/*
 *  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.commons.logging.Log log=
        org.apache.commons.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 );
    }
    
}