dcapwell commented on code in PR #17: URL: https://github.com/apache/cassandra-accord/pull/17#discussion_r1110274033
########## accord-core/src/main/java/accord/utils/async/AsyncResults.java: ########## @@ -0,0 +1,368 @@ +/* + * 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 com.google.common.base.Preconditions; + +import java.util.List; +import java.util.concurrent.*; +import java.util.concurrent.atomic.AtomicReference; +import java.util.concurrent.atomic.AtomicReferenceFieldUpdater; +import java.util.function.BiConsumer; +import java.util.function.BiFunction; +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)); + } + + void setResult(Result<V> result) + { + if (!trySetResult(result)) + throw new IllegalStateException("Result has already been set on " + this); + } + + private AsyncChain<V> newChain() + { + return new AsyncChains.Head<V>() + { + @Override + public void begin(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 null; + } + 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; + } + } + + 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 + public void begin(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<V> ofCallable(Executor executor, Callable<V> callable) + { + Settable<V> result = new Settable<V>(); + executor.execute(() -> { + try + { + result.trySuccess(callable.call()); + } + catch (Exception e) + { + result.tryFailure(e); + } + }); + return result; + } + + public static AsyncResult<Void> ofRunnable(Executor executor, Runnable runnable) + { + Settable<Void> result = new Settable<Void>(); + executor.execute(() -> { + try + { + runnable.run(); + result.trySuccess(null); + } + catch (Exception e) + { + result.tryFailure(e); + } + }); + return result; + } + + public static <V> AsyncResult.Settable<V> settable() + { + return new Settable<>(); + } + + public static <V> AsyncChain<List<V>> all(List<AsyncChain<V>> results) + { + Preconditions.checkArgument(!results.isEmpty()); + return new AsyncChainCombiner.All<>(results); + } + + public static <V> AsyncChain<V> reduce(List<AsyncChain<V>> results, BiFunction<V, V, V> reducer) + { + Preconditions.checkArgument(!results.isEmpty()); + if (results.size() == 1) + return results.get(0); + return new AsyncChainCombiner.Reduce<>(results, reducer); + } + + public static <V> V getBlocking(AsyncResult<V> asyncResult) throws InterruptedException, ExecutionException + { + AtomicReference<Result<V>> callbackResult = new AtomicReference<>(); + CountDownLatch latch = new CountDownLatch(1); + asyncResult.addCallback((result, failure) -> { + callbackResult.set(new Result<>(result, failure)); + latch.countDown(); + }); + + latch.await(); + Result<V> result = callbackResult.get(); + if (result.failure == null) return result.value; + else throw new ExecutionException(result.failure); + } + + public static <V> V getBlocking(AsyncResult<V> asyncResult, long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException + { + AtomicReference<Result<V>> callbackResult = new AtomicReference<>(); + CountDownLatch latch = new CountDownLatch(1); + asyncResult.addCallback((result, failure) -> { + callbackResult.set(new Result(result, failure)); + latch.countDown(); + }); + + if (!latch.await(timeout, unit)) + throw new TimeoutException(); + Result<V> result = callbackResult.get(); + if (result.failure == null) return result.value; + else throw new ExecutionException(result.failure); + } + + public static <V> V getUninterruptibly(AsyncResult<V> asyncResult) + { + try + { + return getBlocking(asyncResult); + } + catch (ExecutionException | InterruptedException e) + { + throw new RuntimeException(e); Review Comment: fixed in `immutable-state` -- This is an automated message from the Apache Git Service. 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