setup-python/node_modules/abab/lib/btoa.js
Danny McCormick 39c08a0eaa Initial pass
2019-06-26 21:12:00 -04:00

67 lines
1.7 KiB
JavaScript

"use strict";
/**
* btoa() as defined by the HTML and Infra specs, which mostly just references
* RFC 4648.
*/
function btoa(s) {
let i;
// String conversion as required by Web IDL.
s = `${s}`;
// "The btoa() method must throw an "InvalidCharacterError" DOMException if
// data contains any character whose code point is greater than U+00FF."
for (i = 0; i < s.length; i++) {
if (s.charCodeAt(i) > 255) {
return null;
}
}
let out = "";
for (i = 0; i < s.length; i += 3) {
const groupsOfSix = [undefined, undefined, undefined, undefined];
groupsOfSix[0] = s.charCodeAt(i) >> 2;
groupsOfSix[1] = (s.charCodeAt(i) & 0x03) << 4;
if (s.length > i + 1) {
groupsOfSix[1] |= s.charCodeAt(i + 1) >> 4;
groupsOfSix[2] = (s.charCodeAt(i + 1) & 0x0f) << 2;
}
if (s.length > i + 2) {
groupsOfSix[2] |= s.charCodeAt(i + 2) >> 6;
groupsOfSix[3] = s.charCodeAt(i + 2) & 0x3f;
}
for (let j = 0; j < groupsOfSix.length; j++) {
if (typeof groupsOfSix[j] === "undefined") {
out += "=";
} else {
out += btoaLookup(groupsOfSix[j]);
}
}
}
return out;
}
/**
* Lookup table for btoa(), which converts a six-bit number into the
* corresponding ASCII character.
*/
function btoaLookup(idx) {
if (idx < 26) {
return String.fromCharCode(idx + "A".charCodeAt(0));
}
if (idx < 52) {
return String.fromCharCode(idx - 26 + "a".charCodeAt(0));
}
if (idx < 62) {
return String.fromCharCode(idx - 52 + "0".charCodeAt(0));
}
if (idx === 62) {
return "+";
}
if (idx === 63) {
return "/";
}
// Throw INVALID_CHARACTER_ERR exception here -- won't be hit in the tests.
return undefined;
}
module.exports = btoa;