diantou/public/resource/share/js/base64.js

/*
编码规则

Base64编码的思想是是采用64个基本的ASCII码字符对数据进行重新编码。
它将需要编码的数据拆分成字节数组。
以3个字节为一组。按顺序排列24 位数据，再把这24位数据分成4组，即每组6位。
再在每组的的最高位前补两个0凑足一个字节。
这样就把一个3字节为一组的数据重新编码成了4个字节。
当所要编码的数据的字节数不是3的整倍数，
也就是说在分组时最后一组不够3个字节。
这时在最后一组填充1到2个0字节。
并在最后编码完成后在结尾添加1到2个 “=”。 
加密解密base64字符串
Add by mazhuang 2016026
 */
var Base64 = {
	//下面是64个基本的编码
	base64EncodeChars:
		'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=',
	base64DecodeChars: new Array(
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		62,
		-1,
		-1,
		-1,
		63,
		52,
		53,
		54,
		55,
		56,
		57,
		58,
		59,
		60,
		61,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		0,
		1,
		2,
		3,
		4,
		5,
		6,
		7,
		8,
		9,
		10,
		11,
		12,
		13,
		14,
		15,
		16,
		17,
		18,
		19,
		20,
		21,
		22,
		23,
		24,
		25,
		-1,
		-1,
		-1,
		-1,
		-1,
		-1,
		26,
		27,
		28,
		29,
		30,
		31,
		32,
		33,
		34,
		35,
		36,
		37,
		38,
		39,
		40,
		41,
		42,
		43,
		44,
		45,
		46,
		47,
		48,
		49,
		50,
		51,
		-1,
		-1,
		-1,
		-1,
		-1
	),
	//编码的方法
	base64encode: function (str) {
		var out, i, len
		var c1, c2, c3
		len = str.length
		i = 0
		out = ''
		while (i < len) {
			c1 = str.charCodeAt(i++) & 0xff
			if (i == len) {
				out += Base64.base64EncodeChars.charAt(c1 >> 2)
				out += Base64.base64EncodeChars.charAt((c1 & 0x3) << 4)
				out += '=='
				break
			}
			c2 = str.charCodeAt(i++)
			if (i == len) {
				out += Base64.base64EncodeChars.charAt(c1 >> 2)
				out += Base64.base64EncodeChars.charAt(
					((c1 & 0x3) << 4) | ((c2 & 0xf0) >> 4)
				)
				out += Base64.base64EncodeChars.charAt((c2 & 0xf) << 2)
				out += '='
				break
			}
			c3 = str.charCodeAt(i++)
			out += Base64.base64EncodeChars.charAt(c1 >> 2)
			out += Base64.base64EncodeChars.charAt(
				((c1 & 0x3) << 4) | ((c2 & 0xf0) >> 4)
			)
			out += Base64.base64EncodeChars.charAt(
				((c2 & 0xf) << 2) | ((c3 & 0xc0) >> 6)
			)
			out += Base64.base64EncodeChars.charAt(c3 & 0x3f)
		}
		return out
	},

	//解码的方法
	base64decode: function (str) {
		var c1, c2, c3, c4
		var i, len, out
		len = str.length
		i = 0
		out = ''
		while (i < len) {
			do {
				c1 = Base64.base64DecodeChars[str.charCodeAt(i++) & 0xff]
			} while (i < len && c1 == -1)
			if (c1 == -1) break
			do {
				c2 = Base64.base64DecodeChars[str.charCodeAt(i++) & 0xff]
			} while (i < len && c2 == -1)
			if (c2 == -1) break
			out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4))
			do {
				c3 = str.charCodeAt(i++) & 0xff
				if (c3 == 61) return out
				c3 = Base64.base64DecodeChars[c3]
			} while (i < len && c3 == -1)
			if (c3 == -1) break
			out += String.fromCharCode(((c2 & 0xf) << 4) | ((c3 & 0x3c) >> 2))
			do {
				c4 = str.charCodeAt(i++) & 0xff
				if (c4 == 61) return out
				c4 = Base64.base64DecodeChars[c4]
			} while (i < len && c4 == -1)
			if (c4 == -1) break
			out += String.fromCharCode(((c3 & 0x03) << 6) | c4)
		}
		return out
	},

	utf16to8: function (str) {
		var out, i, len, c
		out = ''
		len = str.length
		for (i = 0; i < len; i++) {
			c = str.charCodeAt(i)
			if (c >= 0x0001 && c <= 0x007f) {
				out += str.charAt(i)
			} else if (c > 0x07ff) {
				out += String.fromCharCode(0xe0 | ((c >> 12) & 0x0f))
				out += String.fromCharCode(0x80 | ((c >> 6) & 0x3f))
				out += String.fromCharCode(0x80 | ((c >> 0) & 0x3f))
			} else {
				out += String.fromCharCode(0xc0 | ((c >> 6) & 0x1f))
				out += String.fromCharCode(0x80 | ((c >> 0) & 0x3f))
			}
		}
		return out
	},

	utf8to16: function (str) {
		var out, i, len, c
		var char2, char3
		out = ''
		len = str.length
		i = 0
		while (i < len) {
			c = str.charCodeAt(i++)
			switch (c >> 4) {
				case 0:
				case 1:
				case 2:
				case 3:
				case 4:
				case 5:
				case 6:
				case 7:
					// 0xxxxxxx
					out += str.charAt(i - 1)
					break
				case 12:
				case 13:
					// 110x xxxx   10xx xxxx
					char2 = str.charCodeAt(i++)
					out += String.fromCharCode(((c & 0x1f) << 6) | (char2 & 0x3f))
					break
				case 14:
					// 1110 xxxx  10xx xxxx  10xx xxxx
					char2 = str.charCodeAt(i++)
					char3 = str.charCodeAt(i++)
					out += String.fromCharCode(
						((c & 0x0f) << 12) | ((char2 & 0x3f) << 6) | ((char3 & 0x3f) << 0)
					)
					break
			}
		}
		return out
	}, //end
	encode: function (input) {
		return Base64.base64encode(Base64.utf16to8(input))
	},
	decode: function (str) {
		return Base64.utf8to16(Base64.base64decode(str))
	},
	isBase64: function (str) {
		return !str.match(/./g).some((x) => this.base64EncodeChars.indexOf(x) == -1)
	},
}