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| Safe UTF: 64K serialized size | |
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/*
* JBoss, Home of Professional Open Source
* Copyright 2005, JBoss Inc., and individual contributors as indicated
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
/**
*
* A SafeUTF
*
* @author <a href="[email protected]">Tim Fox</a>
* @author <a href="mailto:[email protected]">Adrian Brock</a>
* @version $Revision: 1174 $
*
* $Id: SafeUTF.java 1174 2006-08-02 14:14:32Z timfox $
*
* There is a "bug" in JDK1.4 / 1.5 DataOutputStream.writeUTF()
* which means it does not work with Strings >= 64K serialized size.
* See http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4806007
*
* We work around this by chunking larger strings into smaller pieces.
*
* Note we only support TextMessage and ObjectMessage bodies with serialized length >= 64K
* We DO NOT support Strings written to BytesMessages or StreamMessages or written as keys or values
* in MapMessages, or as String properties or other String fields having serialized length >= 64K
* This is for performance reasons since there is an overhead in coping with large
* Strings
*
*/
public class SafeUTF
{
//Default is 16K chunks
private static final int CHUNK_SIZE = 16 * 1024;
private static final byte NULL = 0;
private static final byte NOT_NULL = 1;
public static SafeUTF instance = new SafeUTF(CHUNK_SIZE);
private int chunkSize;
private int lastReadBufferSize;
public int getLastReadBufferSize()
{
return lastReadBufferSize;
}
public SafeUTF(int chunkSize)
{
this.chunkSize = chunkSize;
}
public void safeWriteUTF(DataOutputStream out, String str) throws IOException
{
if (str == null)
{
out.writeByte(NULL);
}
else
{
int len = str.length();
short numChunks;
if (len == 0)
{
numChunks = 0;
}
else
{
numChunks = (short)(((len - 1) / chunkSize) + 1);
}
out.writeByte(NOT_NULL);
out.writeShort(numChunks);
int i = 0;
while (len > 0)
{
int beginCopy = i * chunkSize;
int endCopy = len <= chunkSize ? beginCopy + len : beginCopy + chunkSize;
String theChunk = str.substring(beginCopy, endCopy);
out.writeUTF(theChunk);
len -= chunkSize;
i++;
}
}
}
public String safeReadUTF(DataInputStream in) throws IOException
{
boolean isNull = in.readByte() == NULL;
if (isNull)
{
return null;
}
short numChunks = in.readShort();
int bufferSize = chunkSize * numChunks;
// special handling for single chunk
if (numChunks == 1)
{
// The text size is likely to be much smaller than the chunkSize
// so set bufferSize to the min of the input stream available
// and the maximum buffer size. Since the input stream
// available() can be <= 0 we check for that and default to
// a small msg size of 256 bytes.
int inSize = in.available();
if (inSize <= 0)
{
inSize = 256;
}
bufferSize = Math.min(inSize, bufferSize);
lastReadBufferSize = bufferSize;
}
StringBuffer buff = new StringBuffer(bufferSize);
for (int i = 0; i < numChunks; i++)
{
String s = in.readUTF();
buff.append(s);
}
return buff.toString();
}
}
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