Basic implementation of the string pattern API #22466
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r? @aturon |
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| #[inline] | ||
| fn match_starts_at(self, haystack: &'a str, idx: usize) -> bool { | ||
| let mut matcher = self.into_searcher(haystack); |
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Could this be self.into_searcher(haystack[idx..]), and then the loop becomes unnecessary?
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Hm, indeed that could work.
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Hm, actually, it may not. E.g. asking if a match for abab starts at 2 in abababab should return false, since the matches are indices 0-4 and 4-8, or does the searching look for all matching substrings, even if they overlap?
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Oh, tricky!
Its true that as defined only all non-overlapping matches are valid, which means you can not slice the haystack as a shortcut. But that also means any potential implementer of this default method could not do that trick either, which makes the method kinda useless to even provide, so I think I have to change something:
- Either allow those methods to give answers that don't need to be identical to the yielded indices of the searcher.
- Remove the index argument and turn them into something like
is_front_match()andis_end_match(), relying on the caller of this method to slice the haystack beforehand.
Both seem fine to me, but the latter is more minimal, so I'll probably go with that one. What do you think?
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I prefer the latter approach. As you say, it's more minimal, and I think it's also more clear.
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OK, I've taken a review pass and this looks basically good to me. There's a lot of detail work -- adding documentation, cleanup, etc -- but I think the core functionality is in reasonable shape to land. Thanks @Kimundi! |
| @@ -677,6 +677,8 @@ macro_rules! iterator { | |||
| fn next(&mut self) -> Option<$elem> { | |||
| // could be implemented with slices, but this avoids bounds checks | |||
| unsafe { | |||
| ::intrinsics::assume(!self.ptr.is_null()); | |||
| ::intrinsics::assume(!self.end.is_null()); | |||
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I talked with dotdash about - its not exactly duplication because the assumes are at a different location, and depending how the code will be inlined there might be cases where either of the two changes might not apply. Also, giving llvm multiple optimization hints can't really hurt.
However, currently these hints are unneeded for my code anyway, because the optimized codepaths that depended on them did not end up in the current iteration of this PR, so if you'd rather have them removed for now I can do that too.
Added a few bugfixes and additional testcases
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⌛ Testing commit c8dd2d0 with merge 41fb6ac... |
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💔 Test failed - auto-win-32-nopt-t |
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@bors: retry |
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⌛ Testing commit c8dd2d0 with merge 562ee80... |
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💔 Test failed - auto-win-32-nopt-t |
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Hm, those failures seem unrelated to the PR? |
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Unless that timeout error is because of the slower string search... |
Kimundi
changed the title
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@bors: retry Looks unrelated |
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⌛ Testing commit c8dd2d0 with merge cf04813... |
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💔 Test failed - auto-mac-64-nopt-t |
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@bors: retry |
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⌛ Testing commit c8dd2d0 with merge e4fff79... |
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💔 Test failed - auto-linux-64-opt |
Could you see if |
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(The |
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@bors: retry Hm. |
This is not a complete implementation of the RFC: - only existing methods got updated, no new ones added - doc comments are not extensive enough yet - optimizations got lost and need to be reimplemented See rust-lang/rfcs#528 Technically a [breaking-change]
This is not a complete implementation of the RFC:
See rust-lang/rfcs#528
Technically a
[breaking-change]