gh-149079: Fix O(n^2) canonical ordering in unicodedata.normalize()#149080
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sethmlarson wants to merge 1 commit intopython:mainfrom
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gh-149079: Fix O(n^2) canonical ordering in unicodedata.normalize()#149080sethmlarson wants to merge 1 commit intopython:mainfrom
sethmlarson wants to merge 1 commit intopython:mainfrom
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…ze() Replace the insertion sort used for canonical ordering of combining characters with a hybrid approach: insertion sort for short runs (< 20) and counting sort for longer runs, reducing worst-case complexity from O(n^2) to O(n). This prevents denial of service via crafted Unicode strings with many combining characters in alternating CCC order. Co-authored-by: Seokchan Yoon <13852925+ch4n3-yoon@users.noreply.github.com>
sethmlarson
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Reviewers: Note that there are pending changes from previous reviews. |
maurycy
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Apr 27, 2026
| self.assertEqual(self.db.normalize('NFC', a), b) | ||
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| def test_long_combining_mark_run(self): | ||
| # GH-XXXXX: avoid quadratic canonical ordering. |
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- # GH-XXXXX: avoid quadratic canonical ordering.
+ # gh-149079: avoid quadratic canonical ordering.| self.assertEqual(self.db.normalize("NFKC", payload), nfc) | ||
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| def test_combining_mark_run_fast_paths(self): | ||
| # GH-XXXXX: cover short runs and already-sorted long runs. |
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- # GH-XXXXX: cover short runs and already-sorted long runs.
+ # gh-149079: cover short runs and already-sorted long runs.|
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| if (run_length > sortbuflen) { | ||
| Py_UCS4 *new_sortbuf = PyMem_Realloc(sortbuf, | ||
| run_length * sizeof(Py_UCS4)); |
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Maybe PyMem_Resize instead of calculating manually?
Lines 58 to 60 in 005555a
serhiy-storchaka
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Apr 28, 2026
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There is a potential for optimization, but in general LGTM. 👍
| Py_ssize_t i, o, osize; | ||
| int kind; | ||
| const void *data; | ||
| int input_kind, result_kind; |
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Why not reuse the same variable?
| data = PyUnicode_DATA(result); | ||
| result_kind = PyUnicode_KIND(result); | ||
| result_data = PyUnicode_DATA(result); | ||
| length = PyUnicode_GET_LENGTH(result); |
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Ideas for optimization:
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Replace the insertion sort used for canonical ordering of combining characters with a hybrid approach: insertion sort for short runs (< 20) and counting sort for longer runs, reducing worst-case complexity from O(n^2) to O(n). This prevents denial of service via crafted Unicode strings with many combining characters with a large number of inversions in combing class order.
unicodedata.normalize("NFC")canonical ordering #149079