Thread: string vector to string pointer manipulation

I'm trying to convert the list of strings into a single string in this form: "Pscript.dll\0QMS810.ppd\0Pscriptui.dll\0Pscriptui .hlp\0Pstest.txt\0\0". However, I'm having some trouble adding the null characters properly. Here is my code and my problem is listed in the comments. Any suggestions?

Code:

// Process the vector into null terminated strings
void func(const vector<wstring> pAdditionalFiles)
{
	LPTSTR pDependentFiles = NULL;

	if(pAdditionalFiles.size())
	{
		// Allocate memory file for the pointers
		pDependentFiles = new TCHAR[pAdditionalFiles.capacity()];
		pDriverInfo->pDependentFiles = new TCHAR[pAdditionalFiles.capacity()];

		_tcscpy(pDependentFiles, L"");

		for(int i=0; i<pAdditionalFiles.size(); i++)
		{
			_tcscat(pDependentFiles, pAdditionalFiles[i].c_str());
			_tcscat(pDependentFiles, L"\0");				// each filename needs to be null-terminated (get exception errors if I use '\0' as the source
		}
		_tcscat(pDependentFiles, L"\0");					// another null-terminator needed to end the list
	}
}

Each _tcscat will (I think) overwrite the ending \0 character with the start of the string that is being added to the end; and I believe it will write the \0 character itself (without you having to do the extra bit yourself). (At least it will if it behaves like the standard C strcat.)

However, I don't know what you mean by this:

I'm trying to convert the list of strings into a single string in this form: "Pscript.dll\0QMS810.ppd\0Pscriptui.dll\0Pscri ptui .hlp\0Pstest.txt\0\0".

It is not possible to have such a string -- the first \0 ends the string, no questions asked. If you want to have a big char array that contains those characters in order, you can certainly do that, but you can't use the string tools to help you -- you'll have to keep track of where you are in the char array yourself.

I'm trying to manipulate the vector into pDependentFiles parameter in http://msdn.microsoft.com/en-us/libr...67(VS.85).aspx

I have pDependentFiles as a temporary buffer to manipulate the buffer, while I need to assign the result into pDriverInfo->pDependentFiles. I'm going to try some other method out before I come back here.

Why not do the concatenation with a wstring and then convert/copy to a character array at the end? If you use += on a wstring it will leave the embedded nulls.

I have managed to manipulate the buffer according to your suggestions. However, now I'm experiencing memory deallocation problem in the line highlighted in red. Is this b/c of the scope problems that I'm experiencing?

Code:

// Process the vector into null terminated strings
	LPTSTR pDependentFiles = NULL;
	LPTSTR p = pDependentFiles;
	BOOL transferP = FALSE;

	if(pAdditionalFiles.size())
	{
		// Allocate memory file for the pointers
		pDependentFiles = new TCHAR[pAdditionalFiles.size() + pAdditionalFiles.capacity() + 1];
		p = pDependentFiles;

		for(int i=1; i<pAdditionalFiles.size(); i++)
		{
			_tcscpy(pDependentFiles, pAdditionalFiles[i].c_str());
			pDependentFiles  += _tcslen( pAdditionalFiles[i].c_str() ) + 1;
			*pDependentFiles = '\0';
		}

		pDependentFiles = new TCHAR;
		pDependentFiles++;
		*pDependentFiles = '\0';
	}

	pDriverInfo->pDependentFiles = p;

	// Add Printer Driver and error check at the same time
	if(!AddPrinterDriver(NULL, 6, (LPBYTE) pDriverInfo))
	{
		wcout << "Adding Printer Driver Unsuccessful: " << GetLastError() << endl;
		delete[] pDependentFiles;
		return FALSE;					// false means an error happened
	}

	// no errors occurred
	delete[] pDependentFiles;               // runtime error here

After I use a really large sized array as the buffer rather than a dynamically-allocated pointer (I'm not very confident with dynamic memory allocation), I'm not experiencing the problems I've been experiencing anymore. Thank you all for your help.

For this application, I think using a large enough array is going to work, as this is a very small application, with all the memory allocated to the scope of the application being deallocated after it's done executing.