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+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Bookmarks Sync.
+ *
+ * The Initial Developer of the Original Code is Mozilla.
+ * Portions created by the Initial Developer are Copyright (C) 2007
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *  Dan Mills <thunder@mozilla.com>
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+const EXPORTED_SYMBOLS = ['Async'];
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+const Cu = Components.utils;
+
+Cu.import("resource://weave/log4moz.js");
+Cu.import("resource://weave/util.js");
+
+/*
+ * Asynchronous generator helpers
+ */
+
+function AsyncException(generator, message) {
+  this.generator = generator;
+  this.message = message;
+  this._trace = this.generator.trace;
+}
+AsyncException.prototype = {
+  get generator() { return this._generator; },
+  set generator(value) {
+    if (!(value instanceof Generator))
+      throw "expected type 'Generator'";
+    this._generator = value;
+  },
+
+  get message() { return this._message; },
+  set message(value) { this._message = value; },
+
+  get trace() { return this._trace; },
+  set trace(value) { this._trace = value; },
+  
+  toString: function AsyncException_toString() {
+    return this.message;
+  }
+};
+
+function Generator(object, method, onComplete, args) {
+  this._log = Log4Moz.Service.getLogger("Async.Generator");
+  this._object = object;
+  this._method = method;
+  this.onComplete = onComplete;
+  this._args = args;
+
+  let frame = Components.stack.caller;
+  if (frame.name == "Async_run")
+    frame = frame.caller;
+  if (frame.name == "Async_sugar")
+    frame = frame.caller;
+
+  this._initFrame = frame;
+}
+Generator.prototype = {
+  get name() { return this._method.name; },
+  get generator() { return this._generator; },
+
+  // set to true to error when generators to bottom out/return.
+  // you will then have to ensure that all generators yield as the
+  // last thing they do, and never call 'return'
+  get errorOnStop() { return this._errorOnStop; },
+  set errorOnStop(value) { this._errorOnStop = value; },
+
+  get cb() {
+    let cb = Utils.bind2(this, function(data) { this.cont(data); });
+    cb.parentGenerator = this;
+    return cb;
+  },
+  get listener() { return new Utils.EventListener(this.cb); },
+
+  get _object() { return this.__object; },
+  set _object(value) {
+    if (typeof value != "object")
+      throw "expected type 'object', got type '" + typeof(value) + "'";
+    this.__object = value;
+  },
+
+  get _method() { return this.__method; },
+  set _method(value) {
+    if (typeof value != "function")
+      throw "expected type 'function', got type '" + typeof(value) + "'";
+    this.__method = value;
+  },
+
+  get onComplete() {
+    if (this._onComplete)
+      return this._onComplete;
+    return function() { this._log.trace("Generator " + this.name + " has no onComplete"); };
+  },
+  set onComplete(value) {
+    if (value && typeof value != "function")
+      throw "expected type 'function', got type '" + typeof(value) + "'";
+    this._onComplete = value;
+  },
+
+  get trace() {
+    return Utils.stackTrace(this._initFrame) +
+      "JS frame :: unknown (async) :: " + this.name;
+  },
+
+  _handleException: function AsyncGen__handleException(e) {
+    if (e instanceof StopIteration) {
+      if (this.errorOnStop) {
+        this._log.error("Generator stopped unexpectedly");
+        this._log.trace("Stack trace:\n" + this.trace);
+        this._exception = "Generator stopped unexpectedly"; // don't propagate StopIteration
+      }
+
+    } else if (this.onComplete.parentGenerator instanceof Generator) {
+      //this._log.trace("Saving exception and stack trace");
+
+      switch (typeof e) {
+      case "string":
+        e = new AsyncException(this, e);
+        break;
+      case "object":
+        if (e.trace) // means we're re-throwing up the stack
+          e.trace = this.trace + "\n" + e.trace;
+        else
+          e.trace = this.trace;
+        break;
+      default:
+        this._log.debug("Unknown exception type: " + typeof(e));
+        break;
+      }
+
+      this._exception = e;
+
+    } else {
+      this._log.error(Async.exceptionStr(this, e));
+      this._log.trace("Stack trace:\n" + this.trace +
+                      (e.trace? "\n" + e.trace : ""));
+    }
+
+    // continue execution of caller.
+    // in the case of StopIteration we could return an error right
+    // away, but instead it's easiest/best to let the caller handle
+    // the error after a yield / in a callback.
+    this.done();
+  },
+
+  run: function AsyncGen_run() {
+    try {
+      this._generator = this._method.apply(this._object, this._args);
+      this.generator.next(); // must initialize before sending
+      this.generator.send(this);
+    } catch (e) {
+      this._handleException(e);
+    }
+  },
+
+  cont: function AsyncGen_cont(data) {
+    try { this.generator.send(data); }
+    catch (e) { this._handleException(e); }
+  },
+
+  throw: function AsyncGen_throw(exception) {
+    try { this.generator.throw(exception); }
+    catch (e) { this._handleException(e); }
+  },
+
+  // async generators can't simply call a callback with the return
+  // value, since that would cause the calling function to end up
+  // running (after the yield) from inside the generator.  Instead,
+  // generators can call this method which sets up a timer to call the
+  // callback from a timer (and cleans up the timer to avoid leaks).
+  // It also closes generators after the timeout, to keep things
+  // clean.
+  done: function AsyncGen_done(retval) {
+    if (this._timer) // the generator/_handleException called self.done() twice
+      return;
+    let self = this;
+    let cb = function() { self._done(retval); };
+    this._timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+    this._timer.initWithCallback(new Utils.EventListener(cb),
+                                 0, this._timer.TYPE_ONE_SHOT);
+  },
+
+  _done: function AsyncGen__done(retval) {
+    this._generator.close();
+    this._generator = null;
+    this._timer = null;
+
+    if (this._exception) {
+      this._log.trace("Propagating exception to parent generator");
+      this.onComplete.parentGenerator.throw(this._exception);
+    } else {
+      try {
+        this.onComplete(retval);
+      } catch (e) {
+        this._log.error("Exception caught from onComplete handler of " +
+                        this.name + " generator");
+        this._log.error("Exception: " + Utils.exceptionStr(e));
+        this._log.trace("Current stack trace:\n" + Utils.stackTrace(Components.stack));
+        this._log.trace("Initial stack trace:\n" + this.trace);
+      }
+    }
+  }
+};
+
+Async = {
+
+  // Use:
+  // let gen = Async.run(this, this.fooGen, ...);
+  // let ret = yield;
+  //
+  // where fooGen is a generator function, and gen is a Generator instance
+  // ret is whatever the generator 'returns' via Generator.done().
+
+  run: function Async_run(object, method, onComplete, args) {
+    let args = Array.prototype.slice.call(arguments, 3);
+    let gen = new Generator(object, method, onComplete, args);
+    gen.run();
+    return gen;
+  },
+
+  // Syntactic sugar for run().  Meant to be used like this in code
+  // that imports this file:
+  //
+  // Function.prototype.async = Async.sugar;
+  //
+  // So that you can do:
+  //
+  // let gen = fooGen.async(...);
+  // let ret = yield;
+  //
+  // Note that 'this' refers to the method being called, not the
+  // Async object.
+
+  sugar: function Async_sugar(object, onComplete, extra_args) {
+    let args = Array.prototype.slice.call(arguments, 1);
+    args.unshift(object, this);
+    Async.run.apply(Async, args);
+  },
+
+  exceptionStr: function Async_exceptionStr(gen, ex) {
+    return "Exception caught in " + gen.name + ": " + Utils.exceptionStr(ex);
+  }
+};