SSL event-emitter.js Sprache: JAVA

/* 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 BAD_LISTENER =
  "The event listener must be a function, or an object that has " +
  "`EventEmitter.handler` Symbol.";

const eventListeners = Symbol("EventEmitter/listeners");
const onceOriginalListener = Symbol("EventEmitter/once-original-listener");
const handler = Symbol("EventEmitter/event-handler");
loader.lazyRequireGetter(this, "flags", "resource://devtools/shared/flags.js");

class EventEmitter {
  /**
   * Registers an event `listener` that is called every time events of
   * specified `type` is emitted on the given event `target`.
   *
   * @param {Object} target
   *    Event target object.
   * @param {String} type
   *    The type of event.
   * @param {Function|Object} listener
   *    The listener that processes the event.
   * @param {Object} options
   * @param {AbortSignal} options.signal
   *     The listener will be removed when linked AbortController’s abort() method is called
   * @returns {Function}
   *    A function that removes the listener when called.
   */
  static on(target, type, listener, { signal } = {}) {
    if (typeof listener !== "function" && !isEventHandler(listener)) {
      throw new Error(BAD_LISTENER);
    }

    if (signal?.aborted === true) {
      // The signal is already aborted so don't setup the listener.
      // We return an empty function as it's the expected returned value.
      return () => {};
    }

    if (!(eventListeners in target)) {
      target[eventListeners] = new Map();
    }

    const events = target[eventListeners];

    if (events.has(type)) {
      events.get(type).add(listener);
    } else {
      events.set(type, new Set([listener]));
    }

    const offFn = () => EventEmitter.off(target, type, listener);

    if (signal) {
      signal.addEventListener("abort", offFn, { once: true });
    }

    return offFn;
  }

  /**
   * Removes an event `listener` for the given event `type` on the given event
   * `target`. If no `listener` is passed removes all listeners of the given
   * `type`. If `type` is not passed removes all the listeners of the given
   * event `target`.
   * @param {Object} target
   *    The event target object.
   * @param {String} [type]
   *    The type of event.
   * @param {Function|Object} [listener]
   *    The listener that processes the event.
   */
  static off(target, type, listener) {
    const length = arguments.length;
    const events = target[eventListeners];

    if (!events) {
      return;
    }

    if (length >= 3) {
      // Trying to remove from the `target` the `listener` specified for the
      // event's `type` given.
      const listenersForType = events.get(type);

      // If we don't have listeners for the event's type, we bail out.
      if (!listenersForType) {
        return;
      }

      // If the listeners list contains the listener given, we just remove it.
      if (listenersForType.has(listener)) {
        listenersForType.delete(listener);
      } else {
        // If it's not present, there is still the possibility that the listener
        // have been added using `once`, since the method wraps the original listener
        // in another function.
        // So we iterate all the listeners to check if any of them is a wrapper to
        // the `listener` given.
        for (const value of listenersForType.values()) {
          if (
            onceOriginalListener in value &&
            value[onceOriginalListener] === listener
          ) {
            listenersForType.delete(value);
            break;
          }
        }
      }
    } else if (length === 2) {
      // No listener was given, it means we're removing all the listeners from
      // the given event's `type`.
      if (events.has(type)) {
        events.delete(type);
      }
    } else if (length === 1) {
      // With only the `target` given, we're removing all the listeners from the object.
      events.clear();
    }
  }

  static clearEvents(target) {
    const events = target[eventListeners];
    if (!events) {
      return;
    }
    events.clear();
  }

