mimebase64encoder.java

用Java写的面相对象的数据库管理系统

/*
 *
 * 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.ozoneDB.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
 */
public final class MimeBase64Encoder {
    
    
    private StringBuffer out = new StringBuffer();
    
    private int buf = 0;
    private int buf_bytes = 0;
    private char[] line = new char[74];
    private int line_length = 0;
    
    private final static byte[] crlf = "\r\n".getBytes();
    
    private final static char[] map = 
            
            {'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', '+', '/'};
    // 0-7
    // 8-15
    // 16-23
    // 24-31
    // 32-39
    // 40-47
    // 48-55
    // 56-63
    
    
    private final void encode_token() {
        int i = line_length;
        line[i] = map[0x3F & buf >> 18];
        line[i + 1] = map[0x3F & buf >> 12];
        line[i + 2] = map[0x3F & buf >> 6];
        line[i + 3] = map[0x3F & buf];
        line_length += 4;
        buf = 0;
        buf_bytes = 0;
    } 
    
    
    private final void encode_partial_token() {
        int i = line_length;
        line[i] = map[0x3F & buf >> 18];
        line[i + 1] = map[0x3F & buf >> 12];
        
        if (buf_bytes == 1) {
            line[i + 2] = '=';
        } else {
            line[i + 2] = map[0x3F & buf >> 6];
        } 
        
        if (buf_bytes <= 2) {
            line[i + 3] = '=';
        } else {
            line[i + 3] = map[0x3F & buf];
        } 
        line_length += 4;
        buf = 0;
        buf_bytes = 0;
    } 
    
    
    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.
     */
    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;
        } 
    } 
    
    
    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()];
        out.getChars( 0, out.length(), ch, 0 );
        return ch;
    } 
}