From a7c66b6aaeb8132540abee12ffa9ac1c1fa2f373 Mon Sep 17 00:00:00 2001
From: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Date: Mon, 3 Dec 2018 17:41:58 -0800
Subject: [PATCH] timers: truncate decimal values

Reverts some timers behavior back to as it was before
2930bd1317d15d12738a4896c0a6c05700411b47

That commit introduced an unintended change which allowed non-integer
timeouts to actually exist since the value is no longer converted to an
integer via a TimeWrap handle directly.

Even with the fix in
e9de43549843da9f4f081cce917945878967df7
non-integer timeouts are still indeterministic, because libuv does not
support them.

This fixes the issue by emulating the old behavior:
truncate the `_idleTimeout` before using it.

See comments in
https://github.com/nodejs/node/pull/24214
for more background on this.

PR-URL: https://github.com/nodejs/node/pull/24819
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
---
 doc/api/timers.md                             |  4 +--
 lib/timers.js                                 |  9 +++--
 .../parallel/test-timers-non-integer-delay.js | 35 +++++++++++++++++++
 3 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/doc/api/timers.md b/doc/api/timers.md
index 4a903b5f5eef0e..9460028928bba1 100644
--- a/doc/api/timers.md
+++ b/doc/api/timers.md
@@ -186,7 +186,7 @@ added: v0.0.1
 Schedules repeated execution of `callback` every `delay` milliseconds.
 
 When `delay` is larger than `2147483647` or less than `1`, the `delay` will be
-set to `1`.
+set to `1`. Non-integer delays are truncated to an integer.
 
 If `callback` is not a function, a [`TypeError`][] will be thrown.
 
@@ -209,7 +209,7 @@ nor of their ordering. The callback will be called as close as possible to the
 time specified.
 
 When `delay` is larger than `2147483647` or less than `1`, the `delay`
-will be set to `1`.
+will be set to `1`. Non-integer delays are truncated to an integer.
 
 If `callback` is not a function, a [`TypeError`][] will be thrown.
 
diff --git a/lib/timers.js b/lib/timers.js
index 0937e73c4abd80..14151d6d81d63e 100644
--- a/lib/timers.js
+++ b/lib/timers.js
@@ -193,10 +193,13 @@ exports._unrefActive = function(item) {
 // 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 insert(item, refed, start) {
-  const msecs = item._idleTimeout;
+  let msecs = item._idleTimeout;
   if (msecs < 0 || msecs === undefined)
     return;
 
+  // Truncate so that accuracy of sub-milisecond timers is not assumed.
+  msecs = Math.trunc(msecs);
+
   item._idleStart = start;
 
   // Use an existing list if there is one, otherwise we need to make a new one.
@@ -378,7 +381,9 @@ function unenroll(item) {
   // clearTimeout that makes it clear that the list should not be deleted.
   // That function could then be used by http and other similar modules.
   if (item[kRefed]) {
-    const list = lists[item._idleTimeout];
+    // Compliment truncation during insert().
+    const msecs = Math.trunc(item._idleTimeout);
+    const list = lists[msecs];
     if (list !== undefined && L.isEmpty(list)) {
       debug('unenroll: list empty');
       queue.removeAt(list.priorityQueuePosition);
diff --git a/test/parallel/test-timers-non-integer-delay.js b/test/parallel/test-timers-non-integer-delay.js
index 017ef28d0f86ef..a57922e3c78fe3 100644
--- a/test/parallel/test-timers-non-integer-delay.js
+++ b/test/parallel/test-timers-non-integer-delay.js
@@ -21,6 +21,7 @@
 
 'use strict';
 const common = require('../common');
+const assert = require('assert');
 
 /*
  * This test makes sure that non-integer timer delays do not make the process
@@ -47,3 +48,37 @@ const interval = setInterval(common.mustCall(() => {
     process.exit(0);
   }
 }, N), TIMEOUT_DELAY);
+
+// Test non-integer delay ordering
+{
+  const ordering = [];
+
+  setTimeout(common.mustCall(() => {
+    ordering.push(1);
+  }), 1);
+
+  setTimeout(common.mustCall(() => {
+    ordering.push(2);
+  }), 1.8);
+
+  setTimeout(common.mustCall(() => {
+    ordering.push(3);
+  }), 1.1);
+
+  setTimeout(common.mustCall(() => {
+    ordering.push(4);
+  }), 1);
+
+  setTimeout(common.mustCall(() => {
+    const expected = [1, 2, 3, 4];
+
+    assert.deepStrictEqual(
+      ordering,
+      expected,
+      `Non-integer delay ordering should be ${expected}, but got ${ordering}`
+    );
+
+    // 2 should always be last of these delays due to ordering guarentees by
+    // the implementation.
+  }), 2);
+}