Fix TLru long ticks policy on macos (#118)

* adjust

* use double

* mac-gate

* rem gate changes

* name

* mac tests

Author: bitfaster

.github/workflows/gate.yml

@@ -1,4 +1,4 @@
-name: Build and Test
+name: Build and Test (windows-latest)
 
 on:
   push:

.github/workflows/mac-gate.yml

@@ -0,0 +1,25 @@
+name: Build and Test (macos-latest)
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+
+    runs-on: macos-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Setup .NET Core
+      uses: actions/setup-dotnet@v1
+      with:
+        dotnet-version: 6.0.x
+    - name: Install dependencies
+      run: dotnet restore
+    - name: Build
+      run: dotnet build --configuration Release --no-restore
+    - name: Test
+      run: dotnet test --no-restore --verbosity normal

BitFaster.Caching.UnitTests/Lru/TlruLongTicksPolicyTests.cs

@@ -49,7 +49,7 @@ public void TouchUpdatesItemWasAccessed()
         public void WhenItemIsExpiredShouldDiscardIsTrue()
         {
             var item = this.policy.CreateItem(1, 2);
-            item.TickCount = Stopwatch.GetTimestamp() - TimeSpan.FromSeconds(11).Ticks;
+            item.TickCount = Stopwatch.GetTimestamp() - TLruLongTicksPolicy<int, int>.ToTicks(TimeSpan.FromSeconds(11));
 
             this.policy.ShouldDiscard(item).Should().BeTrue();
         }
@@ -58,7 +58,7 @@ public void WhenItemIsExpiredShouldDiscardIsTrue()
         public void WhenItemIsNotExpiredShouldDiscardIsFalse()
         {
             var item = this.policy.CreateItem(1, 2);
-            item.TickCount = Stopwatch.GetTimestamp() - TimeSpan.FromSeconds(9).Ticks;
+            item.TickCount = Stopwatch.GetTimestamp() - TLruLongTicksPolicy<int, int>.ToTicks(TimeSpan.FromSeconds(9));
 
             this.policy.ShouldDiscard(item).Should().BeFalse();
         }
@@ -107,7 +107,7 @@ private LongTickCountLruItem<int, int> CreateItem(bool wasAccessed, bool isExpir
 
             if (isExpired)
             {
-                item.TickCount = Stopwatch.GetTimestamp() - TimeSpan.FromSeconds(11).Ticks;
+                item.TickCount = Stopwatch.GetTimestamp() - TLruLongTicksPolicy<int, int>.ToTicks(TimeSpan.FromSeconds(11));
             }
 
             return item;

BitFaster.Caching/Lru/TlruLongTicksPolicy.cs

@@ -17,11 +17,13 @@ namespace BitFaster.Caching.Lru
     /// </remarks>
     public readonly struct TLruLongTicksPolicy<K, V> : IItemPolicy<K, V, LongTickCountLruItem<K, V>>
     {
+        // On some platforms (e.g. MacOS), stopwatch and timespan have different resolution
+        private static readonly double stopwatchAdjustmentFactor = Stopwatch.Frequency / (double)TimeSpan.TicksPerSecond;
         private readonly long timeToLive;
 
         public TLruLongTicksPolicy(TimeSpan timeToLive)
         {
-            this.timeToLive = timeToLive.Ticks;
+            this.timeToLive = ToTicks(timeToLive);
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -94,5 +96,10 @@ public ItemDestination RouteCold(LongTickCountLruItem<K, V> item)
 
             return ItemDestination.Remove;
         }
+
+        public static long ToTicks(TimeSpan timespan)
+        {
+            return (long)(timespan.Ticks * stopwatchAdjustmentFactor);
+        }
     }
 }