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/*
 * 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 org.apache.flink.runtime.state;

import org.apache.flink.util.ExceptionUtils;
import org.apache.flink.util.FutureUtil;

import java.util.concurrent.RunnableFuture;

/**
 * Helpers for {@link StateObject} related code.
 */
public class StateUtil {

	private StateUtil() {
		throw new AssertionError();
	}

	/**
	 * Returns the size of a state object
	 *
	 * @param handle The handle to the retrieved state
	 */
	public static long getStateSize(StateObject handle) {
		return handle == null ? 0 : handle.getStateSize();
	}

	/**
	 * Iterates through the passed state handles and calls discardState() on each handle that is not null. All
	 * occurring exceptions are suppressed and collected until the iteration is over and emitted as a single exception.
	 *
	 * @param handlesToDiscard State handles to discard. Passed iterable is allowed to deliver null values.
	 * @throws Exception exception that is a collection of all suppressed exceptions that were caught during iteration
	 */
	public static void bestEffortDiscardAllStateObjects(
			Iterable handlesToDiscard) throws Exception {

		if (handlesToDiscard != null) {
			Exception exception = null;

			for (StateObject state : handlesToDiscard) {

				if (state != null) {
					try {
						state.discardState();
					}
					catch (Exception ex) {
						exception = ExceptionUtils.firstOrSuppressed(ex, exception);
					}
				}
			}

			if (exception != null) {
				throw exception;
			}
		}
	}

	/**
	 * Discards the given state future by first trying to cancel it. If this is not possible, then
	 * the state object contained in the future is calculated and afterwards discarded.
	 *
	 * @param stateFuture to be discarded
	 * @throws Exception if the discard operation failed
	 */
	public static void discardStateFuture(RunnableFuture stateFuture) throws Exception {
		if (null != stateFuture) {
			if (!stateFuture.cancel(true)) {
				StateObject stateObject = FutureUtil.runIfNotDoneAndGet(stateFuture);

				if (null != stateObject) {
					stateObject.discardState();
				}
			}
		}
	}
}