#ifndef _NTIOAPI_H

/**
 * The NtWriteFile function writes data to an open file.
 *
 * \param[in] FileHandle A handle to the file object representing the file or directory on which the specified action is to be performed.
 * \param[in] Event A handle for a caller-created event. This parameter is optional and can be NULL. It must be NULL if the caller will wait for the FileHandle to be set to the Signaled state.
 * \param[in] ApcRoutine Address of a caller-supplied APC routine to be called when the requested operation completes. This parameter is optional and can be NULL.
 * \param[in] ApcContext Pointer to a caller-determined context area. This parameter value is used as the APC context if the caller supplies an APC, or is used as the completion context if an I/O completion object has been associated with the file object.
 * \param[out] IoStatusBlock Pointer to an IO_STATUS_BLOCK structure that receives the final completion status and information about the operation.
 * \param[in] Buffer Pointer to a caller-allocated buffer that contains the data to write to the file.
 * \param[in] Length The size, in bytes, of the buffer pointed to by Buffer.
 * \param[in] ByteOffset Pointer to a variable that specifies the starting byte offset in the file for beginning the write operation.
 * \param[in] Key Device and intermediate drivers should set this pointer to NULL.
 * \return NTSTATUS Successful or errant status.
 * \sa https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/nf-wdm-zwwritefile
 */
NTSYSCALLAPI
NTSTATUS
NTAPI
NtWriteFile(
    _In_ HANDLE FileHandle,
    _In_opt_ HANDLE Event,
    _In_opt_ PIO_APC_ROUTINE ApcRoutine,
    _In_opt_ PVOID ApcContext,
    _Out_ PIO_STATUS_BLOCK IoStatusBlock,
    _In_reads_bytes_(Length) PVOID Buffer,
    _In_ ULONG Length,
    _In_opt_ PLARGE_INTEGER ByteOffset,
    _In_opt_ PULONG Key
    );

#endif
View code on GitHub

#ifndef _NTZWAPI_H

NTSYSCALLAPI
NTSTATUS
NTAPI
ZwWriteFile(
    _In_ HANDLE FileHandle,
    _In_opt_ HANDLE Event,
    _In_opt_ PIO_APC_ROUTINE ApcRoutine,
    _In_opt_ PVOID ApcContext,
    _Out_ PIO_STATUS_BLOCK IoStatusBlock,
    _In_reads_bytes_(Length) PVOID Buffer,
    _In_ ULONG Length,
    _In_opt_ PLARGE_INTEGER ByteOffset,
    _In_opt_ PULONG Key
    );

#endif
View code on GitHub