NTZ for 0 should be 32/64 resp.

- add tests for NLZ, NTZ
- round out methods for Longs class

1 files changed, 24 insertions, 0 deletions

diff --git a/crypto/src/util/Longs.cs b/crypto/src/util/Longs.cs
index 91dee2b50..66b14b95c 100644
--- a/crypto/src/util/Longs.cs
+++ b/crypto/src/util/Longs.cs
@@ -9,6 +9,30 @@ namespace Org.BouncyCastle.Utilities
         public const int NumBits = 64;
         public const int NumBytes = 8;
 
+        private static readonly byte[] DeBruijnTZ = {
+            0x3F, 0x00, 0x01, 0x34, 0x02, 0x06, 0x35, 0x1A, 0x03, 0x25, 0x28, 0x07, 0x21, 0x36, 0x2F, 0x1B,
+            0x3D, 0x04, 0x26, 0x2D, 0x2B, 0x29, 0x15, 0x08, 0x17, 0x22, 0x3A, 0x37, 0x30, 0x11, 0x1C, 0x0A,
+            0x3E, 0x33, 0x05, 0x19, 0x24, 0x27, 0x20, 0x2E, 0x3C, 0x2C, 0x2A, 0x14, 0x16, 0x39, 0x10, 0x09,
+            0x32, 0x18, 0x23, 0x1F, 0x3B, 0x13, 0x38, 0x0F, 0x31, 0x1E, 0x12, 0x0E, 0x1D, 0x0D, 0x0C, 0x0B };
+
+        public static int NumberOfLeadingZeros(long i)
+        {
+            int x = (int)(i >> 32), n = 0;
+            if (x == 0)
+            {
+                n = 32;
+                x = (int)i;
+            }
+            return n + Integers.NumberOfLeadingZeros(x);
+        }
+
+        public static int NumberOfTrailingZeros(long i)
+        {
+            int n = DeBruijnTZ[(uint)((ulong)((i & -i) * 0x045FBAC7992A70DAL) >> 58)];
+            long m = (((i & 0xFFFFFFFFL) | (long)((ulong)i >> 32)) - 1L) >> 63;
+            return n - (int)m;
+        }
+
         public static long Reverse(long i)
         {
             i = (long)Bits.BitPermuteStepSimple((ulong)i, 0x5555555555555555UL, 1);