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/*******************************************************************************
 * Copyright (c) 2004 Actuate Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *  Actuate Corporation  - initial API and implementation
 *******************************************************************************/

package org.eclipse.birt.report.engine.emitter.html;

import java.io.UnsupportedEncodingException;

/**
 * Provides a method to encode any string into a URL-safe
 * form.
 * Non-ASCII characters are first encoded as sequences of
 * two or three bytes, using the UTF-8 algorithm, before being
 * encoded as %HH escapes.
 * 
 */
public class URLEncoder {

	  final static String[] hex = {
	    "%00", "%01", "%02", "%03", "%04", "%05", "%06", "%07",
	    "%08", "%09", "%0a", "%0b", "%0c", "%0d", "%0e", "%0f",
	    "%10", "%11", "%12", "%13", "%14", "%15", "%16", "%17",
	    "%18", "%19", "%1a", "%1b", "%1c", "%1d", "%1e", "%1f",
	    "%20", "%21", "%22", "%23", "%24", "%25", "%26", "%27",
	    "%28", "%29", "%2a", "%2b", "%2c", "%2d", "%2e", "%2f",
	    "%30", "%31", "%32", "%33", "%34", "%35", "%36", "%37",
	    "%38", "%39", "%3a", "%3b", "%3c", "%3d", "%3e", "%3f",
	    "%40", "%41", "%42", "%43", "%44", "%45", "%46", "%47",
	    "%48", "%49", "%4a", "%4b", "%4c", "%4d", "%4e", "%4f",
	    "%50", "%51", "%52", "%53", "%54", "%55", "%56", "%57",
	    "%58", "%59", "%5a", "%5b", "%5c", "%5d", "%5e", "%5f",
	    "%60", "%61", "%62", "%63", "%64", "%65", "%66", "%67",
	    "%68", "%69", "%6a", "%6b", "%6c", "%6d", "%6e", "%6f",
	    "%70", "%71", "%72", "%73", "%74", "%75", "%76", "%77",
	    "%78", "%79", "%7a", "%7b", "%7c", "%7d", "%7e", "%7f",
	    "%80", "%81", "%82", "%83", "%84", "%85", "%86", "%87",
	    "%88", "%89", "%8a", "%8b", "%8c", "%8d", "%8e", "%8f",
	    "%90", "%91", "%92", "%93", "%94", "%95", "%96", "%97",
	    "%98", "%99", "%9a", "%9b", "%9c", "%9d", "%9e", "%9f",
	    "%a0", "%a1", "%a2", "%a3", "%a4", "%a5", "%a6", "%a7",
	    "%a8", "%a9", "%aa", "%ab", "%ac", "%ad", "%ae", "%af",
	    "%b0", "%b1", "%b2", "%b3", "%b4", "%b5", "%b6", "%b7",
	    "%b8", "%b9", "%ba", "%bb", "%bc", "%bd", "%be", "%bf",
	    "%c0", "%c1", "%c2", "%c3", "%c4", "%c5", "%c6", "%c7",
	    "%c8", "%c9", "%ca", "%cb", "%cc", "%cd", "%ce", "%cf",
	    "%d0", "%d1", "%d2", "%d3", "%d4", "%d5", "%d6", "%d7",
	    "%d8", "%d9", "%da", "%db", "%dc", "%dd", "%de", "%df",
	    "%e0", "%e1", "%e2", "%e3", "%e4", "%e5", "%e6", "%e7",
	    "%e8", "%e9", "%ea", "%eb", "%ec", "%ed", "%ee", "%ef",
	    "%f0", "%f1", "%f2", "%f3", "%f4", "%f5", "%f6", "%f7",
	    "%f8", "%f9", "%fa", "%fb", "%fc", "%fd", "%fe", "%ff"
	  };

	  /**
	   * Encode a string to the "x-www-form-urlencoded" form, enhanced
	   * with the UTF-8-in-URL proposal. This is what happens:
	   *
	   * 
	   * The ASCII characters 'a' through 'z', 'A' through 'Z',
	   *        and '0' through '9' remain the same.
	   *
	   * 
The unreserved characters - _ . ! ~ * ' ( ) remain the same.
	   *
	   * 
The space character ' ' is converted into a plus sign '+'.
	   *
	   * 
All other ASCII characters are converted into the
	   *        3-character string "%xy", where xy is
	   *        the two-digit hexadecimal representation of the character
	   *        code
	   *
	   * 
All non-ASCII characters are encoded in two steps: first
	   *        to a sequence of 2 or 3 bytes, using the UTF-8 algorithm;
	   *        secondly each of these bytes is encoded as "%xx".
	   * 
	   *
	   * @param s The string to be encoded
	   * @return The encoded string
	   */
	  public static String encode(String s, String encoding)
	  {
	    StringBuffer sbuf = new StringBuffer();
	    try
		{
		    byte[] bytes;
			if ( "".equals( encoding ) )
			{
				bytes = s.getBytes();			// use current system encoding
		    }
		    else{
		    	bytes = s.getBytes(encoding);	// use passed-in encoding
		    }
		    
		    int len = bytes.length;
		    for (int i = 0; i < len; i++) {
		      int ch = bytes[i];
		      if (ch < 0)
		      {
		      	ch += 256;
		      }
		      if ('A' <= ch && ch <= 'Z') {		// 'A'..'Z'
		        sbuf.append((char)ch);
		      } else if ('a' <= ch && ch <= 'z') {	// 'a'..'z'
			       sbuf.append((char)ch);
		      } else if ('0' <= ch && ch <= '9') {	// '0'..'9'
			       sbuf.append((char)ch);
		      } else if (ch == ' ') {			// space
			       sbuf.append('+');
		      } else if (ch == '-' || ch == '_'		// unreserved
		          || ch == '.' || ch == '!'
		          || ch == '~' || ch == '*'
		          || ch == '\'' || ch == '('
		          || ch == ')'|| ch == ':'|| ch == '/') {
		        sbuf.append((char)ch);
		      } else {		// other ASCII
			       sbuf.append(hex[ch]);
		      }
		    }
		}
	    catch(UnsupportedEncodingException ex)
		{
	    	// FIXME
	    	assert false;
		}
	    return sbuf.toString();
	  }
}