001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License.
018 *
019 */
020package org.apache.mina.filter.codec.statemachine;
021
022import org.apache.mina.core.buffer.IoBuffer;
023import org.apache.mina.core.session.IoSession;
024import org.apache.mina.filter.codec.ProtocolDecoderOutput;
025
026/**
027 * Represents a state in a decoder state machine used by 
028 * {@link DecodingStateMachine}.
029 * 
030 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
031 */
032public interface DecodingState {
033    /**
034     * Invoked when data is available for this state.
035     * 
036     * @param in the data to be decoded.
037     * @param out used to write decoded objects.
038     * @return the next state if a state transition was triggered (use 
039     *         <code>this</code> for loop transitions) or <code>null</code> if 
040     *         the state machine has reached its end.
041     * @throws Exception if the read data violated protocol specification.
042     */
043    DecodingState decode(IoBuffer in, ProtocolDecoderOutput out) throws Exception;
044
045    /**
046     * Invoked when the associated {@link IoSession} is closed. This method is 
047     * useful when you deal with protocols which don't specify the length of a 
048     * message (e.g. HTTP responses without <tt>content-length</tt> header). 
049     * Implement this method to process the remaining data that 
050     * {@link #decode(IoBuffer, ProtocolDecoderOutput)} method didn't process 
051     * completely.
052     * 
053     * @param out used to write decoded objects.
054     * @return the next state if a state transition was triggered (use 
055     *         <code>this</code> for loop transitions) or <code>null</code> if 
056     *         the state machine has reached its end.
057     * @throws Exception if the read data violated protocol specification.
058     */
059    DecodingState finishDecode(ProtocolDecoderOutput out) throws Exception;
060}