001/*
002 * Logback: the reliable, generic, fast and flexible logging framework.
003 * Copyright (C) 1999-2026, QOS.ch. All rights reserved.
004 *
005 * This program and the accompanying materials are dual-licensed under
006 * either the terms of the Eclipse Public License v2.0 as published by
007 * the Eclipse Foundation
008 *
009 *   or (per the licensee's choosing)
010 *
011 * under the terms of the GNU Lesser General Public License version 2.1
012 * as published by the Free Software Foundation.
013 */
014package ch.qos.logback.core.encoder;
015
016import ch.qos.logback.core.spi.ContextAware;
017import ch.qos.logback.core.spi.LifeCycle;
018
019/**
020 * Encoders are responsible for transform an incoming event into a byte array
021 * 
022 * @author Ceki Gülcü
023 * @author Joern Huxhorn
024 * @author Maarten Bosteels
025 * 
026 * @param <E> event type
027 * @since 0.9.19
028 */
029public interface Encoder<E> extends ContextAware, LifeCycle {
030
031    /**
032     * Get header bytes. This method is typically called upon opening of an output
033     * stream.
034     * 
035     * @return header bytes. Null values are allowed.
036     */
037    byte[] headerBytes();
038
039    /**
040     * Encode an event as bytes.
041     * 
042     * @param event the event to encode
043     * @return the encoded bytes. Null values are allowed.
044     */
045    byte[] encode(E event);
046
047    /**
048     * Get footer bytes. This method is typically called prior to the closing of the
049     * stream where events are written.
050     * 
051     * @return footer bytes. Null values are allowed.
052     */
053    byte[] footerBytes();
054
055    /**
056     * Returns true if the encoder is stateful, false otherwise.
057     *
058     * <p>A stateful encoder keeps state between invocation of {@link #encode(E event)}
059     * method.</p>
060     *
061     * <p>A stateful encoder may produce different output for the same input event
062     * depending on its internal state. A stateless encoder will always produce
063     * the same output for the same input event.</p>
064     *
065     * @return true if the encoder is stateful, false otherwise.
066     * @since 1.6.4
067     */
068    default boolean isStateful() {
069        return false;
070    }
071}