1 files changed, 235 insertions, 0 deletions
diff --git a/toolkit/jetpack/sdk/simple-storage.js b/toolkit/jetpack/sdk/simple-storage.js
new file mode 100644
index 000000000..bcf9b1cb9
--- /dev/null
+++ b/toolkit/jetpack/sdk/simple-storage.js
@@ -0,0 +1,235 @@
+/* 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";
+
+module.metadata = {
+  "stability": "stable"
+};
+
+const { Cc, Ci } = require("chrome");
+const file = require("./io/file");
+const prefs = require("./preferences/service");
+const jpSelf = require("./self");
+const timer = require("./timers");
+const unload = require("./system/unload");
+const { emit, on, off } = require("./event/core");
+
+const WRITE_PERIOD_PREF = "extensions.addon-sdk.simple-storage.writePeriod";
+const WRITE_PERIOD_DEFAULT = 300000; // 5 minutes
+
+const QUOTA_PREF = "extensions.addon-sdk.simple-storage.quota";
+const QUOTA_DEFAULT = 5242880; // 5 MiB
+
+const JETPACK_DIR_BASENAME = "jetpack";
+
+Object.defineProperties(exports, {
+  storage: {
+    enumerable: true,
+    get: function() { return manager.root; },
+    set: function(value) { manager.root = value; }
+  },
+  quotaUsage: {
+    get: function() { return manager.quotaUsage; }
+  }
+});
+
+// A generic JSON store backed by a file on disk.  This should be isolated
+// enough to move to its own module if need be...
+function JsonStore(options) {
+  this.filename = options.filename;
+  this.quota = options.quota;
+  this.writePeriod = options.writePeriod;
+  this.onOverQuota = options.onOverQuota;
+  this.onWrite = options.onWrite;
+
+  unload.ensure(this);
+
+  this.writeTimer = timer.setInterval(this.write.bind(this),
+                                      this.writePeriod);
+}
+
+JsonStore.prototype = {
+  // The store's root.
+  get root() {
+    return this.isRootInited ? this._root : {};
+  },
+
+  // Performs some type checking.
+  set root(val) {
+    let types = ["array", "boolean", "null", "number", "object", "string"];
+    if (types.indexOf(typeof(val)) < 0) {
+      throw new Error("storage must be one of the following types: " +
+                      types.join(", "));
+    }
+    this._root = val;
+    return val;
+  },
+
+  // True if the root has ever been set (either via the root setter or by the
+  // backing file's having been read).
+  get isRootInited() {
+    return this._root !== undefined;
+  },
+
+  // Percentage of quota used, as a number [0, Inf).  > 1 implies over quota.
+  // Undefined if there is no quota.
+  get quotaUsage() {
+    return this.quota > 0 ?
+           JSON.stringify(this.root).length / this.quota :
+           undefined;
+  },
+
+  // Removes the backing file and all empty subdirectories.
+  purge: function JsonStore_purge() {
+    try {
+      // This'll throw if the file doesn't exist.
+      file.remove(this.filename);
+      let parentPath = this.filename;
+      do {
+        parentPath = file.dirname(parentPath);
+        // This'll throw if the dir isn't empty.
+        file.rmdir(parentPath);
+      } while (file.basename(parentPath) !== JETPACK_DIR_BASENAME);
+    }
+    catch (err) {}
+  },
+
+  // Initializes the root by reading the backing file.
+  read: function JsonStore_read() {
+    try {
+      let str = file.read(this.filename);
+
+      // Ideally we'd log the parse error with console.error(), but logged
+      // errors cause tests to fail.  Supporting "known" errors in the test
+      // harness appears to be non-trivial.  Maybe later.
+      this.root = JSON.parse(str);
+    }
+    catch (err) {
+      this.root = {};
+    }
+  },
+
+  // If the store is under quota, writes the root to the backing file.
+  // Otherwise quota observers are notified and nothing is written.
+  write: function JsonStore_write() {
+    if (this.quotaUsage > 1)
+      this.onOverQuota(this);
+    else
+      this._write();
+  },
+
+  // Cleans up on unload.  If unloading because of uninstall, the store is
+  // purged; otherwise it's written.
+  unload: function JsonStore_unload(reason) {
+    timer.clearInterval(this.writeTimer);
+    this.writeTimer = null;
+
+    if (reason === "uninstall")
+      this.purge();
+    else
+      this._write();
+  },
+
+  // True if the root is an empty object.
+  get _isEmpty() {
+    if (this.root && typeof(this.root) === "object") {
+      let empty = true;
+      for (let key in this.root) {
+        empty = false;
+        break;
+      }
+      return empty;
+    }
+    return false;
+  },
+
+  // Writes the root to the backing file, notifying write observers when
+  // complete.  If the store is over quota or if it's empty and the store has
+  // never been written, nothing is written and write observers aren't notified.
+  _write: function JsonStore__write() {
+    // Don't write if the root is uninitialized or if the store is empty and the
+    // backing file doesn't yet exist.
+    if (!this.isRootInited || (this._isEmpty && !file.exists(this.filename)))
+      return;
+
+    // If the store is over quota, don't write.  The current under-quota state
+    // should persist.
+    if (this.quotaUsage > 1)
+      return;
+
+    // Finally, write.
+    let stream = file.open(this.filename, "w");
+    try {
+      stream.writeAsync(JSON.stringify(this.root), function writeAsync(err) {
+        if (err)
+          console.error("Error writing simple storage file: " + this.filename);
+        else if (this.onWrite)
+          this.onWrite(this);
+      }.bind(this));
+    }
+    catch (err) {
+      // writeAsync closes the stream after it's done, so only close on error.
+      stream.close();
+    }
+  }
+};
+
+
+// This manages a JsonStore singleton and tailors its use to simple storage.
+// The root of the JsonStore is lazy-loaded:  The backing file is only read the
+// first time the root's gotten.
+var manager = ({
+  jsonStore: null,
+
+  // The filename of the store, based on the profile dir and extension ID.
+  get filename() {
+    let storeFile = Cc["@mozilla.org/file/directory_service;1"].
+                    getService(Ci.nsIProperties).
+                    get("ProfD", Ci.nsIFile);
+    storeFile.append(JETPACK_DIR_BASENAME);
+    storeFile.append(jpSelf.id);
+    storeFile.append("simple-storage");
+    file.mkpath(storeFile.path);
+    storeFile.append("store.json");
+    return storeFile.path;
+  },
+
+  get quotaUsage() {
+    return this.jsonStore.quotaUsage;
+  },
+
+  get root() {
+    if (!this.jsonStore.isRootInited)
+      this.jsonStore.read();
+    return this.jsonStore.root;
+  },
+
+  set root(val) {
+    return this.jsonStore.root = val;
+  },
+
+  unload: function manager_unload() {
+    off(this);
+  },
+
+  new: function manager_constructor() {
+    let manager = Object.create(this);
+    unload.ensure(manager);
+
+    manager.jsonStore = new JsonStore({
+      filename: manager.filename,
+      writePeriod: prefs.get(WRITE_PERIOD_PREF, WRITE_PERIOD_DEFAULT),
+      quota: prefs.get(QUOTA_PREF, QUOTA_DEFAULT),
+      onOverQuota: emit.bind(null, exports, "OverQuota")
+    });
+
+    return manager;
+  }
+}).new();
+
+exports.on = on.bind(null, exports);
+exports.removeListener = function(type, listener) {
+  off(exports, type, listener);
+};