  /**
   * Registers an event `listener` that is called only the next time an event
   * of the specified `type` is emitted on the given event `target`.
   * It returns a Promise resolved once the specified event `type` is emitted.
   *
   * @param {Object} target
   *    Event target object.
   * @param {String} type
   *    The type of the event.
   * @param {Function|Object} [listener]
   *    The listener that processes the event.
   * @param {Object} options
   * @param {AbortSignal} options.signal
   *     The listener will be removed when linked AbortController’s abort() method is called
   * @return {Promise}
   *    The promise resolved once the event `type` is emitted.
   */
  static once(target, type, listener, options) {
    return new Promise(resolve => {
      // This is the actual listener that will be added to the target's listener, it wraps
      // the call to the original `listener` given.
      const newListener = (first, ...rest) => {
        // To prevent side effects we're removing the listener upfront.
        EventEmitter.off(target, type, newListener);

        let rv;
        if (listener) {
          if (isEventHandler(listener)) {
            // if the `listener` given is actually an object that handles the events
            // using `EventEmitter.handler`, we want to call that function, passing also
            // the event's type as first argument, and the `listener` (the object) as
            // contextual object.
            rv = listener[handler](type, first, ...rest);
          } else {
            // Otherwise we'll just call it
            rv = listener.call(target, first, ...rest);
          }
        }

        // We resolve the promise once the listener is called.
        resolve(first);

        // Listeners may return a promise, so pass it along
        return rv;
      };

      newListener[onceOriginalListener] = listener;
      EventEmitter.on(target, type, newListener, options);
    });
  }

  static emit(target, type, ...rest) {
    EventEmitter._emit(target, type, false, rest);
  }

  static emitAsync(target, type, ...rest) {
    return EventEmitter._emit(target, type, true, rest);
  }

  /**
   * Emit an event of a given `type` on a given `target` object.
   *
   * @param {Object} target
   *    Event target object.
   * @param {String} type
   *    The type of the event.
   * @param {Boolean} async
   *    If true, this function will wait for each listener completion.
   *    Each listener has to return a promise, which will be awaited for.
   * @param {Array} args
   *    The arguments to pass to each listener function.
   * @return {Promise|undefined}
   *    If `async` argument is true, returns the promise resolved once all listeners have resolved.
   *    Otherwise, this function returns undefined;
   */
  static _emit(target, type, async, args) {
    if (loggingEnabled) {
      logEvent(type, args);
    }

    const targetEventListeners = target[eventListeners];
    if (!targetEventListeners) {
      return undefined;
    }

    const listeners = targetEventListeners.get(type);
    if (!listeners?.size) {
      return undefined;
    }

    const promises = async ? [] : null;

    // Creating a temporary Set with the original listeners, to avoiding side effects
    // in emit.
    for (const listener of new Set(listeners)) {
      // If the object was destroyed during event emission, stop emitting.
      if (!(eventListeners in target)) {
        break;
      }

      // If listeners were removed during emission, make sure the
      // event handler we're going to fire wasn't removed.
      if (listeners && listeners.has(listener)) {
        try {
          let promise;
          if (isEventHandler(listener)) {
            promise = listener[handler](type, ...args);
          } else {
            promise = listener.apply(target, args);
          }
          if (async) {
            // Assert the name instead of `constructor != Promise` in order
            // to avoid cross compartment issues where Promise can be multiple.
            if (!promise || promise.constructor.name != "Promise") {
              console.warn(
                `Listener for event '${type}' did not return a promise.`
              );
            } else {
              promises.push(promise);
            }
          }
        } catch (ex) {
          // Prevent a bad listener from interfering with the others.
          console.error(ex);
          const msg = ex + ": " + ex.stack;
          dump(msg + "\n");
        }
      }
    }

    if (async) {
      return Promise.all(promises);
    }

    return undefined;
  }

  /**
   * Returns a number of event listeners registered for the given event `type`
   * on the given event `target`.
   *
   * @param {Object} target
   *    Event target object.
   * @param {String} type
   *    The type of event.
   * @return {Number}
   *    The number of event listeners.
   */
  static count(target, type) {
    if (eventListeners in target) {
      const listenersForType = target[eventListeners].get(type);

      if (listenersForType) {
        return listenersForType.size;
      }
    }

    return 0;
  }

  /**
   * Decorate an object with event emitter functionality; basically using the
   * class' prototype as mixin.
   *
   * @param Object target
   *    The object to decorate.
   * @return Object
   *    The object given, mixed.
   */
  static decorate(target) {
    const descriptors = Object.getOwnPropertyDescriptors(this.prototype);
    delete descriptors.constructor;
    return Object.defineProperties(target, descriptors);
  }

