public Stream MapView(MapAccess access, long offset, IntPtr size)
{
if (!IsOpen)
{
throw new ObjectDisposedException("MMF already closed");
}
IntPtr baseAddress = IntPtr.Zero;
baseAddress = Win32MapApis.MapViewOfFile(
_hMap, (int)access,
(int)((offset >> 32) & 0xFFFFFFFF),
(int)(offset & 0xFFFFFFFF), size
);
if (baseAddress == IntPtr.Zero)
{
throw new FileMapIOException(Marshal.GetHRForLastWin32Error());
}
// Find out what MapProtection to use
// based on the MapAccess flags...
MapProtection protection;
if (access == MapAccess.FileMapRead)
{
protection = MapProtection.PageReadOnly;
}
else
{
protection = MapProtection.PageReadWrite;
}
return(new MapViewStream(baseAddress, size.ToInt64(), protection));
}
public override void Flush()
{
if (!IsOpen)
{
throw new ObjectDisposedException("Stream is closed");
}
// flush the view but leave the buffer intact
// FIX: get rid of cast
Win32MapApis.FlushViewOfFile(_base, (int)_length);
}
/// <summary>
/// Open an existing named File Mapping object
/// </summary>
/// <param name="access">desired access to the map</param>
/// <param name="name">name of object</param>
/// <returns>The memory mapped file instance</returns>
public static MemoryMappedFile Open(MapAccess access, String name)
{
MemoryMappedFile map = new MemoryMappedFile();
map._hMap = Win32MapApis.OpenFileMapping((int)access, false, name);
if (map._hMap == NULL_HANDLE)
{
throw new FileMapIOException(Marshal.GetHRForLastWin32Error());
}
return(map);
}
protected virtual void Dispose(bool disposing)
{
if (IsOpen)
{
Win32MapApis.CloseHandle(_hMap);
}
_hMap = NULL_HANDLE;
if (disposing)
{
GC.SuppressFinalize(this);
}
}
Create(string fileName, MapProtection protection,
long maxSize, String name)
{
MemoryMappedFile map = new MemoryMappedFile();
// open file first
IntPtr hFile = INVALID_HANDLE_VALUE;
if (fileName != null)
{
// determine file access needed
// we'll always need generic read access
int desiredAccess = GENERIC_READ;
if ((protection == MapProtection.PageReadWrite) ||
(protection == MapProtection.PageWriteCopy))
{
desiredAccess |= GENERIC_WRITE;
}
// open or create the file
// if it doesn't exist, it gets created
hFile = Win32MapApis.CreateFile(
fileName, desiredAccess, 0,
IntPtr.Zero, OPEN_ALWAYS, 0, IntPtr.Zero
);
if (hFile == INVALID_HANDLE_VALUE)
{
throw new FileMapIOException(Marshal.GetHRForLastWin32Error());
}
// FIX: Is support neede for zero-length files!?!
}
map._hMap = Win32MapApis.CreateFileMapping(
hFile, IntPtr.Zero, (int)protection,
(int)((maxSize >> 32) & 0xFFFFFFFF),
(int)(maxSize & 0xFFFFFFFF), name
);
// close file handle, we don't need it
if (hFile != INVALID_HANDLE_VALUE)
{
Win32MapApis.CloseHandle(hFile);
}
if (map._hMap == NULL_HANDLE)
{
throw new FileMapIOException(Marshal.GetHRForLastWin32Error());
}
return(map);
}
protected virtual void Dispose(bool disposing)
{
if (IsOpen)
{
Flush();
// FIX: eliminate cast
Win32MapApis.UnmapViewOfFile(_base);
IsOpen = false;
}
if (disposing)
{
GC.SuppressFinalize(this);
}
}
