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Diffstat (limited to 'app/src/main/kotlin/com/pitchedapps/frost/kotlin/Flyweight.kt')
| -rw-r--r-- | app/src/main/kotlin/com/pitchedapps/frost/kotlin/Flyweight.kt | 174 |
1 files changed, 0 insertions, 174 deletions
diff --git a/app/src/main/kotlin/com/pitchedapps/frost/kotlin/Flyweight.kt b/app/src/main/kotlin/com/pitchedapps/frost/kotlin/Flyweight.kt deleted file mode 100644 index 74765b58..00000000 --- a/app/src/main/kotlin/com/pitchedapps/frost/kotlin/Flyweight.kt +++ /dev/null @@ -1,174 +0,0 @@ -/* - * Copyright 2018 Allan Wang - * - * This program is free software: you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation, either version 3 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program. If not, see <http://www.gnu.org/licenses/>. - */ -package com.pitchedapps.frost.kotlin - -import com.pitchedapps.frost.utils.L -import kotlinx.coroutines.CancellationException -import kotlinx.coroutines.CompletableDeferred -import kotlinx.coroutines.CoroutineExceptionHandler -import kotlinx.coroutines.CoroutineScope -import kotlinx.coroutines.Dispatchers -import kotlinx.coroutines.Job -import kotlinx.coroutines.SupervisorJob -import kotlinx.coroutines.channels.Channel -import kotlinx.coroutines.isActive -import kotlinx.coroutines.launch -import kotlinx.coroutines.selects.select -import java.util.concurrent.ConcurrentHashMap - -/** - * Flyweight to keep track of values so long as they are valid. - * Values that have been fetched within [maxAge] from the time of use will be reused. - * If multiple requests are sent with the same key, then the value should only be fetched once. - * Otherwise, they will be fetched using [fetcher]. - * All requests will stem from the supplied [scope]. - */ -class Flyweight<K, V>( - val scope: CoroutineScope, - val maxAge: Long, - private val fetcher: suspend (K) -> V -) { - - // Receives a key and a pending request - private val actionChannel = Channel<Pair<K, CompletableDeferred<V>>>(Channel.UNLIMITED) - - // Receives a key to invalidate the associated value - private val invalidatorChannel = Channel<K>(Channel.UNLIMITED) - - // Receives a key and the resulting value - private val receiverChannel = Channel<Pair<K, Result<V>>>(Channel.UNLIMITED) - - // Keeps track of keys and associated update times - private val conditionMap: MutableMap<K, Long> = mutableMapOf() - - // Keeps track of keys and associated values - private val resultMap: MutableMap<K, Result<V>> = mutableMapOf() - - // Keeps track of unfulfilled actions - // Note that the explicit type is very important here. See https://youtrack.jetbrains.net/issue/KT-18053 - private val pendingMap: MutableMap<K, MutableList<CompletableDeferred<V>>> = ConcurrentHashMap() - - private val job: Job - - private fun CompletableDeferred<V>.completeWith(result: Result<V>) { - if (result.isSuccess) - complete(result.getOrNull()!!) - else - completeExceptionally(result.exceptionOrNull()!!) - } - - private val errHandler = - CoroutineExceptionHandler { _, throwable -> L.d { "FbAuth failed ${throwable.message}" } } - - init { - job = - scope.launch(Dispatchers.IO + SupervisorJob() + errHandler) { - launch { - while (isActive) { - select<Unit> { - /* - * New request received. Continuation should be fulfilled eventually - */ - actionChannel.onReceive { (key, completable) -> - val lastUpdate = conditionMap[key] - val lastResult = resultMap[key] - // Valid value, retrieved within acceptable time - if (lastResult != null && lastUpdate != null && System.currentTimeMillis() - lastUpdate < maxAge) { - completable.completeWith(lastResult) - } else { - val valueRequestPending = key in pendingMap - pendingMap.getOrPut(key) { mutableListOf() }.add(completable) - if (!valueRequestPending) - fulfill(key) - } - } - /* - * Invalidator received. Existing result associated with key should not be used. - * Note that any unfulfilled request and future requests should still operate, but with a new value. - */ - invalidatorChannel.onReceive { key -> - if (key !in resultMap) { - // Nothing to invalidate. - // If pending requests exist, they are already in the process of being updated. - return@onReceive - } - conditionMap.remove(key) - resultMap.remove(key) - if (pendingMap[key]?.isNotEmpty() == true) - // Refetch value for pending requests - fulfill(key) - } - /* - * Value request fulfilled. Should now fulfill pending requests - */ - receiverChannel.onReceive { (key, result) -> - conditionMap[key] = System.currentTimeMillis() - resultMap[key] = result - pendingMap.remove(key)?.forEach { - it.completeWith(result) - } - } - } - } - } - } - } - - /* - * Value request received. Should fetch new value using supplied fetcher - */ - private fun fulfill(key: K) { - scope.launch { - val result = runCatching { - fetcher(key) - } - receiverChannel.send(key to result) - } - } - - /** - * Queues the request, and returns a completable once it is sent to a channel. - * The fetcher will only be suspended if the channels are full. - * - * Note that if the job is already inactive, a cancellation exception will be thrown. - * The message may default to the message for all completables under a cancelled job - */ - fun fetch(key: K): CompletableDeferred<V> { - val completable = CompletableDeferred<V>(job) - if (!job.isActive) completable.completeExceptionally(CancellationException("Flyweight is not active")) - else actionChannel.offer(key to completable) - return completable - } - - suspend fun invalidate(key: K) { - invalidatorChannel.send(key) - } - - fun cancel() { - job.cancel() - if (pendingMap.isNotEmpty()) { - val error = CancellationException("Flyweight cancelled") - pendingMap.values.flatten().forEach { it.completeExceptionally(error) } - pendingMap.clear() - } - actionChannel.close() - invalidatorChannel.close() - receiverChannel.close() - conditionMap.clear() - resultMap.clear() - } -} |