PC World Komputer 1995 November/PCWK1195.iso/inne/win95/sieciowe/hotja32.lzh/hotjava/classsrc/java/util/uuencoder.java

Text File | 1995-08-11 | 6KB | 193 lines

/*
 * @(#)UUEncoder.java    1.3 95/03/16 Chuck McManis
 *
 * Copyright (c) 1994 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies. Please refer to the file "copyright.html"
 * for further important copyright and licensing information.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 */
package java.util;

import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;

/**
 * This class implements a Berkeley uu character encoder. This encoder
 * was made famous by uuencode program.
 *
 * The basic character coding is algorithmic, taking 6 bits of binary
 * data and adding it to an ASCII ' ' (space) character. This converts
 * these six bits into a printable representation. Note that it depends
 * on the ASCII character encoding standard for english. Groups of three
 * bytes are converted into 4 characters by treating the three bytes
 * a four 6 bit groups, group 1 is byte 1's most significant six bits,
 * group 2 is byte 1's least significant two bits plus byte 2's four
 * most significant bits. etc.
 *
 * In this encoding, the buffer prefix is:
 * <pre>
 *     begin [mode] [filename]
 * </pre>
 *
 * This is followed by one or more lines of the form:
 * <pre>
 *    (len)(data)(data)(data) ...
 * </pre>
 * where (len) is the number of bytes on this line. Note that groupings
 * are always four characters, even if length is not a multiple of three
 * bytes. When less than three characters are encoded, the values of the
 * last remaining bytes is undefined and should be ignored.
 *
 * The last line of data in a uuencoded file is represented by a single
 * space character. This is translated by the decoding engine to a line
 * length of zero. This is immediately followed by a line which contains
 * the word 'end[newline]'
 *
 * @version     1.3, 16 Mar 1995
 * @author      Chuck McManis
 * @see        CharacterEncoder
 * @see        UUDecoder
 */
public class UUEncoder extends CharacterEncoder {

    /**
     * This name is stored in the begin line.
     */
    private String bufferName;

    /**
     * Represents UNIX(tm) mode bits. Generally three octal digits representing
     * read, write, and execute permission of the owner, group owner, and
     * others. They should be interpreted as the bit groups:
     * (owner) (group) (others)
     *    rwx      rwx     rwx     (r = read, w = write, x = execute)
     *
     * By default these are set to 644 (UNIX rw-r--r-- permissions).
     */
    private int mode;


    /**
     * Default - buffer begin line will be:
     * <pre>
     *    begin 644 encoder.buf
     * </pre>
     */
    public UUEncoder() {
    bufferName = "encoder.buf";
    mode = 644;
    }

    /**
     * Specifies a name for the encoded bufer, begin line will be:
     * <pre>
     *    begin 644 [FNAME]
     * </pre>
     */
    public UUEncoder(String fname) {
    bufferName = fname;
    mode = 644;
    }

    /**
     * Specifies a name and mode for the encoded bufer, begin line will be:
     * <pre>
     *    begin [MODE] [FNAME]
     * </pre>
     */
    public UUEncoder(String fname, int newMode) {
    bufferName = fname;
    mode = newMode;
    }

    /** number of bytes per atom in uuencoding is 3 */
    int bytesPerAtom() {
    return (3);
    }

    /** number of bytes per line in uuencoding is 45 */
    int bytesPerLine() {
    return (45);
    }

    /**
     * encodeAtom - take three bytes and encodes them into 4 characters
     * If len is less than 3 then remaining bytes are filled with '1'.
     * This insures that the last line won't end in spaces and potentiallly
     * be truncated.
     */
    void encodeAtom(OutputStream outStream, byte data[], int offset, int len) {
    byte    a, b = 1, c = 1;
    int    c1, c2, c3, c4;

    a = data[offset];
    if (len > 1) {
        b = data[offset+1];
    }
    if (len > 2) {
        c = data[offset+2];
    }

    c1 = (a >>> 2) & 0xff;
    c2 = ((a << 4) & 0x30) | ((b >>> 4) & 0xf);
    c3 = ((b << 2) & 0x3c) | ((c >>> 6) & 0x3);
    c4 = c & 0x3f;
    outStream.write(c1 + ' ');
    outStream.write(c2 + ' ');
    outStream.write(c3 + ' ');
    outStream.write(c4 + ' ');
    return;
    }

    /**
     * Encode the line prefix which consists of the single character. The
     * lenght is added to the value of ' ' (32 decimal) and printed.
     */
    void encodeLinePrefix(OutputStream outStream, int length) {
    outStream.write((length & 0x3f) + ' ');
    }


    /**
     * The line suffix for uuencoded files is simply a new line.
     */
    void encodeLineSuffix(OutputStream outStream) {
    pStream.println();
    }

    /**
     * encodeBufferPrefix writes the begin line to the output stream.
     */
    void encodeBufferPrefix(OutputStream a) {
    super.pStream = new PrintStream(a);
    super.pStream.print("begin "+mode+" ");
    if (bufferName != null) {
        super.pStream.println(bufferName);
    } else {
        super.pStream.println("encoder.bin");
    }
    super.pStream.flush();
    }

    /**
     * encodeBufferSuffix writes the single line containing space (' ') and
     * the line containing the word 'end' to the output stream.
     */
    void encodeBufferSuffix(OutputStream a) {
    super.pStream.println(" \nend");
    super.pStream.flush();
    }

}