bitmanipulation.h

#ifndef SIMDJSON_WESTMERE_BITMANIPULATION_H
#define SIMDJSON_WESTMERE_BITMANIPULATION_H
 
namespace simdjson {
namespace SIMDJSON_IMPLEMENTATION {
namespace {
 
// We sometimes call trailing_zero on inputs that are zero,
// but the algorithms do not end up using the returned value.
// Sadly, sanitizers are not smart enough to figure it out.
SIMDJSON_NO_SANITIZE_UNDEFINED
// This function can be used safely even if not all bytes have been
// initialized.
// See issue https://github.com/simdjson/simdjson/issues/1965
SIMDJSON_NO_SANITIZE_MEMORY
simdjson_inline int trailing_zeroes(uint64_t input_num) {
#if SIMDJSON_REGULAR_VISUAL_STUDIO
  unsigned long ret;
  // Search the mask data from least significant bit (LSB)
  // to the most significant bit (MSB) for a set bit (1).
  _BitScanForward64(&ret, input_num);
  return (int)ret;
#else // SIMDJSON_REGULAR_VISUAL_STUDIO
  return __builtin_ctzll(input_num);
#endif // SIMDJSON_REGULAR_VISUAL_STUDIO
}
 
/* result might be undefined when input_num is zero */
simdjson_inline uint64_t clear_lowest_bit(uint64_t input_num) {
  return input_num & (input_num-1);
}
 
/* result might be undefined when input_num is zero */
simdjson_inline int leading_zeroes(uint64_t input_num) {
#if SIMDJSON_REGULAR_VISUAL_STUDIO
  unsigned long leading_zero = 0;
  // Search the mask data from most significant bit (MSB)
  // to least significant bit (LSB) for a set bit (1).
  if (_BitScanReverse64(&leading_zero, input_num))
    return (int)(63 - leading_zero);
  else
    return 64;
#else
  return __builtin_clzll(input_num);
#endif// SIMDJSON_REGULAR_VISUAL_STUDIO
}
 
#if SIMDJSON_REGULAR_VISUAL_STUDIO
simdjson_inline unsigned __int64 count_ones(uint64_t input_num) {
  // note: we do not support legacy 32-bit Windows
  return __popcnt64(input_num);// Visual Studio wants two underscores
}
#else
simdjson_inline long long int count_ones(uint64_t input_num) {
  return _popcnt64(input_num);
}
#endif
 
simdjson_inline bool add_overflow(uint64_t value1, uint64_t value2,
                                uint64_t *result) {
#if SIMDJSON_REGULAR_VISUAL_STUDIO
  return _addcarry_u64(0, value1, value2,
                       reinterpret_cast<unsigned __int64 *>(result));
#else
  return __builtin_uaddll_overflow(value1, value2,
                                   reinterpret_cast<unsigned long long *>(result));
#endif
}
 
} // unnamed namespace
} // namespace SIMDJSON_IMPLEMENTATION
} // namespace simdjson
 
#endif // SIMDJSON_WESTMERE_BITMANIPULATION_H