P/Invoke TickCount64 for .NET Standard on Windows

BitFaster.Caching.UnitTests/DurationTests.cs

@@ -34,9 +34,16 @@ public void SinceEpoch()
                 Duration.SinceEpoch().raw.Should().BeCloseTo(Environment.TickCount64, 15);
             }
 #else
-            // eps is 1/200 of a second
-            ulong eps = (ulong)(Stopwatch.Frequency / 200);
-            Duration.SinceEpoch().raw.Should().BeCloseTo(Stopwatch.GetTimestamp(), eps);
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                Duration.SinceEpoch().raw.Should().BeCloseTo(Duration.GetTickCount64(), 15);
+            }
+            else
+            {
+                // eps is 1/200 of a second
+                ulong eps = (ulong)(Stopwatch.Frequency / 200);
+                Duration.SinceEpoch().raw.Should().BeCloseTo(Stopwatch.GetTimestamp(), eps);
+            }
 #endif
         }
 
@@ -53,8 +60,15 @@ public void ToTimeSpan()
                 new Duration(1000).ToTimeSpan().Should().BeCloseTo(TimeSpan.FromMilliseconds(1000), TimeSpan.FromMilliseconds(10));
             }
 #else
-            // for Stopwatch.GetTimestamp() this is number of ticks
-            new Duration(1 * Stopwatch.Frequency).ToTimeSpan().Should().BeCloseTo(TimeSpan.FromSeconds(1), TimeSpan.FromMilliseconds(10));
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                new Duration(1000).ToTimeSpan().Should().BeCloseTo(TimeSpan.FromMilliseconds(1000), TimeSpan.FromMilliseconds(10));
+            }
+            else
+            {
+                // for Stopwatch.GetTimestamp() this is number of ticks
+                new Duration(1 * Stopwatch.Frequency).ToTimeSpan().Should().BeCloseTo(TimeSpan.FromSeconds(1), TimeSpan.FromMilliseconds(10));
+            }
 #endif    
         }
 
@@ -73,8 +87,16 @@ public void FromTimeSpan()
                     .Should().Be((long)TimeSpan.FromSeconds(1).TotalMilliseconds);
             }
 #else
-            Duration.FromTimeSpan(TimeSpan.FromSeconds(1)).raw
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                Duration.FromTimeSpan(TimeSpan.FromSeconds(1)).raw
+                    .Should().Be((long)TimeSpan.FromSeconds(1).TotalMilliseconds);
+            }
+            else
+            {
+                Duration.FromTimeSpan(TimeSpan.FromSeconds(1)).raw
                 .Should().Be(Stopwatch.Frequency);
+            }
 #endif    
         }
 

BitFaster.Caching.UnitTests/Lru/TlruStopwatchPolicyTests.cs

@@ -32,10 +32,9 @@ public void WhenTtlIsTimeSpanMaxThrow()
         [Fact]
         public void WhenTtlIsCloseToMaxAllow()
         {
-            double maxTicks = long.MaxValue / 100.0d;
-            var ttl = TimeSpan.FromTicks((long)maxTicks) - TimeSpan.FromTicks(10);
+            var ttl = Duration.MaxRepresentable;
 
-            new TLruLongTicksPolicy<int, int>(ttl).TimeToLive.Should().BeCloseTo(ttl, TimeSpan.FromTicks(20));
+            new TLruLongTicksPolicy<int, int>(ttl).TimeToLive.Should().BeCloseTo(ttl, TimeSpan.FromSeconds(1));
         }
 
         [Fact]
@@ -58,9 +57,7 @@ public void CreateItemInitializesTimestampToNow()
         {
             var item = this.policy.CreateItem(1, 2);
 
-            // seconds = ticks / Stopwatch.Frequency
-            ulong epsilon = (ulong)(TimeSpan.FromMilliseconds(20).TotalSeconds * Stopwatch.Frequency);
-            item.TickCount.Should().BeCloseTo(Stopwatch.GetTimestamp(), epsilon);
+            item.TickCount.Should().BeCloseTo(Duration.SinceEpoch().raw, DurationTests.epsilon);
         }
 
         [Fact]
@@ -91,7 +88,7 @@ public async Task UpdateUpdatesTickCount()
         public void WhenItemIsExpiredShouldDiscardIsTrue()
         {
             var item = this.policy.CreateItem(1, 2);
-            item.TickCount = Stopwatch.GetTimestamp() - TLruLongTicksPolicy<int, int>.ToTicks(TimeSpan.FromSeconds(11));
+            item.TickCount = Duration.SinceEpoch().raw - Duration.FromSeconds(11).raw;
 
             this.policy.ShouldDiscard(item).Should().BeTrue();
         }
@@ -100,7 +97,7 @@ public void WhenItemIsExpiredShouldDiscardIsTrue()
         public void WhenItemIsNotExpiredShouldDiscardIsFalse()
         {
             var item = this.policy.CreateItem(1, 2);
-            item.TickCount = Stopwatch.GetTimestamp() - TLruLongTicksPolicy<int, int>.ToTicks(TimeSpan.FromSeconds(9));
+            item.TickCount = Duration.SinceEpoch().raw - Duration.FromSeconds(9).raw;
 
             this.policy.ShouldDiscard(item).Should().BeFalse();
         }
@@ -155,7 +152,7 @@ private LongTickCountLruItem<int, int> CreateItem(bool wasAccessed, bool isExpir
 
             if (isExpired)
             {
-                item.TickCount = Stopwatch.GetTimestamp() - TLruLongTicksPolicy<int, int>.ToTicks(TimeSpan.FromSeconds(11));
+                item.TickCount = Duration.SinceEpoch().raw - Duration.FromSeconds(11).raw;
             }
 
             return item;

BitFaster.Caching/Duration.cs

@@ -28,6 +28,11 @@ public readonly struct Duration
 
 #if NETCOREAPP3_0_OR_GREATER
         private static readonly bool IsMacOS = RuntimeInformation.IsOSPlatform(OSPlatform.OSX);
+#else
+        private static readonly bool IsWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
+
+        [DllImport("kernel32")]
+        internal static extern long GetTickCount64();
 #endif
 
         internal Duration(long raw)
@@ -52,7 +57,15 @@ public static Duration SinceEpoch()
                 return new Duration(Environment.TickCount64);
             }
 #else
-            return new Duration(Stopwatch.GetTimestamp());
+            if (IsWindows)
+            {
+                return new Duration(GetTickCount64());
+            }
+            else
+            {
+                // Warning: not currently covered by unit tests
+                return new Duration(Stopwatch.GetTimestamp());
+            }
 #endif
         }
 
@@ -73,7 +86,15 @@ public TimeSpan ToTimeSpan()
                 return TimeSpan.FromMilliseconds(raw);
             }
 #else
-            return StopwatchTickConverter.FromTicks(raw);
+            if (IsWindows)
+            {
+                return TimeSpan.FromMilliseconds(raw);
+            }
+            else
+            {
+                // Warning: not currently covered by unit tests
+                return StopwatchTickConverter.FromTicks(raw);
+            }
 #endif
         }
 
@@ -95,7 +116,15 @@ public static Duration FromTimeSpan(TimeSpan timeSpan)
                 return new Duration((long)timeSpan.TotalMilliseconds);
             }
 #else
-            return new Duration(StopwatchTickConverter.ToTicks(timeSpan));
+            if (IsWindows)
+            {
+                return new Duration((long)timeSpan.TotalMilliseconds);
+            }
+            else
+            {
+                // Warning: not currently covered by unit tests
+                return new Duration(StopwatchTickConverter.ToTicks(timeSpan));
+            }
 #endif
         }