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| 1 | +/* |
| 2 | + * Copyright 2016-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license. |
| 3 | + */ |
| 4 | +@file:Suppress("UNCHECKED_CAST", "NON_APPLICABLE_CALL_FOR_BUILDER_INFERENCE") // KT-32203 |
| 5 | + |
| 6 | +package kotlinx.coroutines.flow.internal |
| 7 | + |
| 8 | +import kotlinx.coroutines.* |
| 9 | +import kotlinx.coroutines.channels.* |
| 10 | +import kotlinx.coroutines.flow.* |
| 11 | +import kotlinx.coroutines.internal.Symbol |
| 12 | +import kotlinx.coroutines.selects.* |
| 13 | + |
| 14 | +internal fun getNull(): Symbol = NULL // Workaround for JS BE bug |
| 15 | + |
| 16 | +internal suspend inline fun <T1, T2, R> FlowCollector<R>.combineTransformInternal( |
| 17 | + first: Flow<T1>, second: Flow<T2>, |
| 18 | + crossinline transform: suspend FlowCollector<R>.(a: T1, b: T2) -> Unit |
| 19 | +) { |
| 20 | + coroutineScope { |
| 21 | + val firstChannel = asFairChannel(first) |
| 22 | + val secondChannel = asFairChannel(second) |
| 23 | + var firstValue: Any? = null |
| 24 | + var secondValue: Any? = null |
| 25 | + var firstIsClosed = false |
| 26 | + var secondIsClosed = false |
| 27 | + while (!firstIsClosed || !secondIsClosed) { |
| 28 | + select<Unit> { |
| 29 | + onReceive(firstIsClosed, firstChannel, { firstIsClosed = true }) { value -> |
| 30 | + firstValue = value |
| 31 | + if (secondValue !== null) { |
| 32 | + transform(getNull().unbox(firstValue), getNull().unbox(secondValue) as T2) |
| 33 | + } |
| 34 | + } |
| 35 | + |
| 36 | + onReceive(secondIsClosed, secondChannel, { secondIsClosed = true }) { value -> |
| 37 | + secondValue = value |
| 38 | + if (firstValue !== null) { |
| 39 | + transform(getNull().unbox(firstValue) as T1, getNull().unbox(secondValue) as T2) |
| 40 | + } |
| 41 | + } |
| 42 | + } |
| 43 | + } |
| 44 | + } |
| 45 | +} |
| 46 | + |
| 47 | +@PublishedApi |
| 48 | +internal fun <T, R> combine( |
| 49 | + vararg flows: Flow<T>, |
| 50 | + arrayFactory: () -> Array<T?>, |
| 51 | + transform: suspend FlowCollector<R>.(Array<T>) -> Unit |
| 52 | +): Flow<R> = flow { |
| 53 | + coroutineScope { |
| 54 | + val size = flows.size |
| 55 | + val channels = |
| 56 | + Array(size) { asFairChannel(flows[it]) } |
| 57 | + val latestValues = arrayOfNulls<Any?>(size) |
| 58 | + val isClosed = Array(size) { false } |
| 59 | + |
| 60 | + // See flow.combine(other) for explanation. |
| 61 | + while (!isClosed.all { it }) { |
| 62 | + select<Unit> { |
| 63 | + for (i in 0 until size) { |
| 64 | + onReceive(isClosed[i], channels[i], { isClosed[i] = true }) { value -> |
| 65 | + latestValues[i] = value |
| 66 | + if (latestValues.all { it !== null }) { |
| 67 | + val arguments = arrayFactory() |
| 68 | + for (index in 0 until size) { |
| 69 | + arguments[index] = NULL.unbox(latestValues[index]) |
| 70 | + } |
| 71 | + transform(arguments as Array<T>) |
| 72 | + } |
| 73 | + } |
| 74 | + } |
| 75 | + } |
| 76 | + } |
| 77 | + } |
| 78 | +} |
| 79 | + |
| 80 | +private inline fun SelectBuilder<Unit>.onReceive( |
| 81 | + isClosed: Boolean, |
| 82 | + channel: ReceiveChannel<Any>, |
| 83 | + crossinline onClosed: () -> Unit, |
| 84 | + noinline onReceive: suspend (value: Any) -> Unit |
| 85 | +) { |
| 86 | + if (isClosed) return |
| 87 | + channel.onReceiveOrNull { |
| 88 | + // TODO onReceiveOrClosed when boxing issues are fixed |
| 89 | + if (it === null) onClosed() |
| 90 | + else onReceive(it) |
| 91 | + } |
| 92 | +} |
| 93 | + |
| 94 | +// Channel has any type due to onReceiveOrNull. This will be fixed after receiveOrClosed |
| 95 | +private fun CoroutineScope.asFairChannel(flow: Flow<*>): ReceiveChannel<Any> = produce { |
| 96 | + val channel = channel as ChannelCoroutine<Any> |
| 97 | + flow.collect { value -> |
| 98 | + return@collect channel.sendFair(value ?: NULL) |
| 99 | + } |
| 100 | +} |
| 101 | + |
| 102 | +internal fun <T1, T2, R> zipImpl(flow: Flow<T1>, flow2: Flow<T2>, transform: suspend (T1, T2) -> R): Flow<R> = unsafeFlow { |
| 103 | + coroutineScope { |
| 104 | + val first = asChannel(flow) |
| 105 | + val second = asChannel(flow2) |
| 106 | + /* |
| 107 | + * This approach only works with rendezvous channel and is required to enforce correctness |
| 108 | + * in the following scenario: |
| 109 | + * ``` |
| 110 | + * val f1 = flow { emit(1); delay(Long.MAX_VALUE) } |
| 111 | + * val f2 = flowOf(1) |
| 112 | + * f1.zip(f2) { ... } |
| 113 | + * ``` |
| 114 | + * |
| 115 | + * Invariant: this clause is invoked only when all elements from the channel were processed (=> rendezvous restriction). |
| 116 | + */ |
| 117 | + (second as SendChannel<*>).invokeOnClose { |
| 118 | + if (!first.isClosedForReceive) first.cancel(AbortFlowException()) |
| 119 | + } |
| 120 | + |
| 121 | + val otherIterator = second.iterator() |
| 122 | + try { |
| 123 | + first.consumeEach { value -> |
| 124 | + if (!otherIterator.hasNext()) { |
| 125 | + return@consumeEach |
| 126 | + } |
| 127 | + emit(transform(NULL.unbox(value), NULL.unbox(otherIterator.next()))) |
| 128 | + } |
| 129 | + } catch (e: AbortFlowException) { |
| 130 | + // complete |
| 131 | + } finally { |
| 132 | + if (!second.isClosedForReceive) second.cancel(AbortFlowException()) |
| 133 | + } |
| 134 | + } |
| 135 | +} |
| 136 | + |
| 137 | +// Channel has any type due to onReceiveOrNull. This will be fixed after receiveOrClosed |
| 138 | +private fun CoroutineScope.asChannel(flow: Flow<*>): ReceiveChannel<Any> = produce { |
| 139 | + flow.collect { value -> |
| 140 | + return@collect channel.send(value ?: NULL) |
| 141 | + } |
| 142 | +} |
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