Ucs4Decoder4321.cs

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using System.Buffers.Binary;
 
namespace System.Xml;
 
internal sealed class Ucs4Decoder4321 : Ucs4Decoder
{
    internal override int GetFullChars(byte[] bytes, int byteIndex, int byteCount, char[] chars, int charIndex)
    {
        byteCount += byteIndex;
        int i = byteIndex;
        int num = charIndex;
        for (; i + 3 < byteCount; i += 4)
        {
            uint num2 = BinaryPrimitives.ReadUInt32LittleEndian(bytes.AsSpan(i));
            if (num2 > 1114111)
            {
                throw new ArgumentException(System.SR.Format(System.SR.Enc_InvalidByteInEncoding, new object[1] { i }), (string?)null);
            }
            if (num2 > 65535)
            {
                Ucs4ToUTF16(num2, chars, num);
                num++;
            }
            else
            {
                if (XmlCharType.IsSurrogate((int)num2))
                {
                    throw new XmlException(System.SR.Xml_InvalidCharInThisEncoding, string.Empty);
                }
                chars[num] = (char)num2;
            }
            num++;
        }
        return num - charIndex;
    }
}