  static get handler() {
    return handler;
  }

  on(...args) {
    return EventEmitter.on(this, ...args);
  }

  off(...args) {
    EventEmitter.off(this, ...args);
  }

  clearEvents() {
    EventEmitter.clearEvents(this);
  }

  once(...args) {
    return EventEmitter.once(this, ...args);
  }

  emit(...args) {
    EventEmitter.emit(this, ...args);
  }

  emitAsync(...args) {
    return EventEmitter.emitAsync(this, ...args);
  }

  emitForTests(...args) {
    if (flags.testing) {
      EventEmitter.emit(this, ...args);
    }
  }

  count(...args) {
    return EventEmitter.count(this, ...args);
  }
}

module.exports = EventEmitter;

const isEventHandler = listener =>
  listener && handler in listener && typeof listener[handler] === "function";

const {
  getNthPathExcluding,
} = require("resource://devtools/shared/platform/stack.js");
let loggingEnabled = false;

if (!isWorker) {
  loggingEnabled = Services.prefs.getBoolPref("devtools.dump.emit", false);
  const observer = {
    observe: () => {
      loggingEnabled = Services.prefs.getBoolPref("devtools.dump.emit");
    },
  };
  Services.prefs.addObserver("devtools.dump.emit", observer);

  // Also listen for Loader unload to unregister the pref observer and
  // prevent leaking
  const unloadObserver = function (subject) {
    if (subject.wrappedJSObject == require("@loader/unload")) {
      Services.prefs.removeObserver("devtools.dump.emit", observer);
      Services.obs.removeObserver(unloadObserver, "devtools:loader:destroy");
    }
  };
  Services.obs.addObserver(unloadObserver, "devtools:loader:destroy");
}

function serialize(target) {
  const MAXLEN = 60;

  // Undefined
  if (typeof target === "undefined") {
    return "undefined";
  }

  if (target === null) {
    return "null";
  }

  // Number / String
  if (typeof target === "string" || typeof target === "number") {
    return truncate(target, MAXLEN);
  }

  // HTML Node
  if (target.nodeName) {
    let out = target.nodeName;

    if (target.id) {
      out += "#" + target.id;
    }
    if (target.className) {
      out += "." + target.className;
    }

    return out;
  }

  // Array
  if (Array.isArray(target)) {
    return truncate(target.toSource(), MAXLEN);
  }

  // Function
  if (typeof target === "function") {
    return `function ${target.name ? target.name : "anonymous"}()`;
  }

  // Window
  if (target?.constructor?.name === "Window") {
    return `window (${target.location.origin})`;
  }

  // Object
  if (typeof target === "object") {
    let out = "{";

    const entries = Object.entries(target);
    for (let i = 0; i < Math.min(10, entries.length); i++) {
      const [name, value] = entries[i];

      if (i > 0) {
        out += ", ";
      }

      out += `${name}: ${truncate(value, MAXLEN)}`;
    }

    return out + "}";
  }

  // Other
  return truncate(target.toSource(), MAXLEN);
}

function truncate(value, maxLen) {
  // We don't use value.toString() because it can throw.
  const str = String(value);
  return str.length > maxLen ? str.substring(0, maxLen) + "..." : str;
}

function logEvent(type, args) {
  let argsOut = "";

  // We need this try / catch to prevent any dead object errors.
  try {
    argsOut = `${args.map(serialize).join(", ")}`;
  } catch (e) {
    // Object is dead so the toolbox is most likely shutting down,
    // do nothing.
  }

  const path = getNthPathExcluding(0, "devtools/shared/event-emitter.js");

  if (args.length) {
    dump(`EMITTING: emit(${type}, ${argsOut}) from ${path}\n`);
  } else {
    dump(`EMITTING: emit(${type}) from ${path}\n`);
  }
}

quality93%

¤ Dauer der Verarbeitung: 0.32 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.