C / C++ / MFC

Mark Salsbery10-Oct-08 9:06

10-Oct-08 9:06

GetBuffer() is completely unnecessary when you're only reading the string
(i.e. when you only need a const pointer to the string's internal buffer).

The LPCSTR operator is safe and more efficient. GetBuffer() is for when
you need a non-const pointer.

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

led mike10-Oct-08 9:09

led mike

10-Oct-08 9:09

Same ocean, different fish, same bait.

You have lunch yet? Poke tongue | ;-P

led mike

Mark Salsbery10-Oct-08 9:16

10-Oct-08 9:16

led mike wrote:
You have lunch yet?

Heh. I'm going to HAVE to now Poke tongue | ;-P

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

DSPCottage10-Oct-08 9:21

10-Oct-08 9:21

Thanks
It was great

DSPCottage10-Oct-08 9:39

10-Oct-08 9:39

But it appears that VC2005 doesn't support (LPSTR) or (LPCTSTR) operator.
isn't it?
Regards

Cedric Moonen10-Oct-08 9:44

Cedric Moonen

10-Oct-08 9:44

Yes, it is simply because UNICODE is defined by default (which was not the case with VC6). I strongly suggest that you read the article given by Led Mike, things will be much more clear afterwards.

Cédric Moonen
Software developer

Charting control [v1.5]
OpenGL game tutorial in C++

Mark Salsbery10-Oct-08 9:49

10-Oct-08 9:49

The operator is a member of the CSimpleStringT class, which is the base
class of CStringT.

The actual operator is PCXSTR (the ATL type), which is the equivalent of LPCTSTR
(a Win32 type).

Here's your code using generic text types:

TCHAR buffer[MAX_PATH];
GetModuleFileName(NULL,buffer,MAX_PATH);
CString path = buffer;
path = path.Left(path.ReverseFind(_T('\\'))+1);
path += _T("result.mp3");
f = _tfopen( path , _T("wb"));  <code>// <-- implicitly uses CString's PCXSTR operator!</code>

See Generic-Text Mappings in Tchar.h[^]
and for Unicode info: International Programming[^]

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Cedric Moonen10-Oct-08 9:34

Cedric Moonen

10-Oct-08 9:34

Read the documentation about CString::GetBuffer and you will see why you have to absolutely avoids it if you don't know exactly what you are doing.

Cédric Moonen
Software developer

Charting control [v1.5]
OpenGL game tutorial in C++

DSPCottage10-Oct-08 9:37

10-Oct-08 9:37

Visual C++ 2005 doesn't support (LPCTSTR) cast operator.
thus I need an interface to change a CString object to a char*
exactly now I am porting an project from VC6 to VC2005 and it is my problem
Regards
Mahdi

zafersavas10-Oct-08 8:25

zafersavas

10-Oct-08 8:25

There a various ways:
1)

CString str = "filename";

char charPtr[100];
sprintf(charPtr, "%s", str);

CString str = "filename";
char* charPtr = str.GetBuffer(str.GetLength());

super_ttd11-Oct-08 4:28

super_ttd

11-Oct-08 4:28

zafersavas wrote:
str.GetBuffer(str.GetLength());

Memory Leak here !

Why the hell do people use that dangerous GetBuffer() function when it's absolutely useless ? D'Oh! | :doh:

led mike10-Oct-08 8:52

led mike

10-Oct-08 8:52

Gut Mikh Tappe wrote:
Please let me know what to do

Ok I will try. What you need to do is read the documentation.[^]

Also reading this might help as well.[^]

In my experience not all authors match every reader. So if you find reading those sources don't supply your need 100% keep looking for more. The bottom line is what you need to do is read and study rather than type code and forum messages.

led mike

Cedric Moonen10-Oct-08 9:42

Cedric Moonen

10-Oct-08 9:42

led mike wrote:
Also reading this might help as well.[^]

I think that is the best choice to start with Smile | :)

Cédric Moonen
Software developer

Charting control [v1.5]
OpenGL game tutorial in C++

Mark Salsbery10-Oct-08 9:53

10-Oct-08 9:53

led mike wrote:
Also reading this might help as well.[^]

That IS a good link. I bookmarked that to post in the future,

Thanks! Beer | [beer]

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Mark Salsbery10-Oct-08 9:12

10-Oct-08 9:12

In addition to super_ttd's reply...

If you must use fopen(), then you should probably use a CStringA.

CString has a generic internal character type, depending on whether
UNICODE or _UNICODE is defined.

If you want to use the generic text CString, then it will pair nicely
with the generic text version of fopen(), which is _tfopen().

Gut Mikh Tappe wrote:
char buffer[MAX_PATH];
GetModuleFileName(NULL,(LPWCH)buffer,MAX_PATH);

Bad cast!! GetModuleFileName takes a LPTSTR as its second parameter.
Your buffer, therefore, should be a TCHAR type, not char.

Mind your types.....if you need a cast to get something to compile, look at WHY.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

DSPCottage10-Oct-08 9:40

10-Oct-08 9:40

May you please give me an article about UNICODE ?
Regards
Mahdi