RtlUnicodeToMultiByteSize - NtDoc

#ifndef _NTRTL_H

/**
 * The RtlUnicodeToMultiByteSize routine determines the number of bytes that are required to store the multibyte translation for the specified Unicode string.
 * The translation is assumed to use the current system ANSI code page (ACP). The source string is not necessarily from a multibyte character set.
 *
 * \param BytesInMultiByteString Pointer to a caller-allocated variable that receives the number of bytes required to store the translated string.
 * \param UnicodeString Pointer to the Unicode string for which the multibyte length is to be calculated.
 * \param BytesInUnicodeString Length, in bytes, of the source string.
 * \return NTSTATUS Successful or errant status.
 * \sa https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntifs/nf-ntifs-rtlunicodetomultibytesize
 */
NTSYSAPI
NTSTATUS
NTAPI
RtlUnicodeToMultiByteSize(
    _Out_ PULONG BytesInMultiByteString,
    _In_reads_bytes_(BytesInUnicodeString) PCWCH UnicodeString,
    _In_ ULONG BytesInUnicodeString
    );

#endif
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