再造轮子之－Base64与Base62编码

Base64编码

	private static char[] encodes = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
			.toCharArray();
	private static byte[] decodes = new byte[256];
	static {
		for (int i = 0; i < encodes.length; i++) {
			decodes[encodes[i]] = (byte) i;
		}
	}

	public static StringBuffer encodeBase64(byte[] data) {
		StringBuffer sb = new StringBuffer(data.length * 2);
		int pos = 0, val = 0;
		for (int i = 0; i < data.length; i++) {
			val = (val << 8) | (data[i] & 0xFF);
			pos += 8;
			while (pos > 5) {
				sb.append(encodes[val >> (pos -= 6)]);
				val &= ((1 << pos) - 1);
			}
		}
		if (pos > 0) {
			sb.append(encodes[val << (6 - pos)]);
		}
		return sb;
	}

	public static byte[] decodeBase64(char[] data) {
		ByteArrayOutputStream baos = new ByteArrayOutputStream(data.length);
		int pos = 0, val = 0;
		for (int i = 0; i < data.length; i++) {
			val = (val << 6) | decodes[data[i]];
			pos += 6;
			while (pos > 7) {
				baos.write(val >> (pos -= 8));
				val &= ((1 << pos) - 1);
			}
		}
		return baos.toByteArray();
	}

Base62编码

	public static StringBuffer encodeBase62(byte[] data) {
		StringBuffer sb = new StringBuffer(data.length * 2);
		int pos = 0, val = 0;
		for (int i = 0; i < data.length; i++) {
			val = (val << 8) | (data[i] & 0xFF);
			pos += 8;
			while (pos > 5) {
				char c = encodes[val >> (pos -= 6)];
				sb.append(
				/**/c == 'i' ? "ia" :
				/**/c == '+' ? "ib" :
				/**/c == '/' ? "ic" : c);
				val &= ((1 << pos) - 1);
			}
		}
		if (pos > 0) {
			char c = encodes[val << (6 - pos)];
			sb.append(
			/**/c == 'i' ? "ia" :
			/**/c == '+' ? "ib" :
			/**/c == '/' ? "ic" : c);
		}
		return sb;
	}

	public static byte[] decodeBase62(char[] data) {
		ByteArrayOutputStream baos = new ByteArrayOutputStream(data.length);
		int pos = 0, val = 0;
		for (int i = 0; i < data.length; i++) {
			char c = data[i];
			if (c == 'i') {
				c = data[++i];
				c =
				/**/c == 'a' ? 'i' :
				/**/c == 'b' ? '+' :
				/**/c == 'c' ? '/' : data[--i];
			}
			val = (val << 6) | decodes[c];
			pos += 6;
			while (pos > 7) {
				baos.write(val >> (pos -= 8));
				val &= ((1 << pos) - 1);
			}
		}
		return baos.toByteArray();
	}