Implement performance.timeOrigin (#53660)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/53660

Changelog: [internal]

(This is internal because these APIs aren't enabled in OSS yet)

Implements `performance.timeOrigin` to allow converting timestamps from `performance.now()` to be based on the Unix epoch.

This implementation isn't fully spec-compliant to align with the current implementation of `performance.now()`, where the base of the clock is system boot time instead of app startup / navigation time.

Reviewed By: huntie

Differential Revision: D82016724

fbshipit-source-id: e3a066721cecf41e2fd963beb94a0a2f1c5d6493

packages/react-native/ReactCommon/react/nativemodule/webperformance/NativePerformance.cpp

@@ -131,9 +131,18 @@ NativePerformance::NativePerformance(std::shared_ptr<CallInvoker> jsInvoker)
     : NativePerformanceCxxSpec(std::move(jsInvoker)) {}
 
 HighResTimeStamp NativePerformance::now(jsi::Runtime& /*rt*/) {
+  // This is not spec-compliant, as this is the duration from system boot to
+  // now, instead of from app startup to now.
+  // This should be carefully changed eventually.
   return HighResTimeStamp::now();
 }
 
+HighResDuration NativePerformance::timeOrigin(jsi::Runtime& /*rt*/) {
+  // This is not spec-compliant, as this is an approximation from Unix epoch to
+  // system boot, instead of a precise duration from Unix epoch to app startup.
+  return HighResTimeStamp::unsafeOriginFromUnixTimeStamp();
+}
+
 void NativePerformance::reportMark(
     jsi::Runtime& rt,
     const std::string& name,

packages/react-native/ReactCommon/react/nativemodule/webperformance/NativePerformance.h

@@ -88,6 +88,9 @@ class NativePerformance : public NativePerformanceCxxSpec<NativePerformance> {
   // https://www.w3.org/TR/hr-time-3/#now-method
   HighResTimeStamp now(jsi::Runtime& rt);
 
+  // https://www.w3.org/TR/hr-time-3/#timeorigin-attribute
+  HighResDuration timeOrigin(jsi::Runtime& rt);
+
 #pragma mark - User Timing Level 3 functions (https://w3c.github.io/user-timing/)
 
   void reportMark(

packages/react-native/ReactCommon/react/timing/primitives.h

@@ -201,6 +201,11 @@ class HighResTimeStamp {
     return HighResTimeStamp(chronoNow());
   }
 
+  static HighResDuration unsafeOriginFromUnixTimeStamp() noexcept {
+    static auto origin = computeUnsafeOriginFromUnixTimeStamp();
+    return origin;
+  }
+
   static constexpr HighResTimeStamp min() noexcept {
     return HighResTimeStamp(std::chrono::steady_clock::time_point::min());
   }
@@ -285,6 +290,13 @@ class HighResTimeStamp {
 
   std::chrono::steady_clock::time_point chronoTimePoint_;
 
+  static HighResDuration computeUnsafeOriginFromUnixTimeStamp() noexcept {
+    auto systemNow = std::chrono::system_clock::now();
+    auto steadyNow = std::chrono::steady_clock::now();
+    return HighResDuration(
+        systemNow.time_since_epoch() - steadyNow.time_since_epoch());
+  }
+
 #ifdef REACT_NATIVE_DEBUG
   static std::function<std::chrono::steady_clock::time_point()>&
   getTimeStampProvider() {

packages/react-native/flow/bom.js.flow

@@ -199,11 +199,11 @@ declare interface EventCounts {
 }
 
 declare class Performance {
+  +eventCounts: EventCounts;
+  +timeOrigin: DOMHighResTimeStamp;
+
   clearMarks(name?: string): void;
-
   clearMeasures(name?: string): void;
-
-  eventCounts: EventCounts;
   getEntries: (
     options?: PerformanceEntryFilterOptions,
   ) => Array<PerformanceEntry>;
@@ -215,7 +215,7 @@ declare class Performance {
     startMarkOrOptions?: string | PerformanceMeasureOptions,
     endMark?: string,
   ): PerformanceMeasure;
-  now: () => DOMHighResTimeStamp;
+  now(): DOMHighResTimeStamp;
   toJSON(): string;
 }
 

packages/react-native/src/private/webapis/performance/Performance.js

@@ -63,6 +63,7 @@ const cachedReportMeasure = NativePerformance.reportMeasure;
 const cachedGetMarkTime = NativePerformance.getMarkTime;
 const cachedNativeClearMarks = NativePerformance.clearMarks;
 const cachedNativeClearMeasures = NativePerformance.clearMeasures;
+let cachedTimeOrigin: ?DOMHighResTimeStamp;
 
 const MARK_OPTIONS_REUSABLE_OBJECT: PerformanceMarkOptions = {
   startTime: 0,
@@ -139,6 +140,24 @@ export default class Performance {
     });
   }
 
+  /**
+   * Returns the high resolution timestamp that is used as the baseline for
+   * performance-related timestamps.
+   * https://developer.mozilla.org/en-US/docs/Web/API/Performance/timeOrigin
+   */
+  get timeOrigin(): DOMHighResTimeStamp {
+    if (cachedTimeOrigin == null) {
+      if (NativePerformance.timeOrigin) {
+        cachedTimeOrigin = NativePerformance?.timeOrigin();
+      } else {
+        // Very naive polyfill.
+        cachedTimeOrigin = Date.now() - getCurrentTimeStamp();
+      }
+    }
+
+    return cachedTimeOrigin;
+  }
+
   mark(
     markName: string,
     markOptions?: PerformanceMarkOptions,

packages/react-native/src/private/webapis/performance/__tests__/Performance-itest.js

@@ -22,4 +22,37 @@ describe('Performance', () => {
       return new PerformanceEntry();
     }).toThrow("Failed to construct 'PerformanceEntry': Illegal constructor");
   });
+
+  describe('now', () => {
+    it('provides increasing timestamps since boot time', () => {
+      const first = performance.now();
+      const second = performance.now();
+      const third = performance.now();
+
+      expect(typeof first).toBe('number');
+      expect(typeof second).toBe('number');
+      expect(typeof third).toBe('number');
+
+      expect(first).toBeGreaterThan(0);
+      expect(second).toBeGreaterThan(first);
+      expect(third).toBeGreaterThan(second);
+    });
+  });
+
+  describe('timeOrigin', () => {
+    it('allows moving timestamps to Unix epoch', () => {
+      // We need to truncate timestamps because `Date.now()` only provides
+      // integer millisecond precision.
+      const adjustedMonotonicTime = Math.trunc(
+        performance.now() + performance.timeOrigin,
+      );
+      const wallTime = Date.now();
+      const adjustedMonotonicTimeAfter = Math.trunc(
+        performance.now() + performance.timeOrigin,
+      );
+
+      expect(wallTime).toBeGreaterThanOrEqual(adjustedMonotonicTime);
+      expect(adjustedMonotonicTimeAfter).toBeGreaterThanOrEqual(wallTime);
+    });
+  });
 });

packages/react-native/src/private/webapis/performance/specs/NativePerformance.js

@@ -54,6 +54,8 @@ export type PerformanceObserverInit = {
 
 export interface Spec extends TurboModule {
   +now: () => number;
+  +timeOrigin?: () => number;
+
   +reportMark: (name: string, startTime: number, entry: mixed) => void;
   +reportMeasure: (
     name: string,