v6

node_modules/w3c-hr-time/lib/clock-is-accurate.js

@@ -0,0 +1,61 @@
+"use strict";
+
+const { hrtime } = require("./utils");
+
+// The HR-TIME spec calls for 5-μs accuracy. Check that we have that in both hrtime() and Date.now().
+
+function testClockAccuracy() {
+  // Test hrtime() first. The check is simpler and more stable, and we use hrtime() to measure Date.now()'s performance.
+  const roundTrip = hrtime(hrtime());
+  if (roundTrip[0] > 1 || roundTrip[1] > 5e3 * 2) {
+    return false;
+  }
+
+  // Test Date.now() twice: first with a looser bound (10 μs) but with a smaller run time to filter out very bad
+  // Date.now() performance, and then with a tighter bound (5 μs) to check we have the accuracy we need.
+  let times;
+  // eslint-disable-next-line no-unused-vars
+  let cur;
+  let start;
+  let end;
+
+  times = 100;
+  start = hrtime();
+  while (times-- > 0) {
+    cur = Date.now();
+  }
+  end = hrtime(start);
+  if ((end[0] * 1e9 + end[1]) > 1000000) {
+    return false;
+  }
+
+  times = 10000;
+  start = hrtime();
+  while (times-- > 0) {
+    cur = Date.now();
+  }
+  end = hrtime(start);
+  if ((end[0] * 1e9 + end[1]) > 50000000) {
+    return false;
+  }
+
+  return true;
+}
+
+// Warm up the function.
+testClockAccuracy();
+testClockAccuracy();
+testClockAccuracy();
+
+const TIMES = 5;
+const THRESHOLD = 0.6 * TIMES;
+let accurates = 0;
+for (let i = 0; i < TIMES; i++) {
+  if (testClockAccuracy()) {
+    accurates++;
+  }
+}
+
+const isAccurate = accurates >= THRESHOLD;
+
+module.exports = isAccurate;