All files / lib/internal timers.js

99.7% Statements 663/665
98.67% Branches 148/150
100% Functions 30/30
99.7% Lines 663/665

Press n or j to go to the next uncovered block, b, p or k for the previous block.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 66625x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 980x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 154172x 154172x 154172x 154172x 154172x 154172x 154172x 25x 25x 25x 11095x 11095x 11095x 137x 12x 12x 12x 12x 12x 137x 137x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 11095x 25x 25x 25x 87x 87x 87x 87x 87x 87x 87x 25x 25x 25x 11842x 11842x 11838x 11838x 11842x 11842x 25x 25x 25x 75x 68x 68x 68x 68x 75x 25x 25x 25x 3x 3x 3x 3x 3x 3x 25x 25x 25x 3x 25x 25x 1958x 1958x 1958x 1958x 1958x 1958x 1958x 1958x 25x 25x 25x 1x 1x 1x 1x 1x 1x 1x 25x 25x 25x 824x 824x 824x 824x 25x 25x 25x 25x 142606x 27655x 27655x 142491x 114951x 114951x 142606x 25x 25x 25x 25x 25x 12x 5x 5x 12x 12x 7x 7x 12x 12x 12x 12x 12x 12x 12x 12x 25x 25x 7934x 7934x 7934x 7934x 25x 1093x 1093x 1093x 1093x 25x 25x 25x 10x 10x 10x 25x 25x 25x 11848x 11848x 11848x 25x 25x 25x 25x 25x 11858x 11858x 11858x 11858x 3257x 3257x 3257x 3257x 11858x 471x 471x 471x 3257x 10190x 464x 464x 10193x 3x 3x     3x 3257x 11858x 25x 15518x 15518x 15518x 15518x 15518x 15518x 15518x 15518x 1958x 1958x 1958x 1958x 1958x 1958x 1480x 1480x 1480x 1958x 15518x 15518x 15518x 25x 3179x 3179x 3179x 3179x 3179x 3179x 3179x 3179x 3179x 25x 25x 27744x 27744x 27744x 8x 8x 27720x 27720x 27736x 3x 3x 3x 3x 3x 27717x 27717x 27744x 25x 2845x 2845x 2845x 162x 162x 107x 107x 162x 2683x 2845x 25x 8265x 8265x 8265x 25x 412x 412x 412x 412x 412x 412x 412x 115870x 115870x 115870x 115870x 115870x 115870x 115870x 114933x 114933x 114933x 115870x 115870x 115870x 115870x 143502x 143502x 115870x 115870x 142577x 142577x 142577x 142577x 143502x 1x 1x 1x 142576x 142576x 142576x 142576x 142576x 142576x 142576x 142576x 142576x 142576x 142576x 142576x 142576x 142576x 142576x 142576x 142576x 23024x 23024x 143502x 142574x 142574x 142574x 142574x 142574x 142574x 142574x 142553x 142553x 142553x 114922x 114922x 115862x 114922x 115870x 412x 412x 412x 5539x 5539x 5539x 5539x 5539x 5539x 10852x 5156x 5156x 5156x 5696x 10852x 5514x 5514x 5696x 5696x 336x 5539x 412x 412x 5696x 5696x 5696x 5696x 5696x 5696x 5696x 14114x 14114x 14114x 14114x 14114x 4834x 4834x 4834x 4834x 4834x 4834x 9280x 9280x 14114x 5613x 5613x 9280x 9280x 9280x 9280x 9280x 9280x 14114x 4x 3x 3x 3x 3x 3x 3x 3x 3x 4x 4x 9276x 9276x 9276x 9276x 9276x 13459x 9276x 9276x 9276x 9276x 9454x 336x 336x 14114x 9264x 1166x 1166x 9254x 7327x 7327x 7327x 7327x 7327x 7327x 7327x 7327x 9264x 9231x 9231x 9231x 817x 817x 817x 817x 817x 817x 817x 817x 817x 817x 1308x 787x 787x 787x 5696x 412x 412x 412x 412x 412x 412x 25x 25x 25x 142606x 142606x 142606x 142606x 142606x 142606x 142606x 142606x 142606x 142606x 142606x 142606x 142606x 142606x 25x 25x 142610x 142607x 142607x 142607x 142607x 142610x 142610x 25x 25x 12x 11x 11x 11x 11x 12x 12x 25x 25x 2x 2x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x 25x  
'use strict';
 
