Timer.record(_ duration:): protect from overflows

Sources/Metrics/Metrics.swift

@@ -76,20 +76,37 @@ extension Timer {
 }
 
 #if swift(>=5.7)
+
+public enum TimerError: Error {
+    case durationToIntOverflow
+}
+
 extension Timer {
     /// Convenience for recording a duration based on ``Duration``.
-    /// Duration will be recorded in nanoseconds.
     ///
-    /// - parameters:
+    /// `Duration` will be converted to an `Int64` number of nanoseconds, and then recorded with nanosecond precision.
-    ///     - duration: The duration to record.
+    ///
+    /// - Parameters:
+    ///     - duration: The `Duration` to record.
+    ///
+    /// - Throws: `TimerError.durationToIntOverflow` if conversion from `Duration` to `Int64` of Nanoseconds overflowed.
     @available(macOS 13, iOS 16, tvOS 15, watchOS 8, *)
     @inlinable
-    public func record(_ duration: Duration) {
+    public func record(_ duration: Duration) throws {
         // `Duration` doesn't have a nice way to convert it nanoseconds or seconds,
         // so we'll do the multiplication manually.
-        // nanoseconds are the smallest unit Timer can track, so we'll record in that.
+        // Nanoseconds are the smallest unit Timer can track, so we'll record in that.
-        let durationNanoseconds = duration.components.seconds * 1_000_000_000 + duration.components.attoseconds / 1_000_000_000
+        let (seconds, overflow) = duration.components.seconds.multipliedReportingOverflow(by: 1_000_000_000)
-        self.recordNanoseconds(durationNanoseconds)
+        guard !overflow else {
+            throw TimerError.durationToIntOverflow
+        }
+
+        let (nanoseconds, attosecondsOverflow) = seconds.addingReportingOverflow(duration.components.attoseconds / 1_000_000_000)
+        guard !attosecondsOverflow else {
+            throw TimerError.durationToIntOverflow
+        }
+
+        self.recordNanoseconds(nanoseconds)
     }
 }
 #endif

Tests/MetricsTests/MetricsTests.swift

@@ -108,16 +108,20 @@ class MetricsExtensionsTests: XCTestCase {
         MetricsSystem.bootstrapInternal(metrics)
 
         let name = "timer-\(UUID().uuidString)"
+        let timer = Timer(label: name)
+
         let duration = Duration(secondsComponent: 3, attosecondsComponent: 123_000_000_000_000_000)
         let durationInNanoseconds = duration.components.seconds * 1_000_000_000 + duration.components.attoseconds / 1_000_000_000
 
-        let timer = Timer(label: name)
+        XCTAssertNoThrow(try timer.record(duration))
-        timer.record(duration)
 
         let testTimer = try metrics.expectTimer(timer)
         XCTAssertEqual(testTimer.values.count, 1, "expected number of entries to match")
         XCTAssertEqual(testTimer.values.first, durationInNanoseconds, "expected value to match")
         XCTAssertEqual(metrics.timers.count, 1, "timer should have been stored")
+
+        let overflowDuration = Duration(secondsComponent: 10_000_000_000, attosecondsComponent: 123)
+        XCTAssertThrowsError(try timer.record(overflowDuration))
         #endif
     }