Question

I am using the Add-on builder and I need to receive binary data (image). I would like to do this using the request module but as you can see from the documentation:

https://addons.mozilla.org/en-US/developers/docs/sdk/latest/packages/addon-kit/docs/request.html

There are only text and json properties and raw is absent.

How should I receive binary data in the add-on script?

Answer 1

You cannot do this using the request module, you will have to use the regular XMLHttpRequest via chrome authority. Something like this should work:

var {Cc, Ci} = require("chrome");
var request = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"]
                .createInstance(Ci.nsIJSXMLHttpRequest);
request.open("GET", "...");
request.onload = function()
{
  onUnload.unload();

  var arrayBuffer = request.response;
  if (arrayBuffer)
  {
    var byteArray = new Uint8Array(arrayBuffer);
    ...
  }
};
request.onerror = function()
{
  onUnload.unload();
}
request.send(null);

var onUnload = {
  unload: function()
  {
    // Make sure to abort the request if the extension is disabled
    try
    {
      request.abort();
    }
    catch (e) {}
  }
};
require("unload").ensure(onUnload);

The mechanism to ensure that the request is aborted if your extension is suddenly disabled is rather awkward, that’s the main reason the request module exists rather than simply giving you XMLHttpRequest. Note that it is important to call onUnload.unload() once the request finishes, otherwise the Add-on SDK will keep it in the list of methods to be called on unload (a memory leak). See documentation of unload module.