[PR] ByteString performance improvements (small) [pekko]

["pjfanning (via GitHub)" <gi...@apache.org>]

pjfanning opened a new pull request, #3427:
URL: https://github.com/apache/pekko/pull/3427

   Assisted by Claude AI.
   
   These 2 low impact changes should have a reasonable perf benefit.
   
   1. ByteStrings.iterator uses LazyList — significant overhead
   
   File: ByteString.scala:1458
   override def iterator: ByteIterator.MultiByteArrayIterator =
     ByteIterator.MultiByteArrayIterator(bytestrings.to(LazyList).map { _.iterator })
   
   LazyList has per-element thunk allocation and synchronization overhead. Since bytestrings is already a Vector (random-access), a plain Iterator is sufficient:
   
   override def iterator: ByteIterator.MultiByteArrayIterator =
     ByteIterator.MultiByteArrayIterator(bytestrings.iterator.map(_.iterator))
   
   This eliminates lazy evaluation machinery that buys nothing here — the fragments are already materialized in the Vector.
   
   ByteStrings.iterator: Replaced bytestrings.to(LazyList).map(_.iterator) with bytestrings.iterator.map(_.iterator).toList. The LazyList allocated thunks for each element access despite the fragments already being materialized in the Vector. A plain List is a LinearSeq (which MultiByteArrayIterator requires) and avoids the per-element lazy evaluation overhead.
   
   2. ByteStrings.map: Changed bs(i) to bs.byteAtUnchecked(i). Since the loop already constrains i to 0 until bs.length, the bounds check in ByteString1.apply was redundant. byteAtUnchecked skips the checkRangeConvert call (bounds check + offset arithmetic) on every byte.
   


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Re: [PR] ByteString performance improvements (small) [pekko]

["pjfanning (via GitHub)" <gi...@apache.org>]

pjfanning merged PR #3427:
URL: https://github.com/apache/pekko/pull/3427


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