Add fast path for count with predicate

dotnet · May 30, 2024 · fbb7421 · fbb7421
1 parent 1fc1dd8
commit fbb7421
Showing 1 changed file with 30 additions and 6 deletions.
diff --git a/src/libraries/System.Linq/src/System/Linq/Count.cs b/src/libraries/System.Linq/src/System/Linq/Count.cs
@@ -3,6 +3,7 @@
 
 using System.Collections;
 using System.Collections.Generic;
+using System.Diagnostics;
 
 namespace System.Linq
 {
@@ -59,19 +60,42 @@ public static int Count<TSource>(this IEnumerable<TSource> source, Func<TSource,
  ThrowHelper.ThrowArgumentNullException(ExceptionArgument.predicate);
  }
 
- int count = 0;
- foreach (TSource element in source)
+ if (source.TryGetSpan(out ReadOnlySpan<TSource> span))
  {
- checked
+ int count = 0;
+ foreach (TSource element in span)
  {
- if (predicate(element))
+ checked
  {
- count++;
+ if (predicate(element))
+ {
+ count++;
+ }
  }
  }
+
+ return count;
  }
 
- return count;
+ return CountEnumerable(source, predicate);
+
+ [StackTraceHidden]
+ static int CountEnumerable(IEnumerable<TSource> source, Func<TSource, bool> predicate)
+ {
+ int count = 0;
+ foreach (TSource element in source)
+ {
+ checked
+ {
+ if (predicate(element))
+ {
+ count++;
+ }
+ }
+ }
+
+ return count;
+ }
  }
 
  /// <summary>