gistfile1.java

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;


public class URLEncoder {
  
    public static String encode(String s, String enc) 
	throws UnsupportedEncodingException {

	boolean needToChange = false;
	boolean wroteUnencodedChar = false; 
	int maxBytesPerChar = 10; // rather arbitrary limit, but safe for now
	StringBuffer out = new StringBuffer(s.length());
	ByteArrayOutputStream buf = new ByteArrayOutputStream(maxBytesPerChar);

	OutputStreamWriter writer = new OutputStreamWriter(buf, enc);

	for (int i = 0; i < s.length(); i++) {
	    int c = (int) s.charAt(i);
	    if (dontNeedEncoding(c)) {
		if (c == ' ') {
		    c = '+';
		    needToChange = true;
		}
		out.append((char)c);
		wroteUnencodedChar = true;
	    } else {
		try {
		    if (wroteUnencodedChar) { // Fix for 4407610
			writer = new OutputStreamWriter(buf, enc);
			wroteUnencodedChar = false;
		    }
		    writer.write(c);
		    if (c >= 0xD800 && c <= 0xDBFF) {
			if ( (i+1) < s.length()) {
			    int d = (int) s.charAt(i+1);
			    if (d >= 0xDC00 && d <= 0xDFFF) {
				writer.write(d);
				i++;
			    }
			}
		    }
		    writer.flush();
		} catch(IOException e) {
		    buf.reset();
		    continue;
		}
		byte[] ba = buf.toByteArray();
		for (int j = 0; j < ba.length; j++) {
		    out.append('%');
		    char ch = CCharacter.forDigit((ba[j] >> 4) & 0xF, 16);
		    out.append(ch);
		    ch = CCharacter.forDigit(ba[j] & 0xF, 16);
		    out.append(ch);
		}
		buf.reset();
		needToChange = true;
	    }
	}

	return (needToChange? out.toString() : s);
    }
  
    static class CCharacter {
	public static char forDigit(int digit, int radix) {
	    if ((digit >= radix) || (digit < 0)) {
		return '\0';
	    }
	    if ((radix < Character.MIN_RADIX) || (radix > Character.MAX_RADIX)) {
		return '\0';
	    }
	    if (digit < 10) {
		return (char)('0' + digit);
	    }
	    return (char)('a' - 10 + digit);
	}
    }
    public static boolean dontNeedEncoding(int ch){
	int len = _dontNeedEncoding.length();
	boolean en = false;
	for(int i =0;i< len;i++){
	    if(_dontNeedEncoding.charAt(i) == ch)
		{
		    en = true;
		    break;
		}
	}
    
	return en;
    }
    private static String _dontNeedEncoding = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ -_.*";

}