package com.simpleteam.coder;



import com.simpleteam.*;



/**

 * <p>Title: SimpleTeam</p>

 * <p>Description: Base64 Coder</p>

 * <p>Copyright: All rights reserved by www.simpleteam.com. Copyright (c) 2003 ~ 2006</p>

 * <p>Company: www.simpleteam.com</p>

 * @author forest_luo@simpleteam.com

 * @version 1.1.2

 */



public class Base64Coder

{

	//Base64 Alphabet

	private final static String base64Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

	//Masks

	private final static int[] mask = {0,1,3,7,15,31,63,127,255};



	//Type of Coder

	public final static String TYPE                         = "B";



	/**

	 * Encode.

	 *

	 * @param index Value for encoding.

	 * @return

	 *     <p>Encoded value.</p>

	 */

	private static char encode(int index)

	{

		//Check index.

		if(index >= 0 && index <= 63)

		{

			//Return char.

			return base64Alphabet.charAt(index);

		}

		//Return -1.

		return (char)-1;

	}



	/**

	 * Decode.

	 *

	 * @param value Encoded value.

	 * @return

	 *     <p>Value for decoding.</p>

	 */

	private static int decode(char value)

	{

		//Check value in table.

		for(int i = 0;i < 64;i ++)

		{

			//Check value.

			if(base64Alphabet.charAt(i) == value) return i;

		}

		//Return -1.

		return -1;

	}



	/**

	 * Make base64 encode.

	 *

	 * @param bytes Bytes for encoding.

	 * @return

	 *     <p>Encoded bytes.</p>

	 */

	public static String encode(byte[] bytes)

	{

		//Calculate bytes needed.

		int bytesNeeded = bytes.length * 8 / 6 + (((bytes.length * 8 % 6) == 0) ? 0 : 1);

		//System.out.println("Base64Coder.encode : " + bytesNeeded + " bytes needed !");

		int bytesPatched = ((bytesNeeded % 4) != 0) ? (4 - bytesNeeded % 4) : 0;



		//Create buffer.

		StringBuffer buffer = new StringBuffer();

		//Encode bytes.

		for(int i = 0;i < bytesNeeded;i ++)

		{

			//Get index.

			int index = i * 6 / 8;

			//Get offset.

			int offset = i * 6 % 8;

			//System.out.println("Base64Coder.encode : index=" + index + ",offset=" + offset);



			int bitsLeft = (offset > 0) ? (8 - offset) : 0;

			//System.out.println("Base64Coder.encode : bitsLeft=" + bitsLeft);

			int bitsNeeded = (bitsLeft > 0) ? (6 - bitsLeft) : 6;

			//System.out.println("Base64Coder.encode : nBitsNeed=" + bitsNeeded);



			int codeIndex = 0;



			//Check left bits.

			if(bitsLeft > 0)

			{

				//Get index of code.

				codeIndex = ((int)bytes[index]) & mask[bitsLeft];

				//Shift index.

				codeIndex <<= bitsNeeded;

			}



			//Check needed bits.

			if(bitsNeeded > 0)

			{

				//Get bits of shift.

				int bitsShift = 8 - bitsNeeded;

				//Calculate value.

				int value = 0;

				index += (offset <= 2) ? 0 : 1;

				if(index < bytes.length)

				{

					value = bytes[index];

				}

				//Get index of code.

				codeIndex |= (value >> bitsShift) & mask[bitsNeeded];

			}



			//System.out.println("Base64Coder.encode : codeIndex=" + codeIndex);

			buffer.append(encode(codeIndex));

			//System.out.println("Base64Coder.encode : encode=" + (char)temp[i]);

		}

		//Patch bytes.

		for(int i = 0;i < bytesPatched;i ++) buffer.append('=');

		//Return encoded.

		return buffer.toString();

	}



	/**

	 * Make base64 decode bytes.

	 *

	 * @param encoded Encoded bytes.

	 * @return

	 *     <p>Decoded bytes.</p>

	 */

	public static byte[] decode(String encoded)

	{

		//Patched bytes.

		int bytesPatched = 0;

		//Find patched bytes.

		for(int i = encoded.length();i > 0;i --)

		{

			//Check byte.

			if(encoded.charAt(i - 1) != '=') break;

			//Add bytes pathced.

			bytesPatched ++;

		}



		int bytesNeeded = (encoded.length() - bytesPatched) * 6 / 8;

		//System.out.println("Base64Coder.encode : " + bytesNeeded + " bytes needed !");



		//Create decoded bytes.

		byte[] decoded = new byte[bytesNeeded];

		//Decode bytes.

		for(int i = 0;i < bytesNeeded;i ++)

		{

			int index = i * 8 / 6;

			int offset = i * 8 % 6;

			//System.out.println("Base64Coder.encode : index=" + index + ",offset=" + offset);



			int bitsLeft = (offset > 0) ? (6 - offset) : 6;

			//System.out.println("Base64Coder.encode : bitsLeft=" + bitsLeft);

			int bitsNeeded = (bitsLeft > 0) ? (8 - bitsLeft) : 8;

			//System.out.println("Base64Coder.encode : nBitsNeed=" + bitsNeeded);



			int value = 0;



			//Check left bits.

			if(bitsLeft > 0)

			{

				//Get value.

				value = decode(encoded.charAt(index)) & mask[bitsLeft];

				//Shift value.

				value <<= bitsNeeded;

			}



			//Check needed bits.

			if(bitsNeeded > 0)

			{

				//Get bits of shift.

				int bitsShift = 6 - bitsNeeded;

				//Get byte value.

				int byteValue = decode(encoded.charAt(index + 1));

				//Get value.

				value |= (byteValue >> bitsShift) & mask[bitsNeeded];

			}

			//Set decoded byte.

			decoded[i] = (byte)(value & 0xff);

		}

		//Return decoded bytes.

		return decoded;

	}



	/**

	 * Main.

	 *

	 * @param args Arguments.

	 * @return

	 *     <p>No results returned.</p>

	 */

	public static void main(String[] args)

	{

		//Check arguments.

		if(args.length != 1)

		{

			//Print.

			System.out.println("Usage : java Base64Coder [base64 coded string]");

			return;

		}

		//Print encoded string.

		System.out.println("encoded string : " + args[0]);



		try

		{

			//Get bytes.

			byte[] bytes = Base64Coder.decode(args[0]);

			//Print bytes.

			System.out.println("decoded bytes : 0x" + Hex.toString(bytes));

			//Print.

			System.out.println("original bytes : 0x" + Hex.toString("ÂÞˆÒ".getBytes("gb2312")));

			//Print.

			System.out.println("decoded string : " + new String(bytes,"gb2312"));

		}

		catch(Exception e)

		{

			System.out.println("Base64Coder.main : " + e.getMessage());

			System.out.println("Base64Coder.main : unexpected exit !");

		}

	}

}