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using System;
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
using System.Buffers.Binary;
#endif
#if NETCOREAPP3_0_OR_GREATER
using System.Numerics;
using System.Runtime.Intrinsics.X86;
#endif
using Org.BouncyCastle.Math.Raw;
namespace Org.BouncyCastle.Utilities
{
public static class Integers
{
public const int NumBits = 32;
public const int NumBytes = 4;
#if !NETCOREAPP3_0_OR_GREATER
private static readonly byte[] DeBruijnTZ = {
0x1F, 0x00, 0x1B, 0x01, 0x1C, 0x0D, 0x17, 0x02, 0x1D, 0x15, 0x13, 0x0E, 0x18, 0x10, 0x03, 0x07,
0x1E, 0x1A, 0x0C, 0x16, 0x14, 0x12, 0x0F, 0x06, 0x19, 0x0B, 0x11, 0x05, 0x0A, 0x04, 0x09, 0x08 };
#endif
public static int HighestOneBit(int i)
{
return (int)HighestOneBit((uint)i);
}
[CLSCompliant(false)]
public static uint HighestOneBit(uint i)
{
i |= i >> 1;
i |= i >> 2;
i |= i >> 4;
i |= i >> 8;
i |= i >> 16;
return i - (i >> 1);
}
public static int LowestOneBit(int i)
{
return i & -i;
}
[CLSCompliant(false)]
public static uint LowestOneBit(uint i)
{
return (uint)LowestOneBit((int)i);
}
public static int NumberOfLeadingZeros(int i)
{
#if NETCOREAPP3_0_OR_GREATER
return BitOperations.LeadingZeroCount((uint)i);
#else
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;
#endif
}
public static int NumberOfTrailingZeros(int i)
{
#if NETCOREAPP3_0_OR_GREATER
return BitOperations.TrailingZeroCount(i);
#else
int n = DeBruijnTZ[(uint)((i & -i) * 0x0EF96A62) >> 27];
int m = (((i & 0xFFFF) | (int)((uint)i >> 16)) - 1) >> 31;
return n - m;
#endif
}
public static int Reverse(int i)
{
return (int)Reverse((uint)i);
}
[CLSCompliant(false)]
public static uint Reverse(uint i)
{
i = Bits.BitPermuteStepSimple(i, 0x55555555U, 1);
i = Bits.BitPermuteStepSimple(i, 0x33333333U, 2);
i = Bits.BitPermuteStepSimple(i, 0x0F0F0F0FU, 4);
return ReverseBytes(i);
}
public static int ReverseBytes(int i)
{
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
return BinaryPrimitives.ReverseEndianness(i);
#else
return (int)ReverseBytes((uint)i);
#endif
}
[CLSCompliant(false)]
public static uint ReverseBytes(uint i)
{
#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
return BinaryPrimitives.ReverseEndianness(i);
#else
return RotateLeft(i & 0xFF00FF00U, 8) |
RotateLeft(i & 0x00FF00FFU, 24);
#endif
}
public static int RotateLeft(int i, int distance)
{
#if NETCOREAPP3_0_OR_GREATER
return (int)BitOperations.RotateLeft((uint)i, distance);
#else
return (i << distance) | (int)((uint)i >> -distance);
#endif
}
[CLSCompliant(false)]
public static uint RotateLeft(uint i, int distance)
{
#if NETCOREAPP3_0_OR_GREATER
return BitOperations.RotateLeft(i, distance);
#else
return (i << distance) | (i >> -distance);
#endif
}
public static int RotateRight(int i, int distance)
{
#if NETCOREAPP3_0_OR_GREATER
return (int)BitOperations.RotateRight((uint)i, distance);
#else
return (int)((uint)i >> distance) | (i << -distance);
#endif
}
[CLSCompliant(false)]
public static uint RotateRight(uint i, int distance)
{
#if NETCOREAPP3_0_OR_GREATER
return BitOperations.RotateRight(i, distance);
#else
return (i >> distance) | (i << -distance);
#endif
}
}
}
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