alhudz opened a new pull request, #1843: URL: https://github.com/apache/commons-lang/pull/1843
`RandomStringUtils.random(int, int, int, boolean, boolean, char[], Random)` bounds consecutive rejected draws with `Math.max(64, gap * 10)`, added in #1638 so that a range with no acceptable value throws instead of hanging. Each draw takes `gapBits` random bits, so a valid range whose acceptable values are sparse accepts a draw with probability as low as `1 / 2^gapBits`, and the cap fires on input the method's own up-front validation has already accepted. Repro: `chars` is 63 `'-'` plus one `'x'`, then `RandomStringUtils.random(100, 0, 64, true, false, chars, new Random(seed))`. Expected: `"xxx...x"` (100 chars). Actual: `gapBits` is 7, so a draw is accepted with probability 1/128 against a cap of 640; 90 of 200 calls threw `IllegalArgumentException: No acceptable code points found in range [0, 64) within 640 attempts.` The `secure()` / `insecure()` / `secureStrong()` `next(...)` overloads and the static `random*` methods go through the same loop. Cause: the cap is sized by `gap`, but the rejection rate depends on the `2^gapBits` sample space. Fix: cap at `64L << gapBits` (and a `long` counter, so a large `chars` array cannot overflow it). A range with at least one acceptable value now exhausts it with probability below `e^-64` per character. A range with no acceptable value still throws: `testOnlyRejectedCodePoints` (`[0xE000, 0xF900)`) throws after 524,288 draws in about 80 ms, and the widest all-rejected range I could build, `[0xE01F0, 0x10FFFF)`, throws in about 0.75 s. `testSparseAcceptableValuesDoNotTripRejectionCap` fails before the change and passes after. The reproducer goes from 90/200 failures to 0/200. - [x] Read the [contribution guidelines](CONTRIBUTING.md) for this project. - [x] Read the [ASF Generative Tooling Guidance](https://www.apache.org/legal/generative-tooling.html) if you use Artificial Intelligence (AI). - [x] I used AI to create any part of, or all of, this pull request. Which AI tool was used to create this pull request, and to what extent did it contribute? Claude Code (Anthropic) found the defect and drafted the patch, the test and this description; I reviewed all of it before submitting. - [x] Run a successful build using the default [Maven](https://maven.apache.org/) goal with `mvn`; that's `mvn` on the command line by itself. - [x] Write unit tests that match behavioral changes, where the tests fail if the changes to the runtime are not applied. This may not always be possible, but it is a best practice. - [x] Write a pull request description that is detailed enough to understand what the pull request does, how, and why. - [x] Each commit in the pull request should have a meaningful subject line and body. Note that a maintainer may squash commits during the merge process. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
