Bug 1358846: Part 2 - Allow using file compression with JSONFile.jsm. r=rhelmer

MozReview-Commit-ID: 5lHsZqBGq3E

--HG--
extra : rebase_source : 1df59152becd11bd95b97fc94ebca83392c17027
extra : source : cb2518673c56cf3b45e4d4a8f2959191290c00d8

toolkit/modules/JSONFile.jsm

@@ -89,6 +89,8 @@ const kSaveDelayMs = 1500;
  *                      automatically finalize the file when triggered. Defaults
  *                      to `profileBeforeChange`; exposed as an option for
  *                      testing.
+ *        - compression: A compression algorithm to use when reading and
+ *                       writing the data.
  */
 function JSONFile(config) {
   this.path = config.path;
@@ -105,6 +107,11 @@ function JSONFile(config) {
   }
   this._saver = new DeferredTask(() => this._save(), config.saveDelayMs);
 
+  this._options = {};
+  if (config.compression) {
+    this._options.compression = config.compression;
+  }
+
   this._finalizeAt = config.finalizeAt || AsyncShutdown.profileBeforeChange;
   this._finalizeInternalBound = this._finalizeInternal.bind(this);
   this._finalizeAt.addBlocker("JSON store: writing data",
@@ -175,7 +182,7 @@ JSONFile.prototype = {
     let data = {};
 
     try {
-      let bytes = await OS.File.read(this.path);
+      let bytes = await OS.File.read(this.path, this._options);
 
       // If synchronous loading happened in the meantime, exit now.
       if (this.dataReady) {
@@ -285,7 +292,9 @@ JSONFile.prototype = {
       await Promise.resolve(this._beforeSave());
     }
     await OS.File.writeAtomic(this.path, bytes,
-                              { tmpPath: this.path + ".tmp" });
+                              Object.assign(
+                                { tmpPath: this.path + ".tmp" },
+                                this._options));
   },
 
   /**