package org.apache.mina.filter.codec.prefixedstring;
import org.apache.mina.common.IoBuffer;
import org.apache.mina.common.IoSession;
import org.apache.mina.filter.codec.ProtocolEncoderAdapter;
import org.apache.mina.filter.codec.ProtocolEncoderOutput;
import org.apache.mina.filter.codec.ProtocolEncoder;
import java.nio.charset.Charset;
/**
* A {@link ProtocolEncoder} which encodes a string
* using a fixed-length length prefix.
*
* @author The Apache MINA Project (dev@mina.apache.org)
* @version $Rev: 591182 $, $Date: 2007-11-02 01:59:27 +0100 (vr, 02 nov 2007) $,
*/
public class PrefixedStringEncoder extends ProtocolEncoderAdapter {
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;
public PrefixedStringEncoder(Charset charset, int prefixLength, int maxDataLength) {
this.charset = charset;
this.prefixLength = prefixLength;
this.maxDataLength = maxDataLength;
}
public PrefixedStringEncoder(Charset charset, int prefixLength) {
this(charset, prefixLength, DEFAULT_MAX_DATA_LENGTH);
}
public PrefixedStringEncoder(Charset charset) {
this(charset, DEFAULT_PREFIX_LENGTH);
}
public PrefixedStringEncoder() {
this(Charset.defaultCharset());
}
/**
* 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) {
if (prefixLength != 1 && prefixLength != 2 && prefixLength != 4) {
throw new IllegalArgumentException("prefixLength: " + 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 number of bytes allowed for encoding a single String
* (including the prefix)
* <p>
* The encoder will throw a {@link IllegalArgumentException} when more bytes
* are needed to encode a String value.
* The default value is {@link PrefixedStringEncoder#DEFAULT_MAX_DATA_LENGTH}.
* </p>
*
* @param maxDataLength maximum number of bytes allowed for encoding a single String
*/
public void setMaxDataLength(int maxDataLength) {
this.maxDataLength = maxDataLength;
}
/**
* Gets the maximum number of bytes allowed for encoding a single String *
*
* @return maximum number of bytes allowed for encoding a single String (prefix included)
*/
public int getMaxDataLength() {
return maxDataLength;
}
public void encode(IoSession session, Object message, ProtocolEncoderOutput out) throws Exception {
String value = (String) message;
IoBuffer buffer = IoBuffer.allocate(value.length()).setAutoExpand(true);
buffer.putPrefixedString(value, prefixLength, charset.newEncoder());
if (buffer.position() > maxDataLength) {
throw new IllegalArgumentException("Data length: " + buffer.position());
}
buffer.flip();
out.write(buffer);
}
}