DecodeLength()

static LengthDecodeStatus System.Formats.Asn1.AsnDecoder.DecodeLength ( ReadOnlySpan< byte > source, AsnEncodingRules ruleSet, out int? length, out int bytesRead )

inlinestaticprivate

Definition at line 122 of file AsnDecoder.cs.

    {
        length = null;
        bytesRead = 0;
        if (source.IsEmpty)
        {
            return LengthDecodeStatus.NeedMoreData;
        }
        byte b = source[bytesRead];
        bytesRead++;
        if (b == 128)
        {
            if (ruleSet == AsnEncodingRules.DER)
            {
                bytesRead = 0;
                return LengthDecodeStatus.DerIndefinite;
            }
            return LengthDecodeStatus.Success;
        }
        if (b < 128)
        {
            length = b;
            return LengthDecodeStatus.Success;
        }
        if (b == byte.MaxValue)
        {
            bytesRead = 0;
            return LengthDecodeStatus.ReservedValue;
        }
        byte b2 = (byte)(b & 0xFFFFFF7Fu);
        if (b2 + 1 > source.Length)
        {
            bytesRead = 0;
            return LengthDecodeStatus.NeedMoreData;
        }
        bool flag = ruleSet == AsnEncodingRules.DER || ruleSet == AsnEncodingRules.CER;
        if (flag && b2 > 4)
        {
            bytesRead = 0;
            return LengthDecodeStatus.LengthTooBig;
        }
        uint num = 0u;
        for (int i = 0; i < b2; i++)
        {
            byte b3 = source[bytesRead];
            bytesRead++;
            if (num == 0)
            {
                if (flag && b3 == 0)
                {
                    bytesRead = 0;
                    return LengthDecodeStatus.LaxEncodingProhibited;
                }
                if (!flag && b3 != 0 && b2 - i > 4)
                {
                    bytesRead = 0;
                    return LengthDecodeStatus.LengthTooBig;
                }
            }
            num <<= 8;
            num |= b3;
        }
        if (num > int.MaxValue)
        {
            bytesRead = 0;
            return LengthDecodeStatus.LengthTooBig;
        }
        if (flag && num < 128)
        {
            bytesRead = 0;
            return LengthDecodeStatus.LaxEncodingProhibited;
        }
        length = (int)num;
        return LengthDecodeStatus.Success;
    }

References System.length, and System.source.

Referenced by System.Formats.Asn1.AsnDecoder.ReadLength(), and System.Formats.Asn1.AsnDecoder.TryReadLength().