1  using System;
 2  using System.Numerics;
 3  
 4  namespace ARMeilleure.Common
 5  {
 6      static class BitUtils
 7      {
 8          private static ReadOnlySpan<sbyte> HbsNibbleLut => new sbyte[] { -1, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3 };
 9  
10          public static long FillWithOnes(int bits)
11          {
12              return bits == 64 ? -1L : (1L << bits) - 1;
13          }
14  
15          public static int HighestBitSet(int value)
16          {
17              return 31 - BitOperations.LeadingZeroCount((uint)value);
18          }
19  
20          public static int HighestBitSetNibble(int value)
21          {
22              return HbsNibbleLut[value];
23          }
24  
25          public static long Replicate(long bits, int size)
26          {
27              long output = 0;
28  
29              for (int bit = 0; bit < 64; bit += size)
30              {
31                  output |= bits << bit;
32              }
33  
34              return output;
35          }
36  
37          public static int RotateRight(int bits, int shift, int size)
38          {
39              return (int)RotateRight((uint)bits, shift, size);
40          }
41  
42          public static uint RotateRight(uint bits, int shift, int size)
43          {
44              return (bits >> shift) | (bits << (size - shift));
45          }
46  
47          public static long RotateRight(long bits, int shift, int size)
48          {
49              return (long)RotateRight((ulong)bits, shift, size);
50          }
51  
52          public static ulong RotateRight(ulong bits, int shift, int size)
53          {
54              return (bits >> shift) | (bits << (size - shift));
55          }
56      }
57  }