blob: 4bcfbc3eb22de1ce0c61fa872f49de38a29586b8 (
plain)
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
|
"use strict";
// Actual implementation of the Performance class.
const clockIsAccurate = require("./clock-is-accurate");
const calculateClockOffset = require("./calculate-clock-offset");
const { hrtime, toMS } = require("./utils");
const kTimeOrigin = Symbol("time origin");
const kTimeOriginTimestamp = Symbol("time origin timestamp");
class Performance {
constructor() {
// Time origin.
const timeOrigin = hrtime();
this[kTimeOrigin] = timeOrigin;
if (clockIsAccurate) {
// Let |t1| be the DOMHighResTimeStamp representing the high resolution Unix time at which the global monotonic
// clock is zero. This has to be calculated for every Performance object to account for clock drifts.
const t1 = calculateClockOffset();
// Let |t2| be the DOMHighResTimeStamp representing the high resolution time value of the global monotonic clock
// at global's time origin.
const t2 = toMS(timeOrigin);
// Return the sum of |t1| and |t2|.
this[kTimeOriginTimestamp] = t1 + t2;
} else {
// Clock isn't accurate enough. Use millisecond accuracy per spec.
const cur = Date.now();
this[kTimeOriginTimestamp] = cur;
}
}
// The timeOrigin getter actually returns the time origin timestamp, not the raw time origin.
get timeOrigin() {
return this[kTimeOriginTimestamp];
}
now() {
const diff = toMS(hrtime(this[kTimeOrigin]));
return clockIsAccurate ? diff : Math.round(diff);
}
toJSON() {
return {
timeOrigin: this.timeOrigin
};
}
}
module.exports = { Performance };
|
