pjfanning opened a new pull request, #3428:
URL: https://github.com/apache/pekko/pull/3428
Assisted by Claude AI
2. ByteStrings.slice creates two intermediate ByteStrings
File: ByteString.scala:1579-1582
```
override def slice(from: Int, until: Int): ByteString =
if (from <= 0 && until >= length) this
else if (from > length || until <= from) ByteString.empty
else drop(from).dropRight(length - until)
```
This allocates an intermediate ByteStrings from drop(from), then allocates
another from dropRight(...). A direct implementation that locates the start/end
fragments and constructs the result in one pass would halve allocations:
```
override def slice(from: Int, until: Int): ByteString = {
val lo = math.max(from, 0)
val hi = math.min(until, length)
if (lo >= hi) ByteString.empty
else if (lo == 0 && hi == length) this
else {
// find start fragment and offset
var fragIdx = 0
var fragOff = lo
while (fragOff >= bytestrings(fragIdx).length) {
fragOff -= bytestrings(fragIdx).length
fragIdx += 1
}
// collect fragments in range
val builder = new VectorBuilder[ByteString1]
var remaining = hi - lo
var firstOff = fragOff
while (remaining > 0) {
val frag = bytestrings(fragIdx)
val take = math.min(remaining, frag.length - firstOff)
builder += (if (firstOff == 0 && take == frag.length) frag
else ByteString1(frag.bytes, frag.startIndex + firstOff,
take))
remaining -= take
fragIdx += 1
firstOff = 0
}
ByteStrings(builder.result(), hi - lo)
}
}
```
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