Issue 3716 - Split up files stored in storage.local

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 16 matching lines @@
     key += file.path;
   else
     key += file.spec;
 
   if (typeof chunk != "undefined")
     key += ":" + chunk;
 
   return key;
 }
 
-function loadFile(file, successCallback, errorCallback)
+function loadFile(file)
 {
-  let key = fileToKey(file);
-
-  ext.storage.get([key], function(items)
+  return new Promise((resolve, reject) =>
   {
-    let entry = items[key];
-
-    if (entry)
-      successCallback(entry);
-    else
-      errorCallback(new Error("File doesn't exist"));
+    let key = fileToKey(file);
+    ext.storage.get([key], items =>
+    {
+      let entry = items[key];
+      if (entry)
+        resolve(entry);
+      else
+        reject(new Error("File doesn't exist"));
+    });
   });
 }
 
 exports.IO =
 {
   resolveFilePath: function(path)
   {
     return new FakeFile(path);
   },
 
@@ skipping 20 matching lines @@
            for (let key of keys)
              for (let line of items[key])
                listener.process(line);
 
            listener.process(null);
            callback(null);
         });
       }
     }
 
-    loadFile(file, onLoaded, callback);
+    loadFile(file).then(onLoaded, callback);
   },
-  
-  // Write to file, splitting into chunks, if required.

[Sebastian Noack, 2016/03/31 14:08:53]

Nit: This comment is kinda redundant with the comment below.

+
   writeToFile: function(file, data, callback)
   {
-    let key = fileToKey(file);
     let items = {};
-    items[key] = {lastModified: Date.now()};
+    let entry = items[fileToKey(file)] = {lastModified: Date.now()};
 
-    // Edge currently has a limitation of how much data can be stored
-    // using chrome.storage.local.set. The current limit is 1Mb per operation.
-    // Edge uses 'browser' namespace instead of 'chrome'.
     if (typeof browser == "object")
     {
-      // In Edge strings are stored in UTF-16 format, so 2 bytes per char

[Sebastian Noack, 2016/03/31 14:08:53]

How about mentioning that we reserve another 1000 bytes for keys and the array
overhead?

-      let quota = 1024 * 1024 / 2 - 1000;
-      let chunks = [];
-      let chunk = [];
-      let chunkSize = 0;
-      
-      for (let line of data)
+      loadFile(file).catch(() => null)
+                    .then(oldEntry =>
       {
-        if (line.length + chunkSize > quota)
+        let quota = 1024 * 1024 / 2 - 1000;
+        let chunks = [];
+        let chunk = [];
+        let chunkSize = 0;
+
+        for (let line of data)
         {
-          chunks.push(chunk);
-          chunk = [];
-          chunkSize = 0;
+          if (line.length + chunkSize > quota)
+          {
+            chunks.push(chunk);
+            chunk = [];
+            chunkSize = 0;
+          }
+
+          chunk.push(line);
+          chunkSize += line.length;
         }
+        chunks.push(chunk);
 
-        chunk.push(line);
-        chunkSize += line.length;
-      }
-      chunks.push(chunk);
-
-      if (chunks.length > 1)
-      {
         for (let i = 0; i < chunks.length; i++)
           items[fileToKey(file, i)] = chunks[i];
-        items[key].chunks = chunks.length;
+        entry.chunks = chunks.length;
         ext.storage.set(items, callback);
-        return;
-      }
+
+        if (oldEntry && "chunks" in oldEntry)
+          for (let i = entry.chunks; i < oldEntry.chunks; i++)
+            ext.storage.remove(fileToKey(file, i));
+      });
     }
-
-    items[key].content = data;
-    ext.storage.set(items, callback);  
+    else
+    {
+      entry.content = data;
+      ext.storage.set(items, callback);
+    }
   },
 
   statFile: function(file, callback)
   {
     function onLoaded(entry)
     {
       callback(null, {
         exists: true,
         lastModified: entry.lastModified
       });
     }
 
-    loadFile(file, onLoaded, callback);
+    loadFile(file).then(onLoaded, callback);
   }
 };