| /* |
| * 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. |
| */ |
| |
| #ifndef _DECAF_UTIL_CONCURRENT_FUTURE_H_ |
| #define _DECAF_UTIL_CONCURRENT_FUTURE_H_ |
| |
| namespace decaf { |
| namespace util { |
| namespace concurrent { |
| |
| /** |
| * A Future represents the result of an asynchronous computation. Methods |
| * are provided to check if the computation is complete, to wait for its |
| * completion, and to retrieve the result of the computation. The result |
| * can only be retrieved using method get when the computation has |
| * completed, blocking if necessary until it is ready. Cancellation is |
| * performed by the cancel method. Additional methods are provided to |
| * determine if the task completed normally or was canceled. Once a |
| * computation has completed, the computation cannot be canceled. If you |
| * would like to use a Future for the sake of cancellability but not |
| * provide a usable result, you can declare types of the form Future<void*> |
| * and return null as a result of the underlying task. |
| */ |
| template<typename V> |
| class Future { |
| public: |
| |
| virtual ~Future() {} |
| |
| /** |
| * Attempts to cancel execution of this task. This attempt will fail if the |
| * task has already completed, has already been canceled, or could not be |
| * canceled for some other reason. If successful, and this task has not |
| * started when cancel is called, this task should never run. If the task |
| * has already started, then the mayInterruptIfRunning parameter determines |
| * whether the thread executing this task should be interrupted in an attempt |
| * to stop the task. |
| * <p> |
| * After this method returns, subsequent calls to isDone() will always return |
| * true. Subsequent calls to isCancelled() will always return true if this |
| * method returned true. |
| * <p> |
| * @param mayInterruptIfRunning - true if the thread executing this task should |
| * be interrupted; otherwise, in-progress tasks are allowed to complete. |
| * @returns false if the task could not be canceled, typically because it has |
| * already completed normally; true otherwise |
| */ |
| bool cancel( bool mayInterruptIfRunning ) = 0; |
| |
| /** |
| * Returns true if this task was canceled before it completed normally. |
| * @returns true if this task was canceled before it completed |
| */ |
| bool isCancelled() const = 0; |
| |
| /** |
| * Returns true if this task completed. Completion may be due to normal termination, |
| * an exception, or cancellation -- in all of these cases, this method will return |
| * true. |
| * @returns true if this task completed |
| */ |
| bool isDone() const = 0; |
| |
| /** |
| * Waits if necessary for the computation to complete, and then retrieves its result. |
| * @returns the computed result. |
| * @throws CancellationException - if the computation was canceled |
| * @throws ExecutionException - if the computation threw an exception |
| * @throws InterruptedException - if the current thread was interrupted while waiting |
| */ |
| V get() throw( CancellationException, InterruptedException, ExecutionException ) = 0; |
| |
| /** |
| * Waits if necessary for at most the given time for the computation to complete, and |
| * then retrieves its result, if available. |
| * @param timeout - the maximum time to wait |
| * @param unit - the time unit of the timeout argument |
| * @returns the computed result |
| * @throws CancellationException - if the computation was canceled |
| * @throws ExecutionException - if the computation threw an exception |
| * @throws InterruptedException - if the current thread was interrupted while waiting |
| * @throws TimeoutException - if the wait timed out |
| */ |
| V get( long long timeout, TimeUnit unit) |
| throw( InterruptedException, ExecutionException, TimeoutException ) = 0; |
| |
| }; |
| |
| }}} |
| |
| #endif /*_DECAF_UTIL_CONCURRENT_FUTURE_H_*/ |