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.filter.codec.ProtocolDecoderException; 024import org.apache.mina.filter.codec.ProtocolDecoderOutput; 025 026/** 027 * {@link DecodingState} which decodes <code>short</code> values in big-endian 028 * order (high bytes come first). 029 * 030 * @author <a href="http://mina.apache.org">Apache MINA Project</a> 031 */ 032public abstract class ShortIntegerDecodingState implements DecodingState { 033 private int counter; 034 035 /** 036 * {@inheritDoc} 037 */ 038 public DecodingState decode(IoBuffer in, ProtocolDecoderOutput out) throws Exception { 039 int highByte = 0; 040 041 042 while (in.hasRemaining()) { 043 switch (counter) { 044 case 0: 045 highByte = in.getUnsigned(); 046 break; 047 048 case 1: 049 counter = 0; 050 return finishDecode((short) ((highByte << 8) | in.getUnsigned()), out); 051 052 default: 053 throw new InternalError(); 054 } 055 056 counter++; 057 } 058 return this; 059 } 060 061 /** 062 * {@inheritDoc} 063 */ 064 public DecodingState finishDecode(ProtocolDecoderOutput out) throws Exception { 065 throw new ProtocolDecoderException("Unexpected end of session while waiting for a short integer."); 066 } 067 068 /** 069 * Invoked when this state has consumed a complete <code>short</code>. 070 * 071 * @param value the short. 072 * @param out the current {@link ProtocolDecoderOutput} used to write 073 * decoded messages. 074 * @return the next state if a state transition was triggered (use 075 * <code>this</code> for loop transitions) or <code>null</code> if 076 * the state machine has reached its end. 077 * @throws Exception if the read data violated protocol specification. 078 */ 079 protected abstract DecodingState finishDecode(short value, ProtocolDecoderOutput out) throws Exception; 080}