org.apache.mina.filter.codec.prefixedstring.PrefixedStringDecoder Maven / Gradle / Ivy
/**
* Copyright 2007-2015, Kaazing Corporation. All rights reserved.
*
* Licensed 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.prefixedstring;
import org.apache.mina.core.buffer.BufferDataException;
import org.apache.mina.core.buffer.IoBuffer;
import org.apache.mina.core.session.IoSession;
import org.apache.mina.filter.codec.CumulativeProtocolDecoder;
import org.apache.mina.filter.codec.ProtocolDecoder;
import org.apache.mina.filter.codec.ProtocolDecoderOutput;
import java.nio.charset.Charset;
/**
* A {@link ProtocolDecoder} which decodes a String using a fixed-length length prefix.
*
* @author Apache MINA Project
*/
public class PrefixedStringDecoder extends CumulativeProtocolDecoder {
public final static int DEFAULT_PREFIX_LENGTH = 4;
public final static int DEFAULT_MAX_DATA_LENGTH = 2048;
private final Charset charset;
private int prefixLength = DEFAULT_PREFIX_LENGTH;
private int maxDataLength = DEFAULT_MAX_DATA_LENGTH;
/**
* @param charset the charset to use for encoding
* @param prefixLength the length of the prefix
* @param maxDataLength maximum number of bytes allowed for a single String
*/
public PrefixedStringDecoder(Charset charset, int prefixLength, int maxDataLength) {
this.charset = charset;
this.prefixLength = prefixLength;
this.maxDataLength = maxDataLength;
}
public PrefixedStringDecoder(Charset charset, int prefixLength) {
this(charset, prefixLength, DEFAULT_MAX_DATA_LENGTH);
}
public PrefixedStringDecoder(Charset charset) {
this(charset, DEFAULT_PREFIX_LENGTH);
}
/**
* Sets the number of bytes used by the length prefix
*
* @param prefixLength the length of the length prefix (1, 2, or 4)
*/
public void setPrefixLength(int prefixLength) {
this.prefixLength = prefixLength;
}
/**
* Gets the length of the length prefix (1, 2, or 4)
*
* @return length of the length prefix
*/
public int getPrefixLength() {
return prefixLength;
}
/**
* Sets the maximum allowed value specified as data length in the incoming data
*
* Useful for preventing an OutOfMemory attack by the peer.
* The decoder will throw a {@link BufferDataException} when data length
* specified in the incoming data is greater than maxDataLength
* The default value is {@link PrefixedStringDecoder#DEFAULT_MAX_DATA_LENGTH}.
*
*
* @param maxDataLength maximum allowed value specified as data length in the incoming data
*/
public void setMaxDataLength(int maxDataLength) {
this.maxDataLength = maxDataLength;
}
/**
* Gets the maximum number of bytes allowed for a single String
*
* @return maximum number of bytes allowed for a single String
*/
public int getMaxDataLength() {
return maxDataLength;
}
protected boolean doDecode(IoSession session, IoBuffer in, ProtocolDecoderOutput out) throws Exception {
if (in.prefixedDataAvailable(prefixLength, maxDataLength)) {
String msg = in.getPrefixedString(prefixLength, charset.newDecoder());
out.write(msg);
return true;
}
return false;
}
}