return 0;
By following the patterns outlined in this article—dynamic resolution, stamp-based change detection, and graceful fallbacks—you can integrate this powerhouse API into your own tools safely.
NTSTATUS NtQueryWnfStateData( HANDLE StateHandle, // WNF state handle VOID* ChangeStamp, // Optional change stamp VOID* Buffer, // Output data buffer ULONG BufferSize, // Buffer size ULONG* DataSize, // Actual data size ULONG* ChangeStampResult // Resulting change stamp ); Alternatively, some definitions use: ntquerywnfstatedata ntdlldll better
ULONG lastStamp = 0; while (monitoring) ULONG newStamp = 0; ULONG dataSize = 0; NTSTATUS status = NtQueryWnfStateData(stateHandle, &lastStamp, NULL, 0, &dataSize, &newStamp); if (status == 0 && newStamp != lastStamp) // State changed, now fetch actual data with large buffer BYTE buffer[1024]; NtQueryWnfStateData(stateHandle, NULL, buffer, sizeof(buffer), NULL, NULL); ProcessStateChange(buffer); lastStamp = newStamp; Sleep(100); // Or better: wait on a WNF subscription handle
| Method | Latency | Overhead | Access to hidden states | Support | |--------|---------|----------|------------------------|---------| | NtQueryWnfStateData | Microseconds | Syscall | Yes | Undocumented | | WMI Event Queries | Milliseconds | COM/RPC/Large | No | Documented | | Polling Registry | Milliseconds | Disk I/O | No | Stable | | ETW | Microseconds | Medium | Partial | Documented | return 0; By following the patterns outlined in
if (status == 0) // STATUS_SUCCESS printf("Power source state: %s\n", data == 0 ? "Battery" : "AC Power");
The next time you need to monitor power events, network changes, or secret system flags, skip the WMI overhead. Go native. Go NtQueryWnfStateData . Go native
// Assume we discovered the correct Power Source WNF state name // Typically you would use NtCreateWnfStateName to resolve known names #define WNF_POWER_SOURCE_STATE L"WNF_POWER_SOURCE_STATE"