js实现Base64编码解码
夹谷苗宣
js实现标准的Base64编码解码
Base64 是使用64个可打印ASCII字符(A-Z、a-z、0-9、+、/)将任意字节序列数据编码成ASCII字符串，另有“=”符号用作后缀
;(function(global) {
//int转byte
function int2Byte(i) {
var b = i & 0xFF; //[0-255]
var c = 0;
if (b >= 0x80) {
c = b % 0x80;
c = -1 * (0x80 - c);
} else {
c = b;
}
return c;
}
//字符串转byte[]
function str2Bytes(str) {
var ch, stack, result = [];
for (var i = 0, len = str.length; i < len; i++) {
ch = str.charCodeAt(i);
stack = [];
if (ch >= 0x010000 && ch <= 0x10FFFF) {
stack.push(int2Byte(((ch >> 18) & 0x07) | 0xF0));
stack.push(int2Byte(((ch >> 12) & 0x3F) | 0x80));
stack.push(int2Byte(((ch >> 6) & 0x3F) | 0x80));
stack.push(int2Byte((ch & 0x3F) | 0x80));
} else if (ch >= 0x000800 && ch <= 0x00FFFF) {
stack.push(int2Byte(((ch >> 12) & 0x0F) | 0xE0));
stack.push(int2Byte(((ch >> 6) & 0x3F) | 0x80));
stack.push(int2Byte((ch & 0x3F) | 0x80));
} else if (ch >= 0x000080 && ch <= 0x0007FF) {
stack.push(int2Byte(((ch >> 6) & 0x1F) | 0xC0));
stack.push(int2Byte((ch & 0x3F) | 0x80));
} else {
stack.push(ch & 0xFF);
}
result = result.concat(stack);
}
return result;
}
//byte[]转string
function bytes2Str(_arr) {
var unicodeStr = '';
for (var pos = 0, len = _arr.length; pos < len;) {
var flag = _arr[pos];
var unicode = 0;
if ((flag >>> 7) === 0) {
unicodeStr += String.fromCharCode(_arr[pos]);
pos += 1;
} else if ((flag & 0xF0) === 0xF0) {
unicode = (_arr[pos] & 0xF) << 18;
unicode |= (_arr[pos + 1] & 0x3F) << 12;
unicode |= (_arr[pos + 2] & 0x3F) << 6;
unicode |= (_arr[pos + 3] & 0x3F);
unicodeStr += String.fromCodePoint(unicode);
pos += 4;
} else if ((flag & 0xE0) === 0xE0) {
unicode = (_arr[pos] & 0x1F) << 12;;
unicode |= (_arr[pos + 1] & 0x3F) << 6;
unicode |= (_arr[pos + 2] & 0x3F);
unicodeStr += String.fromCharCode(unicode);
pos += 3;
} else if ((flag & 0xC0) === 0xC0) {
unicode = (_arr[pos] & 0x3F) << 6;
unicode |= (_arr[pos + 1] & 0x3F);
unicodeStr += String.fromCharCode(unicode);
pos += 2;
} else {
unicodeStr += String.fromCharCode(_arr[pos]);
pos += 1;
}
}
return unicodeStr;
}
var toBase64 = [
'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', '+', '/'
];
var fromBase64 = new Array();
for (var i = 0, len = 256; i < len; i++) {
fromBase64[i] = -1;
}
for (var j = 0; j < toBase64.length; j++) {
fromBase64[toBase64[j].charCodeAt(0)] = j;
}
fromBase64['='.charCodeAt(0)] = -2;
//base64编码 string return byte[]
function _encodeBase64(src) {
src = src || '';
var bsrc = str2Bytes(src);
var end = bsrc.length;
var off = 0;
var dst = [];
var base64 = [];
for (var i = 0, len = toBase64.length; i < len; i++) {
base64[i] = toBase64[i].charCodeAt(0);
}
var sp = off;
var slen = Math.trunc((end - off) / 3) * 3;
var sl = off + slen;
var dp = 0;
while (sp < sl) {
var sl0 = Math.min(sp + slen, sl);
for (var sp0 = sp, dp0 = dp; sp0 < sl0;) {
var bits = (bsrc[sp0++] & 0xff) << 16 | (bsrc[sp0++] & 0xff) << 8 | (bsrc[sp0++] & 0xff);
dst[dp0++] = int2Byte(base64[(bits >>> 18) & 0x3f]);
dst[dp0++] = int2Byte(base64[(bits >>> 12) & 0x3f]);
dst[dp0++] = int2Byte(base64[(bits >>> 6) & 0x3f]);
dst[dp0++] = int2Byte(base64[bits & 0x3f]);
}
var dlen = (sl0 - sp) / 3 * 4;
dp += dlen;
sp = sl0;
}
if (sp < end) {
var b0 = bsrc[sp++] & 0xff;
dst[dp++] = int2Byte(base64[b0 >> 2]);
if (sp == end) {
dst[dp++] = int2Byte(base64[(b0 << 4) & 0x3f]);
dst[dp++] = '='.charCodeAt(0);
dst[dp++] = '='.charCodeAt(0);
} else {
var b1 = bsrc[sp++] & 0xff;
dst[dp++] = int2Byte(base64[(b0 << 4) & 0x3f | (b1 >> 4)]);
dst[dp++] = int2Byte(base64[(b1 << 2) & 0x3f]);
dst[dp++] = '='.charCodeAt(0);
}
}
return dst;
}
//base64解码 string return byte[]
function _decodeBase64(src) {
src = (src || '').replace(/[^A-z0-9+/]/g, '');
var bsrc = str2Bytes(src);
var sl = bsrc.length;
var sp = 0;
var dst = [];
var base64 = fromBase64;
var dp = 0;
var bits = 0;
var shiftto = 18;
while (sl > sp) {
var b = bsrc[sp++] & 0xff;
if ((b = base64[b]) < 0) {
if (b == -2) {
break;
}
}
bits |= (b << shiftto);
shiftto -= 6;
if (shiftto < 0) {
dst[dp++] = int2Byte(bits >> 16);
dst[dp++] = int2Byte(bits >> 8);
dst[dp++] = int2Byte(bits);
shiftto = 18;
bits = 0;
}
}
if (shiftto == 6) {
dst[dp++] = int2Byte(bits >> 16);
} else if (shiftto == 0) {
dst[dp++] = int2Byte(bits >> 16);
dst[dp++] = int2Byte(bits >> 8);
}
return dst;
}
global.BASE64 = {
decodeBase64: _decodeBase64,
encodeBase64: _encodeBase64,
strToBytes: str2Bytes,
bytesToString: bytes2Str
};
})(window);
如何使用：
var en = BASE64.encodeBase64("js实现Base64编码解码");
console.log(en);//[97, 110, 80, 108, 114, 112, 55, 110, 106, 114, 66, 67, 89, 88, 78, 108, 78, 106, 84, 110, 118, 74, 98, 110, 111, 73, 72, 111, 112, 54, 80, 110, 111, 73, 69, 61]
var enStr = BASE64.bytesToString(en);
console.log(enStr); //anPlrp7njrBCYXNlNjTnvJbnoIHop6PnoIE=
var de = BASE64.decodeBase64(enStr);
console.log(de);//[106, 115, -27, -82, -98, -25, -114, -80, 66, 97, 115, 101, 54, 52, -25, -68, -106, -25, -96, -127, -24, -89, -93, -25, -96, -127]
var deStr = BASE64.bytesToString(de);
console.log(deStr);//js实现Base64编码解码
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