JavaでBase64のエンコード・デコード

1年以上前に作ったJavaでのBase64のエンコード、デコードのクラスです。

ソース

MyBase64.java

class MyBase64 {
	final static char[] base64 = {
		'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', '+', '/'
	};

	public static String encode(String str){
		byte[] b = str.getBytes();
		int[] p = new int[b.length];
		String out = "";
		int i, j, bb = 0;

		for(i = 0; i < b.length; i++){
			if(b[i] < 0)p[i] = b[i] + 256;
			else p[i] = b[i];
		}

		for(i = j = 0; i < p.length; i++){
			bb = (bb << 8) + p[i];
			if(j == 2){
				out += encode24(bb, 2);
				j = bb = 0;
			}
			else j++;
		}
		if(j > 0)out += encode24(bb, j - 1);

		return out;
	}

	private static String encode24(int bb, int srclen){
		String out = "";
		int base, x;

		bb <<= 8 * (2 - srclen);
		for(base = 18, x = 0; x < srclen + 2; x++, base -= 6){
			out += base64[(bb >> base) & 0x3F];
		}
		for(int i = x; i < 4; i++)out += "=";

		return out;
	}

	public static String decode(String str){
		byte[] b = str.getBytes();
		int[] p = new int[b.length];
		int[] map = new int [128];
		byte[] out = new byte[p.length * 3 / 4];
		int i, j, bb = 0, count = 0;

		for(i = 0; i < b.length; i++){
			if(b[i] < 0)p[i] = b[i] + 256;
			else p[i] = b[i];
		}

		map['='] = 0;
		for(i = 0; i < base64.length; i++){
			map[(int)base64[i]] = i;
		}

		for(i = j = 0; i < p.length; i++){
			bb = (bb << 6) + map[(int)p[i]];
			if(j == 3){
				count += decode24(bb, out, count);
				j = bb = 0;
			}
			else j++;
		}

		byte[] out2 = new byte[count];
		for(i = 0; i < count; i++)out2[i] = out[i];

		return new String(out2);
	}

	private static int decode24(int bb, byte[] out, int count){
		int i;
		for(i = 0; bb != 0; i++, bb = (bb << 8) & 0xffffff){
			out[count++] = (byte)((bb & 0x00ff0000) >> 16);
		}
		return i;
	}
}

Test.java

class Test {
	public static void main(String[] args) {
		String str = args[0];

		System.out.println("Plain  : " + str);
		str = MyBase64.encode(str);
		System.out.println("Base64 : " + str);
		str = MyBase64.decode(str);
		System.out.println("Plain? : " + str);
	}
}

実行結果

$ java Test "#include <stdio.h>"
Plain  : #include <stdio.h>
Base64 : I2luY2x1ZGUgPHN0ZGlvLmg+
Plain? : #include <stdio.h>

問題なさそうです。（多分