mimebase64encoder.java

JDBF是一个实现o/r mapping 的软件

/*
 *
 * The contents of this file are subject to the Netscape Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/NPL/
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1999 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Contributor(s): 
 */


package org.jdbf.util;


/**
 * Byte to text encoder using base 64 encoding. To create a base 64
 * encoding of a byte stream call {@link #translate} for every
 * sequence of bytes and {@link #getCharArray} to mark closure of
 * the byte stream and retrieve the text presentation.
 *
 * @author Based on code from the Mozilla Directory SDK<br>
 * @version $Revision: 1.2 $<br>
 * last changed by $Author: gmartone $
 *
 */
public final class MimeBase64Encoder{


    private StringBuffer out = new StringBuffer();
    
    private int buf = 0;                     // a 24-bit quantity

    private int buf_bytes = 0;               // how many octets are set in it

    private char line[] = new char[74];      // output buffer

    private int line_length = 0;             // output buffer fill pointer

    static private final byte crlf[] = "\r\n".getBytes();

    static private final char map[] = {
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',     // 0-7
        'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',     // 8-15
        'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',     // 16-23
        'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',     // 24-31
        'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',     // 32-39
        'o', 'p', 'q', 'r', 's', 't', 'u', 'v',     // 40-47
        'w', 'x', 'y', 'z', '0', '1', '2', '3',     // 48-55
        '4', '5', '6', '7', '8', '9', '+', '/',     // 56-63
    };

	/**
	 * Encodes token
	 *
	 */
    private final void encode_token(){
        int i = line_length;
        line[i]   = map[0x3F & (buf >> 18)];   // sextet 1 (octet 1)
        line[i+1] = map[0x3F & (buf >> 12)];   // sextet 2 (octet 1 and 2)
        line[i+2] = map[0x3F & (buf >> 6)];    // sextet 3 (octet 2 and 3)
        line[i+3] = map[0x3F & buf];           // sextet 4 (octet 3)
        line_length += 4;
        buf = 0;
        buf_bytes = 0;
    }

	/**
	 * Encodes a part of otken
	 *
	 */
    private final void encode_partial_token(){
        int i = line_length;
        line[i]   = map[0x3F & (buf >> 18)];   // sextet 1 (octet 1)
        line[i+1] = map[0x3F & (buf >> 12)];   // sextet 2 (octet 1 and 2)
        
        if (buf_bytes == 1)
            line[i+2] = '=';
        else
            line[i+2] = map[0x3F & (buf >> 6)];  // sextet 3 (octet 2 and 3)
        
        if (buf_bytes <= 2)
            line[i+3] = '=';
        else
            line[i+3] = map[0x3F & buf];         // sextet 4 (octet 3)
        line_length += 4;
        buf = 0;
        buf_bytes = 0;
    }

	/**
	 * Flushes line
	 *
	 */
    private final void flush_line(){
        out.append(line, 0, line_length);
        line_length = 0;
    }


    /**
     * Given a sequence of input bytes, produces a sequence of output bytes
     * using the base64 encoding.  If there are bytes in `out' already, the
     * new bytes are appended, so the caller should do `out.setLength(0)'
     * first if that's desired.
     * 
     * @param in - byte[] to translate
     */
    public final void translate(byte[] in){
        int in_length = in.length;
        
        for (int i = 0; i < in_length; i++) {
            if (buf_bytes == 0)
                buf = (buf & 0x00FFFF) | (in[i] << 16);
            else if (buf_bytes == 1)
                buf = (buf & 0xFF00FF) | ((in[i] << 8) & 0x00FFFF);
            else
                buf = (buf & 0xFFFF00) | (in[i] & 0x0000FF);
            
            if ((++buf_bytes) == 3) {
                encode_token();
                if (line_length >= 72) {
                    flush_line();
                }
            }
            
            if (i == (in_length-1)) {
                if ((buf_bytes > 0) && (buf_bytes < 3))
                    encode_partial_token();
                if (line_length > 0)
                    flush_line();
            }
        }
        
        for (int i=0; i<line.length; i++)
            line[i] = 0;
    }

    
    /**
     * Return a array of characters
     * @return char[]
     */
    public char[] getCharArray(){
        char[] ch;
        
        if (buf_bytes != 0)
            encode_partial_token();
        flush_line();
        for (int i=0; i<line.length; i++)
            line[i] = 0;
        ch = new char[ out.length() ];
        if (out.length() > 0) 
            out.getChars( 0, out.length(), ch, 0 );
        return ch;
    }


}