Question

I’m wondering if, with the new File API exposed in Chrome (I’m not concerned with cross-browser support at this time), it would be possible to write back to files opened via a file input.

You can see an example of what I’m trying to accomplish here: http://www.grehz.com/ide.

I know I can use server side scripts to dynamically create the files and allow the user to download them normally. I’m hoping that there’s a way to accomplish this purely client side. I had read somewhere that you can write to files opened via a file input. I haven’t been able to find any examples of this, though I have seen passing references to a FileWriter class.

I would be completely not surprised if this wasn’t possible though (it seems likely that there are security issues with this). Just looking for some guidance or resources.

UPDATE:

I was reading here: http://dev.w3.org/2009/dap/file-system/file-writer.html

As I was playing around in Chrome, it looks like FileSaver and FileWriter are not implemented, but BlobBuilder is. I can call getBlob() on the BB object, is there any way I can then save that without FileSaver or FileWriter?

UPDATE2:

I found this issue in the Chromium project: http://code.google.com/p/chromium/issues/detail?id=65615&q=FileSaver&colspec=ID%20Stars%20Pri%20Area%20Feature%20Type%20Status%20Summary%20Modified%20Owner%20Mstone%20OS

So it’s clear that it hasn’t been implemented in any version yet (however, no mention of FileWriter – although I believe FileWriter depends on FileSaver).

Moving away from that, I’m considering a server-side solution. When a user clicks save, the contents of the textarea is posted to a script that then writes to a page and is sent back as plaintext or whatever mime-type would be appropriate for the user to download. Any other suggestions? This solution is fine for a “save as” but it’s a little clunky as a general purpose save button.

Answer 1

From:
http://code.google.com/p/chromium/issues/detail?id=58985#c7

FileSystem is really the right place
to store big files (which is what it
sounds like you’re doing) and is
available in Chrome 9. I suggest you
look at these alternatives.

Note the not-extensions label at the top left. It sounds like this may just be for Chromium OS. I emailed Jeremy, the developer who made this comment for clarification.

Update:
Jeremy replied that extensions actually will get access to File API including writes, but that it will be confined to a sandbox. He also linked to some undeployed docs on the matter:
http://code.google.com/p/html5rocks/source/browse/www.html5rocks.com/content/tutorials/file/filesystem/index.html?spec=svn1cbb2aab2d6954a56f3067d2d3b9e997215be441&r=1cbb2aab2d6954a56f3067d2d3b9e997215be441