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Merge pull request #19582 from drewhk/wip-19445-simplify-conflate-drewhk

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#19455 Simplify conflate signature for the common case
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drewhk 2016-02-04 20:37:51 +01:00
commit f3073b89e0
21 changed files with 281 additions and 55 deletions
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38
akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala
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@ -915,6 +915,9 @@ trait FlowOps[+Out, +Mat] {
* until the subscriber is ready to accept them. For example a conflate step might average incoming numbers if the
* upstream publisher is faster.
*
* This version of conflate allows to derive a seed from the first element and change the aggregated type to be
* different than the input type. See [[FlowOps.conflate]] for a simpler version that does not change types.
*
* This element only rolls up elements if the upstream is faster, but if the downstream is faster it will not
* duplicate elements.
*
@ -929,12 +932,39 @@ trait FlowOps[+Out, +Mat] {
* @param seed Provides the first state for a conflated value using the first unconsumed element as a start
* @param aggregate Takes the currently aggregated value and the current pending element to produce a new aggregate
*
* See also [[FlowOps.limit]], [[FlowOps.limitWeighted]] [[FlowOps.batch]] [[FlowOps.batchWeighted]]
* See also [[FlowOps.conflate]], [[FlowOps.limit]], [[FlowOps.limitWeighted]] [[FlowOps.batch]] [[FlowOps.batchWeighted]]
*/
def conflate[S](seed: Out ⇒ S)(aggregate: (S, Out) ⇒ S): Repr[S] = andThen(Conflate(seed, aggregate))
def conflateWithSeed[S](seed: Out ⇒ S)(aggregate: (S, Out) ⇒ S): Repr[S] = andThen(Conflate(seed, aggregate))
//FIXME: conflate can be expressed as a batch
//via(Batch(1L, ConstantFun.zeroLong, seed, aggregate).withAttributes(DefaultAttributes.conflate))
/**
* Allows a faster upstream to progress independently of a slower subscriber by conflating elements into a summary
* until the subscriber is ready to accept them. For example a conflate step might average incoming numbers if the
* upstream publisher is faster.
*
* This version of conflate does not change the output type of the stream. See [[FlowOps.conflateWithSeed]] for a
* more flexible version that can take a seed function and transform elements while rolling up.
*
* This element only rolls up elements if the upstream is faster, but if the downstream is faster it will not
* duplicate elements.
*
* '''Emits when''' downstream stops backpressuring and there is a conflated element available
*
* '''Backpressures when''' never
*
* '''Completes when''' upstream completes
*
* '''Cancels when''' downstream cancels
*
* @param aggregate Takes the currently aggregated value and the current pending element to produce a new aggregate
*
* See also [[FlowOps.conflate]], [[FlowOps.limit]], [[FlowOps.limitWeighted]] [[FlowOps.batch]] [[FlowOps.batchWeighted]]
*/
def conflate[O2 >: Out](aggregate: (O2, O2) => O2): Repr[O2] = conflateWithSeed[O2](ConstantFun.scalaIdentityFunction)(aggregate)
/**
* Allows a faster upstream to progress independently of a slower subscriber by aggregating elements into batches
* until the subscriber is ready to accept them. For example a batch step might store received elements in
@ -951,7 +981,7 @@ trait FlowOps[+Out, +Mat] {
*
* '''Cancels when''' downstream cancels
*
* See also [[FlowOps.conflate]], [[FlowOps.batchWeighted]]
* See also [[FlowOps.conflateWithSeed]], [[FlowOps.batchWeighted]]
*
* @param max maximum number of elements to batch before backpressuring upstream (must be positive non-zero)
* @param seed Provides the first state for a batched value using the first unconsumed element as a start
@ -981,7 +1011,7 @@ trait FlowOps[+Out, +Mat] {
*
* '''Cancels when''' downstream cancels
*
* See also [[FlowOps.conflate]], [[FlowOps.batch]]
* See also [[FlowOps.conflateWithSeed]], [[FlowOps.batch]]
*
* @param max maximum weight of elements to batch before backpressuring upstream (must be positive non-zero)
* @param costFn a function to compute a single element weight