ryujinx/Ryujinx.Common/Utilities/BitUtils.cs

using System;

namespace Ryujinx.Common
{
    public static class BitUtils
    {
        private static ReadOnlySpan<byte> ClzNibbleTbl => new byte[] { 4, 3, 2, 2, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0 };

        public static uint AlignUp(uint value, int size)
        {
            return (uint)AlignUp((int)value, size);
        }

        public static int AlignUp(int value, int size)
        {
            return (value + (size - 1)) & -size;
        }

        public static ulong AlignUp(ulong value, int size)
        {
            return (ulong)AlignUp((long)value, size);
        }

        public static long AlignUp(long value, int size)
        {
            return (value + (size - 1)) & -(long)size;
        }

        public static uint AlignDown(uint value, int size)
        {
            return (uint)AlignDown((int)value, size);
        }

        public static int AlignDown(int value, int size)
        {
            return value & -size;
        }

        public static ulong AlignDown(ulong value, int size)
        {
            return (ulong)AlignDown((long)value, size);
        }

        public static long AlignDown(long value, int size)
        {
            return value & -(long)size;
        }

        public static int DivRoundUp(int value, int dividend)
        {
            return (value + dividend - 1) / dividend;
        }

        public static ulong DivRoundUp(ulong value, uint dividend)
        {
            return (value + dividend - 1) / dividend;
        }

        public static long DivRoundUp(long value, int dividend)
        {
            return (value + dividend - 1) / dividend;
        }

        public static int Pow2RoundUp(int value)
        {
            value--;

            value |= (value >>  1);
            value |= (value >>  2);
            value |= (value >>  4);
            value |= (value >>  8);
            value |= (value >> 16);

            return ++value;
        }

        public static int Pow2RoundDown(int value)
        {
            return IsPowerOfTwo32(value) ? value : Pow2RoundUp(value) >> 1;
        }

        public static bool IsPowerOfTwo32(int value)
        {
            return value != 0 && (value & (value - 1)) == 0;
        }

        public static bool IsPowerOfTwo64(long value)
        {
            return value != 0 && (value & (value - 1)) == 0;
        }

        public static int CountLeadingZeros32(int value)
        {
            return (int)CountLeadingZeros((ulong)value, 32);
        }

        public static int CountLeadingZeros64(long value)
        {
            return (int)CountLeadingZeros((ulong)value, 64);
        }

        private static ulong CountLeadingZeros(ulong value, int size)
        {
            if (value == 0ul)
            {
                return (ulong)size;
            }

            int nibbleIdx = size;
            int preCount, count = 0;

            do
            {
                nibbleIdx -= 4;
                preCount = ClzNibbleTbl[(int)(value >> nibbleIdx) & 0b1111];
                count += preCount;
            }
            while (preCount == 4);

            return (ulong)count;
        }

        public static int CountTrailingZeros32(int value)
        {
            int count = 0;

            while (((value >> count) & 1) == 0)
            {
                count++;
            }

            return count;
        }

        public static long ReverseBits64(long value)
        {
            return (long)ReverseBits64((ulong)value);
        }

        private static ulong ReverseBits64(ulong value)
        {
            value = ((value & 0xaaaaaaaaaaaaaaaa) >> 1 ) | ((value & 0x5555555555555555) << 1 );
            value = ((value & 0xcccccccccccccccc) >> 2 ) | ((value & 0x3333333333333333) << 2 );
            value = ((value & 0xf0f0f0f0f0f0f0f0) >> 4 ) | ((value & 0x0f0f0f0f0f0f0f0f) << 4 );
            value = ((value & 0xff00ff00ff00ff00) >> 8 ) | ((value & 0x00ff00ff00ff00ff) << 8 );
            value = ((value & 0xffff0000ffff0000) >> 16) | ((value & 0x0000ffff0000ffff) << 16);

            return (value >> 32) | (value << 32);
        }
    }
}