// HOW and WHY the timers implementation works the way it does.
//
// Timers are crucial to Node.js. Internally, any TCP I/O connection creates a
// timer so that we can time out of connections. Additionally, many user
// libraries and applications also use timers. As such there may be a
// significantly large amount of timeouts scheduled at any given time.
// Therefore, it is very important that the timers implementation is performant
// and efficient.
//
// Note: It is suggested you first read through the lib/internal/linkedlist.js
// linked list implementation, since timers depend on it extensively. It can be
// somewhat counter-intuitive at first, as it is not actually a class. Instead,
// it is a set of helpers that operate on an existing object.
//
// In order to be as performant as possible, the architecture and data
// structures are designed so that they are optimized to handle the following
// use cases as efficiently as possible:
 
// - Adding a new timer. (insert)
// - Removing an existing timer. (remove)
// - Handling a timer timing out. (timeout)
//
// Whenever possible, the implementation tries to make the complexity of these
// operations as close to constant-time as possible.
// (So that performance is not impacted by the number of scheduled timers.)
//
// Object maps are kept which contain linked lists keyed by their duration in
// milliseconds.
//
/* eslint-disable node-core/non-ascii-character */
//
// ╔════ > Object Map
// ║
// ╠══
// ║ lists: { '40': { }, '320': { etc } } (keys of millisecond duration)
// ╚══          ┌────┘
//              │
// ╔══          │
// ║ TimersList { _idleNext: { }, _idlePrev: (self) }
// ║         ┌────────────────┘
// ║    ╔══  │                              ^
// ║    ║    { _idleNext: { },  _idlePrev: { }, _onTimeout: (callback) }
// ║    ║      ┌───────────┘
// ║    ║      │                                  ^
// ║    ║      { _idleNext: { etc },  _idlePrev: { }, _onTimeout: (callback) }
// ╠══  ╠══
// ║    ║
// ║    ╚════ >  Actual JavaScript timeouts
// ║
// ╚════ > Linked List
//
/* eslint-enable node-core/non-ascii-character */
//
// With this, virtually constant-time insertion (append), removal, and timeout
// is possible in the JavaScript layer. Any one list of timers is able to be
// sorted by just appending to it because all timers within share the same
// duration. Therefore, any timer added later will always have been scheduled to
// timeout later, thus only needing to be appended.
// Removal from an object-property linked list is also virtually constant-time
// as can be seen in the lib/internal/linkedlist.js implementation.
// Timeouts only need to process any timers currently due to expire, which will
// always be at the beginning of the list for reasons stated above. Any timers
// after the first one encountered that does not yet need to timeout will also
// always be due to timeout at a later time.
//
// Less-than constant time operations are thus contained in two places:
// The PriorityQueue — an efficient binary heap implementation that does all
// operations in worst-case O(log n) time — which manages the order of expiring
// Timeout lists and the object map lookup of a specific list by the duration of
// timers within (or creation of a new list). However, these operations combined
// have shown to be trivial in comparison to other timers architectures.
 
const {
  MathMax,
  MathTrunc,
  NumberIsFinite,
  NumberMIN_SAFE_INTEGER,
  ObjectCreate,
  Symbol,
  ReflectApply,
} = primordials;
 
const {
  scheduleTimer,
  toggleTimerRef,
  getLibuvNow,
  immediateInfo,
  toggleImmediateRef
} = internalBinding('timers');
 
const {
  getDefaultTriggerAsyncId,
  newAsyncId,
  initHooksExist,
  destroyHooksExist,
  // The needed emit*() functions.
  emitInit,
  emitBefore,
  emitAfter,
  emitDestroy,
} = require('internal/async_hooks');
 
