futoin-asyncsteps/es5/lib/AsyncTool.js

Mimic traditional threads in single threaded event loop

"use strict";

/**
 * @file
 * @author Andrey Galkin <andrey@futoin.org>
 *
 *
 * Copyright 2014-2017 FutoIn Project (https://futoin.org)
 * Copyright 2014-2017 Andrey Galkin <andrey@futoin.org>
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Neutral interface to event scheduler
 * @member AsyncTool
 */
exports = module.exports = {};

/* istanbul ignore if */
if (typeof setImmediate === 'undefined') {
  // Wrapper for simple setTimeout
  // ---
  exports.callLater = function (func, timeout_ms) {
    return setTimeout(func, timeout_ms);
  };
  exports.cancelCall = function (func) {
    return clearTimeout(func);
  };

  // Workaround for security-delayed setTimeout
  // ---

  // workaround possible multiple instances of AsyncSteps

  window._FutoInEventLoopQueue = window._FutoInEventLoopQueue || [];
  var TIME_LIMIT = 10; // support browser with 100ms precision

  var queue = window._FutoInEventLoopQueue;
  var performance = window.performance;
  var process_handle = null;
  var sched_immed_process = function sched_immed_process() {
    if (process_handle) {
      clearTimeout(process_handle);
    }
    process_handle = setTimeout(process_queue, 0);
  };
  var process_queue = function process_queue() {
    process_handle = null;
    var end_time = performance.now() + TIME_LIMIT;
    while (queue.length) {
      var r = queue.shift();
      try {
        r();
      } catch (e) {
        sched_immed_process();
        throw e;
      }
      if (performance.now() >= end_time) {
        sched_immed_process();
        break;
      }
    }
  };
  exports.callImmediate = function (func) {
    if (!queue.length) {
      sched_immed_process();
    }
    var handle = function handle() {
      func();
    }; // same func can be added multiple times
    queue.push(handle);
    return handle;
  };
  exports.cancelImmediate = function (handle) {
    var i = queue.indexOf(handle);
    if (i >= 0) {
      queue.splice(i, 1);
    }
  };
} else {
  /**
   * Wrapper for setTimeout()
   * @param {Function} func - callback to execute
   * @param {number} [timeout_ms] - optional timeout in ms
   * @returns {object} - timer handle
   * @alias AsyncTool.callLater
   */
  exports.callLater = function (func, timeout_ms) {
    return setTimeout(func, timeout_ms);
  };

  /**
   * Wrapper for clearTimeout()/clearImmediate()
   * @param {object} handle - Handle returned from AsyncTool.callLater
   * @alias AsyncTool.cancelCall
   */
  exports.cancelCall = function (handle) {
    clearTimeout(handle);
  };

  /**
   * Wrapper for setImmediate()
   * @param {Function} func - callback to execute
   * @returns {object} - timer handle
   * @alias AsyncTool.callImmediate
   */
  exports.callImmediate = function (func) {
    return setImmediate(func);
  };

  /**
   * Wrapper for clearImmediate()
   * @param {object} handle - Handle returned from AsyncTool.callImmediate
   * @alias AsyncTool.cancelImmediate
   */
  exports.cancelImmediate = function (handle) {
    clearImmediate(handle);
  };
}
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