Bit reverse
(Mylib/Bit/bit_reverse.cpp)

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• Last update: 2021-04-23 23:44:44+09:00

Operations

Requirements

Notes

Problems

References

Code

#pragma once
#include <cstdint>

namespace haar_lib {
  constexpr uint32_t bit_reverse(uint32_t a) {
    a = ((a & 0x55555555) << 1) | ((a & 0xaaaaaaaa) >> 1);
    a = ((a & 0x33333333) << 2) | ((a & 0xcccccccc) >> 2);
    a = ((a & 0x0f0f0f0f) << 4) | ((a & 0xf0f0f0f0) >> 4);
    a = ((a & 0x00ff00ff) << 8) | ((a & 0xff00ff00) >> 8);
    a = (a << 16) | (a >> 16);
    return a;
  }

  constexpr uint64_t bit_reverse_ll(uint64_t a) {
    a = ((a & 0x5555555555555555) << 1) | ((a & 0xaaaaaaaaaaaaaaaa) >> 1);
    a = ((a & 0x3333333333333333) << 2) | ((a & 0xcccccccccccccccc) >> 2);
    a = ((a & 0x0f0f0f0f0f0f0f0f) << 4) | ((a & 0xf0f0f0f0f0f0f0f0) >> 4);
    a = ((a & 0x00ff00ff00ff00ff) << 8) | ((a & 0xff00ff00ff00ff00) >> 8);
    a = ((a & 0x0000ffff0000ffff) << 16) | ((a & 0xffff0000ffff0000) >> 16);
    a = (a << 32) | (a >> 32);
    return a;
  }
}  // namespace haar_lib

#line 2 "Mylib/Bit/bit_reverse.cpp"
#include <cstdint>

namespace haar_lib {
  constexpr uint32_t bit_reverse(uint32_t a) {
    a = ((a & 0x55555555) << 1) | ((a & 0xaaaaaaaa) >> 1);
    a = ((a & 0x33333333) << 2) | ((a & 0xcccccccc) >> 2);
    a = ((a & 0x0f0f0f0f) << 4) | ((a & 0xf0f0f0f0) >> 4);
    a = ((a & 0x00ff00ff) << 8) | ((a & 0xff00ff00) >> 8);
    a = (a << 16) | (a >> 16);
    return a;
  }

  constexpr uint64_t bit_reverse_ll(uint64_t a) {
    a = ((a & 0x5555555555555555) << 1) | ((a & 0xaaaaaaaaaaaaaaaa) >> 1);
    a = ((a & 0x3333333333333333) << 2) | ((a & 0xcccccccccccccccc) >> 2);
    a = ((a & 0x0f0f0f0f0f0f0f0f) << 4) | ((a & 0xf0f0f0f0f0f0f0f0) >> 4);
    a = ((a & 0x00ff00ff00ff00ff) << 8) | ((a & 0xff00ff00ff00ff00) >> 8);
    a = ((a & 0x0000ffff0000ffff) << 16) | ((a & 0xffff0000ffff0000) >> 16);
    a = (a << 32) | (a >> 32);
    return a;
  }
}  // namespace haar_lib

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