chessy/src/BitOperations.h

#ifndef CHESSY_BITOPERATIONS_H
#define CHESSY_BITOPERATIONS_H 

#include <cinttypes>

#ifdef _MSC_VER
#include <intrin.h>
#include <stdlib.h>
#endif


namespace chessy
{
    using U64 = uint64_t;
    using U32 = uint32_t;
    using U16 = uint16_t;
    using U8  = uint8_t;


    /*!
     * reverses the byte order of a 64-bit integer
     */
    inline U64 byteswap(U64 x)
    {
#if __GNUC__ > 4 && __GNUC_MINOR__ >= 3
        return __builtin_bswap64(x);
#elif defined(_MSC_VER)
        return _byteswap_uint64(x);
#else
        return (x << 56) |
            ((x & 0xFF00) << 40) |
            ((x & 0xFF0000) << 24) |
            ((x & 0xFF000000) << 8) |
            ((x & 0xFF00000000) >> 8) |
            ((x & 0xFF0000000000) >> 24) |
            ((x & 0xFF000000000000) >> 40) |
            (x >> 56);
#endif
    }

    /*!
    * counts the trailing zeroes on a 64 bit integer
    */
    inline int trailingZeroes(U64 x) {
#if __GNUC__ > 4 && 0
        return __builtin_ctzll(x)
#elif defined(_MSC_VER)
        unsigned long out;
        if (_BitScanForward64(&out, x))
            return out;
        else
            return 0;
#else
        for (int i = 0; i < 64; i++)
            if (x & (1ULL << i))
                return i;
        return 0;
#endif
    }


    /*!
    * counts the leading zeroes on a 64 bit integer
    */
    inline int leadingZeroes(U64 x) {
#if __GNUC__ > 4
        return __builtin_clzll(x);
#elif defined(_MSC_VER) && defined(_M_X64)
        return __lzcnt64(x);
#else
        for (int i = 0; i < 64; i++)
            if (x & (1ULL << (63 - i)))
                return i;
        return 0;
#endif
    }

    inline int popcount(U64 x) {
#if __GNUC__ > 4
        return __builtin_popcount(x);
#elif defined(_MSC_VER) && defined(_M_X64)
        return _mm_popcnt_u64(x);
#else
        int result = 0;
        for (int i = 0; i < 64; i++)
            if (x & (1ULL << i))
                result++;
        return result;
#endif
    }
}


#endif // CHESSY_BITOPERATIONS_H