BMPEncoding.cs

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namespace System.Formats.Asn1;
 
internal sealed class BMPEncoding : SpanBasedEncoding
{
    protected override int GetBytes(ReadOnlySpan<char> chars, Span<byte> bytes, bool write)
    {
        if (chars.IsEmpty)
        {
            return 0;
        }
        int num = 0;
        for (int i = 0; i < chars.Length; i++)
        {
            char c = chars[i];
            if (char.IsSurrogate(c))
            {
                base.EncoderFallback.CreateFallbackBuffer().Fallback(c, i);
                throw new InvalidOperationException();
            }
            ushort num2 = c;
            if (write)
            {
                bytes[num + 1] = (byte)num2;
                bytes[num] = (byte)(num2 >> 8);
            }
            num += 2;
        }
        return num;
    }
 
    protected override int GetChars(ReadOnlySpan<byte> bytes, Span<char> chars, bool write)
    {
        if (bytes.IsEmpty)
        {
            return 0;
        }
        if (bytes.Length % 2 != 0)
        {
            base.DecoderFallback.CreateFallbackBuffer().Fallback(bytes.Slice(bytes.Length - 1).ToArray(), bytes.Length - 1);
            throw new InvalidOperationException();
        }
        int num = 0;
        for (int i = 0; i < bytes.Length; i += 2)
        {
            int num2 = (bytes[i] << 8) | bytes[i + 1];
            char c = (char)num2;
            if (char.IsSurrogate(c))
            {
                base.DecoderFallback.CreateFallbackBuffer().Fallback(bytes.Slice(i, 2).ToArray(), i);
                throw new InvalidOperationException();
            }
            if (write)
            {
                chars[num] = c;
            }
            num++;
        }
        return num;
    }
 
    public override int GetMaxByteCount(int charCount)
    {
        return checked(charCount * 2);
    }
 
    public override int GetMaxCharCount(int byteCount)
    {
        return byteCount / 2;
    }
}