// Symbols for storing async id state.
const async_id_symbol = Symbol('asyncId');
const trigger_async_id_symbol = Symbol('triggerId');
 
const kHasPrimitive = Symbol('kHasPrimitive');
 
const {
  ERR_OUT_OF_RANGE
} = require('internal/errors').codes;
const {
  validateCallback,
  validateNumber,
} = require('internal/validators');
 
const L = require('internal/linkedlist');
const PriorityQueue = require('internal/priority_queue');
 
const { inspect } = require('internal/util/inspect');
let debug = require('internal/util/debuglog').debuglog('timer', (fn) => {
  debug = fn;
});
 
// *Must* match Environment::ImmediateInfo::Fields in src/env.h.
const kCount = 0;
const kRefCount = 1;
const kHasOutstanding = 2;
 
// Timeout values > TIMEOUT_MAX are set to 1.
const TIMEOUT_MAX = 2 ** 31 - 1;
 
let timerListId = NumberMIN_SAFE_INTEGER;
 
const kRefed = Symbol('refed');
 
// Create a single linked list instance only once at startup
const immediateQueue = new ImmediateList();
 
let nextExpiry = Infinity;
let refCount = 0;
 
// This is a priority queue with a custom sorting function that first compares
// the expiry times of two lists and if they're the same then compares their
// individual IDs to determine which list was created first.
const timerListQueue = new PriorityQueue(compareTimersLists, setPosition);
 
// Object map containing linked lists of timers, keyed and sorted by their
// duration in milliseconds.
//
// - key = time in milliseconds
// - value = linked list
const timerListMap = ObjectCreate(null);
 
function initAsyncResource(resource, type) {
  const asyncId = resource[async_id_symbol] = newAsyncId();
  const triggerAsyncId =
    resource[trigger_async_id_symbol] = getDefaultTriggerAsyncId();
  if (initHooksExist())
    emitInit(asyncId, type, triggerAsyncId, resource);
}
 
// Timer constructor function.
// The entire prototype is defined in lib/timers.js
function Timeout(callback, after, args, isRepeat, isRefed) {
  after *= 1; // Coalesce to number or NaN
  if (!(after >= 1 && after <= TIMEOUT_MAX)) {
    if (after > TIMEOUT_MAX) {
      process.emitWarning(`${after} does not fit into` +
                          ' a 32-bit signed integer.' +
                          '\nTimeout duration was set to 1.',
                          'TimeoutOverflowWarning');
    }
    after = 1; // Schedule on next tick, follows browser behavior
  }
 
  this._idleTimeout = after;
  this._idlePrev = this;
  this._idleNext = this;
  this._idleStart = null;
  // This must be set to null first to avoid function tracking
  // on the hidden class, revisit in V8 versions after 6.2
  this._onTimeout = null;
  this._onTimeout = callback;
  this._timerArgs = args;
  this._repeat = isRepeat ? after : null;
  this._destroyed = false;
 
  if (isRefed)
    incRefCount();
  this[kRefed] = isRefed;
  this[kHasPrimitive] = false;
 
  initAsyncResource(this, 'Timeout');
}
 
// Make sure the linked list only shows the minimal necessary information.
Timeout.prototype[inspect.custom] = function(_, options) {
  return inspect(this, {
    ...options,
    // Only inspect one level.
    depth: 0,
    // It should not recurse.
    customInspect: false
  });
};
 
Timeout.prototype.refresh = function() {
  if (this[kRefed])
    active(this);
  else
    unrefActive(this);
 
  return this;
};
 
Timeout.prototype.unref = function() {
  if (this[kRefed]) {
    this[kRefed] = false;
    if (!this._destroyed)
      decRefCount();
  }
  return this;
};
 
