1 files changed, 67 insertions, 0 deletions
diff --git a/src/System.Private.CoreLib/shared/System/Threading/Semaphore.cs b/src/System.Private.CoreLib/shared/System/Threading/Semaphore.cs
new file mode 100644
index 000000000..6014fcd1c
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Threading/Semaphore.cs
@@ -0,0 +1,67 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Win32;
+using Microsoft.Win32.SafeHandles;
+using System.IO;
+using System.Runtime.InteropServices;
+
+namespace System.Threading
+{
+    public sealed partial class Semaphore : WaitHandle
+    {
+        // creates a nameless semaphore object
+        // Win32 only takes maximum count of int.MaxValue
+        public Semaphore(int initialCount, int maximumCount) : this(initialCount, maximumCount, null) { }
+
+        public Semaphore(int initialCount, int maximumCount, string name) :
+            this(initialCount, maximumCount, name, out _)
+        {
+        }
+
+        public Semaphore(int initialCount, int maximumCount, string name, out bool createdNew)
+        {
+            if (initialCount < 0)
+                throw new ArgumentOutOfRangeException(nameof(initialCount), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            if (maximumCount < 1)
+                throw new ArgumentOutOfRangeException(nameof(maximumCount), SR.ArgumentOutOfRange_NeedPosNum);
+
+            if (initialCount > maximumCount)
+                throw new ArgumentException(SR.Argument_SemaphoreInitialMaximum);
+
+            CreateSemaphoreCore(initialCount, maximumCount, name, out createdNew);
+        }
+
+        public static Semaphore OpenExisting(string name)
+        {
+            Semaphore result;
+            switch (OpenExistingWorker(name, out result))
+            {
+                case OpenExistingResult.NameNotFound:
+                    throw new WaitHandleCannotBeOpenedException();
+                case OpenExistingResult.NameInvalid:
+                    throw new WaitHandleCannotBeOpenedException(SR.Format(SR.Threading_WaitHandleCannotBeOpenedException_InvalidHandle, name));
+                case OpenExistingResult.PathNotFound:
+                    throw new IOException(SR.Format(SR.IO_PathNotFound_Path, name));
+                default:
+                    return result;
+            }
+        }
+
+        public static bool TryOpenExisting(string name, out Semaphore result) =>
+            OpenExistingWorker(name, out result) == OpenExistingResult.Success;
+
+        public int Release() => ReleaseCore(1);
+
+        // increase the count on a semaphore, returns previous count
+        public int Release(int releaseCount)
+        {
+            if (releaseCount < 1)
+                throw new ArgumentOutOfRangeException(nameof(releaseCount), SR.ArgumentOutOfRange_NeedNonNegNum);
+
+            return ReleaseCore(releaseCount);
+        }
+    }
+}