HexConverter.cs

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using System.Runtime.CompilerServices;
 
namespace System;
 
internal static class HexConverter
{
    public enum Casing : uint
    {
        Upper = 0u,
        Lower = 8224u
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static void ToCharsBuffer(byte value, Span<char> buffer, int startingIndex = 0, Casing casing = Casing.Upper)
    {
        uint num = (uint)(((value & 0xF0) << 4) + (value & 0xF) - 35209);
        uint num2 = ((((0 - num) & 0x7070) >> 4) + num + 47545) | (uint)casing;
        buffer[startingIndex + 1] = (char)(num2 & 0xFFu);
        buffer[startingIndex] = (char)(num2 >> 8);
    }
 
    public static void EncodeToUtf16(ReadOnlySpan<byte> bytes, Span<char> chars, Casing casing = Casing.Upper)
    {
        for (int i = 0; i < bytes.Length; i++)
        {
            ToCharsBuffer(bytes[i], chars, i * 2, casing);
        }
    }
 
    public unsafe static string ToString(ReadOnlySpan<byte> bytes, Casing casing = Casing.Upper)
    {
        fixed (byte* ptr = bytes)
        {
            return string.Create(bytes.Length * 2, ((IntPtr)ptr, bytes.Length, casing), delegate(Span<char> chars, (IntPtr Ptr, int Length, Casing casing) args)
            {
                ReadOnlySpan<byte> bytes2 = new ReadOnlySpan<byte>((void*)args.Ptr, args.Length);
                EncodeToUtf16(bytes2, chars, args.casing);
            });
        }
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static int FromLowerChar(int c)
    {
        switch (c)
        {
        case 48:
        case 49:
        case 50:
        case 51:
        case 52:
        case 53:
        case 54:
        case 55:
        case 56:
        case 57:
            return c - 48;
        case 97:
        case 98:
        case 99:
        case 100:
        case 101:
        case 102:
            return c - 97 + 10;
        default:
            return 255;
        }
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static bool IsHexLowerChar(int c)
    {
        if ((uint)(c - 48) > 9u)
        {
            return (uint)(c - 97) <= 5u;
        }
        return true;
    }
}