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   8    * particular file as subject to the "Classpath" exception as provided
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  13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14    * version 2 for more details (a copy is included in the LICENSE file that
  15    * accompanied this code).
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package com.gingersoft.gsa.cloud.common.utils.encryption;

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

import Decoder.CharacterEncoder;

/**
 * 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]);
		}
	}
}