src/utils/base64.js
/*
* BSD 3-Clause License
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/**
* Base64 encode data
*
* @param {Buffer|ArrayBuffer} buffer - input buffer
* @author Jon Leighton
* @license MIT
* @see https://gist.github.com/jonleighton/958841
* @returns {string} - base 64 encoded data
* @private
*/
export function base64Encode (buffer) {
let base64 = '';
const encodings = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
const bytes = new Uint8Array(buffer);
const byteLength = bytes.byteLength;
const byteRemainder = byteLength % 3;
const mainLength = byteLength - byteRemainder;
let a, b, c, d;
let chunk;
// Main loop deals with bytes in chunks of 3
for (let i = 0; i < mainLength; i += 3) {
// Combine the three bytes into a single integer
chunk = bytes[i] * 65536 | bytes[i + 1] * 256 | bytes[i + 2];
// Use bitmasks to extract 6-bit segments from the triplet
a = (chunk & 16515072) >> 18; // 16515072 = (2^6 - 1) << 18
b = (chunk & 258048) >> 12; // 258048 = (2^6 - 1) << 12
c = (chunk & 4032) >> 6; // 4032 = (2^6 - 1) << 6
d = chunk & 63; // 63 = 2^6 - 1
// Convert the raw binary segments to the appropriate ASCII encoding
base64 += encodings[a] + encodings[b] + encodings[c] + encodings[d];
}
// Deal with the remaining bytes and padding
if (byteRemainder === 1) {
chunk = bytes[mainLength];
a = (chunk & 252) >> 2; // 252 = (2^6 - 1) << 2
// Set the 4 least significant bits to zero
b = (chunk & 3) << 4; // 3 = 2^2 - 1
base64 += `${encodings[a] + encodings[b]}==`;
} else if (byteRemainder === 2) {
chunk = bytes[mainLength] * 256 | bytes[mainLength + 1];
a = (chunk & 64512) >> 10; // 64512 = (2^6 - 1) << 10
b = (chunk & 1008) >> 4; // 1008 = (2^6 - 1) << 4
// Set the 2 least significant bits to zero
c = (chunk & 15) << 2; // 15 = 2^4 - 1
base64 += `${encodings[a] + encodings[b] + encodings[c]}=`;
}
return base64;
}