Flow size- and time-based chunked #2378
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| * Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license. | ||
| */ | ||
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| @file:JvmMultifileClass | ||
| @file:JvmName("FlowKt") | ||
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| package kotlinx.coroutines.flow | ||
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| import kotlinx.coroutines.* | ||
| import kotlinx.coroutines.channels.* | ||
| import kotlinx.coroutines.flow.internal.* | ||
| import kotlinx.coroutines.selects.* | ||
| import kotlin.jvm.* | ||
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| /** | ||
| * Groups emissions from this Flow into lists, according to the chosen ChunkingMethod. Time based implementations | ||
| * collect upstream and emit to downstream in separate coroutines - concurrently, like Flow.buffer() operator. | ||
| * Exact timing of emissions is not guaranteed, as it depends on collector coroutine availability. | ||
| * | ||
| * Size based chunking happens in a single coroutine and is purely sequential. | ||
| * | ||
| * Emissions always preserve order. | ||
| * | ||
| * It is possible to pass custom implementation of ChunkingMethod to chunked() operator. | ||
| * | ||
| * @param method Defines constrains on chunk size and time of its emission. | ||
| */ | ||
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| @ExperimentalCoroutinesApi | ||
| public fun <T> Flow<T>.chunked(method: ChunkingMethod): Flow<List<T>> = with(method) { chunk() } | ||
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| @ExperimentalCoroutinesApi | ||
| public interface ChunkingMethod { | ||
| public fun <T> Flow<T>.chunk(): Flow<List<T>> | ||
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| public companion object { | ||
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| /** | ||
| * Collects upstream and emits to downstream in separate coroutines - as soon as possible. If consumer keeps | ||
| * up with the producer, it emits lists with single element. | ||
| * | ||
| * In case of slow consumer, it groups emissions into bigger lists. When consumer "speeds up", chunks | ||
| * will get smaller. | ||
| * | ||
| * @param maxSize Maximum size of a single chunk. If reached, producer gets suspended until consumer "consumes" | ||
| * a chunk. If maxSize is not specified, then chunk may grow indefinitely until jvm runs out of memory. | ||
| */ | ||
| @Suppress("FunctionName") | ||
| public fun Natural(maxSize: Int = Int.MAX_VALUE): ChunkingMethod = NaturalChunking(maxSize) | ||
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| /** | ||
| * Collects upstream into a buffer and emits its content as a list at every interval. When upstream completes | ||
| * (or is empty), it will try to emit immediately what is left of a chunk, omitting the interval. | ||
| * | ||
| * @param intervalMs Interval between emissions in milliseconds. Every emission happens only after | ||
| * interval passes, unless upstream Flow completes sooner. | ||
| * | ||
| * @param maxSize Maximum size of a single chunk. If reached, producer gets suspended until consumer "consumes" | ||
| * a chunk. If maxSize is not specified, then chunk may grow indefinitely until jvm runs out of memory. | ||
| */ | ||
| @Suppress("FunctionName") | ||
| public fun ByTime(intervalMs: Long, maxSize: Int = Int.MAX_VALUE): ChunkingMethod = | ||
| TimeBased(intervalMs, maxSize) | ||
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| /** | ||
| * Collects upstream into a buffer and emits its content as a list at every interval or when its buffer reaches | ||
| * maximum size. When upstream completes (or is empty), it will try to emit immediately what is left of | ||
| * a chunk, omitting the interval and maxSize constraints. | ||
| * | ||
| * @param intervalMs Interval between emissions in milliseconds. Every emission happens only after | ||
| * interval passes, unless upstream Flow completes sooner or maximum size of a chunk is reached. | ||
| * | ||
| * @param maxSize Maximum size of a single chunk. If reached, it will try to emit a chunk, ignoring the | ||
| * interval constraint. If so happens, time-to-next-chunk gets reset to the interval value. | ||
| */ | ||
| @Suppress("FunctionName") | ||
| public fun ByTimeOrSize(intervalMs: Long, maxSize: Int): ChunkingMethod = TimeOrSizeBased(intervalMs, maxSize) | ||
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| /** | ||
| * Collects upstream into a buffer and emits its content as a list, when specified size is reached. | ||
| * This implementation is purely sequential. If concurrent upstream collection and downstream emissions are | ||
| * desired, one can use a buffer() operator after chunking | ||
| * | ||
| * @param size Exact size of emitted chunks. Only the last emission may be smaller. | ||
| */ | ||
| @Suppress("FunctionName") | ||
| public fun BySize(size: Int): ChunkingMethod = SizeBased(size) | ||
| } | ||
| } | ||
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| private class NaturalChunking(private val maxSize: Int) : ChunkingMethod { | ||
