How to download large file and store it locally in Adobe HTML5 Extension?

Question

I am developing Adobe Photoshop/Illustrator HTML5 extension. I need to get large file from server and store it locally.

So far, I have found only one way how to write file - the cep.fs.writeFile(path, data, encoding) function (as documented in http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/cs-extension-builder/pdfs/CC_Extension_SDK.pdf). I can query server using XMLHttpRequest, and store it using cep.fs.writeFile.

But this would require to hold the whole content of the file in javascript string, which does not sound very effective for huge files.

Is there a better way?