pjfanning opened a new pull request, #2838:
URL: https://github.com/apache/pekko/pull/2838
`ByteArrayIterator.getShort/getInt/getLong` called `next()` 2/4/8 times
individually. `ByteString.lastIndexOf` fell back to element-by-element scan.
`ByteString.hashCode` was recomputed on every call despite immutability.
## SWARUtil — extended VarHandle infrastructure
- Added `byteArrayViewVarHandle` instances for `short` (BE+LE), `int`
(BE+LE), `long` (LE)
- Added `getShort(array, index, bigEndian)`, `getInt(...)`, `getLong(array,
index, bigEndian)` using VarHandle with manual bit-shift fallback
- Added `getLastIndex(word)` — finds rightmost byte match in SWAR result
using `numberOfTrailingZeros`
## ByteIterator (Scala 2.13 + Scala 3) — VarHandle-based multi-byte reads
Overrides `getShort`/`getInt`/`getLong` in `ByteArrayIterator` to read
directly from the underlying byte array via `SWARUtil` in a single VarHandle
call. On Java 17 the JIT lowers these to a single native load, vs. 8 sequential
bounds-checked element reads before.
```scala
// Before: 8 calls to next(), each bounds-checking array(from++)
override def getLong(implicit byteOrder: ByteOrder): Long = ...
// After: one VarHandle load directly into a long
override def getLong(implicit byteOrder: ByteOrder): Long = {
if (len < 8) throw new NoSuchElementException("next on empty iterator")
val result = SWARUtil.getLong(array, from, byteOrder ==
ByteOrder.BIG_ENDIAN)
from += 8
result
}
```
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