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// Copyright 2010 The Closure Library Authors. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//      http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS-IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/**
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 * @fileoverview A global registry for entry points into a program,
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 * so that they can be instrumented. Each module should register their
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 * entry points with this registry. Designed to be compiled out
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 * if no instrumentation is requested.
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 *
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 * Entry points may be registered before or after a call to
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 * goog.debug.entryPointRegistry.monitorAll. If an entry point is registered
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 * later, the existing monitor will instrument the new entry point.
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 *
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 * @author [email protected] (Nick Santos)
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 */
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goog.provide('goog.debug.EntryPointMonitor');
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goog.provide('goog.debug.entryPointRegistry');
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goog.require('goog.asserts');
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/**
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 * @interface
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 */
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goog.debug.EntryPointMonitor = function() {};
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/**
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 * Instruments a function.
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 *
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 * @param {!Function} fn A function to instrument.
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 * @return {!Function} The instrumented function.
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 */
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goog.debug.EntryPointMonitor.prototype.wrap;
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/**
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 * Try to remove an instrumentation wrapper created by this monitor.
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 * If the function passed to unwrap is not a wrapper created by this
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 * monitor, then we will do nothing.
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 *
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 * Notice that some wrappers may not be unwrappable. For example, if other
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 * monitors have applied their own wrappers, then it will be impossible to
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 * unwrap them because their wrappers will have captured our wrapper.
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 *
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 * So it is important that entry points are unwrapped in the reverse
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 * order that they were wrapped.
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 *
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 * @param {!Function} fn A function to unwrap.
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 * @return {!Function} The unwrapped function, or {@code fn} if it was not
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 *     a wrapped function created by this monitor.
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 */
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goog.debug.EntryPointMonitor.prototype.unwrap;
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/**
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 * An array of entry point callbacks.
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 * @type {!Array<function(!Function)>}
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 * @private
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 */
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goog.debug.entryPointRegistry.refList_ = [];
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/**
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 * Monitors that should wrap all the entry points.
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 * @type {!Array<!goog.debug.EntryPointMonitor>}
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 * @private
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 */
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goog.debug.entryPointRegistry.monitors_ = [];
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/**
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 * Whether goog.debug.entryPointRegistry.monitorAll has ever been called.
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 * Checking this allows the compiler to optimize out the registrations.
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 * @type {boolean}
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 * @private
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 */
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goog.debug.entryPointRegistry.monitorsMayExist_ = false;
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/**
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 * Register an entry point with this module.
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 *
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 * The entry point will be instrumented when a monitor is passed to
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 * goog.debug.entryPointRegistry.monitorAll. If this has already occurred, the
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 * entry point is instrumented immediately.
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 *
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 * @param {function(!Function)} callback A callback function which is called
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 *     with a transforming function to instrument the entry point. The callback
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 *     is responsible for wrapping the relevant entry point with the
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 *     transforming function.
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 */
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goog.debug.entryPointRegistry.register = function(callback) {
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  // Don't use push(), so that this can be compiled out.
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  goog.debug.entryPointRegistry
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      .refList_[goog.debug.entryPointRegistry.refList_.length] = callback;
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  // If no one calls monitorAll, this can be compiled out.
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  if (goog.debug.entryPointRegistry.monitorsMayExist_) {
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    var monitors = goog.debug.entryPointRegistry.monitors_;
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    for (var i = 0; i < monitors.length; i++) {
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      callback(goog.bind(monitors[i].wrap, monitors[i]));
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    }
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  }
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};
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/**
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 * Configures a monitor to wrap all entry points.
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 *
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 * Entry points that have already been registered are immediately wrapped by
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 * the monitor. When an entry point is registered in the future, it will also
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 * be wrapped by the monitor when it is registered.
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 *
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 * @param {!goog.debug.EntryPointMonitor} monitor An entry point monitor.
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 */
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goog.debug.entryPointRegistry.monitorAll = function(monitor) {
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  goog.debug.entryPointRegistry.monitorsMayExist_ = true;
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  var transformer = goog.bind(monitor.wrap, monitor);
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  for (var i = 0; i < goog.debug.entryPointRegistry.refList_.length; i++) {
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    goog.debug.entryPointRegistry.refList_[i](transformer);
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  }
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  goog.debug.entryPointRegistry.monitors_.push(monitor);
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};
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/**
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 * Try to unmonitor all the entry points that have already been registered. If
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 * an entry point is registered in the future, it will not be wrapped by the
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 * monitor when it is registered. Note that this may fail if the entry points
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 * have additional wrapping.
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 *
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 * @param {!goog.debug.EntryPointMonitor} monitor The last monitor to wrap
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 *     the entry points.
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 * @throws {Error} If the monitor is not the most recently configured monitor.
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 */
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goog.debug.entryPointRegistry.unmonitorAllIfPossible = function(monitor) {
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  var monitors = goog.debug.entryPointRegistry.monitors_;
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  goog.asserts.assert(
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      monitor == monitors[monitors.length - 1],
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      'Only the most recent monitor can be unwrapped.');
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  var transformer = goog.bind(monitor.unwrap, monitor);
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  for (var i = 0; i < goog.debug.entryPointRegistry.refList_.length; i++) {
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    goog.debug.entryPointRegistry.refList_[i](transformer);
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  }
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  monitors.length--;
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};
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