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Tomcat example source code file (UTF8Decoder.java)

This example Tomcat source code file (UTF8Decoder.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Tomcat tags/keywords

b2cconverter, charchunk, conversion, conversion, convert, convert, eof, error, io, ioexception, ioexception, utf8decoder, utf8decoder

The Tomcat UTF8Decoder.java source code

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.tomcat.util.buf;

import java.io.IOException;

/**
 * Moved from ByteChunk - code to convert from UTF8 bytes to chars.
 * Not used in the current tomcat3.3 : the performance gain is not very
 * big if the String is created, only if we avoid that and work only
 * on char[]. Until than, it's better to be safe. ( I tested this code
 * with 2 and 3 bytes chars, and it works fine in xerces )
 * 
 * Cut from xerces' UTF8Reader.copyMultiByteCharData() 
 *
 * @author Costin Manolache
 * @author ( Xml-Xerces )
 */
public final class UTF8Decoder extends B2CConverter {
    
    
    private static org.apache.juli.logging.Log log=
        org.apache.juli.logging.LogFactory.getLog(UTF8Decoder.class );
    
    // may have state !!
    
    public UTF8Decoder() {

    }
    
    public void recycle() {
    }

    public void convert(ByteChunk mb, CharChunk cb )
	throws IOException
    {
	int bytesOff=mb.getOffset();
	int bytesLen=mb.getLength();
	byte bytes[]=mb.getBytes();
	
	int j=bytesOff;
	int end=j+bytesLen;

	while( j< end ) {
	    int b0=0xff & bytes[j];

	    if( (b0 & 0x80) == 0 ) {
		cb.append((char)b0);
		j++;
		continue;
	    }
	    
	    // 2 byte ?
	    if( j++ >= end ) {
		// ok, just ignore - we could throw exception
		throw new IOException( "Conversion error - EOF " );
	    }
	    int b1=0xff & bytes[j];
	    
	    // ok, let's the fun begin - we're handling UTF8
	    if ((0xe0 & b0) == 0xc0) { // 110yyyyy 10xxxxxx (0x80 to 0x7ff)
		int ch = ((0x1f & b0)<<6) + (0x3f & b1);
		if(debug>0)
		    log("Convert " + b0 + " " + b1 + " " + ch + ((char)ch));
		
		cb.append((char)ch);
		j++;
		continue;
	    }
	    
	    if( j++ >= end ) 
		return ;
	    int b2=0xff & bytes[j];
	    
	    if( (b0 & 0xf0 ) == 0xe0 ) {
		if ((b0 == 0xED && b1 >= 0xA0) ||
		    (b0 == 0xEF && b1 == 0xBF && b2 >= 0xBE)) {
		    if(debug>0)
			log("Error " + b0 + " " + b1+ " " + b2 );

		    throw new IOException( "Conversion error 2"); 
		}

		int ch = ((0x0f & b0)<<12) + ((0x3f & b1)<<6) + (0x3f & b2);
		cb.append((char)ch);
		if(debug>0)
		    log("Convert " + b0 + " " + b1+ " " + b2 + " " + ch +
			((char)ch));
		j++;
		continue;
	    }

	    if( j++ >= end ) 
		return ;
	    int b3=0xff & bytes[j];

	    if (( 0xf8 & b0 ) == 0xf0 ) {
		if (b0 > 0xF4 || (b0 == 0xF4 && b1 >= 0x90)) {
		    if(debug>0)
			log("Convert " + b0 + " " + b1+ " " + b2 + " " + b3);
		    throw new IOException( "Conversion error ");
		}
		int ch = ((0x0f & b0)<<18) + ((0x3f & b1)<<12) +
		    ((0x3f & b2)<<6) + (0x3f & b3);

		if(debug>0)
		    log("Convert " + b0 + " " + b1+ " " + b2 + " " + b3 + " " +
			ch + ((char)ch));

		if (ch < 0x10000) {
		    cb.append( (char)ch );
		} else {
		    cb.append((char)(((ch-0x00010000)>>10)+
						   0xd800));
		    cb.append((char)(((ch-0x00010000)&0x3ff)+
						   0xdc00));
		}
		j++;
		continue;
	    } else {
		// XXX Throw conversion exception !!!
		if(debug>0)
		    log("Convert " + b0 + " " + b1+ " " + b2 + " " + b3);
		throw new IOException( "Conversion error 4" );
	    }
	}
    }

    private static int debug=1;
    void log(String s ) {
        if (log.isDebugEnabled())
            log.debug("UTF8Decoder: " + s );
    }
    
}

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