dcapwell commented on code in PR #33: URL: https://github.com/apache/cassandra-accord/pull/33#discussion_r1123798003
########## accord-core/src/main/java/accord/utils/async/AsyncResults.java: ########## @@ -0,0 +1,329 @@ +/* + * 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.api.VisibleForImplementation; +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); Review Comment: ```suggestion throw new IllegalStateException("Result failed", result.failure); ``` so we don't loose the stack trace -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
