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 java.util.Queue; 023import java.util.concurrent.ConcurrentLinkedQueue; 024 025import org.apache.mina.core.buffer.IoBuffer; 026import org.apache.mina.core.session.IoSession; 027import org.apache.mina.filter.codec.ProtocolDecoder; 028import org.apache.mina.filter.codec.ProtocolDecoderOutput; 029 030/** 031 * {@link ProtocolDecoder} which uses a {@link DecodingState} to decode data. 032 * Use a {@link DecodingStateMachine} as {@link DecodingState} to create 033 * a state machine which can decode your protocol. 034 * <p> 035 * NOTE: This is a stateful decoder. You should create one instance per session. 036 * </p> 037 * 038 * @author <a href="http://mina.apache.org">Apache MINA Project</a> 039 */ 040public class DecodingStateProtocolDecoder implements ProtocolDecoder { 041 private final DecodingState state; 042 043 private final Queue<IoBuffer> undecodedBuffers = new ConcurrentLinkedQueue<IoBuffer>(); 044 045 private IoSession session; 046 047 /** 048 * Creates a new instance using the specified {@link DecodingState} 049 * instance. 050 * 051 * @param state the {@link DecodingState}. 052 * @throws IllegalArgumentException if the specified state is <code>null</code>. 053 */ 054 public DecodingStateProtocolDecoder(DecodingState state) { 055 if (state == null) { 056 throw new IllegalArgumentException("state"); 057 } 058 this.state = state; 059 } 060 061 /** 062 * {@inheritDoc} 063 */ 064 public void decode(IoSession session, IoBuffer in, ProtocolDecoderOutput out) throws Exception { 065 if (this.session == null) { 066 this.session = session; 067 } else if (this.session != session) { 068 throw new IllegalStateException(getClass().getSimpleName() + " is a stateful decoder. " 069 + "You have to create one per session."); 070 } 071 072 undecodedBuffers.offer(in); 073 for (;;) { 074 IoBuffer b = undecodedBuffers.peek(); 075 if (b == null) { 076 break; 077 } 078 079 int oldRemaining = b.remaining(); 080 state.decode(b, out); 081 int newRemaining = b.remaining(); 082 if (newRemaining != 0) { 083 if (oldRemaining == newRemaining) { 084 throw new IllegalStateException(DecodingState.class.getSimpleName() + " must " 085 + "consume at least one byte per decode()."); 086 } 087 } else { 088 undecodedBuffers.poll(); 089 } 090 } 091 } 092 093 /** 094 * {@inheritDoc} 095 */ 096 public void finishDecode(IoSession session, ProtocolDecoderOutput out) throws Exception { 097 state.finishDecode(out); 098 } 099 100 /** 101 * {@inheritDoc} 102 */ 103 public void dispose(IoSession session) throws Exception { 104 // Do nothing 105 } 106}