hust-epi/whepi-ui/static/js/base64.js

/**
* UTF16和UTF8转换对照表
* U+00000000 – U+0000007F 	0xxxxxxx
* U+00000080 – U+000007FF 	110xxxxx 10xxxxxx
* U+00000800 – U+0000FFFF 	1110xxxx 10xxxxxx 10xxxxxx
* U+00010000 – U+001FFFFF 	11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
* U+00200000 – U+03FFFFFF 	111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
* U+04000000 – U+7FFFFFFF 	1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
*/
var Base64 = {
	// 转码表
	table : [
			'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', '+', '/'
	],
	UTF16ToUTF8 : function(str) {
		var res = [], len = str.length;
		for (var i = 0; i < len; i++) {
			var code = str.charCodeAt(i);
			if (code > 0x0000 && code <= 0x007F) {
				// 单字节，这里并不考虑0x0000，因为它是空字节
				// U+00000000 – U+0000007F 	0xxxxxxx
				res.push(str.charAt(i));
			} else if (code >= 0x0080 && code <= 0x07FF) {
				// 双字节
				// U+00000080 – U+000007FF 	110xxxxx 10xxxxxx
				// 110xxxxx
				var byte1 = 0xC0 | ((code >> 6) & 0x1F);
				// 10xxxxxx
				var byte2 = 0x80 | (code & 0x3F);
				res.push(
					String.fromCharCode(byte1), 
					String.fromCharCode(byte2)
				);
			} else if (code >= 0x0800 && code <= 0xFFFF) {
				// 三字节
				// U+00000800 – U+0000FFFF 	1110xxxx 10xxxxxx 10xxxxxx
				// 1110xxxx
				var byte1 = 0xE0 | ((code >> 12) & 0x0F);
				// 10xxxxxx
				var byte2 = 0x80 | ((code >> 6) & 0x3F);
				// 10xxxxxx
				var byte3 = 0x80 | (code & 0x3F);
				res.push(
					String.fromCharCode(byte1), 
					String.fromCharCode(byte2), 
					String.fromCharCode(byte3)
				);
			} else if (code >= 0x00010000 && code <= 0x001FFFFF) {
				// 四字节
				// U+00010000 – U+001FFFFF 	11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
			} else if (code >= 0x00200000 && code <= 0x03FFFFFF) {
				// 五字节
				// U+00200000 – U+03FFFFFF 	111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
			} else /** if (code >= 0x04000000 && code <= 0x7FFFFFFF)*/ {
				// 六字节
				// U+04000000 – U+7FFFFFFF 	1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
			}
		}

		return res.join('');
	},
	UTF8ToUTF16 : function(str) {
		var res = [], len = str.length;
		var i = 0;
		for (var i = 0; i < len; i++) {
			var code = str.charCodeAt(i);
			// 对第一个字节进行判断
			if (((code >> 7) & 0xFF) == 0x0) {
				// 单字节
				// 0xxxxxxx
				res.push(str.charAt(i));
			} else if (((code >> 5) & 0xFF) == 0x6) {
				// 双字节
				// 110xxxxx 10xxxxxx
				var code2 = str.charCodeAt(++i);
				var byte1 = (code & 0x1F) << 6;
				var byte2 = code2 & 0x3F;
				var utf16 = byte1 | byte2;
				res.push(Sting.fromCharCode(utf16));
			} else if (((code >> 4) & 0xFF) == 0xE) {
				// 三字节
				// 1110xxxx 10xxxxxx 10xxxxxx
				var code2 = str.charCodeAt(++i);
				var code3 = str.charCodeAt(++i);
				var byte1 = (code << 4) | ((code2 >> 2) & 0x0F);
				var byte2 = ((code2 & 0x03) << 6) | (code3 & 0x3F);
				var utf16 = ((byte1 & 0x00FF) << 8) | byte2
				res.push(String.fromCharCode(utf16));
			} else if (((code >> 3) & 0xFF) == 0x1E) {
				// 四字节
				// 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
			} else if (((code >> 2) & 0xFF) == 0x3E) {
				// 五字节
				// 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
			} else /** if (((code >> 1) & 0xFF) == 0x7E)*/ {
				// 六字节
				// 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
			}
		}

		return res.join('');
	},
	encode : function(str) {
		if (!str) {
			return '';
		}
		var utf8    = this.UTF16ToUTF8(str); // 转成UTF8
		var i = 0; // 遍历索引
		var len = utf8.length;
		var res = [];
		while (i < len) {
			var c1 = utf8.charCodeAt(i++) & 0xFF;
			res.push(this.table[c1 >> 2]);
			// 需要补2个=
			if (i == len) {
				res.push(this.table[(c1 & 0x3) << 4]);
				res.push('==');
				break;
			}
			var c2 = utf8.charCodeAt(i++);
			// 需要补1个=
			if (i == len) {
				res.push(this.table[((c1 & 0x3) << 4) | ((c2 >> 4) & 0x0F)]);
				res.push(this.table[(c2 & 0x0F) << 2]);
				res.push('=');
				break;
			}
			var c3 = utf8.charCodeAt(i++);
			res.push(this.table[((c1 & 0x3) << 4) | ((c2 >> 4) & 0x0F)]);
			res.push(this.table[((c2 & 0x0F) << 2) | ((c3 & 0xC0) >> 6)]);
			res.push(this.table[c3 & 0x3F]);
		}

		return res.join('');
	},
	decode : function(str) {
		if (!str) {
			return '';
		}

		var len = str.length;
		var i   = 0;
		var res = [];

		while (i < len) {
			code1 = this.table.indexOf(str.charAt(i++));
			code2 = this.table.indexOf(str.charAt(i++));
			code3 = this.table.indexOf(str.charAt(i++));
			code4 = this.table.indexOf(str.charAt(i++));

			c1 = (code1 << 2) | (code2 >> 4);
			c2 = ((code2 & 0xF) << 4) | (code3 >> 2);
			c3 = ((code3 & 0x3) << 6) | code4;

			res.push(String.fromCharCode(c1));

			if (code3 != 64) {
				res.push(String.fromCharCode(c2));
			}
			if (code4 != 64) {
				res.push(String.fromCharCode(c3));
			}

		}

		return this.UTF8ToUTF16(res.join(''));
	}
};

/*
console.group('Test Base64: ');
var b64 = Base64.encode('Hello, oschina！又是一年春来到~');
console.log(b64);
console.log(Base64.decode(b64));
console.groupEnd();
*/