/// <summary>
/// peek at current location in input array for a 5250 data stream header. If is
/// a valid header, return a DataStreamHeader. Otherwise, return null.
/// </summary>
/// <param name="InputArray"></param>
/// <returns></returns>
public static DataStreamHeader PeekDataStreamHeader(this InputByteArray InputArray)
{
DataStreamHeader dsh = null;
if (InputArray.IsDataStreamHeader( ) == true)
{
var buf = new InputByteArray(InputArray.PeekBytesLenient(100));
var rv = DataStreamHeader.Factory(buf);
dsh = rv.Item1;
}
return(dsh);
}
public static Tuple <DataStreamHeader, string> Factory(InputByteArray InputArray)
{
DataStreamHeader dsh = null;
string errmsg = null;
int rcdLgth = 0;
byte[] buf = null;
DataStreamCode dataStreamCode = DataStreamCode.Terminal;
if (InputArray.RemainingLength < 10)
{
errmsg = "Not enough bytes for data stream header";
}
if (errmsg == null)
{
buf = InputArray.PeekBytesLenient(20);
// the first 6 bytes are logical record length, 2 byte marker and 2 bytes
// DataStreamCode.
rcdLgth = buf.BigEndianBytesToShort(0);
var rcdType = buf.SubArray(2, 2);
if ((rcdType[0] != 0x12) || (rcdType[1] != 0xa0))
{
errmsg = "Invalid record type";
}
else if (rcdLgth < 10)
{
errmsg = "Invalid record length";
}
}
// isolate the data stream code.
if (errmsg == null)
{
var nullableCode = buf.SubArray(4, 2).ToDataStreamCode();
if (nullableCode == null)
{
errmsg = "not valid data stream code";
}
else
{
dataStreamCode = nullableCode.Value;
}
}
if (errmsg == null)
{
if (dataStreamCode == DataStreamCode.Terminal)
{
dsh = new TerminalDataStreamHeader(InputArray);
}
else if (dataStreamCode == DataStreamCode.PrinterStartup)
{
dsh = new PrinterStartupDataStreamHeader(InputArray);
}
else if (dataStreamCode == DataStreamCode.PrinterPrint)
{
var payloadBx = InputArray.PeekDataStreamHeaderLength();
var payloadBuf = InputArray.PeekBytesLenient(payloadBx, 3);
if (payloadBuf.CompareEqual(StartPrinterFileMarkerBytes) == true)
{
dsh = new StartPrinterFileDataStreamHeader(InputArray);
}
else
{
dsh = new PrinterDataStreamHeader(InputArray, "Printer");
}
}
else if (dataStreamCode == DataStreamCode.PrinterResponse)
{
dsh = new PrinterDataStreamHeader(InputArray, "PrintResponse");
}
}
return(new Tuple <DataStreamHeader, string>(dsh, errmsg));
}