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

   1 // ==++==
   2 //
   3 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 // ==--==
   6 /*============================================================
   7 **
   8 ** Class:    MemoryMappedViewStream
   9 **
  10 ** Purpose:  View stream 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 MemoryMappedViewStream : UnmanagedMemoryStream {
  25
  26         private MemoryMappedView m_view;
  27
  28         [System.Security.SecurityCritical]
  29         internal unsafe MemoryMappedViewStream(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 override void SetLength(long value) {
  46             throw new NotSupportedException(SR.GetString(SR.NotSupported_MMViewStreamsFixedLength));
  47         }
  48
  49         public long PointerOffset
  50         {
  51             get
  52             {
  53                 if (m_view == null)
  54                 {
  55                     throw new InvalidOperationException(SR.GetString(SR.InvalidOperation_ViewIsNull));
  56                 }
  57
  58                 return m_view.PointerOffset;
  59             }
  60         }
  61
  62         [SecuritySafeCritical]
  63         protected override void Dispose(bool disposing) {
  64             try {
  65                 if (disposing && m_view != null && !m_view.IsClosed) {
  66                     Flush();
  67                 }
  68             }
  69             finally {
  70                 try {
  71                     if (m_view != null) {
  72                         m_view.Dispose();
  73                     }
  74                 }
  75                 finally {
  76                     base.Dispose(disposing);
  77                 }
  78             }
  79         }
  80
  81         // Flushes the changes such that they are in [....] with the FileStream bits (ones obtained
  82         // with the win32 ReadFile and WriteFile functions).  Need to call FileStream's Flush to
  83         // flush to the disk.
  84         // NOTE: This will flush all bytes before and after the view up until an offset that is a
  85         // multiple of SystemPageSize.
  86         [System.Security.SecurityCritical]
  87         public override void Flush() {
  88             if (!CanSeek) {
  89                 __Error.StreamIsClosed();
  90             }
  91
  92             unsafe {
  93                 if (m_view != null) {
  94                     m_view.Flush((IntPtr)Capacity);
  95                 }
  96             }
  97         }
  98
  99     }
 100 }