Defining More Data
Fields Than Are Actually Received
When you define the "Input Data
Record Structure" in the Wedge, you first define the events that
determine the start and the end of each data record. You then define
how you want the Wedge to parse each data record by selecting a
"Record Structure". You can have it parse your data records based on
either the positions of delimiter characters within each record or
by byte position in the record. The Wedge always stops reading in
data when it encounters the specific "End Of Record Event" that you
specify. If you define more data fields than are actually present in
the data record then the remaining fields will be left empty. You
could take advantage of additional empty data fields by using them
to perform calculations on previous data fields using a "Math
Expression" in the empty fields. For example suppose that you had a
device that transmitted a pair of numbers, X1 and X2, in the
following comma delimited format with a carriage return at the end
of the data record:
X1,X2<Cr>
Suppose also that you wanted to
pass these two numbers to another program along with the difference
between the two numbers. To do this, you could define the input data
record structure by specifying the End Of Record Event as "Carriage
Return or CrLf Received" and then specifying the "Record Structure"
as "Multiple Delimited Data Fields" with a comma as the delimiter
and specifying three for the maximum number of data fields.
The actual data has only two data fields before the carriage return
so by specifying three for the maximum number of fields, you will
end up with a third empty data field in the Wedge. For each field
that you define in the Wedge, you can also define a Math Expression
to be applied to the field. Math expressions in the Wedge can
contain references to previous data fields by using the "Field(n)"
expression. If you specified "Field(2) - Field(1)" for the math
expression for Field(3) (the empty field), then you would end up
with the difference between the two numbers X1 and X2 in Field(3) in
the Wedge. |
