1 files changed, 163 insertions, 0 deletions
diff --git a/toolkit/components/messaging-system/lib/SharedDataMap.jsm b/toolkit/components/messaging-system/lib/SharedDataMap.jsm
new file mode 100644
index 0000000000..b61b112a1d
--- /dev/null
+++ b/toolkit/components/messaging-system/lib/SharedDataMap.jsm
@@ -0,0 +1,163 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const EXPORTED_SYMBOLS = ["SharedDataMap"];
+
+const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
+const { EventEmitter } = ChromeUtils.import(
+  "resource://gre/modules/EventEmitter.jsm"
+);
+ChromeUtils.defineModuleGetter(
+  this,
+  "PromiseUtils",
+  "resource://gre/modules/PromiseUtils.jsm"
+);
+
+const IS_MAIN_PROCESS =
+  Services.appinfo.processType === Services.appinfo.PROCESS_TYPE_DEFAULT;
+
+ChromeUtils.defineModuleGetter(
+  this,
+  "JSONFile",
+  "resource://gre/modules/JSONFile.jsm"
+);
+const { XPCOMUtils } = ChromeUtils.import(
+  "resource://gre/modules/XPCOMUtils.jsm"
+);
+
+class SharedDataMap extends EventEmitter {
+  constructor(sharedDataKey, options = { isParent: IS_MAIN_PROCESS }) {
+    super();
+
+    this._sharedDataKey = sharedDataKey;
+    this._isParent = options.isParent;
+    this._isReady = false;
+    this._readyDeferred = PromiseUtils.defer();
+    this._data = null;
+
+    if (this.isParent) {
+      // Lazy-load JSON file that backs Storage instances.
+      XPCOMUtils.defineLazyGetter(this, "_store", () => {
+        let path = options.path;
+        let store = null;
+        if (!path) {
+          try {
+            const profileDir = Services.dirsvc.get("ProfD", Ci.nsIFile).path;
+            path = PathUtils.join(profileDir, `${sharedDataKey}.json`);
+          } catch (e) {
+            Cu.reportError(e);
+          }
+        }
+        try {
+          store = new JSONFile({ path });
+        } catch (e) {
+          Cu.reportError(e);
+        }
+        return store;
+      });
+    } else {
+      this._syncFromParent();
+      Services.cpmm.sharedData.addEventListener("change", this);
+    }
+  }
+
+  async init() {
+    if (!this._isReady && this.isParent) {
+      await this._store.load();
+      this._data = this._store.data;
+      this._syncToChildren({ flush: true });
+      this._checkIfReady();
+    }
+  }
+
+  get sharedDataKey() {
+    return this._sharedDataKey;
+  }
+
+  get isParent() {
+    return this._isParent;
+  }
+
+  ready() {
+    return this._readyDeferred.promise;
+  }
+
+  get(key) {
+    if (!this._data) {
+      return null;
+    }
+    return this._data[key];
+  }
+
+  set(key, value) {
+    if (!this.isParent) {
+      throw new Error(
+        "Setting values from within a content process is not allowed"
+      );
+    }
+    this._store.data[key] = value;
+    this._store.saveSoon();
+    this._syncToChildren();
+    this._notifyUpdate();
+  }
+
+  // Only used in tests
+  _deleteForTests(key) {
+    if (!this.isParent) {
+      throw new Error(
+        "Setting values from within a content process is not allowed"
+      );
+    }
+    if (this.has(key)) {
+      delete this._store.data[key];
+      this._store.saveSoon();
+      this._syncToChildren();
+      this._notifyUpdate();
+    }
+  }
+
+  has(key) {
+    return Boolean(this.get(key));
+  }
+
+  /**
+   * Notify store listeners of updates
+   * Called both from Main and Content process
+   */
+  _notifyUpdate(process = "parent") {
+    for (let key of Object.keys(this._data || {})) {
+      this.emit(`${process}-store-update:${key}`, this._data[key]);
+    }
+  }
+
+  _syncToChildren({ flush = false } = {}) {
+    Services.ppmm.sharedData.set(this.sharedDataKey, this._data);
+    if (flush) {
+      Services.ppmm.sharedData.flush();
+    }
+  }
+
+  _syncFromParent() {
+    this._data = Services.cpmm.sharedData.get(this.sharedDataKey);
+    this._checkIfReady();
+    this._notifyUpdate("child");
+  }
+
+  _checkIfReady() {
+    if (!this._isReady && this._data) {
+      this._isReady = true;
+      this._readyDeferred.resolve();
+    }
+  }
+
+  handleEvent(event) {
+    if (event.type === "change") {
+      if (event.changedKeys.includes(this.sharedDataKey)) {
+        this._syncFromParent();
+      }
+    }
+  }
+}