System.Net.Security.NegotiateStream.ProcessRead C# (CSharp) Method

        private int ProcessRead(byte[] buffer, int offset, int count, AsyncProtocolRequest asyncRequest)
        {
            ValidateParameters(buffer, offset, count);

            if (Interlocked.Exchange(ref _NestedRead, 1) == 1)
            {
                throw new NotSupportedException(SR.Format(SR.net_io_invalidnestedcall, (asyncRequest != null ? "BeginRead" : "Read"), "read"));
            }

            bool failed = false;
            try
            {
                if (InternalBufferCount != 0)
                {
                    int copyBytes = InternalBufferCount > count ? count : InternalBufferCount;
                    if (copyBytes != 0)
                    {
                        Buffer.BlockCopy(InternalBuffer, InternalOffset, buffer, offset, copyBytes);
                        DecrementInternalBufferCount(copyBytes);
                    }
                    asyncRequest?.CompleteUser(copyBytes);
                    return copyBytes;
                }

                // Performing actual I/O.
                return StartReading(buffer, offset, count, asyncRequest);
            }
            catch (Exception e)
            {
                failed = true;
                if (e is IOException)
                {
                    throw;
                }
                throw new IOException(SR.net_io_read, e);
            }
            finally
            {
                if (asyncRequest == null || failed)
                {
                    _NestedRead = 0;
                }
            }
        }