Javascript function that converts an ArrayBuffer to a base64-encoded string

ArrayBufferToBase64.js

function ArrayBufferToBase64 (buff) {
var alph = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
    enc = "",
    n,p,bits;
d=new Uint8Array(buff);
var len = buff.byteLength*8;
for (var offset=0; offset<len; offset+=6){
  n = (offset/8)|0;
  p = offset%8;
  bits = ((d[n]||0)<<p)>>2;
  if(p>2){bits|=(d[n+1]||0)>>(10-p)}
  enc += alph.charAt(bits&63);
}
enc += (p==4)?'=':(p==6)?'==':'';
return enc;
}