/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * particular file as subject to the "Classpath" exception as provided

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 */

package sun.misc;

import java.io.OutputStream;

import java.io.InputStream;

import java.io.PrintStream;

import java.io.IOException;

/**

 * This class implements a BASE64 Character encoder as specified in RFC1521.

 * This RFC is part of the MIME specification as published by the Internet

 * Engineering Task Force (IETF). Unlike some other encoding schemes there

 * is nothing in this encoding that indicates

 * where a buffer starts or ends.

 *

 * This means that the encoded text will simply start with the first line

 * of encoded text and end with the last line of encoded text.

 *

 * @author      Chuck McManis

 * @see         CharacterEncoder

 * @see         BASE64Decoder

 */

public class BASE64Encoder extends CharacterEncoder {

    /** this class encodes three bytes per atom. */

    protected int bytesPerAtom() {

        return (3);

    }

    /**

     * this class encodes 57 bytes per line. This results in a maximum

     * of 57/3 * 4 or 76 characters per output line. Not counting the

     * line termination.

     */

    protected int bytesPerLine() {

        return (57);

    }

    /** This array maps the characters to their 6 bit values */

    private final static char pem_array[] = {

        //       0   1   2   3   4   5   6   7

                'A','B','C','D','E','F','G','H', // 0

                'I','J','K','L','M','N','O','P', // 1

                'Q','R','S','T','U','V','W','X', // 2

                'Y','Z','a','b','c','d','e','f', // 3

                'g','h','i','j','k','l','m','n', // 4

                'o','p','q','r','s','t','u','v', // 5

                'w','x','y','z','0','1','2','3', // 6

                '4','5','6','7','8','9','+','/'  // 7

        };

    /**

     * encodeAtom - Take three bytes of input and encode it as 4

     * printable characters. Note that if the length in len is less

     * than three is encodes either one or two '=' signs to indicate

     * padding characters.

     */

    protected void encodeAtom(OutputStream outStream, byte data[], int offset, int len)

        throws IOException {

        byte a, b, c;

        if (len == 1) {

            a = data[offset];

            b = 0;

            c = 0;

            outStream.write(pem_array[(a >>> 2) & 0x3F]);

            outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);

            outStream.write('=');

            outStream.write('=');

        } else if (len == 2) {

            a = data[offset];

            b = data[offset+1];

            c = 0;

            outStream.write(pem_array[(a >>> 2) & 0x3F]);

            outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);

            outStream.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);

            outStream.write('=');

        } else {

            a = data[offset];

            b = data[offset+1];

            c = data[offset+2];

            outStream.write(pem_array[(a >>> 2) & 0x3F]);

            outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);

            outStream.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);

            outStream.write(pem_array[c & 0x3F]);

        }

    }

}