RtlInitUnicodeString实现

VOID
RtlInitUnicodeString(
    OUT PUNICODE_STRING DestinationString,
    IN PCWSTR SourceString OPTIONAL //一般是常量字符串
    )
{
    ULONG Length;

    DestinationString->Buffer = (PWSTR)SourceString;
    if (ARGUMENT_PRESENT( SourceString )) {
		// 不包含空字符的字节数
        Length = wcslen( SourceString ) * sizeof( WCHAR ); 
        DestinationString->Length = (USHORT)Length;
		// 上面的字节数+2
        DestinationString->MaximumLength = (USHORT)(Length + sizeof(UNICODE_NULL));
        }
    else {
        DestinationString->MaximumLength = 0;
        DestinationString->Length = 0;
        }
}