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regexp can match by using a Boyer-Moore-like table. This is done by identifying non-greedy non-capturing loops in the nodes that eat any character one at a time. For example in the middle of the regexp /foo[\s\S]*?bar/ we find such a loop. There is also such a loop implicitly inserted at the start of any non-anchored regexp. When we have found such a loop we look ahead in the nodes to find the set of characters that can come at given distances. For example for the regexp /.?foo/ we know that there are at least 3 characters ahead of us, and the sets of characters that can occur are [any, [f, o], [o]]. We find a range in the lookahead info where the set of characters is reasonably constrained. In our example this is from index 1 to 2 (0 is not constrained). We can now look 3 characters ahead and if we don't find one of [f, o] (the union of [f, o] and [o]) then we can skip forwards by the range size (in this case 2). For Unicode input strings we do the same, but modulo 128. We also look at the first string fed to the regexp and use that to get a hint of the character frequencies in the inputs. This affects the assessment of whether the set of characters is 'reasonably constrained'. We still have the old lookahead mechanism, which uses a wide load of multiple characters followed by a mask and compare to determine whether a match is possible at this point. Review URL: http://codereview.chromium.org/9965010 git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11204 ce2b1a6d-e550-0410-aec6-3dcde31c8c00 |
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| benchmarks | ||
| build | ||
| include | ||
| preparser | ||
| samples | ||
| src | ||
| test | ||
| tools | ||
| .gitignore | ||
| AUTHORS | ||
| ChangeLog | ||
| LICENSE | ||
| LICENSE.strongtalk | ||
| LICENSE.v8 | ||
| LICENSE.valgrind | ||
| Makefile | ||
| SConstruct | ||