62 lines
1.4 KiB
JavaScript
62 lines
1.4 KiB
JavaScript
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"use strict";
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const { hrtime } = require("./utils");
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// The HR-TIME spec calls for 5-μs accuracy. Check that we have that in both hrtime() and Date.now().
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function testClockAccuracy() {
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// Test hrtime() first. The check is simpler and more stable, and we use hrtime() to measure Date.now()'s performance.
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const roundTrip = hrtime(hrtime());
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if (roundTrip[0] > 1 || roundTrip[1] > 5e3 * 2) {
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return false;
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}
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// Test Date.now() twice: first with a looser bound (10 μs) but with a smaller run time to filter out very bad
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// Date.now() performance, and then with a tighter bound (5 μs) to check we have the accuracy we need.
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let times;
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// eslint-disable-next-line no-unused-vars
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let cur;
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let start;
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let end;
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times = 100;
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start = hrtime();
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while (times-- > 0) {
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cur = Date.now();
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}
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end = hrtime(start);
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if ((end[0] * 1e9 + end[1]) > 1000000) {
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return false;
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}
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times = 10000;
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start = hrtime();
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while (times-- > 0) {
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cur = Date.now();
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}
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end = hrtime(start);
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if ((end[0] * 1e9 + end[1]) > 50000000) {
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return false;
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}
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return true;
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}
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// Warm up the function.
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testClockAccuracy();
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testClockAccuracy();
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testClockAccuracy();
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const TIMES = 5;
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const THRESHOLD = 0.6 * TIMES;
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let accurates = 0;
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for (let i = 0; i < TIMES; i++) {
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if (testClockAccuracy()) {
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accurates++;
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}
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}
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const isAccurate = accurates >= THRESHOLD;
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module.exports = isAccurate;
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