Progressive ArrayBuffer Loading

loadBufferProgressive.js

var stringToArrayBuffer = function(str, soffset, buf, boffset) {
  var ui8a = new Uint8Array(buf, boffset);
  for (var si = soffset, ai = 0; si < str.length; si++, ai++)
    ui8a[ai] = (str.charCodeAt(si) & 0xff);
};

var loadBufferProgressive = function(url, cb) {
  var req = new XMLHttpRequest();
  req.open("GET", url);
  req.overrideMimeType("text/plain; charset=x-user-defined");

  var buffer;
  var bufferOffset = 0;
  req.onprogress = function(e) {
    if (req.status !== 200)
      return;

    // first time alloc buffer
    if (!buffer) {
      // NOTE: length should be specified, Content-Length not always reliable
      var length = parseInt(req.getResponseHeader("Content-Length"));
      buffer = new ArrayBuffer(length);
    }

    var byteLoaded = req.responseText.length;
    var byteLength = buffer.byteLength;

    stringToArrayBuffer(req.responseText, bufferOffset, buffer, bufferOffset);
    bufferOffset = byteLoaded; // update offset

    cb(buffer, byteLoaded, byteLength);
  };

  req.send();
};