/// \copyright SPDX-License-Identifier: Apache-2.0
/// \author Леонид Юрьев aka Leonid Yuriev <leo@yuriev.ru> \date 2015-2024

#include "internals.h"

MDBX_MAYBE_UNUSED MDBX_NOTHROW_CONST_FUNCTION MDBX_INTERNAL unsigned log2n_powerof2(size_t value_uintptr) {
  assert(value_uintptr > 0 && value_uintptr < INT32_MAX && is_powerof2(value_uintptr));
  assert((value_uintptr & -(intptr_t)value_uintptr) == value_uintptr);
  const uint32_t value_uint32 = (uint32_t)value_uintptr;
#if __GNUC_PREREQ(4, 1) || __has_builtin(__builtin_ctz)
  STATIC_ASSERT(sizeof(value_uint32) <= sizeof(unsigned));
  return __builtin_ctz(value_uint32);
#elif defined(_MSC_VER)
  unsigned long index;
  STATIC_ASSERT(sizeof(value_uint32) <= sizeof(long));
  _BitScanForward(&index, value_uint32);
  return index;
#else
  static const uint8_t debruijn_ctz32[32] = {0,  1,  28, 2,  29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4,  8,
                                             31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6,  11, 5,  10, 9};
  return debruijn_ctz32[(uint32_t)(value_uint32 * 0x077CB531ul) >> 27];
#endif
}

MDBX_NOTHROW_CONST_FUNCTION MDBX_INTERNAL uint64_t rrxmrrxmsx_0(uint64_t v) {
  /* Pelle Evensen's mixer, https://bit.ly/2HOfynt */
  v ^= (v << 39 | v >> 25) ^ (v << 14 | v >> 50);
  v *= UINT64_C(0xA24BAED4963EE407);
  v ^= (v << 40 | v >> 24) ^ (v << 15 | v >> 49);
  v *= UINT64_C(0x9FB21C651E98DF25);
  return v ^ v >> 28;
}