Re: How to get at the entire input buffer string from inside lexer?

I am past this, but since you asked:


I am dealing with a data format that comprises strings of the form:
[leader_string]<tail_string><crlf>




Where the optional leader_string looks like:
<delimiter><variable_data><checksum><delimiter>


And the required tail_string looks like:
<header><variable_data_depending_on_header><checksum>


So there are two different kinds of embedded checksum: one is a check
on the optional leading sequence, the other is on the required
trailing sentence. There is no checksum for the entire line. Since I
am already committed to parsing one line at a time (which is what I
get from client programs), I wanted to leverage the intelligence in
the lexer to spot the delimiters and pick out the checksum sequences
for processing. I could just pre-process the entire string as soon as
I see it, scanning for checksums as I go, but then I have to map the
recovered checksums to the fragments identified by the lexer and
parser, which does me no good in the long run. So the problem as I got
it was, "when the lexer sees a delimiter for beginning or end of a
fragment, how do I know what the original string looked like between
those points?". And I came up with an answer I can live with.


Thanks to all as usual.


Eric

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