public bool Read(long pageNumber, byte *buffer, int count)
{
if (_readHandle == null)
{
_readHandle = Win32NativeFileMethods.CreateFile(_filename,
Win32NativeFileAccess.GenericRead,
Win32NativeFileShare.Write | Win32NativeFileShare.Read | Win32NativeFileShare.Delete,
IntPtr.Zero,
Win32NativeFileCreationDisposition.OpenExisting,
Win32NativeFileAttributes.Normal,
IntPtr.Zero);
}
long position = pageNumber * AbstractPager.PageSize;
var overlapped = new Overlapped((int)(position & 0xffffffff), (int)(position >> 32), IntPtr.Zero, null);
NativeOverlapped *nativeOverlapped = overlapped.Pack(null, null);
try
{
while (count > 0)
{
int read;
if (Win32NativeFileMethods.ReadFile(_readHandle, buffer, count, out read, nativeOverlapped) == false)
{
int lastWin32Error = Marshal.GetLastWin32Error();
if (lastWin32Error == Win32NativeFileMethods.ErrorHandleEof)
{
return(false);
}
throw new Win32Exception(lastWin32Error);
}
count -= read;
buffer += read;
position += read;
nativeOverlapped->OffsetLow = (int)(position & 0xffffffff);
nativeOverlapped->OffsetHigh = (int)(position >> 32);
}
return(true);
}
finally
{
Overlapped.Free(nativeOverlapped);
}
}