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Optimise zio.stream.ZStream#takeRight #9398

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Merged
merged 3 commits into from
Jan 5, 2025
Merged

Optimise zio.stream.ZStream#takeRight #9398

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ab664d9
Optimise `zio.stream.ZStream#takeRight`
guizmaii Dec 12, 2024
b19a8c0
Merge branch 'series/2.x' into opt_ZStream_takeRight
guizmaii Jan 5, 2025
c26caf8
Merge branch 'series/2.x' into opt_ZStream_takeRight
kyri-petrou Jan 5, 2025
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41 changes: 20 additions & 21 deletions streams/shared/src/main/scala/zio/stream/ZStream.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -3188,28 +3188,27 @@ final class ZStream[-R, +E, +A] private (val channel: ZChannel[R, Any, Any, Any,
* Takes the last specified number of elements from this stream.
*/
def takeRight(n: => Int)(implicit trace: Trace): ZStream[R, E, A] =
ZStream.succeed(n).flatMap { n =>
if (n <= 0) ZStream.empty
else
new ZStream(
ZChannel.unwrap(
for {
queue <- ZIO.succeed(SingleThreadedRingBuffer[A](n))
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I'm not sure to understand why it was wrapped in a ZIO 🤔

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No clue either 🤷

} yield {
lazy val reader: ZChannel[Any, E, Chunk[A], Any, E, Chunk[A], Unit] = ZChannel.readWithCause(
(in: Chunk[A]) => {
in.foreach(queue.put)
reader
},
ZChannel.refailCause,
(_: Any) => ZChannel.write(queue.toChunk) *> ZChannel.unit
)
new ZStream(
ZChannel.suspend {
val n0 = n
if (n0 <= 0) ZChannel.unit
else {
val queue = SingleThreadedRingBuffer[A](n0)

(self.channel >>> reader)
}
)
)
}
lazy val reader: ZChannel[Any, E, Chunk[A], Any, E, Chunk[A], Unit] =
ZChannel.readWithCause(
in = (in: Chunk[A]) => {
in.foreach(queue.put)
reader
},
halt = ZChannel.refailCause,
done = (_: Any) => ZChannel.write(queue.toChunk) *> ZChannel.unit
)

self.channel >>> reader
}
}
)

/**
* Takes all elements of the stream until the specified predicate evaluates to
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