001/*
002 * (C) Copyright 2017 Nuxeo (http://nuxeo.com/) and others.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 *
016 * Contributors:
017 *     Florent Guillaume
018 */
019package org.nuxeo.ecm.core.storage.kv;
020
021/**
022 * Key/Value Store.
023 * <p>
024 * This is the interface for a Key/Value store, which stores simple values associated to keys.
025 * <p>
026 * A Key/Value store is thread-safe.
027 *
028 * @since 9.1
029 */
030public interface KeyValueStore {
031
032    /**
033     * Sets the value associated to the key.
034     *
035     * @param key the key
036     * @param value the value, which may be {@code null}
037     */
038    void put(String key, byte[] value);
039
040    /**
041     * Retrieves the value associated to the key.
042     *
043     * @param key the key
044     * @return the value, or {@code null} if there is no value
045     */
046    byte[] get(String key);
047
048    /**
049     * Atomically sets the value associated to the key to the given value if the current value is the expected value.
050     * <p>
051     * Note value comparison is done by value and not by reference.
052     *
053     * @param key the key
054     * @param expected the expected value, which may be {@code null}
055     * @param value the updated value, which may be {@code null}
056     * @return {@code true} if the value was updated, or {@code false} if not (the expected value was not found)
057     */
058    boolean compareAndSet(String key, byte[] expected, byte[] value);
059
060}