Net.Pkcs11Interop.HighLevelAPI81.Session.Decrypt C# (CSharp) Method

        public void Decrypt(Mechanism mechanism, ObjectHandle keyHandle, Stream inputStream, Stream outputStream, int bufferLength)
        {
            if (this._disposed)
                throw new ObjectDisposedException(this.GetType().FullName);

            if (mechanism == null)
                throw new ArgumentNullException("mechanism");
            
            if (keyHandle == null)
                throw new ArgumentNullException("keyHandle");
            
            if (inputStream == null)
                throw new ArgumentNullException("inputStream");
            
            if (outputStream == null)
                throw new ArgumentNullException("outputStream");
            
            if (bufferLength < 1)
                throw new ArgumentException("Value has to be positive number", "bufferLength");

            CK_MECHANISM ckMechanism = mechanism.CkMechanism;

            CKR rv = _p11.C_DecryptInit(_sessionId, ref ckMechanism, keyHandle.ObjectId);
            if (rv != CKR.CKR_OK)
                throw new Pkcs11Exception("C_DecryptInit", rv);

            byte[] encryptedPart = new byte[bufferLength];
            byte[] part = new byte[bufferLength];
            ulong partLen = Convert.ToUInt64(part.Length);

            int bytesRead = 0;
            while ((bytesRead = inputStream.Read(encryptedPart, 0, encryptedPart.Length)) > 0)
            {
                partLen = Convert.ToUInt64(part.Length);
                rv = _p11.C_DecryptUpdate(_sessionId, encryptedPart, Convert.ToUInt64(bytesRead), part, ref partLen);
                if (rv != CKR.CKR_OK)
                    throw new Pkcs11Exception("C_DecryptUpdate", rv);

                outputStream.Write(part, 0, Convert.ToInt32(partLen));
            }

            byte[] lastPart = null;
            ulong lastPartLen = 0;
            rv = _p11.C_DecryptFinal(_sessionId, null, ref lastPartLen);
            if (rv != CKR.CKR_OK)
                throw new Pkcs11Exception("C_DecryptFinal", rv);

            lastPart = new byte[lastPartLen];
            rv = _p11.C_DecryptFinal(_sessionId, lastPart, ref lastPartLen);
            if (rv != CKR.CKR_OK)
                throw new Pkcs11Exception("C_DecryptFinal", rv);

            if (lastPartLen > 0)
                outputStream.Write(lastPart, 0, Convert.ToInt32(lastPartLen));
        }