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63 lines
1.6 KiB
JavaScript

"use strict";
/**
* btoa() as defined by the HTML and Infra specs, which mostly just references
* RFC 4648.
*/
function btoa(s) {
if (arguments.length === 0) {
throw new TypeError("1 argument required, but only 0 present.");
}
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.
*/
const keystr =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
function btoaLookup(index) {
if (index >= 0 && index < 64) {
return keystr[index];
}
// Throw INVALID_CHARACTER_ERR exception here -- won't be hit in the tests.
return undefined;
}
module.exports = btoa;