IOCTL_BATTERY_QUERY_TAG

Using the IOCTL_BATTERY_QUERY_TAG operation obtains the battery's current tag.

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

BOOL DeviceIoControl(
  (HANDLE) hDevice,            // handle to battery
  IOCTL_BATTERY_QUERY_TAG,     // dwIoControlCode operation
  (LPVOID) lpInBuffer,         // input buffer
  (DWORD) nInBufferSize,       // size of input buffer
  (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 battery from which the tag is to be obtained. To obtain a device handle, call the CreateFile function.

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 IOCTL_BATTERY_QUERY_TAG for this operation.

lpInBuffer

[in] Pointer to a ULONG input buffer. The value indicates the number of milliseconds to wait if there is no battery. A value of -1 indicates the request will wait indefinitely (or until canceled by some other event).

nInBufferSize

[in] Size, in bytes, of the input buffer.

lpOutBuffer

[out] Pointer to a ULONG output buffer, which, on success, contains the current battery tag.

nOutBufferSize

[in] Size, in bytes, of the output buffer.

lpBytesReturned

[out] Pointer to a variable that receives the size, in bytes, of the data stored in the buffer pointed to by lpOutBuffer.

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 retrieve 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, 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, lpOverlapped 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.

If the operation fails, DeviceIoControl returns zero. To get extended error information, call GetLastError.

Remarks

This battery IOCTL returns the battery's current tag. The battery tag is a unique nonzero value for any specified handle to the battery devices per battery, and changes whenever the physical battery changes. When a battery is not present, this request will wait the indicated time, and then return ERROR_FILE_NOT_FOUND. (See Battery Tags for more information.)

All requests for other battery information require the caller to supply the matching battery tag. This ensures that the caller is receiving information for the same battery for every request and ensures that the caller is aware of battery changes without constant polling.

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

Requirements

  Windows NT/2000: Requires Windows 2000.
  Windows 95/98: Unsupported.
  Header: Declared in Batclass.h.

See Also

Device Input and Output Overview, Device Input and Output Control Codes, DeviceIoControl, IOCTL_BATTERY_QUERY_INFORMATION, IOCTL_BATTERY_QUERY_STATUS, IOCTL_BATTERY_SET_INFORMATION