Timeout.prototype.ref = function() {
  if (!this[kRefed]) {
    this[kRefed] = true;
    if (!this._destroyed)
      incRefCount();
  }
  return this;
};
 
Timeout.prototype.hasRef = function() {
  return this[kRefed];
};
 
function TimersList(expiry, msecs) {
  this._idleNext = this; // Create the list with the linkedlist properties to
  this._idlePrev = this; // Prevent any unnecessary hidden class changes.
  this.expiry = expiry;
  this.id = timerListId++;
  this.msecs = msecs;
  this.priorityQueuePosition = null;
}
 
// Make sure the linked list only shows the minimal necessary information.
TimersList.prototype[inspect.custom] = function(_, options) {
  return inspect(this, {
    ...options,
    // Only inspect one level.
    depth: 0,
    // It should not recurse.
    customInspect: false
  });
};
 
// A linked list for storing `setImmediate()` requests
function ImmediateList() {
  this.head = null;
  this.tail = null;
}
 
// Appends an item to the end of the linked list, adjusting the current tail's
// next pointer and the item's previous pointer where applicable
ImmediateList.prototype.append = function(item) {
  if (this.tail !== null) {
    this.tail._idleNext = item;
    item._idlePrev = this.tail;
  } else {
    this.head = item;
  }
  this.tail = item;
};
 
// Removes an item from the linked list, adjusting the pointers of adjacent
// items and the linked list's head or tail pointers as necessary
ImmediateList.prototype.remove = function(item) {
  if (item._idleNext) {
    item._idleNext._idlePrev = item._idlePrev;
  }
 
  if (item._idlePrev) {
    item._idlePrev._idleNext = item._idleNext;
  }
 
  if (item === this.head)
    this.head = item._idleNext;
  if (item === this.tail)
    this.tail = item._idlePrev;
 
  item._idleNext = null;
  item._idlePrev = null;
};
 
function incRefCount() {
  if (refCount++ === 0)
    toggleTimerRef(true);
}
 
function decRefCount() {
  if (--refCount === 0)
    toggleTimerRef(false);
}
 
// Schedule or re-schedule a timer.
// The item must have been enroll()'d first.
function active(item) {
  insertGuarded(item, true);
}
 
// Internal APIs that need timeouts should use `unrefActive()` instead of
// `active()` so that they do not unnecessarily keep the process open.
function unrefActive(item) {
  insertGuarded(item, false);
}
 
// The underlying logic for scheduling or re-scheduling a timer.
//
// Appends a timer onto the end of an existing timers list, or creates a new
// list if one does not already exist for the specified timeout duration.
function insertGuarded(item, refed, start) {
  const msecs = item._idleTimeout;
  if (msecs < 0 || msecs === undefined)
    return;
 
  insert(item, msecs, start);
 
  const isDestroyed = item._destroyed;
  if (isDestroyed || !item[async_id_symbol]) {
    item._destroyed = false;
    initAsyncResource(item, 'Timeout');
  }
 
  if (isDestroyed) {
    if (refed)
      incRefCount();
  } else if (refed === !item[kRefed]) {
    if (refed)
      incRefCount();
    else
      decRefCount();
  }
  item[kRefed] = refed;
}
 
function insert(item, msecs, start = getLibuvNow()) {
  // Truncate so that accuracy of sub-millisecond timers is not assumed.
  msecs = MathTrunc(msecs);
  item._idleStart = start;
 
  // Use an existing list if there is one, otherwise we need to make a new one.
  let list = timerListMap[msecs];
  if (list === undefined) {
    debug('no %d list was found in insert, creating a new one', msecs);
    const expiry = start + msecs;
    timerListMap[msecs] = list = new TimersList(expiry, msecs);
    timerListQueue.insert(list);
 
    if (nextExpiry > expiry) {
      scheduleTimer(msecs);
      nextExpiry = expiry;
    }
  }
 
