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Posted to notifications@pekko.apache.org by "pjfanning (via GitHub)" <gi...@apache.org> on 2026/04/19 07:41:29 UTC
[PR] Fix early-exit bound in indexOf(elem, from, to) [pekko]
pjfanning opened a new pull request, #2876:
URL: https://github.com/apache/pekko/pull/2876
After scanning the tail bytes (remainder < 8), `ByteString1C` and `ByteString1` both checked `offset == length` instead of `offset >= toIndex` to decide whether to skip the SWAR loop. When `toIndex < length` and the entire search range fits in the tail bytes, the SWAR loop was entered unnecessarily (with `longCount == 0`), missing the early exit.
Not a correctness bug — `longCount` is 0 so the loop body never executes — but a missed optimization.
## Changes
- **`ByteString1C.indexOf(Byte, from, to)`** (~line 289): `offset == length` → `offset >= toIndex`
- **`ByteString1.indexOf(Byte, from, to)`** (~line 672): same fix
## Tests
Added cases to `"indexOf from/to"` in `ByteStringSpec` targeting the exact path: `ByteString` with `length > 8`, search range with `toIndex < length` and `searchLength < 8` (all in tail bytes, `longCount == 0`). Covers both `ByteString1C` (compact) and `ByteString1` (with `startIndex` offset).
```scala
// length=26, search range [0,5): searchLength=5 < 8, toIndex=5 < length=26
val bs = ByteString1.fromString("abcdefghijklmnopqrstuvwxyz").compact
bs.indexOf('e'.toByte, 0, 5) // 4 — last in-range hit
bs.indexOf('f'.toByte, 0, 5) // -1 — exactly at toIndex, out of range
bs.indexOf('z'.toByte, 0, 5) // -1 — well beyond toIndex
```
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Re: [PR] Fix early-exit bound in indexOf(elem, from, to) [pekko]
Posted by "pjfanning (via GitHub)" <gi...@apache.org>.
pjfanning merged PR #2876:
URL: https://github.com/apache/pekko/pull/2876
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