Verify Serial Key with standalone DLL file - convert function NSIS => Prototype => Pascal

Question

Could you help me with creating Serial Check Function that bases on DLL file? Unfortunately I do not have Function Prototype.

What I have is NSIS version of the function:

SetOutPath $PLUGINSDIR
  File "serialtest.dll"
   System::Call "serialtest::_sn_serialtest(t r1) i .r2 ?u"
  ${If} $2 == 0
   Messagebox MB_OK|MB_ICONSTOP \
    "Invalid Serial Number!"
   Abort
  ${Endif}

t - text, string (LPCSTR, pointer to first character)

r1-r9 - these are $1-$9 for NSIS (can be input or output). In this case r1 is $1 and $1 is Serial Number with delimiters '-'.

i - int (includes char, byte, short, handles, pointers and so on)

. - means no input

u - unload DLL

Additional info: NSIS Script is written in ANSI and I am using Unicode version of Inno Setup.

If possible, Serial Number should be imported from Edit Boxes - I have asked a question regarding Custom Serial Page here: CustomPage for Serial Number in Inno Setup

Answer 1

I don't know NSIS at all, so the following is just an attempt of the script interpretation:

serialtest::_sn_serialtest(t r1) i .r2 ?u

I understand like this:

serialtest.dll - is the library, where the function is imported from
t - the input string typed as LPCSTR
i - integer result put into the no input variable (so just output variable)

So your prototype might looked like this:

int _sn_serialtest(
  __in LPCSTR sn
);

What am I missing here is some calling convention notation, so the following prototype might not work, if you know that the library were written in C (what are most of the NSIS plugins as I've Googled), then it's probably cdecl, like below, but it's just my guess, it might be different:

function _sn_serialtest(sn: AnsiString): Integer;
  external '_sn_serialtest@files:serialtest.dll cdecl';

Answer 2

The other answer was accepted before I had a chance to respond so I'll just add some additional information:

While NSIS plugins use cdecl for its exported functions, System::Call by default is stdcall since it is usually used to call the WinAPI. (For cdecl you need ?c at the end)

The t type depends on the NSIS version, in the normal build it is char* and in the unicode build it is WCHAR* (t is like TCHAR, you also have w and m for WCHAR and char).

The C prototype for the function in your question is int WINAPI _sn_serialtest(LPCTSTR); and in your case LPCTSTR = LPCSTR and WINAPI = __stdcall.