Does anybody know how to get local path of file cached by Firefox based on its URL from an XPCOM component?
To access cached items, new cache session must be created using createSession method provided in nsICacheService. This method creates nsICacheSession object. Information about cache item can be obtained using openCacheEntry method of the session object (method return nsICacheEntryDescriptor). To read data user must open input stream using openInputStream method of the cache entry object.
来源：https://stackoverflow.com/questions/61453/accessing-firefox-cache-from-an-xpcom-component