51  *
  52  * In the CharacterEncoder and CharacterDecoder classes, one complete
  53  * chunk of data is referred to as a <i>buffer</i>. Encoded buffers
  54  * are all text, and decoded buffers (sometimes just referred to as
  55  * buffers) are binary octets.
  56  *
  57  * To create a custom encoder, you must, at a minimum,  overide three
  58  * abstract methods in this class.
  59  * <DL>
  60  * <DD>bytesPerAtom which tells the encoder how many bytes to
  61  * send to encodeAtom
  62  * <DD>encodeAtom which encodes the bytes sent to it as text.
  63  * <DD>bytesPerLine which tells the encoder the maximum number of
  64  * bytes per line.
  65  * </DL>
  66  *
  67  * Several useful encoders have already been written and are
  68  * referenced in the See Also list below.
  69  *
  70  * @author      Chuck McManis
  71  * @see         CharacterDecoder;
  72  * @see         UCEncoder
  73  * @see         UUEncoder
  74  * @see         BASE64Encoder
  75  */
  76 public abstract class CharacterEncoder {
  77 
  78     /** Stream that understands "printing" */
  79     protected PrintStream pStream;
  80 
  81     /** Return the number of bytes per atom of encoding */
  82     abstract protected int bytesPerAtom();
  83 
  84     /** Return the number of bytes that can be encoded per line */
  85     abstract protected int bytesPerLine();
  86 
  87     /**
  88      * Encode the prefix for the entire buffer. By default is simply
  89      * opens the PrintStream for use by the other functions.
  90      */
  91     protected void encodeBufferPrefix(OutputStream aStream) throws IOException {
  92         pStream = new PrintStream(aStream);
  93     }
  94 
  95     /**
  96      * Encode the suffix for the entire buffer.
  97      */
  98     protected void encodeBufferSuffix(OutputStream aStream) throws IOException {
  99     }
 100 
 101     /**
 102      * Encode the prefix that starts every output line.
 103      */
 104     protected void encodeLinePrefix(OutputStream aStream, int aLength)
 105     throws IOException {
 106     }
 107 
 108     /**
 109      * Encode the suffix that ends every output line. By default
 110      * this method just prints a <newline> into the output stream.
 111      */
 112     protected void encodeLineSuffix(OutputStream aStream) throws IOException {
 113         pStream.println();
 114     }
 115 
 116     /** Encode one "atom" of information into characters. */
 117     abstract protected void encodeAtom(OutputStream aStream, byte someBytes[],
 118                 int anOffset, int aLength) throws IOException;
 119 
 120     /**
 121      * This method works around the bizarre semantics of BufferedInputStream's
 122      * read method.
 123      */
 124     protected int readFully(InputStream in, byte buffer[])
 125         throws java.io.IOException {
 126         for (int i = 0; i < buffer.length; i++) {
 127             int q = in.read();
 128             if (q == -1)
 129                 return i;
 130             buffer[i] = (byte)q;

  51  *
  52  * In the CharacterEncoder and CharacterDecoder classes, one complete
  53  * chunk of data is referred to as a <i>buffer</i>. Encoded buffers
  54  * are all text, and decoded buffers (sometimes just referred to as
  55  * buffers) are binary octets.
  56  *
  57  * To create a custom encoder, you must, at a minimum,  overide three
  58  * abstract methods in this class.
  59  * <DL>
  60  * <DD>bytesPerAtom which tells the encoder how many bytes to
  61  * send to encodeAtom
  62  * <DD>encodeAtom which encodes the bytes sent to it as text.
  63  * <DD>bytesPerLine which tells the encoder the maximum number of
  64  * bytes per line.
  65  * </DL>
  66  *
  67  * Several useful encoders have already been written and are
  68  * referenced in the See Also list below.
  69  *
  70  * @author      Chuck McManis
  71  * @see         CharacterDecoder
  72  * @see         UCEncoder
  73  * @see         UUEncoder
  74  * @see         BASE64Encoder
  75  */
  76 public abstract class CharacterEncoder {
  77 
  78     /** Stream that understands "printing" */
  79     protected PrintStream pStream;
  80 
  81     /** Return the number of bytes per atom of encoding */
  82     abstract protected int bytesPerAtom();
  83 
  84     /** Return the number of bytes that can be encoded per line */
  85     abstract protected int bytesPerLine();
  86 
  87     /**
  88      * Encode the prefix for the entire buffer. By default is simply
  89      * opens the PrintStream for use by the other functions.
  90      */
  91     protected void encodeBufferPrefix(OutputStream aStream) throws IOException {
  92         pStream = new PrintStream(aStream);
  93     }
  94 
  95     /**
  96      * Encode the suffix for the entire buffer.
  97      */
  98     protected void encodeBufferSuffix(OutputStream aStream) throws IOException {
  99     }
 100 
 101     /**
 102      * Encode the prefix that starts every output line.
 103      */
 104     protected void encodeLinePrefix(OutputStream aStream, int aLength)
 105     throws IOException {
 106     }
 107 
 108     /**
 109      * Encode the suffix that ends every output line. By default
 110      * this method just prints a newline into the output stream.
 111      */
 112     protected void encodeLineSuffix(OutputStream aStream) throws IOException {
 113         pStream.println();
 114     }
 115 
 116     /** Encode one "atom" of information into characters. */
 117     abstract protected void encodeAtom(OutputStream aStream, byte someBytes[],
 118                 int anOffset, int aLength) throws IOException;
 119 
 120     /**
 121      * This method works around the bizarre semantics of BufferedInputStream's
 122      * read method.
 123      */
 124     protected int readFully(InputStream in, byte buffer[])
 125         throws java.io.IOException {
 126         for (int i = 0; i < buffer.length; i++) {
 127             int q = in.read();
 128             if (q == -1)
 129                 return i;
 130             buffer[i] = (byte)q;