Issue 4023 - Move storage of subscription lists to localStorage

lib/io.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 44 matching lines @@
   {
     return new FakeFile(path);
   },
 
   readFromFile: function(file, listener, callback)
   {
     function onLoaded(entry)
     {
       if ("content" in entry)
       {
-        if ("compressed" in entry)

[Sebastian Noack, 2016/09/08 15:27:22]

Please check for entry["compressed"], otherwise, if it is set to false, we'd
still try to decompress it. I know that we currently don't set it to false, but
still that way the logic is more accurrate.

+        if (entry["compressed"])
           entry.content = JSON.parse(LZString.decompressFromUTF16(entry.content));
         for (let line of entry.content)
           listener.process(line);
       }
       callback(null);
     }
 
     loadFile(file).then(onLoaded, callback);
   },
 
   writeToFile: function(file, data, callback)
   {
     let entry = {};
     let key = fileToKey(file);
 
     if (typeof browser == "undefined")
     {
       entry[key] = {lastModified: Date.now(), content: data};
       ext.storage.set(entry, callback);
     }
     else
     {
       // Edge cannot write files larger than 1Mb (500k string in UTF-16) via 
       // storage API. However it does not always raise an exception when trying
       // to do so. The solution is to compress and fallback to localStorage.
       let processedData = LZString.compressToUTF16(JSON.stringify(data));

[Sebastian Noack, 2016/09/08 15:27:22]

(Why) do we need to call JSON.stringifiy() here? Isn't data always a string
here?

[Oleksandr, 2016/09/08 23:51:57]

'data' here is an array of strings, which are lines from the easylist file.

       ext.storage.remove(key);
       entry[key] = {lastModified: Date.now(), content: processedData,
                     compressed: true};
       window.localStorage.setItem(key, JSON.stringify(entry[key]));
       callback();
     }
   },
 
   statFile: function(file, callback)
   {
     function onLoaded(entry)
     {
       callback(null, {
         exists: true,
         lastModified: entry.lastModified
       });
     }
 
     loadFile(file).then(onLoaded, callback);
   }
 };