public Asn1Object ReadObject()
        {
            int tag = ReadByte();
            if (tag <= 0)
            {
                if (tag == 0)
                    throw new IOException("unexpected end-of-contents marker");

                return null;
            }

            //
            // calculate tag number
            //
            int tagNo = ReadTagNumber(this.s, tag);

            bool isConstructed = (tag & Asn1Tags.Constructed) != 0;

            //
            // calculate length
            //
            int length = ReadLength(this.s, limit);

            if (length < 0) // indefinite length method
            {
                if (!isConstructed)
                    throw new IOException("indefinite length primitive encoding encountered");

                IndefiniteLengthInputStream indIn = new IndefiniteLengthInputStream(this.s, limit);
                Asn1StreamParser sp = new Asn1StreamParser(indIn, limit);

                if ((tag & Asn1Tags.Application) != 0)
                {
                    return new BerApplicationSpecificParser(tagNo, sp).ToAsn1Object();
                }

                if ((tag & Asn1Tags.Tagged) != 0)
                {
                    return new BerTaggedObjectParser(true, tagNo, sp).ToAsn1Object();
                }

                // TODO There are other tags that may be constructed (e.g. BitString)
                switch (tagNo)
                {
                    case Asn1Tags.OctetString:
                        return new BerOctetStringParser(sp).ToAsn1Object();
                    case Asn1Tags.Sequence:
                        return new BerSequenceParser(sp).ToAsn1Object();
                    case Asn1Tags.Set:
                        return new BerSetParser(sp).ToAsn1Object();
                    case Asn1Tags.External:
                        return new DerExternalParser(sp).ToAsn1Object();
                    default:
                        throw new IOException("unknown BER object encountered");
                }
            }
            else
            {
                try
                {
                    return BuildObject(tag, tagNo, length);
                }
                catch (ArgumentException e)
                {
                    throw new Asn1Exception("corrupted stream detected", e);
                }
            }
        }
        public virtual IAsn1Convertible ReadObject()
        {
            int tag = _in.ReadByte();
            if (tag == -1)
                return null;

            // turn of looking for "00" while we resolve the tag
            Set00Check(false);

            //
            // calculate tag number
            //
            int tagNo = Asn1InputStream.ReadTagNumber(_in, tag);

            bool isConstructed = (tag & Asn1Tags.Constructed) != 0;

            //
            // calculate length
            //
            int length = Asn1InputStream.ReadLength(_in, _limit);

            if (length < 0) // indefinite length method
            {
                if (!isConstructed)
                    throw new IOException("indefinite length primitive encoding encountered");

                IndefiniteLengthInputStream indIn = new IndefiniteLengthInputStream(_in, _limit);
                Asn1StreamParser sp = new Asn1StreamParser(indIn, _limit);

                if ((tag & Asn1Tags.Application) != 0)
                {
                    return new BerApplicationSpecificParser(tagNo, sp);
                }

                if ((tag & Asn1Tags.Tagged) != 0)
                {
                    return new BerTaggedObjectParser(true, tagNo, sp);
                }

                return sp.ReadIndef(tagNo);
            }
            else
            {
                DefiniteLengthInputStream defIn = new DefiniteLengthInputStream(_in, length);

                if ((tag & Asn1Tags.Application) != 0)
                {
                    return new DerApplicationSpecific(isConstructed, tagNo, defIn.ToArray());
                }

                if ((tag & Asn1Tags.Tagged) != 0)
                {
                    return new BerTaggedObjectParser(isConstructed, tagNo, new Asn1StreamParser(defIn));
                }

                if (isConstructed)
                {
                    // TODO There are other tags that may be constructed (e.g. BitString)
                    switch (tagNo)
                    {
                        case Asn1Tags.OctetString:
                            //
                            // yes, people actually do this...
                            //
                            return new BerOctetStringParser(new Asn1StreamParser(defIn));
                        case Asn1Tags.Sequence:
                            return new DerSequenceParser(new Asn1StreamParser(defIn));
                        case Asn1Tags.Set:
                            return new DerSetParser(new Asn1StreamParser(defIn));
                        case Asn1Tags.External:
                            return new DerExternalParser(new Asn1StreamParser(defIn));
                        default:
                            throw new IOException("unknown tag " + tagNo + " encountered");
                    }
                }

                // Some primitive encodings can be handled by parsers too...
                switch (tagNo)
                {
                    case Asn1Tags.OctetString:
                        return new DerOctetStringParser(defIn);
                }

                try
                {
                    return Asn1InputStream.CreatePrimitiveDerObject(tagNo, defIn, tmpBuffers);
                }
                catch (ArgumentException e)
                {
                    throw new Asn1Exception("corrupted stream detected", e);
                }
            }
        }