sharpemu/src/SharpEmu.GUI/Atrac9/Utilities/Bit.cs

#nullable disable
namespace LibAtrac9.Utilities
{
    internal static class Bit
    {
        private static uint BitReverse32(uint value)
        {
            value = ((value & 0xaaaaaaaa) >> 1) | ((value & 0x55555555) << 1);
            value = ((value & 0xcccccccc) >> 2) | ((value & 0x33333333) << 2);
            value = ((value & 0xf0f0f0f0) >> 4) | ((value & 0x0f0f0f0f) << 4);
            value = ((value & 0xff00ff00) >> 8) | ((value & 0x00ff00ff) << 8);
            return (value >> 16) | (value << 16);
        }
        private static uint BitReverse32(uint value, int bitCount) => BitReverse32(value) >> (32 - bitCount);
        public static int BitReverse32(int value, int bitCount) => (int) BitReverse32((uint) value, bitCount);

        public static int SignExtend32(int value, int bits)
        {
            int shift = 8 * sizeof(int) - bits;
            return (value << shift) >> shift;
        }
    }
}