base64tools.java

学生成绩管理系统

package com.stuman.util;

public class Base64Tools {
	public static final char[] alphabet = { 'A', 'B', 'C', 'D', 'E', 'F', 'G',
			'H', // 0 to 7
			'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 8 to 15
			'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 16 to 23
			'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', // 24 to 31
			'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', // 32 to 39
			'o', 'p', 'q', 'r', 's', 't', 'u', 'v', // 40 to 47
			'w', 'x', 'y', 'z', '0', '1', '2', '3', // 48 to 55
			'4', '5', '6', '7', '8', '9', '+', '/' }; // 56 to 63

	public static String encode(String s) {
		return encode(s.getBytes());
	}

	public static String encode(byte[] octetString) {
		int bits24;
		int bits6;
		char[] out = new char[((octetString.length - 1) / 3 + 1) * 4];
		int outIndex = 0;
		int i = 0;
		while ((i + 3) <= octetString.length) {
			// store the octets
			bits24 = (octetString[i++] & 0xFF) << 16;
			bits24 |= (octetString[i++] & 0xFF) << 8;
			bits24 |= (octetString[i++] & 0xFF) << 0;

			bits6 = (bits24 & 0x00FC0000) >> 18;
			out[outIndex++] = alphabet[bits6];
			bits6 = (bits24 & 0x0003F000) >> 12;
			out[outIndex++] = alphabet[bits6];
			bits6 = (bits24 & 0x00000FC0) >> 6;
			out[outIndex++] = alphabet[bits6];
			bits6 = (bits24 & 0x0000003F);
			out[outIndex++] = alphabet[bits6];
		}

		if (octetString.length - i == 2) {
			bits24 = (octetString[i] & 0xFF) << 16;
			bits24 |= (octetString[i + 1] & 0xFF) << 8;
			bits6 = (bits24 & 0x00FC0000) >> 18;
			out[outIndex++] = alphabet[bits6];
			bits6 = (bits24 & 0x0003F000) >> 12;
			out[outIndex++] = alphabet[bits6];
			bits6 = (bits24 & 0x00000FC0) >> 6;
			out[outIndex++] = alphabet[bits6];
			// padding
			out[outIndex++] = '=';
		} else if (octetString.length - i == 1) {
			// store the octets
			bits24 = (octetString[i] & 0xFF) << 16;
			bits6 = (bits24 & 0x00FC0000) >> 18;
			out[outIndex++] = alphabet[bits6];
			bits6 = (bits24 & 0x0003F000) >> 12;
			out[outIndex++] = alphabet[bits6];
			// padding
			out[outIndex++] = '=';
			out[outIndex++] = '=';
		}
		return new String(out);
	}

}