pycore_bitutils.h | Explore in Territory

/* Bit and bytes utilities.

   Bytes swap functions, reverse order of bytes:

   - _Py_bswap16(uint16_t)
   - _Py_bswap32(uint32_t)
   - _Py_bswap64(uint64_t)
*/

#ifndef Py_INTERNAL_BITUTILS_H
#define Py_INTERNAL_BITUTILS_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
#  include <intrin.h>             // _byteswap_uint64()
#endif


static inline uint16_t
_Py_bswap16(uint16_t word)
{ … }

static inline uint32_t
_Py_bswap32(uint32_t word)
{ … }

static inline uint64_t
_Py_bswap64(uint64_t word)
{ … }


// Population count: count the number of 1's in 'x'
// (number of bits set to 1), also known as the hamming weight.
//
// Implementation note. CPUID is not used, to test if x86 POPCNT instruction
// can be used, to keep the implementation simple. For example, Visual Studio
// __popcnt() is not used this reason. The clang and GCC builtin function can
// use the x86 POPCNT instruction if the target architecture has SSE4a or
// newer.
static inline int
_Py_popcount32(uint32_t x)
{ … }


// Return the index of the most significant 1 bit in 'x'. This is the smallest
// integer k such that x < 2**k. Equivalent to floor(log2(x)) + 1 for x != 0.
static inline int
_Py_bit_length(unsigned long x)
{ … }


#ifdef __cplusplus
}
#endif
#endif /* !Py_INTERNAL_BITUTILS_H */
cpython/Include/internal/pycore_bitutils.h
