pjfanning opened a new pull request, #1443:
URL: https://github.com/apache/poi/pull/1443
Follow-up to the regex backtracking fixes (#1437, #1440).
Repro: with `setUse4DigitYearsInAllDateFormats(true)`, formatting a cell
whose format is `"yy/".repeat(50_000)` throws `StackOverflowError`. The format
string can come from styles.xml or an HSSF FORMAT record.
Cause: `adjustTo4DigitYearsIfConfigured` recursed once per `yy`. Each call
also ran `indexOf("yyy")` and `indexOf("yyyy")` over the whole rest of the
format and copied it with `substring`.
Fix: a loop over the `yy` occurrences with `startsWith` checks at each one.
As before:
- `yyyy` is kept as it is.
- `yy` becomes `yyyy`.
- A `yyy` leaves the rest of the format unchanged.
Equivalence: old and new give identical output for all 7.2M strings up to
length 14 over `y`, `Y`, `/`. The new version takes about 1 ms on 150k chars.
Tests: added `testAdjustTo4DigitYearsWithLongFormat`, which throws
`StackOverflowError` before the change and passes after, and a `yy/yyy/yy` case
for the existing 3-digit-year behaviour. `TestDataFormatter` and
`TestHSSFDataFormatter` pass.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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