byte swaps not defined." | |
#endif | |
#endif // _ENDIANNESS_H |
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