Issue 4721 - Use IndexedDB for storage in Edge

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
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 const keyPrefix = "file:";
 
 function fileToKey(file)
 {
   return keyPrefix + (file instanceof FakeFile ? file.path : file.spec);
 }
 
 function loadFile(file, successCallback, errorCallback)
 {
   let key = fileToKey(file);
 
-  ext.storage.get([key], function(items)
+  // Make sure we do not have subscriptions in localStorage from older
+  // versions first
+  let entry = localStorage.getItem(key);
+  if (typeof entry == "string")
   {
-    let entry = items[key];
-
-    if (entry)
-      successCallback(entry);
+    try
+    {
+      entry = JSON.parse(entry);
+    }
+    catch(err) 
+    {
+      setTimeout(errorCallback(new Error("File is corrupted")));
+      return;
+    }
+    setTimeout(successCallback(entry));
+    return;
+  }
+  // Now try to read from IndexedDB
+  localforage.getItem(key, function(err, value) 
+  {
+    if (err || !value)
+      errorCallback(new Error("File doesn't exist"));
     else
-      errorCallback(new Error("File doesn't exist"));
+      successCallback(value);
   });
 }
 
 function saveFile(file, data, callback)
 {
-  ext.storage.set(
-    fileToKey(file),
-    {
-      content: Array.from(data),
-      lastModified: Date.now()
-    },
-    callback
-  );
+  var key = fileToKey(file);
+  var entry = {
+    content: Array.from(data),
+    lastModified: Date.now()
+  };
+
+  localStorage.removeItem(key);
+  localforage.setItem(key, entry, callback);
 }
 
 exports.IO =
 {
   resolveFilePath: function(path)
   {
     return new FakeFile(path);
   },
 
   readFromFile: function(file, listener, callback)
   {
     function onLoaded(entry)
     {
-      for (let line of entry.content)
-        listener.process(line);
-
+      if ("content" in entry)
+      {
+        for (let line of entry.content)
+          listener.process(line);
+      }
       listener.process(null);
       callback(null);
     }
 
     loadFile(file, onLoaded, callback);
   },
 
   writeToFile: function(file, data, callback)
   {
     saveFile(file, data, callback);
@@ skipping 33 matching lines @@
     {
       callback(null, {
         exists: true,
         lastModified: entry.lastModified
       });
     }
 
     loadFile(file, onLoaded, callback);
   }
 };