AllowedBmpCodePointsBitmap.cs

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using System.Buffers.Binary;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Text.Unicode;
 
namespace System.Text.Encodings.Web;
 
internal struct AllowedBmpCodePointsBitmap
{
    private unsafe fixed uint Bitmap[2048];
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public unsafe void AllowChar(char value)
    {
        _GetIndexAndOffset(value, out UIntPtr index, out int offset);
        ref uint reference = ref Bitmap[(ulong)index];
        reference |= (uint)(1 << offset);
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public unsafe void ForbidChar(char value)
    {
        _GetIndexAndOffset(value, out UIntPtr index, out int offset);
        ref uint reference = ref Bitmap[(ulong)index];
        reference &= (uint)(~(1 << offset));
    }
 
    public void ForbidHtmlCharacters()
    {
        ForbidChar('<');
        ForbidChar('>');
        ForbidChar('&');
        ForbidChar('\'');
        ForbidChar('"');
        ForbidChar('+');
    }
 
    public unsafe void ForbidUndefinedCharacters()
    {
        fixed (uint* pointer = Bitmap)
        {
            ReadOnlySpan<byte> values = UnicodeHelpers.GetDefinedBmpCodePointsBitmapLittleEndian();
            Span<uint> span = new Span<uint>(pointer, 2048);
            if (Vector.IsHardwareAccelerated && BitConverter.IsLittleEndian)
            {
                while (!values.IsEmpty)
                {
                    (new Vector<uint>(values) & new Vector<uint>(span)).CopyTo(span);
                    values = values.Slice(Vector<byte>.Count);
                    span = span.Slice(Vector<uint>.Count);
                }
                return;
            }
            for (int i = 0; i < span.Length; i++)
            {
                span[i] &= BinaryPrimitives.ReadUInt32LittleEndian(values.Slice(i * 4));
            }
        }
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public unsafe readonly bool IsCharAllowed(char value)
    {
        _GetIndexAndOffset(value, out UIntPtr index, out int offset);
        if ((Bitmap[(ulong)index] & (uint)(1 << offset)) != 0)
        {
            return true;
        }
        return false;
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public unsafe readonly bool IsCodePointAllowed(uint value)
    {
        if (!System.Text.UnicodeUtility.IsBmpCodePoint(value))
        {
            return false;
        }
        _GetIndexAndOffset(value, out UIntPtr index, out int offset);
        if ((Bitmap[(ulong)index] & (uint)(1 << offset)) != 0)
        {
            return true;
        }
        return false;
    }
 
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private static void _GetIndexAndOffset(uint value, out nuint index, out int offset)
    {
        index = value >> 5;
        offset = (int)(value & 0x1F);
    }
}