  L.append(list, item);
}
 
function setUnrefTimeout(callback, after) {
  // Type checking identical to setTimeout()
  validateCallback(callback);
 
  const timer = new Timeout(callback, after, undefined, false, false);
  insert(timer, timer._idleTimeout);
 
  return timer;
}
 
// Type checking used by timers.enroll() and Socket#setTimeout()
function getTimerDuration(msecs, name) {
  validateNumber(msecs, name);
  if (msecs < 0 || !NumberIsFinite(msecs)) {
    throw new ERR_OUT_OF_RANGE(name, 'a non-negative finite number', msecs);
  }
 
  // Ensure that msecs fits into signed int32
  if (msecs > TIMEOUT_MAX) {
    process.emitWarning(`${msecs} does not fit into a 32-bit signed integer.` +
                        `\nTimer duration was truncated to ${TIMEOUT_MAX}.`,
                        'TimeoutOverflowWarning');
    return TIMEOUT_MAX;
  }
 
  return msecs;
}
 
function compareTimersLists(a, b) {
  const expiryDiff = a.expiry - b.expiry;
  if (expiryDiff === 0) {
    if (a.id < b.id)
      return -1;
    if (a.id > b.id)
      return 1;
  }
  return expiryDiff;
}
 
function setPosition(node, pos) {
  node.priorityQueuePosition = pos;
}
 
function getTimerCallbacks(runNextTicks) {
  // If an uncaught exception was thrown during execution of immediateQueue,
  // this queue will store all remaining Immediates that need to run upon
  // resolution of all error handling (if process is still alive).
  const outstandingQueue = new ImmediateList();
 
  function processImmediate() {
    const queue = outstandingQueue.head !== null ?
      outstandingQueue : immediateQueue;
    let immediate = queue.head;
 
    // Clear the linked list early in case new `setImmediate()`
    // calls occur while immediate callbacks are executed
    if (queue !== outstandingQueue) {
      queue.head = queue.tail = null;
      immediateInfo[kHasOutstanding] = 1;
    }
 
    let prevImmediate;
    let ranAtLeastOneImmediate = false;
    while (immediate !== null) {
      if (ranAtLeastOneImmediate)
        runNextTicks();
      else
        ranAtLeastOneImmediate = true;
 
      // It's possible for this current Immediate to be cleared while executing
      // the next tick queue above, which means we need to use the previous
      // Immediate's _idleNext which is guaranteed to not have been cleared.
      if (immediate._destroyed) {
        outstandingQueue.head = immediate = prevImmediate._idleNext;
        continue;
      }
 
      immediate._destroyed = true;
 
      immediateInfo[kCount]--;
      if (immediate[kRefed])
        immediateInfo[kRefCount]--;
      immediate[kRefed] = null;
 
      prevImmediate = immediate;
 
      const asyncId = immediate[async_id_symbol];
      emitBefore(asyncId, immediate[trigger_async_id_symbol], immediate);
 
      try {
        const argv = immediate._argv;
        if (!argv)
          immediate._onImmediate();
        else
          immediate._onImmediate(...argv);
      } finally {
        immediate._onImmediate = null;
 
        if (destroyHooksExist())
          emitDestroy(asyncId);
 
        outstandingQueue.head = immediate = immediate._idleNext;
      }
 
      emitAfter(asyncId);
    }
 
    if (queue === outstandingQueue)
      outstandingQueue.head = null;
    immediateInfo[kHasOutstanding] = 0;
  }
 
 
  function processTimers(now) {
    debug('process timer lists %d', now);
    nextExpiry = Infinity;
 
    let list;
    let ranAtLeastOneList = false;
    while (list = timerListQueue.peek()) {
      if (list.expiry > now) {
        nextExpiry = list.expiry;
        return refCount > 0 ? nextExpiry : -nextExpiry;
      }
      if (ranAtLeastOneList)
        runNextTicks();
      else
        ranAtLeastOneList = true;
      listOnTimeout(list, now);
    }
    return 0;
  }
 
  function listOnTimeout(list, now) {
    const msecs = list.msecs;
 
    debug('timeout callback %d', msecs);
 
    let ranAtLeastOneTimer = false;
    let timer;
    while (timer = L.peek(list)) {
      const diff = now - timer._idleStart;
 
