FSCTL_QUERY_FAT_BPB

[This is preliminary documentation and subject to change.]

The FSCTL_QUERY_FAT_BPB operation returns the first 36 bytes of a FAT16 or FAT12 volume.

This operation is obsolete. Use GetVolumeInformation, GetDriveType, and other related functions to obtain some of the same information in a more structured manner. If you cannot get the necessary information in any other way, use CreateFile to open the volume as a file, and use ReadFile to access the raw hard drive.

To perform this operation, call the DeviceIoControl function with the following parameters.

BOOL DeviceIoControl(
  (HANDLE) hDevice,        // handle to device of interest
  FSCTL_QUERY_FAT_BPB,     // dwIoControlCode, control code of
                           // operation to perform
  NULL,                    // lpInBuffer is not used; must be NULL
  0,                       // nInBufferSize is not used; must be zero
  (LPVOID) lpOutBuffer,    // a pointer to an
                           // FSCTL_QUERY_FAT_BPB_BUFFER
  (DWORD) nOutBufferSize,  // size of the output buffer
  (LPDWORD) lpBytesReturned,   // pointer to variable to receive
                           // output byte count
  (LPOVERLAPPED) lpOverlapped  // pointer to OVERLAPPED structure
                           // for asynchronous operation
);
 

Parameters

hDevice

Handle to the object on which the operation is to be performed. Call the CreateFile function to obtain a device handle. The handle can only be to a FAT12 or FAT16 volume. The call will fail on a FAT32 volume.

dwIoControlCode

Control code for the operation. This value identifies the specific operation to be performed and the type of device on which it is to be performed. Use FSCTL_QUERY_FAT_BPB for this operation.

lpInBuffer

Pointer to the input buffer. Not used; must be NULL.

nInBufferSize

Size of the input buffer, in bytes. Not used; must be zero.

lpOutBuffer

Pointer to the output buffer. This will be an FSCTL_QUERY_FAT_BPB_BUFFER structure.

nOutBufferSize

Size of the output buffer, in bytes, which is sizeof(FSCTL_QUERY_FAT_BPB_BUFFER).

lpBytesReturned

Pointer to a DWORD variable that receives the size, in bytes, of output data returned. If the lpOutBuffer buffer is too small, lpBytesReturned receives the required buffer size.

If lpOverlapped is NULL (nonoverlapped I/O), lpBytesReturned cannot be NULL.

If lpOverlapped is not NULL (overlapped I/O), lpBytesReturned can be NULL. If this is an overlapped operation, you can get the number of bytes returned by calling the GetOverlappedResult function. If hDevice is associated with an I/O completion port, you can get the number of bytes returned by calling the GetQueuedCompletionStatus function.

lpOverlapped

Pointer to an OVERLAPPED structure.

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, this parameter must point to a valid OVERLAPPED structure. In this case, DeviceIoControl is performed as an overlapped (asynchronous) operation. If the device was opened with the FILE_FLAG_OVERLAPPED flag and lpOverlapped is NULL, the function fails in unpredictable ways.

If hDevice was opened without specifying the FILE_FLAG_OVERLAPPED flag, this parameter is ignored and the DeviceIoControl function does not return until the operation has been completed, or until an error occurs.

Return Values

If the operation succeeds, DeviceIoControl returns a nonzero value, and the output buffer pointed to by lpvOutBuffer contains a valid FSCTL_QUERY_FAT_BPB_BUFFER structure.

If the operation fails, DeviceIoControl returns zero. The contents of the output buffer pointed to by lpvOutBuffer are meaningless.

Remarks

For the implications of overlapped I/O on this operation, see the Remarks section of the DeviceIoControl topic.

See Also

Device Input and Output Overview, Device Input and Output Operations, DeviceIoControl, CreateFile, FSCTL_QUERY_FAT_BPB_BUFFER, GetVolumeInformation, GetDriveType, ReadFile, GetOverlappedResult, GetQueuedCompletionStatus, Windows 95 Features