FSCTL_QUERY_FAT_BPB

Using the FSCTL_QUERY_FAT_BPB control code 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This operation is obsolete.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 a volume
  FSCTL_QUERY_FAT_BPB,         // dwIoControlCode operation
  NULL,                        // lpInBuffer; must be NULL
  0,                           // nInBufferSize; must be zero
  (LPVOID) lpOutBuffer,        // output buffer
  (DWORD) nOutBufferSize,      // size of output buffer
  (LPDWORD) lpBytesReturned,   // number of bytes returned
  (LPOVERLAPPED) lpOverlapped  // OVERLAPPED structure
);

Parameters

hDevice

[in] Handle to the volume to be queried. 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

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

lpInBuffer

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

nInBufferSize

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

lpOutBuffer

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

nOutBufferSize

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

lpBytesReturned

[out] Pointer to a variable that receives the size, in bytes, of output data returned.

If the output buffer is too small to return any data, then the call fails, GetLastError returns the error code ERROR_INSUFFICIENT_BUFFER, and the returned byte count is zero.

If the output buffer is too small to hold all of the data but can hold some entries, then the operating system returns as much as fits, the call fails, GetLastError returns the error code ERROR_MORE_DATA, and lpBytesReturned indicates the amount of data returned. Your application should call DeviceIoControl again with the same operation, specifying a new starting point.

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

[in] Pointer to an OVERLAPPED structure.

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, lpOverlapped must point to a valid OVERLAPPED structure. In this case, the operation 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, lpOverlapped is ignored and DeviceIoControl 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 DeviceIoControl.

Requirements

  Windows NT/2000: Requires Windows NT 3.5 or later.
  Windows 95/98: Unsupported.
  Header: Declared in Winioctl.h.

See Also

Device Input and Output Overview, Device Input and Output Control Codes, DeviceIoControl, CreateFile, FSCTL_QUERY_FAT_BPB_BUFFER, GetVolumeInformation, GetDriveType, ReadFile, GetOverlappedResult, GetQueuedCompletionStatus, FAT32 File System