#ifndef _NTLPCAPI_H
// begin_private

NTSYSCALLAPI
NTSTATUS
NTAPI
NtAlpcQueryInformationMessage(
    _In_ HANDLE PortHandle,
    _In_ PPORT_MESSAGE PortMessage,
    _In_ ALPC_MESSAGE_INFORMATION_CLASS MessageInformationClass,
    _Out_writes_bytes_to_opt_(Length, *ReturnLength) PVOID MessageInformation,
    _In_ ULONG Length,
    _Out_opt_ PULONG ReturnLength
    );

// end_private
#endif
View code on GitHub

#ifndef _NTZWAPI_H

NTSYSCALLAPI
NTSTATUS
NTAPI
ZwAlpcQueryInformationMessage(
    _In_ HANDLE PortHandle,
    _In_ PPORT_MESSAGE PortMessage,
    _In_ ALPC_MESSAGE_INFORMATION_CLASS MessageInformationClass,
    _Out_writes_bytes_to_opt_(Length, *ReturnLength) PVOID MessageInformation,
    _In_ ULONG Length,
    _Out_opt_ PULONG ReturnLength
    );

#endif
View code on GitHub