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@sergeevabc
Forked from jonleighton/base64ArrayBuffer.js
Last active August 29, 2015 14:07
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// Converts an ArrayBuffer directly to base64, without any intermediate 'convert to string then
// use window.btoa' step. According to my tests, this appears to be a faster approach:
// http://jsperf.com/encoding-xhr-image-data/5
function base64ArrayBuffer(arrayBuffer) {
var base64 = '';
var encodings = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
var bytes = new Uint8Array(arrayBuffer);
var byteLength = bytes.byteLength;
var byteRemainder = byteLength % 3;
var mainLength = byteLength - byteRemainder;
var a, b, c, d;
var chunk;
for (var i = 0; i < mainLength; i = i + 3) {
chunk = bytes[i] << 16 | bytes[i + 1] << 8 | bytes[i + 2];
a = (chunk & 16515072) >> 18;
b = (chunk & 258048) >> 12;
c = (chunk & 4032) >> 6;
d = chunk & 63;
base64 += encodings[a] + encodings[b] + encodings[c] + encodings[d];
}
if (byteRemainder == 1) {
chunk = bytes[mainLength];
a = (chunk & 252) >> 2;
b = (chunk & 3) << 4;
base64 += encodings[a] + encodings[b] + '==';
} else if (byteRemainder == 2) {
chunk = bytes[mainLength] << 8 | bytes[mainLength + 1];
a = (chunk & 64512) >> 10;
b = (chunk & 1008) >> 4;
c = (chunk & 15) << 2;
base64 += encodings[a] + encodings[b] + encodings[c] + '=';
}
return base64;
}
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