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The Labs \ Source Viewer \ SSCLI \ System.IO \ PinnedBufferMemoryStream

SSCLI
  1. // ==++==
  2. //
  3. //
  4. // Copyright (c) 2006 Microsoft Corporation. All rights reserved.
  5. //
  6. // The use and distribution terms for this software are contained in the file
  7. // named license.txt, which can be found in the root of this distribution.
  8. // By using this software in any fashion, you are agreeing to be bound by the
  9. // terms of this license.
  10. //
  11. // You must not remove this notice, or any other, from this software.
  12. //
  13. //
  14. // ==--==
  15. /*============================================================
  16. **
  17. ** Class:  PinnedBufferMemoryStream
  18. **
  19. **
  20. ** Purpose: Pins a byte[], exposing it as an unmanaged memory
  21. **          stream.  Used in ResourceReader for corner cases.
  22. **
  23. **
  24. ===========================================================*/
  25. using System;
  26. using System.Runtime.InteropServices;
  28. namespace System.IO
  29. {
  30.     unsafe internal sealed class PinnedBufferMemoryStream : UnmanagedMemoryStream
  31.     {
  32.         private byte[] _array;
  33.         private GCHandle _pinningHandle;
  34.        
  35.         internal PinnedBufferMemoryStream(byte[] array)
  36.         {
  37.             BCLDebug.Assert(array != null, "Array can't be null");
  38.            
  39.             int len = array.Length;
  40.             // Handle 0 length byte arrays specially.
  41.             if (len == 0) {
  42.                 array = new byte[1];
  43.                 len = 0;
  44.             }
  45.            
  46.             _array = array;
  47.             _pinningHandle = new GCHandle(array, GCHandleType.Pinned);
  48.             // Now the byte[] is pinned for the lifetime of this instance.
  49.             // But I also need to get a pointer to that block of memory...
  50.             fixed (byte* ptr = _array)
  51.                 Initialize(ptr, len, len, FileAccess.Read, true);
  52.         }
  53.        
  54.         ~PinnedBufferMemoryStream()
  55.         {
  56.             Dispose(false);
  57.         }
  58.        
  59.         protected override void Dispose(bool disposing)
  60.         {
  61.             if (_isOpen) {
  62.                 _pinningHandle.Free();
  63.                 _isOpen = false;
  64.             }
  65.             #if _DEBUG
  66.             // To help track down lifetime issues on checked builds, force
  67.             //a full GC here.
  68.             if (disposing) {
  69.                 GC.Collect();
  70.                 GC.WaitForPendingFinalizers();
  71.             }
  72.             #endif
  73.             base.Dispose(disposing);
  74.         }
  75.     }
  76. }

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