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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.mina.filter.codec;

import org.apache.mina.core.buffer.IoBuffer;
import org.apache.mina.core.session.IoSession;

/**
 * Decodes binary or protocol-specific data into higher-level message objects.
 * MINA invokes {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}
 * method with read data, and then the decoder implementation puts decoded
 * messages into {@link ProtocolDecoderOutput} by calling
 * {@link ProtocolDecoderOutput#write(Object)}.
 * 
 * Please refer to
 * TextLineDecoder
 * example.
 *
 * @author Apache MINA Project
 * 
 * @see ProtocolDecoderException
 */
public interface ProtocolDecoder {
    /**
     * Decodes binary or protocol-specific content into higher-level message objects.
     * MINA invokes {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}
     * method with read data, and then the decoder implementation puts decoded
     * messages into {@link ProtocolDecoderOutput}.
     *
     * @param session The current Session
     * @param in the buffer to decode
     * @param out The {@link ProtocolDecoderOutput} that will receive the decoded message
     * @throws Exception if the read data violated protocol specification
     */
    void decode(IoSession session, IoBuffer in, ProtocolDecoderOutput out) throws Exception;

    /**
     * Invoked when the specified session is closed.  This method is useful
     * when you deal with the protocol which doesn't specify the length of a message
     * such as HTTP response without content-length header. Implement this
     * method to process the remaining data that {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}
     * method didn't process completely.
     *
     * @param session The current Session
     * @param out The {@link ProtocolDecoderOutput} that contains the decoded message
     * @throws Exception if the read data violated protocol specification
     */
    void finishDecode(IoSession session, ProtocolDecoderOutput out) throws Exception;

    /**
     * Releases all resources related with this decoder.
     *
     * @param session The current Session
     * @throws Exception if failed to dispose all resources
     */
    void dispose(IoSession session) throws Exception;
}