How do you convert C++ _tcscpy, _tcscat to Delphi?

Question

I'm converting this code from C++ to Delphi but I don't get the following part of the code. Can anyone explain me what the following code means; what's happening to the szBuff buffer ?

I'm pretty sure it's such kind of formatting (replacement), but I don't even know what is expected as a result and I can't find any sensible documentation of the used functions (maybe I'm just a lame :)

Can anyone help me with the translation of this code to Delphi (or direct me to proper documentation) ?

I don't like this how do you convert kind of questions by myself, so I mentioned at least function names in the question title so it might searchable to someone else in the future.

function TSecInfo.BuildSecurityAttributes(var SecAttrs: TSecurityAttributes): boolean;
var
  pszSidUser: PChar;
  szBuff: array [0..1024] of Char;
begin

// pszSidUser at this time contains user SID like this
// S-1-5-21-1454471165-1004336348-1606980848-5555

// TCHAR szBuff[1024]; // I'm not sure with array [0..1024] of Char;

  _tcscpy(szBuff, _T("D:"));
  _tcscat(szBuff, _T("(A;;GA;;;"));
  _tcscat(szBuff, pszSidUser);
  _tcscat(szBuff, _T(")"));
  _tcscat(szBuff, _T("(A;;GWGR;;;AN)"));
  _tcscat(szBuff, _T("(A;;GWGR;;;WD)"));

...

  _tcscat(szBuff, _T("S:(ML;;NW;;;S-1-16-0)"));

end;

For those who are interested in what's the whole code from the link about I can tell it should be a trick how to access network pipes for writing as an anonymous user on Windows Vista above. To the whole article follow this link.

Thanks for your time
Regards

Mesomorphic

Are you sure it is c++? Doesn't look like – Barbee

@VJo - no; sure not; but the source code files has *.cpp extension and library linking like this #include <windows.h> – Mesomorphic

@VJo: The original code behind the link is C++. – Narine

In fact it originates from this example where they are using Microsoft Visual C++ – Mesomorphic

This is C++ code embedded inside a Pascal function. – Unparalleled

szBuff[1024] implies there are 1024 elements. array [0..1024] is 1025 elements. You need array[0..1024 - 1], sometimes written array[0..1023]. – Unparalleled

@Andreas - yeah; it is; with a special ... command :) Maybe I might omit the header. – Mesomorphic

@Andreas - thanks for this point; I would say there is reserve though but would you use PChar rather than array of Char ? – Mesomorphic

If I'm reading it correctly the sample code also uses "Shlemiel the Painter's) string concatenation (joelonsoftware.com/articles/fog0000000319.html) – Hemato

Answer 1

_tcscpy and _tcscat are TCHAR macro versions of C standard library functions strcpy and strcat for copying and concatenating C strings. They evaluate to ANSI or Unicode versions depending on whether or the type of project you are targeting. It's really C code rather than C++ code in my view.

In Delphi you would simply use string variables like this:

function TSecInfo.BuildSecurityAttributes(var SecAttrs: TSecurityAttributes): boolean;
var
  pszSidUser: PChar;
  Buff: string;
begin
  // pszSidUser at this time contains user SID like this
  // S-1-5-21-1454471165-1004336348-1606980848-5555

  Buff := 'D:(A;;GA;;;'+pszSidUser+')(A;;GWGR;;;AN)(A;;GWGR;;;WD)S:(ML;;NW;;;S-1-16-0)';
  SomeOtherWindowsAPICall(PChar(Buff));    
end;

Presumably in the C code there is a call to another Windows API function that receives an LPCTSTR. The C code will pass szBuff but you can simply pass PChar(Buff) as I have shown above.

The C code is using a fixed length buffer because it doesn't have available a dynamically allocated string class like Delphi's string or std::string in C++. Fixed length buffers like this often lead to buffer overruns. In Delphi don't use a fixed length buffer if you can avoid it.

This is a classic example of why languages with built in string handling are so much easier to work with than C.

Housebroken

+1 and accept. Thanks for the explanation; Yes the ConvertStringSecurityDescriptorToSecurityDescriptor is called after this where I'll use what you suggested. – Mesomorphic

God bless this dynamic allocation in Delphi :) The C code still looks for me like a spilled tea. – Mesomorphic

@daemon_x The C code would be a lot better if it dropped support for dual ANSI/Unicode builds, and better still if it was C++ and used std::wstring. – Housebroken

Answer 2

It looks like the code is using TCHARS, basically they are a macro which makes going from unicode to non-unicode easier. _tcscpy is copying the parameter to szBuff, _tcscat is appending the parameter to szBuff. If you are familar with strcpy and strcat they do the same thing.

_tcscpy(szBuff, _T("D:")); //szBuff == "D:"
_tcscat(szBuff, _T("(A;;GA;;;")); //szBuff == "D:A;;GA;;;"
...

Stenographer

Thanks; so this means that the subsequent calling of strcat only concatenates all those strings together and it's used probably to the code be more readable ? Aren't there any special characters ? – Mesomorphic

Yes, that is correct. Also _T("string") will be "string" w/o UNICODE or will be L"string" with UNICODE. – Stenographer