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This commit hacks in a bug fix for handling look-around across multiple lines. The main problem is that by the time the matching lines are sent to the printer, the surrounding context---which some look-behind or look-ahead might have matched---could have been dropped if it wasn't part of the set of matching lines. Therefore, when the printer re-runs the regex engine in some cases (to do replacements, color matches, etc etc), it won't be guaranteed to see the same matches that the searcher found. Overall, this is a giant clusterfuck and suggests that the way I divided the abstraction boundary between the printer and the searcher is just wrong. It's likely that the searcher needs to handle more of the work of matching and pass that info on to the printer. The tricky part is that this additional work isn't always needed. Ultimately, this means a serious re-design of the interface between searching and printing. Sigh. The way this fix works is to smuggle the underlying buffer used by the searcher through into the printer. Since these bugs only impact multi-line search (otherwise, searches are only limited to matches across a single line), and since multi-line search always requires having the entire file contents in a single contiguous slice (memory mapped or on the heap), it follows that the buffer we pass through when we need it is, in fact, the entire haystack. So this commit refactors the printer's regex searching to use that buffer instead of the intended bundle of bytes containing just the relevant matching portions of that same buffer. There is one last little hiccup: PCRE2 doesn't seem to have a way to specify an ending position for a search. So when we re-run the search to find matches, we can't say, "but don't search past here." Since the buffer is likely to contain the entire file, we really cannot do anything here other than specify a fixed upper bound on the number of bytes to search. So if look-ahead goes more than N bytes beyond the match, this code will break by simply being unable to find the match. In practice, this is probably pretty rare. I believe that if we did a better fix for this bug by fixing the interfaces, then we'd probably try to have PCRE2 find the pertinent matches up front so that it never needs to re-discover them. Fixes #1412 |
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grep-printer
Print results from line oriented searching in a human readable, aggregate or JSON Lines format.
Dual-licensed under MIT or the UNLICENSE.
Documentation
NOTE: You probably don't want to use this crate directly. Instead, you
should prefer the facade defined in the
grep
crate.
Usage
Add this to your Cargo.toml:
[dependencies]
grep-printer = "0.1"
and this to your crate root:
extern crate grep_printer;