/**
		* base constructor
		*
		* @param signedContent the content that was signed.
		* @param sigData the signature object.
		*/
		public CmsSignedDataParser(
			CmsTypedStream	signedContent,
			Stream			sigData)
			: base(sigData)
		{
			try
			{
				this._signedContent = signedContent;
				this._signedData = SignedDataParser.GetInstance(this.contentInfo.GetContent(Asn1Tags.Sequence));
				this._digests = Platform.CreateHashtable();
				this._digestOids = new HashSet();

				Asn1SetParser digAlgs = _signedData.GetDigestAlgorithms();
				IAsn1Convertible o;

				while ((o = digAlgs.ReadObject()) != null)
				{
					AlgorithmIdentifier id = AlgorithmIdentifier.GetInstance(o.ToAsn1Object());

					try
					{
						string digestOid = id.ObjectID.Id;
						string digestName = Helper.GetDigestAlgName(digestOid);

						if (!this._digests.Contains(digestName))
						{
							this._digests[digestName] = Helper.GetDigestInstance(digestName);
							this._digestOids.Add(digestOid);
						}
					}
					catch (SecurityUtilityException)
					{
						// TODO Should do something other than ignore it
					}
				}

				//
				// If the message is simply a certificate chain message GetContent() may return null.
				//
				ContentInfoParser cont = _signedData.GetEncapContentInfo();
				Asn1OctetStringParser octs = (Asn1OctetStringParser)
					cont.GetContent(Asn1Tags.OctetString);

				if (octs != null)
				{
					CmsTypedStream ctStr = new CmsTypedStream(
						cont.ContentType.Id, octs.GetOctetStream());

					if (_signedContent == null)
					{
						this._signedContent = ctStr;
					}
					else
					{
						//
						// content passed in, need to read past empty encapsulated content info object if present
						//
						ctStr.Drain();
					}
				}

				_signedContentType = _signedContent == null
					?	cont.ContentType
					:	new DerObjectIdentifier(_signedContent.ContentType);
			}
			catch (IOException e)
			{
				throw new CmsException("io exception: " + e.Message, e);
			}

			if (_digests.Count < 1)
			{
				throw new CmsException("no digests could be created for message.");
			}
		}
        /**
        * base constructor
        *
        * @param signedContent the content that was signed.
        * @param sigData the signature object.
        */
        public CmsSignedDataParser(
			CmsTypedStream	signedContent,
			Stream			sigData)
            : base(sigData)
        {
            try
            {
                this._signedContent = signedContent;
                this._signedData = SignedDataParser.GetInstance(this.contentInfo.GetContent(Asn1Tags.Sequence));
                this._digests = new Hashtable();

                Asn1SetParser digAlgs = _signedData.GetDigestAlgorithms();
                IAsn1Convertible o;

                while ((o = digAlgs.ReadObject()) != null)
                {
                    AlgorithmIdentifier id = AlgorithmIdentifier.GetInstance(o.ToAsn1Object());

                    try
                    {
                        string digestName = Helper.GetDigestAlgName(id.ObjectID.Id);
                        IDigest dig = DigestUtilities.GetDigest(digestName);

                        this._digests[digestName] = dig;
                    }
                    catch (SecurityUtilityException)
                    {
                        //  ignore
                    }
                }

                if (_signedContent == null)
                {
                    //
                    // If the message is simply a certificate chain message GetContent() may return null.
                    //
                    Asn1OctetStringParser octs = (Asn1OctetStringParser)
                        _signedData.GetEncapContentInfo().GetContent(Asn1Tags.OctetString);

                    if (octs != null)
                    {
                        this._signedContent = new CmsTypedStream(octs.GetOctetStream());
                    }
                }
                else
                {
                    //
                    // content passed in, need to read past empty encapsulated content info object if present
                    //
                    Asn1OctetStringParser octs = (Asn1OctetStringParser)
                        _signedData.GetEncapContentInfo().GetContent(Asn1Tags.OctetString);

                    if (octs != null)
                    {
                        Stream inStream = octs.GetOctetStream();

                        while (inStream.ReadByte() >= 0)
                        {
                            // ignore
                        }
                    }
                }
            }
            catch (IOException e)
            {
                throw new CmsException("io exception: " + e.Message, e);
            }

            if (_digests.Count < 1)
            {
                throw new CmsException("no digests could be created for message.");
            }
        }