ASN.1 BER length generator. Pass a length l to the function, outputs an array with a BER format length. JavaScript.

BER Length

function berLength(l) {
  var ll, bl;
  
  if (l < 128) { 
    bl = [l];
  } else {
    ll = Math.floor(Math.log(l)/Math.log(256))+1;
    bl = [128 + ll];

    while (ll-- > 0)
      bl.push( (l >> (ll*8)) & 255 );
  }

  return bl;
}