#ifndef _NTIOAPI_H

/**
 * The NtCreateMailslotFile routine creates a mailslot.
 *
 * \param[out] FileHandle Pointer to a variable that receives a handle to the mailslot.
 * \param[in] DesiredAccess The requested access to the mailslot.
 * \param[in] ObjectAttributes Pointer to an OBJECT_ATTRIBUTES structure.
 * \param[out] IoStatusBlock Pointer to an IO_STATUS_BLOCK structure.
 * \param[in] CreateOptions Specifies the options to be applied when creating the mailslot.
 * \param[in] MailslotQuota Specifies the amount of memory that the mailslot can use for its messages.
 * \param[in] MaximumMessageSize Specifies the maximum size of a message that can be written to the mailslot.
 * \param[in] ReadTimeout Specifies the maximum time a read operation can wait for a message to be written to the mailslot.
 * \return NTSTATUS Successful or errant status.
 * \sa https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createmailslotw
 */
NTSYSCALLAPI
NTSTATUS
NTAPI
NtCreateMailslotFile(
    _Out_ PHANDLE FileHandle,
    _In_ ACCESS_MASK DesiredAccess,
    _In_ PCOBJECT_ATTRIBUTES ObjectAttributes,
    _Out_ PIO_STATUS_BLOCK IoStatusBlock,
    _In_ ULONG CreateOptions,
    _In_ ULONG MailslotQuota,
    _In_ ULONG MaximumMessageSize,
    _In_ PLARGE_INTEGER ReadTimeout
    );

#endif
View code on GitHub

#ifndef _NTZWAPI_H

NTSYSCALLAPI
NTSTATUS
NTAPI
ZwCreateMailslotFile(
    _Out_ PHANDLE FileHandle,
    _In_ ACCESS_MASK DesiredAccess,
    _In_ PCOBJECT_ATTRIBUTES ObjectAttributes,
    _Out_ PIO_STATUS_BLOCK IoStatusBlock,
    _In_ ULONG CreateOptions,
    _In_ ULONG MailslotQuota,
    _In_ ULONG MaximumMessageSize,
    _In_ PLARGE_INTEGER ReadTimeout
    );

#endif
View code on GitHub