cohost.js-fork/lib/b64arraybuffer.js

66 lines
1.6 KiB
JavaScript

var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
// Use a lookup table to find the index.
var lookup = new Uint8Array(256);
for (var i = 0; i < chars.length; i++) {
lookup[chars.charCodeAt(i)] = i;
}
function encode(arraybuffer) {
var bytes = new Uint8Array(arraybuffer),
i,
len = bytes.length,
base64 = "";
for (i = 0; i < len; i += 3) {
base64 += chars[bytes[i] >> 2];
base64 += chars[((bytes[i] & 3) << 4) | (bytes[i + 1] >> 4)];
base64 += chars[((bytes[i + 1] & 15) << 2) | (bytes[i + 2] >> 6)];
base64 += chars[bytes[i + 2] & 63];
}
if (len % 3 === 2) {
base64 = base64.substring(0, base64.length - 1) + "=";
} else if (len % 3 === 1) {
base64 = base64.substring(0, base64.length - 2) + "==";
}
return base64;
}
function decode(base64) {
var bufferLength = base64.length * 0.75,
len = base64.length,
i,
p = 0,
encoded1,
encoded2,
encoded3,
encoded4;
if (base64[base64.length - 1] === "=") {
bufferLength--;
if (base64[base64.length - 2] === "=") {
bufferLength--;
}
}
var arraybuffer = new ArrayBuffer(bufferLength),
bytes = new Uint8Array(arraybuffer);
for (i = 0; i < len; i += 4) {
encoded1 = lookup[base64.charCodeAt(i)];
encoded2 = lookup[base64.charCodeAt(i + 1)];
encoded3 = lookup[base64.charCodeAt(i + 2)];
encoded4 = lookup[base64.charCodeAt(i + 3)];
bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
bytes[p++] = ((encoded3 & 3) << 6) | (encoded4 & 63);
}
return arraybuffer;
}
module.exports = { encode, decode };