File	Doc	Category	Size	Date	Package
Rot13Charset.java	API Doc	Example	8264	Mon May 20 00:24:30 BST 2002	com.ronsoft.books.nio.charset

Rot13Charset

• java.lang.Object
  • java.nio.charset.Charset

Fields Summary
private static final String	BASE_CHARSET_NAME
Charset	baseCharset

Constructors Summary
protected Rot13Charset(String canonical, String[] aliases) Constructor for the Rot13 charset. Call the superclass constructor to pass along the name(s) we'll be known by. Then save a reference to the delegate Charset. super (canonical, aliases); // Save the base charset we're delegating to. baseCharset = Charset.forName (BASE_CHARSET_NAME);

Methods Summary
public boolean	contains(java.nio.charset.Charset cs) This method must be implemented by concrete Charsets. We always say no, which is safe. return (false);
public static void	main(java.lang.String[] argv) Unit test for the Rot13 Charset. This main() will open and read an input file if named on the command line, or stdin if no args are provided, and write the contents to stdout via the X-ROT13 charset encoding. The "encryption" implemented by the Rot13 algorithm is symmetrical. Feeding in a plain-text file, such as Java source code for example, will output a scrambled version. Feeding the scrambled version back in will yield the original plain-text document. BufferedReader in; if (argv.length > 0) { // open the named file in = new BufferedReader (new FileReader (argv [0])); } else { // wrap a BufferedReader around stdin in = new BufferedReader (new InputStreamReader (System.in)); } // Create a PrintStream which uses the Rot13 encoding PrintStream out = new PrintStream (System.out, false, "X-ROT13"); String s = null; // Read all input and write it to the output // As the data passes through the PrintStream // it will be Rot13 encoded. while ((s = in.readLine()) != null) { out.println (s); } out.flush();
public java.nio.charset.CharsetDecoder	newDecoder() Called by users of this Charset to obtain a decoder. This implementation instantiates an instance of a private class (defined below) and passes it a decoder from the base Charset. return new Rot13Decoder (this, baseCharset.newDecoder());
public java.nio.charset.CharsetEncoder	newEncoder() Called by users of this Charset to obtain an encoder. This implementation instantiates an instance of a private class (defined below) and passes it an encoder from the base Charset. return new Rot13Encoder (this, baseCharset.newEncoder());
private void	rot13(java.nio.CharBuffer cb) Common routine to rotate all the ASCII alpha chars in the given CharBuffer by 13. Note that this code explicitly compares for upper and lower case ASCII chars rather than using the methods Character.isLowerCase and Character.isUpperCase. This is because the rotate-by-13 scheme only works properly for the alphabetic characters of the ASCII charset and those methods can return true for non-ASCII Unicode chars. for (int pos = cb.position(); pos < cb.limit(); pos++) { char c = cb.get (pos); char a = '\u0000"; // Is it lower case alpha? if ((c >= 'a") && (c <= 'z")) { a = 'a"; } // Is it upper case alpha? if ((c >= 'A") && (c <= 'Z")) { a = 'A"; } // If either, roll it by 13 if (a != '\u0000") { c = (char)((((c - a) + 13) % 26) + a); cb.put (pos, c); } }