#ifndef _NTEXAPI_H
#if (PHNT_MODE != PHNT_MODE_KERNEL)

/**
 * The NtWaitForKeyedEvent routine pairs with one matching keyed-event release, blocking until a match or
 * interruption. Use it as the wait half of a user-mode synchronization protocol, not to wait on a persistent
 * signal state; a matching release may arrive before or after this call.
 *
 * \param KeyedEventHandle Handle with KEYEDEVENT_WAIT (0x1), or NULL for the system's
 * default keyed event (ExpCritSecOutOfMemoryEvent).
 * \param KeyValue Opaque pointer-sized matching key, not an object handle (including a
 * registry key handle). An address may be used as the key, but the kernel does not
 * dereference it or inspect the memory contents, unlike the Address parameter of
 * WaitOnAddress.
 * Its low bit must be zero; NULL is a valid zero key, not a wildcard. The matching
 * release must use the same object and key and belong to the same process.
 * \param Alertable Whether a blocking wait can be interrupted by an alert or user APC.
 * \param Timeout Optional timeout in 100-nanosecond units: negative for a relative
 * interval, positive for an absolute deadline, zero for polling, or NULL for no deadline.
 * \return STATUS_SUCCESS only when paired with a matching release; STATUS_TIMEOUT,
 * STATUS_ALERTED or STATUS_USER_APC can end an unmatched blocking wait.
 * On x64, an odd KeyValue returns STATUS_INVALID_PARAMETER_1
 * (despite KeyValue being the second parameter), before handle validation.
 * \remarks Test for STATUS_SUCCESS, not just NT_SUCCESS, to distinguish a match
 * from timeout or interruption. A successful wait consumes one matching release.
 * If the match wins a timeout/APC race, the kernel completes the rendezvous and
 * may return STATUS_SUCCESS instead of the interrupt.
 */
_Kernel_entry_
NTSYSCALLAPI
NTSTATUS
NTAPI
NtWaitForKeyedEvent(
    _In_opt_ HANDLE KeyedEventHandle,
    _In_opt_ PVOID KeyValue,
    _In_ BOOLEAN Alertable,
    _In_opt_ PLARGE_INTEGER Timeout
    );

#endif
#endif
View code on GitHub

#ifndef _NTZWAPI_H

_Kernel_entry_
NTSYSCALLAPI
NTSTATUS
NTAPI
ZwWaitForKeyedEvent(
    _In_opt_ HANDLE KeyedEventHandle,
    _In_opt_ PVOID KeyValue,
    _In_ BOOLEAN Alertable,
    _In_opt_ PLARGE_INTEGER Timeout
    );

#endif
View code on GitHub