      // Check if this loop iteration is too early for the next timer.
      // This happens if there are more timers scheduled for later in the list.
      if (diff < msecs) {
        list.expiry = MathMax(timer._idleStart + msecs, now + 1);
        list.id = timerListId++;
        timerListQueue.percolateDown(1);
        debug('%d list wait because diff is %d', msecs, diff);
        return;
      }
 
      if (ranAtLeastOneTimer)
        runNextTicks();
      else
        ranAtLeastOneTimer = true;
 
      // The actual logic for when a timeout happens.
      L.remove(timer);
 
      const asyncId = timer[async_id_symbol];
 
      if (!timer._onTimeout) {
        if (!timer._destroyed) {
          timer._destroyed = true;
 
          if (timer[kRefed])
            refCount--;
 
          if (destroyHooksExist())
            emitDestroy(asyncId);
        }
        continue;
      }
 
      emitBefore(asyncId, timer[trigger_async_id_symbol], timer);
 
      let start;
      if (timer._repeat)
        start = getLibuvNow();
 
      try {
        const args = timer._timerArgs;
        if (args === undefined)
          timer._onTimeout();
        else
          ReflectApply(timer._onTimeout, timer, args);
      } finally {
        if (timer._repeat && timer._idleTimeout !== -1) {
          timer._idleTimeout = timer._repeat;
          insert(timer, timer._idleTimeout, start);
        } else if (!timer._idleNext && !timer._idlePrev && !timer._destroyed) {
          timer._destroyed = true;
 
          if (timer[kRefed])
            refCount--;
 
          if (destroyHooksExist())
            emitDestroy(asyncId);
        }
      }
 
      emitAfter(asyncId);
    }
 
    // If `L.peek(list)` returned nothing, the list was either empty or we have
    // called all of the timer timeouts.
    // As such, we can remove the list from the object map and
    // the PriorityQueue.
    debug('%d list empty', msecs);
 
    // The current list may have been removed and recreated since the reference
    // to `list` was created. Make sure they're the same instance of the list
    // before destroying.
    if (list === timerListMap[msecs]) {
      delete timerListMap[msecs];
      timerListQueue.shift();
    }
  }
 
  return {
    processImmediate,
    processTimers
  };
}
 
class Immediate {
  constructor(callback, args) {
    this._idleNext = null;
    this._idlePrev = null;
    this._onImmediate = callback;
    this._argv = args;
    this._destroyed = false;
    this[kRefed] = false;
 
    initAsyncResource(this, 'Immediate');
 
    this.ref();
    immediateInfo[kCount]++;
 
    immediateQueue.append(this);
  }
 
  ref() {
    if (this[kRefed] === false) {
      this[kRefed] = true;
      if (immediateInfo[kRefCount]++ === 0)
        toggleImmediateRef(true);
    }
    return this;
  }
 
  unref() {
    if (this[kRefed] === true) {
      this[kRefed] = false;
      if (--immediateInfo[kRefCount] === 0)
        toggleImmediateRef(false);
    }
    return this;
  }
 
  hasRef() {
    return !!this[kRefed];
  }
}
 
module.exports = {
  TIMEOUT_MAX,
  kTimeout: Symbol('timeout'), // For hiding Timeouts on other internals.
  async_id_symbol,
  trigger_async_id_symbol,
  Timeout,
  Immediate,
  kRefed,
  kHasPrimitive,
  initAsyncResource,
  setUnrefTimeout,
  getTimerDuration,
  immediateQueue,
  getTimerCallbacks,
  immediateInfoFields: {
    kCount,
    kRefCount,
    kHasOutstanding
  },
  active,
  unrefActive,
  insert,
  timerListMap,
  timerListQueue,
  decRefCount,
  incRefCount
};