1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, 13 * software distributed under the License is distributed on an 14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 15 * KIND, either express or implied. See the License for the 16 * specific language governing permissions and limitations 17 * under the License. 18 * 19 */ 20 package org.apache.mina.codec.delimited; 21 22 import java.nio.ByteBuffer; 23 24 import org.apache.mina.codec.IoBuffer; 25 import org.apache.mina.codec.ProtocolDecoder; 26 import org.apache.mina.codec.ProtocolDecoderException; 27 import org.apache.mina.codec.StatelessProtocolDecoder; 28 import org.apache.mina.codec.delimited.ints.RawInt32; 29 import org.apache.mina.codec.delimited.ints.VarInt; 30 31 /** 32 * Abstract class providing both encoding and decoding methods between a given 33 * type and ByteBuffers. 34 * 35 * <p> 36 * Transcoder is stateless class providing encoding and decoding facilities. 37 * Additionally this abstract requires two methods which allows to determine the 38 * size of a given message and to write it directly to a previously allocated 39 * ByteBuffer. 40 * </p> 41 * 42 * @param <INPUT> 43 * the type of the messages which will be encoded in ByteBuffers and 44 * decoded from ByteBuffers. 45 * 46 * @author <a href="http://mina.apache.org">Apache MINA Project</a> 47 */ 48 public abstract class IoBufferDecoder<INPUT> implements StatelessProtocolDecoder<IoBuffer, INPUT> { 49 /** 50 * Being stateless, this method is left empty 51 * 52 * @see ProtocolDecoder#createDecoderState() 53 */ 54 @Override 55 public final Void createDecoderState() { 56 // stateless ! 57 return null; 58 } 59 60 /** 61 * Decodes a message from a {@link IoBuffer} 62 * 63 * <p> 64 * When a truncated input is given to this method it <b>may</b> return null. 65 * Not all decoder will be able to detect this issue and report it that way. 66 * Thanks to prefixing of messages, decoder will only receive appropriately 67 * sized ByteBuffers. 68 * </p> 69 * 70 * <p> 71 * n.b. The decoders used for the prefixing (i.e. {@link RawInt32} and 72 * {@link VarInt}) <b>have</b> to detect truncated ByteBuffers. 73 * </p> 74 * 75 * @param input 76 * data to be decoded as a TYPE message 77 * @return the decoded message on success, null otherwise 78 * 79 * @throws ProtocolDecoderException 80 */ 81 public abstract INPUT decode(IoBuffer input); 82 83 /** 84 * Decodes a message from a {@link ByteBuffer} 85 * <p> 86 * The actual decoding needs to be implemented in the abstract method 87 * {@link IoBufferDecoder#decode(ByteBuffer)} 88 * </p> 89 */ 90 @Override 91 public final INPUT decode(IoBuffer input, Void context) { 92 return decode(input); 93 } 94 95 /** 96 * Being stateless, this method is left empty 97 * 98 * @see ProtocolDecoder#finishDecode(Object) 99 */ 100 @Override 101 public final void finishDecode(Void context) { 102 // stateless ! 103 } 104 105 }