On Sun, 16 Aug 2015, Giuseppe D'Angelo wrote: > My idea was that if the lookbehind amount is known at compile time > (and it /should/ be, since lookbehinds are anyhow fixed-length; plus > things like \b which need to inspect a fixed amount of data), then the > check could be limited to the range > > [ max(offset - lookbehind_length, 0) , length ) > > instead of spenning the entire subject string.
Yes, but not quite. The maximum lookbehind length is known, but it is in *characters* not in code units. My idea is to count backwards through the max lookbehind characters - without trying to check them - and then do a forwards check from there to the end. I have now implemented this in PCRE2 and committed the code. It was a bit more fiddly than expected, and (as always) sorting out some tests and updating the documentation took almost as long as working on the code. Philip -- Philip Hazel -- ## List details at https://lists.exim.org/mailman/listinfo/pcre-dev
