mimebase64decoder.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;


import java.io.ByteArrayOutputStream;


/**
 * Base 64 text to byte decoded. To produce the binary  array from
 * base 64 encoding call {@link #translate} for each sequence of
 * characters and {@link #getByteArray} to mark closure of the
 * character stream and retrieve the binary contents.
 *
 * @author Based on code from the Mozilla Directory SDK
 */
public final class MimeBase64Decoder {
    
    
    private ByteArrayOutputStream out = new ByteArrayOutputStream();
    
    private byte[] token = new byte[4];
    private byte[] bytes = new byte[3];
    private int token_length = 0;
    
    private final static byte NUL = 127;
    private final static byte EOF = 126;
    
    private final static byte[] map = 
            
            {NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, 62, NUL, NUL, NUL, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, NUL, NUL, NUL, EOF, NUL, NUL, NUL, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, NUL, NUL, NUL, NUL, NUL, NUL, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL, NUL};
    //   000-007
    //   010-017
    //   020-027
    //   030-037
    //   040-047   !"#$%&'
    //   050-057  ()*+,-./
    //   060-067  01234567
    //   070-077  89:;<=>?
    
    //   100-107  @ABCDEFG
    //   110-117  HIJKLMNO
    //   120-127  PQRSTUVW
    //   130-137  XYZ[\]^_
    //   140-147  `abcdefg
    //   150-157  hijklmno
    //   160-167  pqrstuvw
    //   170-177  xyz{|}~
    
    //   200-207
    //   210-217
    //   220-227
    //   230-237
    //   240-247
    //   250-257
    //   260-267
    //   270-277
    
    //   300-307
    //   310-317
    //   320-327
    //   330-337
    //   340-347
    //   350-357
    //   360-367
    //   370-377
    
    
    // Fast routine that assumes full 4-char tokens with no '=' in them.
    //
    private void decode_token() {
        int num = token[0] << 18 | token[1] << 12 | token[2] << 6 | token[3];
        
        bytes[0] = (byte)(0xFF & num >> 16);
        bytes[1] = (byte)(0xFF & num >> 8);
        bytes[2] = (byte)(0xFF & num);
        
        out.write( bytes, 0, 3 );
    } 
    
    
    // Hairier routine that deals with the final token, which can have fewer
    // than four characters, and that might be padded with '='.
    //
    private final void decode_final_token() {
        
        byte b0 = token[0];
        byte b1 = token[1];
        byte b2 = token[2];
        byte b3 = token[3];
        
        int eq_count = 0;
        
        if (b0 == EOF) {
            b0 = 0;
            eq_count++;
        } 
        if (b1 == EOF) {
            b1 = 0;
            eq_count++;
        } 
        if (b2 == EOF) {
            b2 = 0;
            eq_count++;
        } 
        if (b3 == EOF) {
            b3 = 0;
            eq_count++;
        } 
        
        int num = b0 << 18 | b1 << 12 | b2 << 6 | b3;
        
        // eq_count will be 0, 1, or 2.
        // No "=" padding means 4 bytes mapped to 3, the normal case,
        //        not handled in this routine.
        // "xxx=" means 3 bytes mapped to 2.
        // "xx==" means 2 bytes mapped to 1.
        // "x===" can't happen, because "x" would then be encoding
        //        only 6 bits, not 8, the minimum possible.
        
        out.write( (byte)(num >> 16) );
        if (eq_count <= 1) {
            out.write( (byte)(num >> 8 & 0xFF) );
            if (eq_count == 0) {
                out.write( (byte)(num & 0xFF) );
            } 
        } 
    } 
    
    
    public final void translate( char[] ch ) {
        translate( ch, 0, ch.length );
    } 
    
    
    public final void translate( char[] ch, int offset, int length ) {
        
        if (token == null) {
            return;
        } 
        
        for (int i = offset; i < offset + length; i++) {
            byte t = map[ch[i] & 0xff];
            
            if (t == EOF) {
                eof();
            } else {
                if (t != NUL) {
                    token[token_length++] = t;
                } 
            } 
            if (token_length == 4) {
                decode_token();
                token_length = 0;
            } 
        } 
    } 
    
    
    private void eof() {
        if (token != null && token_length != 0) {
            while (token_length < 4) {
                token[token_length++] = EOF;
            } 
            decode_final_token();
        } 
        token_length = 0;
        token = new byte[4];
        bytes = new byte[3];
    } 
    
    
    public byte[] getByteArray() {
        eof();
        return out.toByteArray();
    } 
}