diff options
Diffstat (limited to 'crypto/src/util/Integers.cs')
| -rw-r--r-- | crypto/src/util/Integers.cs | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/crypto/src/util/Integers.cs b/crypto/src/util/Integers.cs index e746b0ef4..b243b88b2 100644 --- a/crypto/src/util/Integers.cs +++ b/crypto/src/util/Integers.cs @@ -1,9 +1,50 @@ using System; +using Org.BouncyCastle.Math.Raw; + namespace Org.BouncyCastle.Utilities { public abstract class Integers { + private static readonly byte[] DeBruijnTZ = { + 0x00, 0x01, 0x02, 0x18, 0x03, 0x13, 0x06, 0x19, 0x16, 0x04, 0x14, 0x0A, + 0x10, 0x07, 0x0C, 0x1A, 0x1F, 0x17, 0x12, 0x05, 0x15, 0x09, 0x0F, 0x0B, + 0x1E, 0x11, 0x08, 0x0E, 0x1D, 0x0D, 0x1C, 0x1B }; + + public static int NumberOfLeadingZeros(int i) + { + if (i <= 0) + return (~i >> (31 - 5)) & (1 << 5); + + uint u = (uint)i; + int n = 1; + if (0 == (u >> 16)) { n += 16; u <<= 16; } + if (0 == (u >> 24)) { n += 8; u <<= 8; } + if (0 == (u >> 28)) { n += 4; u <<= 4; } + if (0 == (u >> 30)) { n += 2; u <<= 2; } + n -= (int)(u >> 31); + return n; + } + + public static int NumberOfTrailingZeros(int i) + { + return DeBruijnTZ[(uint)((i & -i) * 0x04D7651F) >> 27]; + } + + public static int Reverse(int i) + { + i = (int)Bits.BitPermuteStepSimple((uint)i, 0x55555555U, 1); + i = (int)Bits.BitPermuteStepSimple((uint)i, 0x33333333U, 2); + i = (int)Bits.BitPermuteStepSimple((uint)i, 0x0F0F0F0FU, 4); + return ReverseBytes(i); + } + + public static int ReverseBytes(int i) + { + return RotateLeft((int)((uint)i & 0xFF00FF00U), 8) | + RotateLeft((int)((uint)i & 0x00FF00FFU), 24); + } + public static int RotateLeft(int i, int distance) { return (i << distance) ^ (int)((uint)i >> -distance); |