Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System/compmod/microsoft/win32/safehandles/SafeFileMapViewHandle.cs

@@ -0,0 +1,53 @@
+// ==++==
+// 
+//   Copyright (c) Microsoft Corporation.  All rights reserved.
+// 
+// ==--==
+/*============================================================
+**
+** Class:  SafeFileMapViewHandle
+**
+** <EMAIL>Author: Brian Grunkemeyer ([....]) </EMAIL>
+**
+** A wrapper for handles returned from MapViewOfFile, used
+** for shared memory.
+**
+** Date:  August 7, 2002
+** 
+===========================================================*/
+
+using System;
+using System.Security;
+using System.Security.Permissions;
+using System.Runtime.InteropServices;
+using System.Runtime.CompilerServices;
+using Microsoft.Win32;
+using Microsoft.Win32.SafeHandles;
+using System.Runtime.ConstrainedExecution;
+using System.Runtime.Versioning;
+
+namespace Microsoft.Win32.SafeHandles {
+    [HostProtectionAttribute(MayLeakOnAbort = true)]
+    [SuppressUnmanagedCodeSecurityAttribute]
+    internal sealed class SafeFileMapViewHandle : SafeHandleZeroOrMinusOneIsInvalid
+    { 
+        // Note that MapViewOfFile returns 0 on failure
+
+        internal SafeFileMapViewHandle() : base(true) {}
+        
+        [DllImport(ExternDll.Kernel32, ExactSpelling=true, CharSet=CharSet.Auto)]
+        [ResourceExposure(ResourceScope.Machine)]
+        internal static extern SafeFileMapViewHandle MapViewOfFile(SafeFileMappingHandle hFileMappingObject, int dwDesiredAccess, int dwFileOffsetHigh, int dwFileOffsetLow, UIntPtr dwNumberOfBytesToMap);
+
+        [DllImport(ExternDll.Kernel32, ExactSpelling=true, SetLastError=true)]
+        [ResourceExposure(ResourceScope.None)]
+        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
+        private static extern bool UnmapViewOfFile(IntPtr handle);
+
+        override protected bool ReleaseHandle()
+        {
+            return UnmapViewOfFile(handle);
+        }
+
+    }
+}