Base64.java

/*
 * Created on May 13, 2005
 *
 *Copyright Reliable Response, 2005
 */
package net.reliableresponse.notification.util;

/**
 * @author drig
 *
 * Copyright 2004 - David Rudder
 */
public class Base64 {
	
	public static String byteArrayToBase64(byte[] a) {
		int aLen = a.length;
		int numFullGroups = aLen / 3;
		int numBytesInPartialGroup = aLen - 3 * numFullGroups;
		int resultLen = 4 * ((aLen + 2) / 3);
		StringBuffer result = new StringBuffer(resultLen);
		char[] intToAlpha = intToBase64;

		// Translate all full groups from byte array elements to Base64
		int inCursor = 0;
		for (int i = 0; i < numFullGroups; i++) {
			int byte0 = a[inCursor++] & 0xff;
			int byte1 = a[inCursor++] & 0xff;
			int byte2 = a[inCursor++] & 0xff;
			result.append(intToAlpha[byte0 >> 2]);
			result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
			result.append(intToAlpha[(byte1 << 2) & 0x3f | (byte2 >> 6)]);
			result.append(intToAlpha[byte2 & 0x3f]);
		}

		// Translate partial group if present
		if (numBytesInPartialGroup != 0) {
			int byte0 = a[inCursor++] & 0xff;
			result.append(intToAlpha[byte0 >> 2]);
			if (numBytesInPartialGroup == 1) {
				result.append(intToAlpha[(byte0 << 4) & 0x3f]);
				result.append("==");
			} else {
				// assert numBytesInPartialGroup == 2;
				int byte1 = a[inCursor++] & 0xff;
				result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
				result.append(intToAlpha[(byte1 << 2) & 0x3f]);
				result.append('=');
			}
		}
		// assert inCursor == a.length;
		// assert result.length() == resultLen;
		return result.toString();
	}

	/**
	 * This array is a lookup table that translates 6-bit positive integer
	 * index values into their "Base64 Alphabet" equivalents as specified 
	 * in Table 1 of RFC 2045.
	 */
	public static final char intToBase64[] = { 'A', 'B', 'C', 'D', 'E', 'F',
			'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S',
			'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
			'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
			't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5',
			'6', '7', '8', '9', '+', '/' };


}