| commit | f31b7928ae622811043a426141aec73ad050dda3 | [log] [tgz] |
|---|---|---|
| author | Stevie Strickland <sstrickl@google.com> | Thu Mar 14 14:26:47 2019 +0000 |
| committer | commit-bot@chromium.org <commit-bot@chromium.org> | Thu Mar 14 14:26:47 2019 +0000 |
| tree | 125102a4214decd6fbad07b2afbe4c6a0f709301 | |
| parent | dfb6d250b1c161b1661c9de94aed207909da0342 [diff] |
[VM] Adding regexp lookbehind assertion support. See https://github.com/tc39/proposal-regexp-lookbehind for a high-level description of the feature and examples. This is one of the features requested in https://github.com/dart-lang/sdk/issues/34935. This work takes the feature as present in the v8 engine and appropriately merges it into our irregexp fork. Notable changes to the irregexp codebase to introduce this feature: ----- We can no longer assume that all matching proceeds forwards, since lookbehind matching proceeds backwards. Similarly, we cannot assume that we can only be at the start of a string if we started matching from that point. The direction of matching must also be taken into consideration when doing bounds checking, which previously assumed the engine would never attempt to look before the start of a string. ----- We may now parse backreferences to captures before the capture they reference, since we parse regular expressions left to right, but lookbehinds perform captures as they evaluate the string from right to left. Since RegExpBackReference objects contain a pointer to their corresponding capture, this means that we may need to create RegExpCapture objects prior to the parsing of the corresponding captured subexpression. Thus, RegExpCapture objects are now only initialized with their index, and the body is set later when the subexpression is encountered and parsed. This means any method that operates on the body of a RegExpCapture can no longer be const, which also affects the rest of the RegExpTree class hierarchy. This also means that we don't have a valid max_match length for backreferences based off the capture body, and must assume they can end up being any length. ----- Change-Id: Iffe0e71b17b1a0c6fea77235e8aee5c093005811 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/94540 Commit-Queue: Stevie Strickland <sstrickl@google.com> Reviewed-by: Martin Kustermann <kustermann@google.com>
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