base64encoder.java

实现了一个基于j2me移动gps定位系统

/*
 * $Id: Base64Encoder.java 145 2007-11-30 09:51:57Z khanh.lnq $
 * $URL: https://jvnmobilegis.googlecode.com/svn/trunk/src/org/bouncycastle/util/encoders/Base64Encoder.java $
 * $Author: khanh.lnq $
 * $Revision: 145 $
 * $Date: 2007-11-30 16:51:57 +0700 (Fri, 30 Nov 2007) $
 *
 * ====================================================================
 *
 * Copyright (C) 2006-2007 by JVNGIS
 *
 * All copyright notices regarding JVNMobileGIS MUST remain
 * intact in the Java codes and resource files.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Support can be obtained from project homepage at:
 * http://code.google.com/p/jvnmobilegis/
 *
 * Correspondence and Marketing Questions can be sent to:
 * khanh.lnq AT gmail.com
 *
 * @version: 1.0
 * @author: Khanh Le
 * @Date Created: 31 Aug 2007
 */

package org.bouncycastle.util.encoders;

import java.io.IOException;
import java.io.OutputStream;

public class Base64Encoder implements Encoder {
    protected final byte[] encodingTable = { (byte) 'A', (byte) 'B',
            (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
            (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L',
            (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P', (byte) 'Q',
            (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V',
            (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z', (byte) 'a',
            (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f',
            (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k',
            (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o', (byte) 'p',
            (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u',
            (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z',
            (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4',
            (byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9',
            (byte) '+', (byte) '/' };

    protected byte padding = (byte) '=';

    /*
     * set up the decoding table.
     */
    protected final byte[] decodingTable = new byte[128];

    protected void initialiseDecodingTable() {
        for (int i = 0; i < encodingTable.length; i++) {
            decodingTable[encodingTable[i]] = (byte) i;
        }
    }

    public Base64Encoder() {
        this.initialiseDecodingTable();
    }

    /**
     * encode the input data producing a base 64 output stream.
     * 
     * @return the number of bytes produced.
     */
    public int encode(byte[] data, int off, int length, OutputStream out)
            throws IOException {
        int modulus = length % 3;
        int dataLength = (length - modulus);
        int a1, a2, a3;

        for (int i = off; i < off + dataLength; i += 3) {
            a1 = data[i] & 0xff;
            a2 = data[i + 1] & 0xff;
            a3 = data[i + 2] & 0xff;

            out.write(encodingTable[(a1 >>> 2) & 0x3f]);
            out.write(encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f]);
            out.write(encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f]);
            out.write(encodingTable[a3 & 0x3f]);
        }

        /*
         * process the tail end.
         */
        int b1, b2, b3;
        int d1, d2;

        switch (modulus) {
        case 0: /* nothing left to do */
            break;
        case 1:
            d1 = data[off + dataLength] & 0xff;
            b1 = (d1 >>> 2) & 0x3f;
            b2 = (d1 << 4) & 0x3f;

            out.write(encodingTable[b1]);
            out.write(encodingTable[b2]);
            out.write(padding);
            out.write(padding);
            break;
        case 2:
            d1 = data[off + dataLength] & 0xff;
            d2 = data[off + dataLength + 1] & 0xff;

            b1 = (d1 >>> 2) & 0x3f;
            b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
            b3 = (d2 << 2) & 0x3f;

            out.write(encodingTable[b1]);
            out.write(encodingTable[b2]);
            out.write(encodingTable[b3]);
            out.write(padding);
            break;
        }

        return (dataLength / 3) * 4 + ((modulus == 0) ? 0 : 4);
    }

    private boolean ignore(char c) {
        return (c == '\n' || c == '\r' || c == '\t' || c == ' ');
    }

    /**
     * decode the base 64 encoded byte data writing it to the given output
     * stream, whitespace characters will be ignored.
     * 
     * @return the number of bytes produced.
     */
    public int decode(byte[] data, int off, int length, OutputStream out)
            throws IOException {
        byte b1, b2, b3, b4;
        int outLen = 0;

        int end = off + length;

        while (end > off) {
            if (!ignore((char) data[end - 1])) {
                break;
            }

            end--;
        }

        int i = off;
        int finish = end - 4;

        i = nextI(data, i, finish);

        while (i < finish) {
            b1 = decodingTable[data[i++]];

            i = nextI(data, i, finish);

            b2 = decodingTable[data[i++]];

            i = nextI(data, i, finish);

            b3 = decodingTable[data[i++]];

            i = nextI(data, i, finish);

            b4 = decodingTable[data[i++]];

            out.write((b1 << 2) | (b2 >> 4));
            out.write((b2 << 4) | (b3 >> 2));
            out.write((b3 << 6) | b4);

            outLen += 3;

            i = nextI(data, i, finish);
        }

        outLen += decodeLastBlock(out, (char) data[end - 4],
                (char) data[end - 3], (char) data[end - 2],
                (char) data[end - 1]);

        return outLen;
    }

    private int nextI(byte[] data, int i, int finish) {
        while ((i < finish) && ignore((char) data[i])) {
            i++;
        }
        return i;
    }

    /**
     * decode the base 64 encoded String data writing it to the given output
     * stream, whitespace characters will be ignored.
     * 
     * @return the number of bytes produced.
     */
    public int decode(String data, OutputStream out) throws IOException {
        byte b1, b2, b3, b4;
        int length = 0;

        int end = data.length();

        while (end > 0) {
            if (!ignore(data.charAt(end - 1))) {
                break;
            }

            end--;
        }

        int i = 0;
        int finish = end - 4;

        i = nextI(data, i, finish);

        while (i < finish) {
            b1 = decodingTable[data.charAt(i++)];

            i = nextI(data, i, finish);

            b2 = decodingTable[data.charAt(i++)];

            i = nextI(data, i, finish);

            b3 = decodingTable[data.charAt(i++)];

            i = nextI(data, i, finish);

            b4 = decodingTable[data.charAt(i++)];

            out.write((b1 << 2) | (b2 >> 4));
            out.write((b2 << 4) | (b3 >> 2));
            out.write((b3 << 6) | b4);

            length += 3;

            i = nextI(data, i, finish);
        }

        length += decodeLastBlock(out, data.charAt(end - 4), data
                .charAt(end - 3), data.charAt(end - 2), data.charAt(end - 1));

        return length;
    }

    private int decodeLastBlock(OutputStream out, char c1, char c2, char c3,
            char c4) throws IOException {
        byte b1, b2, b3, b4;

        if (c3 == padding) {
            b1 = decodingTable[c1];
            b2 = decodingTable[c2];

            out.write((b1 << 2) | (b2 >> 4));

            return 1;
        } else if (c4 == padding) {
            b1 = decodingTable[c1];
            b2 = decodingTable[c2];
            b3 = decodingTable[c3];

            out.write((b1 << 2) | (b2 >> 4));
            out.write((b2 << 4) | (b3 >> 2));

            return 2;
        } else {
            b1 = decodingTable[c1];
            b2 = decodingTable[c2];
            b3 = decodingTable[c3];
            b4 = decodingTable[c4];

            out.write((b1 << 2) | (b2 >> 4));
            out.write((b2 << 4) | (b3 >> 2));
            out.write((b3 << 6) | b4);

            return 3;
        }
    }

    private int nextI(String data, int i, int finish) {
        while ((i < finish) && ignore(data.charAt(i))) {
            i++;
        }
        return i;
    }
}