1 files changed, 109 insertions, 0 deletions
diff --git a/ARMeilleure/Common/BitUtils.cs b/ARMeilleure/Common/BitUtils.cs
new file mode 100644
index 00000000..55344608
--- /dev/null
+++ b/ARMeilleure/Common/BitUtils.cs
@@ -0,0 +1,109 @@
+using System.Runtime.CompilerServices;
+
+namespace ARMeilleure.Common
+{
+    static class BitUtils
+    {
+        private const int DeBrujinSequence = 0x77cb531;
+
+        private static int[] DeBrujinLbsLut;
+
+        static BitUtils()
+        {
+            DeBrujinLbsLut = new int[32];
+
+            for (int index = 0; index < DeBrujinLbsLut.Length; index++)
+            {
+                uint lutIndex = (uint)(DeBrujinSequence * (1 << index)) >> 27;
+
+                DeBrujinLbsLut[lutIndex] = index;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int LowestBitSet(int value)
+        {
+            if (value == 0)
+            {
+                return -1;
+            }
+
+            int lsb = value & -value;
+
+            return DeBrujinLbsLut[(uint)(DeBrujinSequence * lsb) >> 27];
+        }
+
+        public static int HighestBitSet(int value)
+        {
+            if (value == 0)
+            {
+                return -1;
+            }
+
+            for (int bit = 31; bit >= 0; bit--)
+            {
+                if (((value >> bit) & 1) != 0)
+                {
+                    return bit;
+                }
+            }
+
+            return -1;
+        }
+
+        private static readonly sbyte[] HbsNibbleLut = { -1, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3 };
+
+        public static int HighestBitSetNibble(int value) => HbsNibbleLut[value & 0b1111];
+
+        public static long Replicate(long bits, int size)
+        {
+            long output = 0;
+
+            for (int bit = 0; bit < 64; bit += size)
+            {
+                output |= bits << bit;
+            }
+
+            return output;
+        }
+
+        public static int CountBits(int value)
+        {
+            int count = 0;
+
+            while (value != 0)
+            {
+                value &= ~(value & -value);
+
+                count++;
+            }
+
+            return count;
+        }
+
+        public static long FillWithOnes(int bits)
+        {
+            return bits == 64 ? -1L : (1L << bits) - 1;
+        }
+
+        public static int RotateRight(int bits, int shift, int size)
+        {
+            return (int)RotateRight((uint)bits, shift, size);
+        }
+
+        public static uint RotateRight(uint bits, int shift, int size)
+        {
+            return (bits >> shift) | (bits << (size - shift));
+        }
+
+        public static long RotateRight(long bits, int shift, int size)
+        {
+            return (long)RotateRight((ulong)bits, shift, size);
+        }
+
+        public static ulong RotateRight(ulong bits, int shift, int size)
+        {
+            return (bits >> shift) | (bits << (size - shift));
+        }
+    }
+}