RtlxUnicodeStringToAnsiSize

UINT64 __stdcall RtlxUnicodeStringToAnsiSize(_UNICODE_STRING *UnicodeString){
  UINT64 Length; 
  wchar_t *Buffer; 
  UINT64 BytesInMultiByteString; 

  Length = UnicodeString->Length;
  Buffer = UnicodeString->Buffer;
  LODWORD(BytesInMultiByteString) = 0;
  RtlUnicodeToMultiByteSize(&BytesInMultiByteString, Buffer, Length);
  return(unsigned int)(BytesInMultiByteString + 1);
}

Referenced by:

DbgUnicodeStringToAnsiString
ExpSystemErrorHandler2
NtQuerySystemEnvironmentValue
NtSetSystemEnvironmentValue
ObCreateObjectTypeEx
RtlUpcaseUnicodeStringToAnsiString