coder.java

来自「一款Java实现的HTTP代理服务器」· Java 代码 · 共 158 行

package rabbit.util;

import java.io.UnsupportedEncodingException;

/** This class encodes/decodes stuff to/from the web.
 */
public class Coder {
  
    /** dont construct this
     */
    private Coder () {
	// nah.
    }
  
    /** the base64 characters 
     */
    private static final int pr2six[] = {
	64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,
	64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,62,64,64,64,63,
	52,53,54,55,56,57,58,59,60,61,64,64,64,64,64,64,64,0,1,2,3,4,5,6,7,8,9,
	10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,64,64,64,64,64,64,26,27,
	28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,
	64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,
	64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,
	64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,
	64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,
	64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,64,
	64,64,64,64,64,64,64,64,64,64,64,64,64
    };


    /** The base64 characters.
     */
    private static final char uu_base64[] = {
	'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P',
	'Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f',
	'g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v',
	'w','x','y','z','0','1','2','3','4','5','6','7','8','9','+','/'
    };    

    /** uudecode(base64) the given string.
     *  useful for decoding basic Authentication 
     * @param base64string the String to decode.
     * @return the decoded string.
     */
    public static String uudecode (String base64string) {
	StringBuilder ret = new StringBuilder (base64string.length () * 3 / 4);
    
	while ((base64string.length () % 4) != 0)
	    base64string += "=";           // that should be safe.
	int i = 0;
	int c1 = 0, c2 = 0, c3 = 0, c4 = 0;
	while (i < base64string.length () && 
	       pr2six[base64string.charAt (i)] <= 63) {
	    c1 = pr2six[base64string.charAt (i)];
	    c2 = pr2six[base64string.charAt (i+1)];
	    c3 = pr2six[base64string.charAt (i+2)];
	    c4 = pr2six[base64string.charAt (i+3)];
	    ret.append ((char)(c1 << 2 | c2 >> 4));
	    ret.append ((char)((c2 << 4 | c3 >> 2) % 256));
	    ret.append ((char)((c3 << 6 | c4) % 256));      
	    i += 4;
	}    
    
	if (c3 > 63)
	    ret.setLength (ret.length () - 2);
	else if (c4 > 63)
	    ret.setLength (ret.length () - 1);
	return ret.toString ();
    }

    /** uuencode(base64) the given String.
     *  useful for encoding basic authentication.
     * @param str the String to encode.
     * @return the encoded string.
     */ 
    public static String uuencode (String str) {
	StringBuilder ret = new StringBuilder (str.length () * 4 / 3);
	char ch, ch1, ch2, ch3;
	int i;
	
	for (i = 0; i+2 < str.length (); i+=3) {	    
	    ch1 = str.charAt (i);
	    ch2 = str.charAt (i+1);
	    ch3 = str.charAt (i+2);
	    ch = uu_base64[((ch1 >> 2) & 077)];
	    ret.append (ch);
	    
	    ch = uu_base64[(((ch1 << 4) & 060) | ((ch2 >> 4) & 017))];
	    ret.append (ch);
	    
	    ch = uu_base64[(((ch2 << 2) & 074) | ((ch3 >> 6) & 03))];
	    ret.append (ch);
	    
	    ch = uu_base64[(ch3 & 077)];
	    ret.append (ch);
	}
	
	// are we done yet?
	if (i == str.length ()) 
	    return ret.toString ();

	// no so handle the trailing characters.
	ch1 = str.charAt (i);
	ch2 = str.length() > i + 1 ? str.charAt (i+1) : (char)0;
	
	ch = uu_base64[((ch1 >> 2) & 077)];
	ret.append (ch);
	
	ch = uu_base64[(((ch1 << 4) & 060) | ((ch2 >> 4) & 017))];
	ret.append (ch);
	
	if (str.length () > i + 1) {
	    ch = uu_base64[((ch2 << 2) & 074)];
	    ret.append (ch);
	} else {
	    ret.append ('=');
	}
	ret.append ('=');
	return ret.toString ();
    }

    /** URLDecode a string. This is useful when your handling CGI-arguments..
     * @param enc the encoded String.
     * @return an unescaped String. ('%dd' => 'c', '+' => ' ')
     */
    public static String URLdecode (String enc) {
	enc = enc.replace ('+', ' ');
	int i = 0;
	while (true) {
	    i = enc.indexOf ('%', i);
	    if (i < 0) 
		break;
	    try {
		char c = (char) Integer.parseInt (enc.substring (i + 1,i + 3), 16);
		enc = enc.substring (0, i) + c + enc.substring (i + 3);
	    } catch (NumberFormatException e) {
		// ignore
	    }
	}
	return enc;
    }

    /** URLEncode a string. Only a convenience function for 
     *  java.net.URLEncoder.encode ()
     * @param str the String to URLEncode.
     */ 
    public static String URLEncode (String str) {
	try {
	    return java.net.URLEncoder.encode (str, "UTF-8");
	} catch (UnsupportedEncodingException e) {
	    e.printStackTrace ();
	} 
	return str;
    }
}