Where to save files from Firefox add-on?

Question

I am working on a Firefox add-on which among other stuff generates thumbnails of websites for use by the add-on. So far I\'ve been storing them by their image data URL using sim

Answer 1

As of Firefox 32, the place to store data for your add-on is supposed to be: [profile]/extension-data/[add-on ID]. This was established by the resolution of "Bug 915838 - Provide add-ons a standard directory to store data, settings". There is a follow-on bug, "Bug 952304 - (JSONStore) JSON storage API for addons to use in storing data and settings" which is supposed to provide an API for easy access.

For the Addon-SDK, you can obtain the addon ID (which you define in package.json) with:

let self = require("sdk/self");
let addonID = self.id;

For XUL and restartless extensions, you should be able to get the ID of your addon (which you define in the install.rdf file) with:

Components.utils.import("resource://gre/modules/Services.jsm");
let addonID = Services.appInfo.ID

You can then do the following to generate a URI for a file in that directory:

userProfileDirectoryPath = Components.classes["@mozilla.org/file/directory_service;1"]
                                     .getService( Components.interfaces.nsIProperties)
                                     .get("ProfD", Components.interfaces.nsIFile).path,

/**
 * Generate URI for a filename in the extension's data directory under the preferences
 *   directory.
 */
function generateURIForFileInPrefExtensionDataDirectory (fileName) {
    //Account for the path separator being OS dependent
    let toReturn = "file://" + userProfileDirectoryPath.replace(/\\/g,"/");

    return toReturn +"/extension-data/" + addonID + "/" + fileName;
    }
}

The object myExtension.addonData is a copy that I store of the Bootstrap data provided to entry points in bootstrap.js.