bnes-libretro/nall/bit.hpp

#ifndef NALL_BIT_HPP
#define NALL_BIT_HPP

namespace nall {
  template<int bits> constexpr inline unsigned uclamp(const unsigned x) {
    enum { y = (1U << (bits - 1)) + ((1U << (bits - 1)) - 1) };
    return y + ((x - y) & -(x < y));  //min(x, y);
  }

  template<int bits> constexpr inline unsigned uclip(const unsigned x) {
    enum { m = (1U << (bits - 1)) + ((1U << (bits - 1)) - 1) };
    return (x & m);
  }

  template<int bits> constexpr inline signed sclamp(const signed x) {
    enum { b = 1U << (bits - 1), m = (1U << (bits - 1)) - 1 };
    return (x > m) ? m : (x < -b) ? -b : x;
  }

  template<int bits> constexpr inline signed sclip(const signed x) {
    enum { b = 1U << (bits - 1), m = (1U << bits) - 1 };
    return ((x & m) ^ b) - b;
  }

  namespace bit {
    //lowest(0b1110) == 0b0010
    template<typename T> constexpr inline T lowest(const T x) {
      return x & -x;
    }

    //clear_lowest(0b1110) == 0b1100
    template<typename T> constexpr inline T clear_lowest(const T x) {
      return x & (x - 1);
    }

    //set_lowest(0b0101) == 0b0111
    template<typename T> constexpr inline T set_lowest(const T x) {
      return x | (x + 1);
    }

    //round up to next highest single bit:
    //round(15) == 16, round(16) == 16, round(17) == 32
    inline unsigned round(unsigned x) {
      if((x & (x - 1)) == 0) return x;
      while(x & (x - 1)) x &= x - 1;
      return x << 1;
    }
  }
}

#endif