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/*
 *  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.CharArrayWriter;
import java.io.IOException;
import java.io.Writer;
import java.util.BitSet;

/** Efficient implementation for encoders.
 *  This class is not thread safe - you need one encoder per thread.
 *  The encoder will save and recycle the internal objects, avoiding
 *  garbage.
 * 
 *  You can add extra characters that you want preserved, for example
 *  while encoding a URL you can add "/".
 *
 *  @author Costin Manolache
 */
public final class UEncoder {

    private static final org.apache.juli.logging.Log log=
        org.apache.juli.logging.LogFactory.getLog(UEncoder.class );
    
    // Not static - the set may differ ( it's better than adding
    // an extra check for "/", "+", etc
    private BitSet safeChars=null;
    private C2BConverter c2b=null;
    private ByteChunk bb=null;

    private String encoding="UTF8";
    
    public UEncoder() {
        initSafeChars();
    }

    public void setEncoding( String s ) {
        encoding=s;
    }

    public void addSafeCharacter( char c ) {
        safeChars.set( c );
    }


    /** URL Encode string, using a specified encoding.
     *
     * @param buf The writer
     * @param s string to be encoded
     * @throws IOException If an I/O error occurs
     */
    public void urlEncode( Writer buf, String s )
            throws IOException {
        if( c2b==null ) {
            bb=new ByteChunk(16); // small enough.
            c2b=new C2BConverter( bb, encoding );
        }

        for (int i = 0; i < s.length(); i++) {
            int c = s.charAt(i);
            if( safeChars.get( c ) ) {
                if(log.isDebugEnabled())
                    log.debug("Encoder: Safe: " + (char)c);
                buf.write((char)c);
            } else {
                if(log.isDebugEnabled())
                    log.debug("Encoder: Unsafe:  " + (char)c);
                c2b.convert( (char)c );
                
                // "surrogate" - UTF is _not_ 16 bit, but 21 !!!!
                // ( while UCS is 31 ). Amazing...
                if (c >= 0xD800 && c <= 0xDBFF) {
                    if ( (i+1) < s.length()) {
                        int d = s.charAt(i+1);
                        if (d >= 0xDC00 && d <= 0xDFFF) {
                            if(log.isDebugEnabled())
                                log.debug("Encoder: Unsafe:  " + c);
                            c2b.convert( (char)d);
                            i++;
                        }
                    }
                }

                c2b.flushBuffer();
                
                urlEncode( buf, bb.getBuffer(), bb.getOffset(),
                           bb.getLength() );
                bb.recycle();
            }
        }
    }

    /**
     */
    public void urlEncode( Writer buf, byte bytes[], int off, int len)
            throws IOException {
        for( int j=off; j< len; j++ ) {
            buf.write( '%' );
            char ch = Character.forDigit((bytes[j] >> 4) & 0xF, 16);
            if(log.isDebugEnabled())
                log.debug("Encoder: Encode:  " + ch);
            buf.write(ch);
            ch = Character.forDigit(bytes[j] & 0xF, 16);
            if(log.isDebugEnabled())
                log.debug("Encoder: Encode:  " + ch);
            buf.write(ch);
        }
    }
    
    /**
     * Utility function to re-encode the URL.
     * Still has problems with charset, since UEncoder mostly
     * ignores it.
     */
    public String encodeURL(String uri) {
        String outUri=null;
        try {
            // XXX optimize - recycle, etc
            CharArrayWriter out = new CharArrayWriter();
            urlEncode(out, uri);
            outUri=out.toString();
        } catch (IOException iex) {
        }
        return outUri;
    }
    

    // -------------------- Internal implementation --------------------
    
    private void initSafeChars() {
        safeChars=new BitSet(128);
        int i;
        for (i = 'a'; i <= 'z'; i++) {
            safeChars.set(i);
        }
        for (i = 'A'; i <= 'Z'; i++) {
            safeChars.set(i);
        }
        for (i = '0'; i <= '9'; i++) {
            safeChars.set(i);
        }
        //safe
        safeChars.set('$');
        safeChars.set('-');
        safeChars.set('_');
        safeChars.set('.');

        // Dangerous: someone may treat this as " "
        // RFC1738 does allow it, it's not reserved
        //    safeChars.set('+');
        //extra
        safeChars.set('!');
        safeChars.set('*');
        safeChars.set('\'');
        safeChars.set('(');
        safeChars.set(')');
        safeChars.set(',');
    }
}