Function PerfectShuffle

libs/base/bits.hpp:48–56

Perform a perfect shuffle of the bits of 64-bit integer, shuffling bits from 'abcd efgh ijkl mnop ABCD EFGH IJKL MNOP' to 'aAbB cCdD eEfF gGhH iIjJ kKlL mMnN oOpP'. See http://www.icodeguru.com/Embedded/Hacker's-Delight/047.htm

// 'abcd efgh ijkl mnop ABCD EFGH IJKL MNOP' to 'aAbB cCdD eEfF gGhH iIjJ kKlL mMnN oOpP'.
// See http://www.icodeguru.com/Embedded/Hacker's-Delight/047.htm
constexpr uint64_t PerfectShuffle(uint64_t x)
{
  x = ((x & 0x00000000FFFF0000ULL) << 16) | ((x >> 16) & 0x00000000FFFF0000ULL) | (x & 0xFFFF00000000FFFFULL);
  x = ((x & 0x0000FF000000FF00ULL) << 8) | ((x >> 8) & 0x0000FF000000FF00ULL) | (x & 0xFF0000FFFF0000FFULL);
  x = ((x & 0x00F000F000F000F0ULL) << 4) | ((x >> 4) & 0x00F000F000F000F0ULL) | (x & 0xF00FF00FF00FF00FULL);
  x = ((x & 0x0C0C0C0C0C0C0C0CULL) << 2) | ((x >> 2) & 0x0C0C0C0C0C0C0C0CULL) | (x & 0xC3C3C3C3C3C3C3C3ULL);
  x = ((x & 0x2222222222222222ULL) << 1) | ((x >> 1) & 0x2222222222222222ULL) | (x & 0x9999999999999999ULL);
  return x;
}

// Reverses the perfect shuffle of bits in a 64-bit integer
constexpr uint64_t PerfectUnshuffle(uint64_t x)