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| init { | ||
| requirePositive(maxSize) | ||
| } | ||
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| override fun <T> Flow<T>.chunk(): Flow<List<T>> = scopedFlow { downstream -> | ||
| val upstream = buffer(maxSize).produceIn(this) | ||
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| while (!upstream.isClosedForReceive) { | ||
| val chunk = upstream.awaitFirstAndDrain(maxSize) | ||
| if (chunk.isNotEmpty()) downstream.emit(chunk) | ||
| } | ||
| } | ||
| } | ||
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| private class TimeBased(private val intervalMs: Long, private val maxSize: Int) : ChunkingMethod { | ||
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| init { | ||
| requirePositive(intervalMs) | ||
| requirePositive(maxSize) | ||
| } | ||
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| override fun <T> Flow<T>.chunk(): Flow<List<T>> = scopedFlow { downstream -> | ||
| val upstreamCollection = Job() | ||
| val upstream = produce<T>(capacity = maxSize) { | ||
| collect { element -> channel.send(element) } | ||
| upstreamCollection.complete() | ||
| } | ||
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| whileSelect { | ||
| upstreamCollection.onJoin { | ||
| val chunk = upstream.drain(maxElements = maxSize) | ||
| if (chunk.isNotEmpty()) downstream.emit(chunk) | ||
| false | ||
| } | ||
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| onTimeout(intervalMs) { | ||
| val chunk = upstream.drain(maxElements = maxSize) | ||
| if (chunk.isNotEmpty()) downstream.emit(chunk) | ||
| true | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| private class SizeBased(private val size: Int) : ChunkingMethod { | ||
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| init { | ||
| requirePositive(size) | ||
| } | ||
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| override fun <T> Flow<T>.chunk(): Flow<List<T>> = flow { | ||
| val accumulator = ArrayList<T>(size) | ||
| collect { element -> | ||
| accumulator.add(element) | ||
| if (accumulator.size == size) emit(accumulator.drain()) | ||
| } | ||
| if (accumulator.isNotEmpty()) emit(accumulator) | ||
| } | ||
| } | ||
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| private class TimeOrSizeBased(private val intervalMs: Long, private val maxSize: Int) : ChunkingMethod { | ||
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| init { | ||
| requirePositive(intervalMs) | ||
| requirePositive(maxSize) | ||
| } | ||
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| override fun <T> Flow<T>.chunk(): Flow<List<T>> = scopedFlow { downstream -> | ||
| val emitNowAndMaybeContinue = Channel<Boolean>(capacity = Channel.RENDEZVOUS) | ||
| val elements = produce<T>(capacity = maxSize) { | ||
| collect { element -> | ||
| val hasCapacity = channel.trySend(element).isSuccess | ||
| if (!hasCapacity) { | ||
|
There was a problem hiding this comment. what do you think about size instead of maxSize like SizedBased? when channel reached to size it should be emit |
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| emitNowAndMaybeContinue.send(true) | ||
| channel.send(element) | ||
| } | ||
| } | ||
| emitNowAndMaybeContinue.send(false) | ||
| } | ||
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| whileSelect { | ||
| emitNowAndMaybeContinue.onReceive { shouldContinue -> | ||
| val chunk = elements.drain(maxElements = maxSize) | ||
| if (chunk.isNotEmpty()) downstream.emit(chunk) | ||
| shouldContinue | ||
| } | ||
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| onTimeout(intervalMs) { | ||
| val chunk = elements.drain(maxElements = maxSize) | ||
| if (chunk.isNotEmpty()) downstream.emit(chunk) | ||
| true | ||
| } | ||
| } | ||
| } | ||
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| } | ||
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| private suspend fun <T> ReceiveChannel<T>.awaitFirstAndDrain(maxElements: Int): List<T> = try { | ||
| val first = receive() | ||
| drain(mutableListOf(first), maxElements) | ||
| } catch (e: ClosedReceiveChannelException) { | ||
| emptyList() | ||
| } | ||
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| private tailrec fun <T> ReceiveChannel<T>.drain(acc: MutableList<T> = mutableListOf(), maxElements: Int): List<T> = | ||
| if (acc.size == maxElements) acc | ||
| else { | ||
| val nextValue = tryReceive().getOrElse { error: Throwable? -> error?.let { throw(it) } ?: return acc } | ||
| acc.add(nextValue) | ||
| drain(acc, maxElements) | ||
| } | ||
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| private fun <T> MutableList<T>.drain() = toList().also { this.clear() } | ||
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| private fun requirePositive(size: Int) = require(size > 0) | ||
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| private fun requirePositive(intervalMs: Long) = require(intervalMs > 0) | ||
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This file has been apparently changed on master but not on develop - with PR: Improve readability. #2563