processNextField maps an input field to the correct locations in the
outputFields array.
processNextField should be called once for each field on the line, in the order
found. The processing of the line can terminate once allFieldsFilled returns
true.
The return value is the number of output fields the input field maps to. Zero
means the field is not mapped to the output fields array.
If, prior to allFieldsProcessed returning true, any fields on the input line
are not passed to processNextField, the caller should either ensure the fields
are not part of the output fields or have partial lines enabled.
processNextField maps an input field to the correct locations in the outputFields array.
processNextField should be called once for each field on the line, in the order found. The processing of the line can terminate once allFieldsFilled returns true.
The return value is the number of output fields the input field maps to. Zero means the field is not mapped to the output fields array.
If, prior to allFieldsProcessed returning true, any fields on the input line are not passed to processNextField, the caller should either ensure the fields are not part of the output fields or have partial lines enabled.