v6

node_modules/w3c-hr-time/lib/performance.js

@@ -0,0 +1,53 @@
+"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 };