Edit: pycore_byteswap.h
/* Bytes swap functions, reverse order of bytes: - _Py_bswap16(uint16_t) - _Py_bswap32(uint32_t) - _Py_bswap64(uint64_t) */ #ifndef Py_INTERNAL_BSWAP_H #define Py_INTERNAL_BSWAP_H #ifdef __cplusplus extern "C" { #endif #ifndef Py_BUILD_CORE # error "this header requires Py_BUILD_CORE define" #endif #if defined(__GNUC__) \ && ((__GNUC__ >= 5) || (__GNUC__ == 4) && (__GNUC_MINOR__ >= 8)) /* __builtin_bswap16() is available since GCC 4.8, __builtin_bswap32() is available since GCC 4.3, __builtin_bswap64() is available since GCC 4.3. */ # define _PY_HAVE_BUILTIN_BSWAP #endif #ifdef _MSC_VER /* Get _byteswap_ushort(), _byteswap_ulong(), _byteswap_uint64() */ # include <intrin.h> #endif static inline uint16_t _Py_bswap16(uint16_t word) { #if defined(_PY_HAVE_BUILTIN_BSWAP) || _Py__has_builtin(__builtin_bswap16) return __builtin_bswap16(word); #elif defined(_MSC_VER) Py_BUILD_ASSERT(sizeof(word) == sizeof(unsigned short)); return _byteswap_ushort(word); #else // Portable implementation which doesn't rely on circular bit shift return ( ((word & UINT16_C(0x00FF)) << 8) | ((word & UINT16_C(0xFF00)) >> 8)); #endif } static inline uint32_t _Py_bswap32(uint32_t word) { #if defined(_PY_HAVE_BUILTIN_BSWAP) || _Py__has_builtin(__builtin_bswap32) return __builtin_bswap32(word); #elif defined(_MSC_VER) Py_BUILD_ASSERT(sizeof(word) == sizeof(unsigned long)); return _byteswap_ulong(word); #else // Portable implementation which doesn't rely on circular bit shift return ( ((word & UINT32_C(0x000000FF)) << 24) | ((word & UINT32_C(0x0000FF00)) << 8) | ((word & UINT32_C(0x00FF0000)) >> 8) | ((word & UINT32_C(0xFF000000)) >> 24)); #endif } static inline uint64_t _Py_bswap64(uint64_t word) { #if defined(_PY_HAVE_BUILTIN_BSWAP) || _Py__has_builtin(__builtin_bswap64) return __builtin_bswap64(word); #elif defined(_MSC_VER) return _byteswap_uint64(word); #else // Portable implementation which doesn't rely on circular bit shift return ( ((word & UINT64_C(0x00000000000000FF)) << 56) | ((word & UINT64_C(0x000000000000FF00)) << 40) | ((word & UINT64_C(0x0000000000FF0000)) << 24) | ((word & UINT64_C(0x00000000FF000000)) << 8) | ((word & UINT64_C(0x000000FF00000000)) >> 8) | ((word & UINT64_C(0x0000FF0000000000)) >> 24) | ((word & UINT64_C(0x00FF000000000000)) >> 40) | ((word & UINT64_C(0xFF00000000000000)) >> 56)); #endif } #ifdef __cplusplus } #endif #endif /* !Py_INTERNAL_BSWAP_H */
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