#ifndef _NTIOAPI_H

/**
 * Opens an existing named I/O completion port without removing queued packets.
 *
 * \param[out] IoCompletionHandle Receives a caller-owned handle; close with NtClose.
 * \param[in] DesiredAccess Requested access: IO_COMPLETION_QUERY_STATE (0x1)
 * for depth queries and IO_COMPLETION_MODIFY_STATE (0x2) for posting/removing.
 * \param[in] ObjectAttributes Identifies the port by name and optional root directory.
 * \return NTSTATUS indicating whether a handle was opened.
 * \remarks Native name-lookup failure leaves the output handle
 * unchanged; WoW64 copies its zero-initialized local after the native call, including
 * on this failure. Do not depend on failure-output preservation across architectures.
 */
_Kernel_entry_
NTSYSCALLAPI
NTSTATUS
NTAPI
NtOpenIoCompletion(
    _Out_ PHANDLE IoCompletionHandle,
    _In_ ACCESS_MASK DesiredAccess,
    _In_ PCOBJECT_ATTRIBUTES ObjectAttributes
    );

#endif
View code on GitHub

#ifndef _NTZWAPI_H

_Kernel_entry_
NTSYSCALLAPI
NTSTATUS
NTAPI
ZwOpenIoCompletion(
    _Out_ PHANDLE IoCompletionHandle,
    _In_ ACCESS_MASK DesiredAccess,
    _In_ PCOBJECT_ATTRIBUTES ObjectAttributes
    );

#endif
View code on GitHub