mcs/class/referencesource/System.Core/System/IO/MemoryMappedFiles/MemoryMappedViewAccessor.cs

   1 // ==++==
   2 //
   3 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 // ==--==
   6 /*============================================================
   7 **
   8 ** Class:  MemoryMappedViewAccessor
   9 **
  10 ** Purpose: View accessor for managed MemoryMappedFiles
  11 **
  12 ** Date:  February 7, 2007
  13 **
  14 ===========================================================*/
  15
  16 using System;
  17 using System.Diagnostics;
  18 using System.Security;
  19 using System.Security.Permissions;
  20 using Microsoft.Win32.SafeHandles;
  21
  22 namespace System.IO.MemoryMappedFiles {
  23
  24     public sealed class MemoryMappedViewAccessor : UnmanagedMemoryAccessor {
  25
  26         private MemoryMappedView m_view;
  27
  28         [System.Security.SecurityCritical]
  29         internal MemoryMappedViewAccessor(MemoryMappedView view) {
  30             Debug.Assert(view != null, "view is null");
  31
  32             m_view = view;
  33             Initialize(m_view.ViewHandle, m_view.PointerOffset, m_view.Size, MemoryMappedFile.GetFileAccess(m_view.Access));
  34         }
  35
  36         public SafeMemoryMappedViewHandle SafeMemoryMappedViewHandle {
  37
  38             [System.Security.SecurityCritical]
  39             [SecurityPermissionAttribute(SecurityAction.Demand, Flags = SecurityPermissionFlag.UnmanagedCode)]
  40             get {
  41                 return m_view != null ? m_view.ViewHandle : null;
  42             }
  43         }
  44
  45         public long PointerOffset
  46         {
  47             get
  48             {
  49                 if (m_view == null)
  50                 {
  51                     throw new InvalidOperationException(SR.GetString(SR.InvalidOperation_ViewIsNull));
  52                 }
  53
  54                 return m_view.PointerOffset;
  55             }
  56         }
  57
  58         [SecuritySafeCritical]
  59         protected override void Dispose(bool disposing) {
  60             try {
  61                 // Explicitly flush the changes.  The OS will do this for us anyway, but not until after the
  62                 // MemoryMappedFile object itself is closed.
  63                 if (disposing && m_view != null && !m_view.IsClosed) {
  64                     Flush();
  65                 }
  66             }
  67             finally {
  68                 try {
  69                     if (m_view != null) {
  70                         m_view.Dispose();
  71                     }
  72                 }
  73                 finally {
  74                     base.Dispose(disposing);
  75                 }
  76             }
  77         }
  78
  79         // Flushes the changes such that they are in sync with the FileStream bits (ones obtained
  80         // with the win32 ReadFile and WriteFile functions).  Need to call FileStream's Flush to
  81         // flush to the disk.
  82         // NOTE: This will flush all bytes before and after the view up until an offset that is a
  83         // multiple of SystemPageSize.
  84         [System.Security.SecurityCritical]
  85         public void Flush() {
  86             if (!IsOpen) {
  87                 throw new ObjectDisposedException("MemoryMappedViewAccessor", SR.GetString(SR.ObjectDisposed_ViewAccessorClosed));
  88             }
  89
  90             unsafe {
  91                 if (m_view != null) {
  92                     m_view.Flush((IntPtr)Capacity);
  93                 }
  94             }
  95         }
  96
  97     }
  98 }