Hex2Int32

Hex2Int32.cs

using System;
using System.IO;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;

namespace Repos
{
	public static class Misc
	{
		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		private static bool ValidateHex(ReadOnlySpan<char> span)
		{
			foreach (var c in span)
			{
				if (c is >= '0' and <= '9' or >= 'a' and <= 'f' or >= 'A' and <= 'F') continue;
				return false;
			}
			return true;
		}

		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		public static unsafe int HexToInt32Simd(ReadOnlySpan<char> span)
		{
			var spanLength = span.Length;
			ThrowIfFalse(((spanLength ^ 0) | (spanLength ^ 8)) > 0 && ValidateHex(span));

			var vc = Sse2.LoadVector128((ushort*)Unsafe.AsPointer(ref MemoryMarshal.GetReference(span)));
			var v20 = Vector128.Create((ushort)0x2020);
			var v30 = Vector128.Create((ushort)0x3030);
			var v0f = Vector128.Create((ushort)0x0f0f);

			var t = Sse2.ShiftRightLogical(Sse2.Xor(Sse2.And(Sse2.Xor(Sse2.Subtract(vc, Sse2.And(vc, v20)), v20), v30), v30), 4);
			var tt = Sse2.ShiftLeftLogical(Sse2.Add(Sse2.Add(Sse2.Subtract(Sse2.And(Sse2.Subtract(vc, v30), v0f), t), Sse2.ShiftLeftLogical(t, 3)), Sse2.ShiftLeftLogical(t, 1)), 4);
			var r1 = Ssse3.Shuffle(tt.AsByte(), Vector128.Create(12, 8, 4, 0, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255));
			var r2 = Ssse3.Shuffle(tt.AsByte(), Vector128.Create(14, 10, 6, 2, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255));
			var r = Sse2.Or(r1, Sse2.ShiftRightLogical(r2.AsInt16(), 4).AsByte());

			var i32 = 0;
			Sse2.Store(&i32, r.AsInt32());
			return (int) ((uint) i32 >> ((8 - spanLength) << 2));
		}

		[MethodImpl(MethodImplOptions.AggressiveInlining)]
		public static unsafe int HexToInt32(ReadOnlySpan<char> span)
		{
			var spanLength = span.Length;
			ThrowIfFalse(((spanLength ^ 0) | (spanLength ^ 8)) > 0 && ValidateHex(span));

			var buffer = (0x0030003000300030, 0x0030003000300030);
			var pBuffer = (char*) &buffer;
			var length = Math.Min(8, spanLength);
			for (int i = 0, j = 8 - length; i < length; i++, j++)
			{
				pBuffer[j] = span[i];
			}

			var packedInput = ((long)pBuffer[0] << 56) | ((long)pBuffer[1] << 48) | ((long)pBuffer[2] << 40) | ((long)pBuffer[3] << 32) | ((long)pBuffer[4] << 24) | ((long)pBuffer[5] << 16) | ((long)pBuffer[6] << 8) | pBuffer[7];
			var calc = (((packedInput - (packedInput & 0x2020202020202020) ^ 0x2020202020202020) & 0x3030303030303030) ^ 0x3030303030303030) >> 4;
			calc = ((packedInput - 0x3030303030303030) & 0x0f0f0f0f0f0f0f0f) - calc + (calc << 3) + (calc << 1) << 4;
			return (int)((((calc >> 32) | (calc >> 28)) & 0xff000000) | (((calc >> 24) | (calc >> 20)) & 0xff0000) | (((calc >> 16) | (calc >> 12)) & 0xff00) | (((calc >> 8) | (calc >> 4)) & 0xff));
		}

		public static void ThrowIfFalse(bool cond)
		{
			if (cond) return;
			throw new InvalidDataException();
		}
	}
}