LPCTSTR

[arenner]

Hello all. I think I'm making a newbie mistake. I'm trying to use the DoFileOpen function to open up a mastercam X file. I'm reading the help on it in Core/MFile_CH.h. It says that the variable it calls "filen" "MUST be complete path to file". So I wrote this:

 

LPCTSTR filen = "C:Program Filesmcamxchook_testsOpen_FileIGES_1.mcx";

 

Then in main I wrote this:

 

DoFileOpen(filen, merge, astext, checkUnits);

 

While debugging it says there's a bad pointer:

 

filen 0xcccccccc const char *

 

As I said, I think I'm making a stupid newbie mistake. After searching online for uses of LPCTSTR, I just got more confused. Any help is appreciated. Thanks in advance.

[Jon Griffin CNC Software]

You didn't allocate memory for your string. LPCTSTR refers to a string on the heap (dynamically allocated memory), so such assignment/allocation isn't going to work. The string type you've chosen isn't the best for what you're doing.

 

There's quite a few ways to allocate a string, for instance:

code:

---

char s[] = "yadayadayada";  //simple ASCII

TCHAR s1[] = _T("string"); //handles UNICODE too

char * st = new char[10];

strcpy(st, "yelp!"); //deprecated

string tempString; //stl::string

tempString = "temp"; //allows assignment

CString mfcString = "Microsoft uses these";

 

try something more like:

 

char filen[] = "C:yadayadayada.mcx"[/indent]

or

[indent]code:

---

TCHAR filen[] = _T("c:...");

---

[/indent]

which would put it on the stack instead (handling allocation for you)

 

or even (cutting a step)

[indent]code:

---

DoFileOpen("C:yadafile.txt", /*more arguments*/);

---

[/indent]

cutting the entire allocation problem altogether.

 

Remember also, you may need to double up on the char, because it's used as an escape character. E.g. "C:mcamxchooksmychook.dll"

 

Here's a link to a more complete tutorial on the subject:

Tutorial

[arenner]

Thanks very much Jon. Thanks for the Tutorial link too. I figured it was a newbie mistake.

[Jon Griffin CNC Software]

Here's a decent primer on the std::string class, which is what you want to end up using. It's far more powerfull than a simple character array:

 

String Class

 

Pay particular attention to these two entries:

/*Character array to string*/ s = ch; //Converts character array ch into string s.

/*String to character array*/ cp = s.c_str(); //Pointer cp points to a character array with the same characters as s.

 

Conversion comes up a lot, and typecasting isn't always the best idea when using these

 

what you'd end up with is code like this:

code:

---

#include <string>

using namespace std;

 

//... skipping stuff...

string filen = "C:mcamxdirfile.mcx";

DoFileOpen(filen.c_str(), /*args*/);

---

[arenner]

Thanks for tutorial on the string class. I'll read through that to figure out it's benefits. I was able to open up the file that I wanted using DoFileOpen, with simply:

 

char filen[]= "C:Program Filesmcamxchook_testsOpen_FileIGES_1.mcx";

 

It's great info, and I'm sure I'll need the more robus string class at some point soon.

[arenner]

Forgot to mention, I can make my code available to anyone who wants it, not much to it.