/**
 *   Provides encoding of raw bytes to base64-encoded characters, and
 *  decoding of base64 characters to raw bytes.
 *
 * @author Kevin Kelley (kelley@iguana.ruralnet.net)
 * @version 1.0
 * @date 06 August 1998
 */

package com.gallery.GalleryRemote;

public class Base64 {
	public static String encode(String data) {
		return new String(encode(data.getBytes()));
	}

	public static String decode(String data) {
		char[] dataArr = new char[data.length()];
		data.getChars(0, data.length(), dataArr, 0);
		return new String(decode(dataArr));
	}

	/**
	 * returns an array of base64-encoded characters to represent the
	 * passed data array.
	 * 
	 * @param data the array of bytes to encode
	 * @return base64-coded character array.
	 */

	static public char[] encode(byte[] data) {
		char[] out = new char[((data.length + 2) / 3) * 4];

		//
		// 3 bytes encode to 4 chars.  Output is always an even
		// multiple of 4 characters.
		//
		for (int i = 0, index = 0; i < data.length; i += 3, index += 4) {
			boolean quad = false;
			boolean trip = false;

			int val = (0xFF & (int) data[i]);
			val <<= 8;
			if ((i + 1) < data.length) {
				val |= (0xFF & (int) data[i + 1]);
				trip = true;
			}
			val <<= 8;
			if ((i + 2) < data.length) {
				val |= (0xFF & (int) data[i + 2]);
				quad = true;
			}
			out[index + 3] = alphabet[(quad ? (val & 0x3F) : 64)];
			val >>= 6;
			out[index + 2] = alphabet[(trip ? (val & 0x3F) : 64)];
			val >>= 6;
			out[index + 1] = alphabet[val & 0x3F];
			val >>= 6;
			out[index + 0] = alphabet[val & 0x3F];
		}
		return out;
	}

	/**
	 * Returns an array of bytes which were encoded in the passed
	 * character array.
	 * 
	 * @param data the array of base64-encoded characters
	 * @return decoded data array
	 */
	static public byte[] decode(char[] data) {
		int len = ((data.length + 3) / 4) * 3;
		if (data.length > 0 && data[data.length - 1] == '=') --len;
		if (data.length > 1 && data[data.length - 2] == '=') --len;
		byte[] out = new byte[len];

		int shift = 0;   // # of excess bits stored in accum
		int accum = 0;   // excess bits
		int index = 0;

		for (int ix = 0; ix < data.length; ix++) {
			int value = codes[data[ix] & 0xFF];   // ignore high byte of char
			if (value >= 0) {                     // skip over non-code
				accum <<= 6;            // bits shift up by 6 each time thru
				shift += 6;             // loop, with new bits being put in
				accum |= value;         // at the bottom.
				if (shift >= 8) {     // whenever there are 8 or more shifted in,
					shift -= 8;         // write them out (from the top, leaving any
					out[index++] = // excess at the bottom for next iteration.
							(byte) ((accum >> shift) & 0xff);
				}
			}
		}
		if (index != out.length)
			throw new Error("miscalculated data length!");

		return out;
	}

	//
	// code characters for values 0..63
	//
	static private char[] alphabet =
			"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
			.toCharArray();

	//
	// lookup table for converting base64 characters to value in range 0..63
	//
	static private byte[] codes = new byte[256];

	static {
		for (int i = 0; i < 256; i++) codes[i] = -1;
		for (int i = 'A'; i <= 'Z'; i++) codes[i] = (byte) (i - 'A');
		for (int i = 'a'; i <= 'z'; i++) codes[i] = (byte) (26 + i - 'a');
		for (int i = '0'; i <= '9'; i++) codes[i] = (byte) (52 + i - '0');
		codes['+'] = 62;
		codes['/'] = 63;
	}
}
