1 files changed, 64 insertions, 0 deletions
diff --git a/src/mscorlib/shared/System/IO/PinnedBufferMemoryStream.cs b/src/mscorlib/shared/System/IO/PinnedBufferMemoryStream.cs
new file mode 100644
index 0000000000..c8e720b7ac
--- /dev/null
+++ b/src/mscorlib/shared/System/IO/PinnedBufferMemoryStream.cs
@@ -0,0 +1,64 @@
+// 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.
+
+/*============================================================
+**
+** 
+** 
+**
+**
+** Purpose: Pins a byte[], exposing it as an unmanaged memory 
+**          stream.  Used in ResourceReader for corner cases.
+**
+**
+===========================================================*/
+
+using System;
+using System.Runtime.InteropServices;
+using System.Diagnostics;
+using System.Diagnostics.Contracts;
+
+namespace System.IO
+{
+    internal sealed unsafe class PinnedBufferMemoryStream : UnmanagedMemoryStream
+    {
+        private byte[] _array;
+        private GCHandle _pinningHandle;
+
+        internal PinnedBufferMemoryStream(byte[] array)
+        {
+            Debug.Assert(array != null, "Array can't be null");
+
+            int len = array.Length;
+            // Handle 0 length byte arrays specially.
+            if (len == 0)
+            {
+                array = new byte[1];
+                len = 0;
+            }
+
+            _array = array;
+            _pinningHandle = GCHandle.Alloc(array, GCHandleType.Pinned);
+            // Now the byte[] is pinned for the lifetime of this instance.
+            // But I also need to get a pointer to that block of memory...
+            fixed (byte* ptr = &_array[0])
+                Initialize(ptr, len, len, FileAccess.Read);
+        }
+
+        ~PinnedBufferMemoryStream()
+        {
+            Dispose(false);
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (_pinningHandle.IsAllocated)
+            {
+                _pinningHandle.Free();
+            }
+
+            base.Dispose(disposing);
+        }
+    }
+}