belliottsmith commented on code in PR #33: URL: https://github.com/apache/cassandra-accord/pull/33#discussion_r1122917309
########## accord-core/src/main/java/accord/utils/async/AsyncResults.java: ########## @@ -0,0 +1,327 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package accord.utils.async; + +import accord.utils.Invariants; + +import java.util.concurrent.Callable; +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; +import java.util.function.BiConsumer; +import java.util.function.Function; + +public class AsyncResults +{ + private AsyncResults() {} + + private static class Result<V> + { + final V value; + final Throwable failure; + + public Result(V value, Throwable failure) + { + this.value = value; + this.failure = failure; + } + } + + static class AbstractResult<V> implements AsyncResult<V> + { + private static final AtomicReferenceFieldUpdater<AbstractResult, Object> STATE = AtomicReferenceFieldUpdater.newUpdater(AbstractResult.class, Object.class, "state"); + + private volatile Object state; + + private static class Listener<V> + { + final BiConsumer<? super V, Throwable> callback; + Listener<V> next; + + public Listener(BiConsumer<? super V, Throwable> callback) + { + this.callback = callback; + } + } + + private void notify(Listener<V> listener, Result<V> result) + { + while (listener != null) + { + listener.callback.accept(result.value, result.failure); + listener = listener.next; + } + } + + boolean trySetResult(Result<V> result) + { + while (true) + { + Object current = state; + if (current instanceof Result) + return false; + Listener<V> listener = (Listener<V>) current; + if (STATE.compareAndSet(this, current, result)) + { + notify(listener, result); + return true; + } + } + } + + boolean trySetResult(V result, Throwable failure) + { + return trySetResult(new Result<>(result, failure)); + } + + private AsyncChain<V> newChain() + { + return new AsyncChains.Head<V>() + { + @Override + protected void start(BiConsumer<? super V, Throwable> callback) + { + AbstractResult.this.addCallback(callback); + } + }; + } + + void setResult(V result, Throwable failure) + { + if (!trySetResult(result, failure)) + throw new IllegalStateException("Result has already been set on " + this); + } + + @Override + public <T> AsyncChain<T> map(Function<? super V, ? extends T> mapper) + { + return newChain().map(mapper); + } + + @Override + public <T> AsyncChain<T> flatMap(Function<? super V, ? extends AsyncChain<T>> mapper) + { + return newChain().flatMap(mapper); + } + + @Override + public AsyncResult<V> addCallback(BiConsumer<? super V, Throwable> callback) + { + Listener<V> listener = null; + while (true) + { + Object current = state; + if (current instanceof Result) + { + Result<V> result = (Result<V>) current; + callback.accept(result.value, result.failure); + return this; + } + if (listener == null) + listener = new Listener<>(callback); + + listener.next = (Listener<V>) current; + if (STATE.compareAndSet(this, current, listener)) + return this; + } + } + + @Override + public boolean isDone() + { + return state instanceof Result; + } + + @Override + public boolean isSuccess() + { + Object current = state; + return current instanceof Result && ((Result) current).failure == null; + } + + private Result<V> getResult() + { + Object current = state; + Invariants.checkState(current instanceof Result); + return (Result<V>) current; + } + + public V result() + { + Result<V> result = getResult(); + if (result.failure != null) + throw new IllegalStateException("Result failed " + result.failure); + return result.value; + } + + public Throwable failure() + { + Result<V> result = getResult(); + if (result.failure == null) + throw new IllegalStateException("Result succeeded"); + return result.failure; + } + } + + static class Chain<V> extends AbstractResult<V> + { + public Chain(AsyncChain<V> chain) + { + chain.begin(this::setResult); + } + } + + public static class Settable<V> extends AbstractResult<V> implements AsyncResult.Settable<V> + { + @Override + public boolean trySuccess(V value) + { + return trySetResult(value, null); + } + + @Override + public boolean tryFailure(Throwable throwable) + { + return trySetResult(null, throwable); + } + } + + static class Immediate<V> implements AsyncResult<V> + { + private final V value; + private final Throwable failure; + + Immediate(V value) + { + this.value = value; + this.failure = null; + } + + Immediate(Throwable failure) + { + this.value = null; + this.failure = failure; + } + + private AsyncChain<V> newChain() + { + return new AsyncChains.Head<V>() + { + @Override + protected void start(BiConsumer<? super V, Throwable> callback) + { + AsyncResults.Immediate.this.addCallback(callback); + } + }; + } + + @Override + public <T> AsyncChain<T> map(Function<? super V, ? extends T> mapper) + { + return newChain().map(mapper); + } + + @Override + public <T> AsyncChain<T> flatMap(Function<? super V, ? extends AsyncChain<T>> mapper) + { + return newChain().flatMap(mapper); + } + + @Override + public AsyncResult<V> addCallback(BiConsumer<? super V, Throwable> callback) + { + callback.accept(value, failure); + return this; + } + + @Override + public boolean isDone() + { + return true; + } + + @Override + public boolean isSuccess() + { + return failure == null; + } + } + + /** + * Creates an AsyncResult for the given chain. This calls begin on the supplied chain + */ + public static <V> AsyncResult<V> forChain(AsyncChain<V> chain) + { + return new Chain<>(chain); + } + + public static <V> AsyncResult<V> success(V value) + { + return new Immediate<>(value); + } + + public static <V> AsyncResult<V> failure(Throwable failure) + { + return new Immediate<>(failure); + } + + public static <V> AsyncResult.Settable<V> settable() + { + return new Settable<>(); + } + + /** + * An AsyncResult that also implements Runnable + * @param <V> + */ + public static class Unscheduled<V> extends AbstractResult<V> implements Runnable Review Comment: `RunnableResult`? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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