[Flex-help] Building a push parser

[Jerome H. <jer...@gm...>]

Hi,

Thank you all for your excellent work on flex, I am happy to be able to
stand on the shoulders of giants (not that I compare myself the least to
the genius Newton).

Now, I am really sorry if I missed a ressource that documents my needs, and
I would be grateful to be pointed to it.

I would like to build a push parser, and would like the lexer to behave in
accordance.
I found this excellent ressource (https://github.com/mwberry/yacc-examples),
but its data is available beforehand or needs to be fed through blocking in
YY_INPUT (for example with a thread, which I cannot use in my case). This
is what I would call a PULL lexer.

Is it (or would it be without breaking the internals of flex) possible to
return a special value from YY_INPUT saying "I don't have any more data
JUST YET" and later being able to be called again and feed the new data
(either from YY_INPUT or from a buffer re-filling function). This would
then be a PUSH lexer.

Also, on another point, I sometimes feel that I need to enter a new start
state but this is not recognizable by the lexer, but only by the parser. Am
I doing something wrong? Is the grammar I am trying to implement broken? Or
is it legitimate?

Best regards,
Jérôme.