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Encode/decode ASCII string to/from base64
/**
* Encode string into Base64, as defined by RFC 4648 [http://tools.ietf.org/html/rfc4648].
* As per RFC 4648, no newlines are added.
*
* Characters in str must be within ISO-8859-1 with Unicode code point <= 256.
*
* Can be achieved JavaScript with btoa(), but this approach may be useful in other languages.
*
* @param {string} str ASCII/ISO-8859-1 string to be encoded as base-64.
* @returns {string} Base64-encoded string.
*/
function Base64Encode(str) {
if (/([^\u0000-\u00ff])/.test(str)) throw Error('String must be ASCII');
var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
var o1, o2, o3, bits, h1, h2, h3, h4, e=[], pad = '', c;
c = str.length % 3; // pad string to length of multiple of 3
if (c > 0) { while (c++ < 3) { pad += '='; str += '\0'; } }
// note: doing padding here saves us doing special-case packing for trailing 1 or 2 chars
for (c=0; c<str.length; c+=3) { // pack three octets into four hexets
o1 = str.charCodeAt(c);
o2 = str.charCodeAt(c+1);
o3 = str.charCodeAt(c+2);
bits = o1<<16 | o2<<8 | o3;
h1 = bits>>18 & 0x3f;
h2 = bits>>12 & 0x3f;
h3 = bits>>6 & 0x3f;
h4 = bits & 0x3f;
// use hextets to index into code string
e[c/3] = b64.charAt(h1) + b64.charAt(h2) + b64.charAt(h3) + b64.charAt(h4);
}
str = e.join(''); // use Array.join() for better performance than repeated string appends
// replace 'A's from padded nulls with '='s
str = str.slice(0, str.length-pad.length) + pad;
return str;
}
/**
* Decode string from Base64, as defined by RFC 4648 [http://tools.ietf.org/html/rfc4648].
* As per RFC 4648, newlines are not catered for.
*
* Can be achieved JavaScript with atob(), but this approach may be useful in other languages.
*
* @param {string} str Base64-encoded string.
* @returns {string} Decoded ASCII/ISO-8859-1 string.
*/
function Base64Decode(str) {
if (!(/^[a-z0-9+/]+={0,2}$/i.test(str)) || str.length%4 != 0) throw Error('Not base64 string');
var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
var o1, o2, o3, h1, h2, h3, h4, bits, d=[];
for (var c=0; c<str.length; c+=4) { // unpack four hexets into three octets
h1 = b64.indexOf(str.charAt(c));
h2 = b64.indexOf(str.charAt(c+1));
h3 = b64.indexOf(str.charAt(c+2));
h4 = b64.indexOf(str.charAt(c+3));
bits = h1<<18 | h2<<12 | h3<<6 | h4;
o1 = bits>>>16 & 0xff;
o2 = bits>>>8 & 0xff;
o3 = bits & 0xff;
d[c/4] = String.fromCharCode(o1, o2, o3);
// check for padding
if (h4 == 0x40) d[c/4] = String.fromCharCode(o1, o2);
if (h3 == 0x40) d[c/4] = String.fromCharCode(o1);
}
str = d.join(''); // use Array.join() for better performance than repeated string appends
return str;
}

Hi: what would be the license for this code?

Owner

chrisveness commented Mar 22, 2017

Sorry I didn't notice this comment. All my code is licensed under MIT, you are free to use and/or adapt it.

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