/// <summary> /// Read a single line from intake. In case of X12, the line means segment (so, CR/LF is not (necessarily) a delimiter). /// </summary> /// <returns>A tuple consisting of the line sequence number (1-based), source number (1-based) and the line read from intake; or null as EOD mark</returns> internal Tuple <int, int, ExternalLine> GetLineFromIntake() { // linePlus is a Tuple<ExternalLine,int>: Item1 = line, Item2 = source number // End-of-data indicators: * non-null linePlus.Item1 means data // * null linePlus.Item1 means end-of-data for a single source (only if asynchronous) // * null linePlus means end-of-data for all sources Tuple <ExternalLine, int> linePlus; do //note that this loop is for consistency with async intake from files where tuple with end-of-data mark denotes end of each source (but not the entire intake) { // (even though in case of synchronous intake, tuples with null contents should not be received from LineFeeder or IntakeSupplier). //IOW, this loop should always execute a single iteration. linePlus = _intakeFromReader ? _intakeReader.GetNextLine() : _config.IntakeSupplier(_globalCache); Debug.Assert(linePlus == null || linePlus.Item1 != null); }while (linePlus != null && linePlus.Item1 == null); // ignore tuples with null lines (end-of-data marks for individual sources) if (linePlus == null) { return(null); // EOD mark } var lineCnt = Interlocked.Increment(ref _lineCnt); // adjustment for header row(s) may be needed return(Tuple.Create(lineCnt, linePlus.Item2, linePlus.Item1)); }