Vsevolod Tolstopyatov | 44c4c56 | 2019-07-25 16:17:12 +0300 | [diff] [blame] | 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 | } |