Issue 5050 - Make legacy extension use WebExtensions I/O

webextension/io.js

Index: webextension/io.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/webextension/io.js
@@ -0,0 +1,109 @@
+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2017 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/>.
+ */
+
+"use strict";

[Wladimir Palant, 2017/04/10 11:35:17]

Note that the code here is based on io.js from adblockpluschrome but uses
promises for simplicity (makes messaging with the parent much more
straightforward). Ideally, io.js in adblockpluschrome will use promises as well
soon, this is part of https://issues.adblockplus.org/ticket/5059.

+
+(function(exports)
+{
+  const keyPrefix = "file:";
+
+  function fileToKey(fileName)
+  {
+    return keyPrefix + fileName;
+  }
+
+  function loadFile(file)
+  {
+    let key = fileToKey(file);
+
+    return browser.storage.local.get(key).then(items =>
+    {
+      if (items.hasOwnProperty(key))
+        return items[key];
+
+      throw "NoSuchFile";
+    });
+  }
+
+  function saveFile(file, data)
+  {
+    return browser.storage.local.set({
+      [fileToKey(file)]: {
+        content: Array.from(data),
+        lastModified: Date.now()
+      }
+    });
+  }
+
+  function removeFile(file)
+  {
+    return browser.storage.local.remove(fileToKey(file));
+  }
+
+  exports.IO =
+  {
+    readFromFile(file)
+    {
+      return loadFile(file).then(entry =>
+      {
+        return entry.content;
+      });
+    },
+
+    writeToFile(file, data)
+    {
+      return saveFile(file, data);
+    },
+
+    copyFile(fromFile, toFile)
+    {
+      return loadFile(fromFile).then(entry =>
+      {
+        return saveFile(toFile, entry.content);
+      });
+    },
+
+    renameFile(fromFile, newName)
+    {
+      return loadFile(fromFile).then(entry =>
+      {
+        return browser.storage.local.set({
+          [fileToKey(newName)]: entry
+        });
+      }).then(() =>
+      {
+        return removeFile(fromFile);
+      });
+    },
+
+    removeFile(file)
+    {
+      return removeFile(file);
+    },
+
+    statFile(file)
+    {
+      return loadFile(file).then(entry =>
+      {
+        return {
+          exists: true,
+          lastModified: entry.lastModified
+        };
+      });

[Wladimir Palant, 2017/04/10 11:35:17]

Note that statFile would normally catch NoSuchFile and return exists:false - but
here it is undesirable because we need to go into the fallback in the parent.

+    }
+  };
+})(this);