#ifndef _NTIOAPI_H

/**
 * Retrieves a snapshot of the number of packets queued on an I/O completion port. Querying does not remove a
 * packet; the result is not a reservation for a later dequeue.
 *
 * \param[in] IoCompletionHandle Handle with IO_COMPLETION_QUERY_STATE (0x1).
 * \param[in] IoCompletionInformationClass IoCompletionBasicInformation (0).
 * \param[out] IoCompletionInformation Writable IO_COMPLETION_BASIC_INFORMATION. User-mode output must be
 * 4-byte aligned on native x64 and WoW64.
 * \param[in] IoCompletionInformationLength Exactly 4 bytes.
 * \param[out, optional] ReturnLength Receives 4 on success; invalid class, size, alignment and access checks
 * leave it unchanged.
 * \return STATUS_INVALID_INFO_CLASS for unsupported classes, STATUS_INFO_LENGTH_MISMATCH for incorrect size,
 * or the query's NTSTATUS. A NULL/zero-size call is not a supported size-discovery protocol.
 */
_Kernel_entry_
NTSYSCALLAPI
NTSTATUS
NTAPI
NtQueryIoCompletion(
    _In_ HANDLE IoCompletionHandle,
    _In_ IO_COMPLETION_INFORMATION_CLASS IoCompletionInformationClass,
    _Out_writes_bytes_(IoCompletionInformationLength) PVOID IoCompletionInformation,
    _In_ ULONG IoCompletionInformationLength,
    _Out_opt_ PULONG ReturnLength
    );

#endif
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#ifndef _NTZWAPI_H

_Kernel_entry_
NTSYSCALLAPI
NTSTATUS
NTAPI
ZwQueryIoCompletion(
    _In_ HANDLE IoCompletionHandle,
    _In_ IO_COMPLETION_INFORMATION_CLASS IoCompletionInformationClass,
    _Out_writes_bytes_(IoCompletionInformationLength) PVOID IoCompletionInformation,
    _In_ ULONG IoCompletionInformationLength,
    _Out_opt_ PULONG ReturnLength
    );

#endif
View code on GitHub