No Python 3.2, estou criando um objeto de estrutura a partir dos dados retornados pela função ctypes.windll.kernel32.DeviceIoControl. Depois disso, posso acessar os campos Estrutura e retornar os dados. No entanto, se eu fizer algo que usa uma memória, como abrir um arquivo, os dados dentro da estrutura são modificados. Na primeira parte do resultado que colei nos resultados, é o que se espera. No entanto, após a abertura de um arquivo e os campos de estruturas impressos novamente, os valores foram alterados. Não sei por que os dados estão sendo modificados ou como impedir que eles aconteça

Structures:

class DISK_GEOMETRY(ctypes.Structure):
    '''
    Disk Geometry Data Structure
    http://msdn.microsoft.com/en-us/library/aa363972(v=vs.85).aspx
    '''
    _fields_ = [("Cylinders", wintypes.LARGE_INTEGER),
                ("MediaType", wintypes.BYTE), #MEDIA_TYPE
                ("TracksPerCylinder", wintypes.DWORD),
                ("SectorsPerTrack", wintypes.DWORD),
                ("BytesPerSector", wintypes.DWORD)]


class DISK_GEOMETRY_EX(ctypes.Structure):
    '''
    Disk Geometry EX Data Structure
    http://msdn.microsoft.com/en-us/library/aa363970(v=vs.85).aspx
    '''
    _fields_ = [("Geometry", DISK_GEOMETRY),
                ("DiskSize", wintypes.LARGE_INTEGER),
                ("Data[1]", wintypes.BYTE)]

DeviceIoControl:

class DeviceIoControl:
    def __init__(self, path):
        self.path = path

    def __DeviceIoControl(self, devicehandle, IoControlCode, input, output):
        '''
        DeviceIoControl Function
        http://msdn.microsoft.com/en-us/library/aa363216(v=vs.85).aspx
        '''
        DevIoCtl = ctypes.windll.kernel32.DeviceIoControl
        DevIoCtl.argtypes = [
            wintypes.HANDLE, #HANDLE hDevice
            wintypes.DWORD, #DWORD dwIoControlCode
            wintypes.LPVOID, #LPVOID lpInBuffer
            wintypes.DWORD, #DWORD nInBufferSize
            wintypes.LPVOID, #LPVOID lpOutBuffer
            wintypes.DWORD, #DWORD nOutBufferSize
            ctypes.POINTER(wintypes.DWORD), #LPDWORD lpBytesReturned
            wintypes.LPVOID] #LPOVERLAPPED lpOverlapped
        DevIoCtl.restype = wintypes.BOOL

        if isinstance(output, int):
            output = ctypes.create_string_buffer(output)

        input_size = len(input) if input is not None else 0
        output_size = len(output)
        assert isinstance(output, ctypes.Array)

        BytesReturned = wintypes.DWORD()

        status = DevIoCtl(devicehandle, IoControlCode, input, input_size, output, output_size, BytesReturned, None)
        return output[:BytesReturned.value] if status is not 0 else -1

    def GetDriveGeometry(self):
        diskhandle = winapi.CreateHandle(
                self.path,
                winapi.NULL,
                winapi.FILE_SHARE_READ|winapi.FILE_SHARE_WRITE,
                winapi.LPSECURITY_ATTRIBUTES(),
                winapi.OPEN_EXISTING,
                winapi.FILE_ATTRIBUTE_NORMAL,
                winapi.NULL)
        if diskhandle == winapi.INVALID_HANDLE_VALUE:
            return -1

        temp = ctypes.cast(self.__DeviceIoControl(diskhandle, winioctl.IOCTL_DISK_GET_DRIVE_GEOMETRY_EX, None, 1024), ctypes.POINTER(winioctl.DISK_GEOMETRY_EX)).contents
        winapi.CloseHandle(diskhandle)
        return temp

A Principal

device = DeviceIoControl(r"\\.\PhysicalDrive0")
devicegeo = device.GetDriveGeometry()
print("Disk Size: " +str(devicegeo.DiskSize))
print("BytesPerSector: "+str(devicegeo.Geometry.BytesPerSector))
print("Cylinders: "+str(devicegeo.Geometry.Cylinders))
print("MediaType: "+str(hex(devicegeo.Geometry.MediaType)))
print("CtypesAddressOf: "+str(ctypes.addressof(devicegeo)))

with open(r"\\.\PhysicalDrive0", 'rb') as f:
    f.seek(0)
    MBRdata = f.read(512)
print("\nOpened a file\n")        

print("Disk Size: "+str(devicegeo.DiskSize))
print("BytesPerSector: "+str(devicegeo.Geometry.BytesPerSector))
print("Cylinders: "+str(devicegeo.Geometry.Cylinders))
print("MediaType: "+str(hex(devicegeo.Geometry.MediaType)))
print("CtypesAddressOf: "+str(ctypes.addressof(devicegeo)))

Saída

Disk Size: 80000000000
BytesPerSector: 512
Cylinders: 9726
MediaType: 0xc
CtypesAddressOf: 12322040

Opened a file

Disk Size: 0
BytesPerSector: 1
Cylinders: 2170477562872987649
MediaType: -0x40
CtypesAddressOf: 12322040