C / C++ / MFC

14-Sep-06 23:16

Hello comunity,
it is posible to modify an content from an LPCTSTR variable!?
Example:

<code>
CString csStringContent = "This is an String"; // modify to "This is String" or replace a part of them
LPCTSTR lpsz = csStringContent;
// modify lpsz?
</code>

with best regards
break;

Nibu babu thomas14-Sep-06 23:18

14-Sep-06 23:18

break; wrote:
CString csStringContent = "This is an String"; // modify to "This is String" or replace a part of themLPCTSTR lpsz = csStringContent;// modify lpsz?

with best regards

csStringContent = "This is String"; // modify to "This is String" or replace a part of them
 
LPTSTR lpsz = csStringContent.GetBuffer();// modify lpsz
lpsz[0] = _T( 't' ); // This change will be reflected in the string. "<code>t</code>his is String"
 
csStringContent.ReleaseBuffer(); // You should call this after GetBuffer

csStringContent = "This is String"; // modify to "This is String" or replace a part of them
 
LPCTSTR lpszC = csStringContent;// modify lpszC
LPTSTR lpsz[0] = const_cast< LPTSTR >( lpsz ); // Remove const'ness from string, not a good idea and should be avoided.
lpsz[0] = _T( 't' ); // This change will be reflected in the string. "<code>t</code>his is String"

Nibu thomas
A Developer

Programming tips[^] My site[^]

Andrei Muraru15-Sep-06 1:09

Andrei Muraru

15-Sep-06 1:09

Nibu babu thomas wrote:
CString csStringContent = "This is an String"; // modify to "This is String" or replace a part of themLPCTSTR lpsz = csStringContent;// modify lpsz?

Generally, if you want to modify the LPCTSTR, then you are making something wrong.

You can:
1. csStringContent[0] = 'a';
2. use various member function of CString
3. use CString only when necessary:

TCHAR str[100] = "This is a string";<br />
_tcscpy(str[2], "aaa";<br />
CString cstr = str;

4. use CString::GetBuffer() as already described;

Playing with the LPCTSTR ... no way.

Stephen Hewitt15-Sep-06 1:24

Stephen Hewitt

15-Sep-06 1:24

Agreed, casting the const away as done above is not on - I'd fire someone for doing this.

Steve

Stephen Hewitt15-Sep-06 1:27

Stephen Hewitt

15-Sep-06 1:27

Your second method is just plain evil - although you mentioned it sould be avoided I'd go as for as to say you shouldn't have even mentioned it as an option. Even if it works on one MFC verion it may stop working in a later version.

Steve

Nibu babu thomas15-Sep-06 1:42

15-Sep-06 1:42

Stephen Hewitt wrote:
Your second method is just plain evil - although you mentioned it sould be avoided I'd go as for as to say you shouldn't have even mentioned it as an option. Even if it works on one MFC verion it may stop working in a later version.

Sometimes when you don't have any other option you are forced to do this. But it should be avoided. I just mentioned this so that if he didn't have any other option he can use this. I just went for his question.

Nibu thomas
A Developer

Programming tips[^] My site[^]

bosfan15-Sep-06 3:04

15-Sep-06 3:04

Hello,
i dont need to delete some chars from the LPCTSTR, it is ok when i can change them,
my solution is this:

<code>
LPCTSTR lpsz = csContent.GetBuffer();
LPSTR lpstr = (LPSTR) lpsz;
while(*lpstr)
{
// now change..
  if(something)
  {
    _strnset(lpstr, ' ', 1); // replace current character wit an empty char
  }
}
/*
on the finish in the lpsz are all characters replaced what i dont need!
but i dont know where is the risk on my solution???
*/
</code>

regards
break;

Stephen Hewitt16-Sep-06 1:28

Stephen Hewitt

16-Sep-06 1:28

GetBuffer returns a non-const pointer. Make your code look like this:

LPTSTR lpsz = csContent.GetBuffer(100);
// Do stuff...
csContent.ReleaseBuffer();

You don't need to have a LPCTSTR which you cast to LPSTR; this is strange and confusing to say the least. Also note that you need to call ReleaseBuffer and that GetBuffer takes a minimum buffer size parameter.

You should not be calling GetBuffer at all however: this is designed when you need to manipulate the contents of a CString with code that doesn't know anything about CStrings. If your writing code to manipulate the CString you should use its member functions. Why use a string wrapper if you're just going to get a pointer to the underlying buffer and manipulate it directly?

What exactly are you tring to do?

Steve

bosfan15-Sep-06 2:04

15-Sep-06 2:04

Hello,
i dont need to delete some chars from the LPCTSTR, it is ok when i can change them,
my solution is this:

<code>
LPCTSTR lpsz = csContent.GetBuffer();
LPSTR lpstr = (LPSTR) lpsz;
while(*lpstr)
{
// now change..
  if(something)
  {
    _strnset(lpstr, ' ', 1); // replace current character wit an empty char
  }
}
/*
on the finish in the lpsz are all characters replaced what i dont need!
but i dont know where is the risk on my solution???
*/
</code>

regards
break;

Zac Howland15-Sep-06 3:51

Zac Howland

15-Sep-06 3:51

There are several things wrong with what you are asking, and I'll try to hit on a few of them.

1) You are using CString, which gives you access to the buffer, will manage the memory for you, and can be modified in many ways using its given member functions ... yet you want to grab the buffer from it and operate on it yourself? To me, this indicates that you haven't read the documentation on what CString actually does for you.

2) LPCTSTR stands for "long pointer to a constant t-string". You do NOT want to modify a constant, period. Casting away the const (which is what your "solution" code is doing) is both dangerous and wrong.

3) Because you called GetBuffer, and never called ReleaseBuffer, you created a memory leak. This problem goes away immediately when you fix #1 by using CString's methods.

A much better solution would be to do something along the lines of this:

// csContent is a CString with data in it
csContent.Replace(SomeValueIWantChanged, _T(' '));

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

bosfan15-Sep-06 6:54

15-Sep-06 6:54

Hello,
thanx for answer, well, i read about CString and i love it to use, and i use it hier only for posting, in real the source come from a file, open with fopen();
maybe from an html file to.I need some quick method to lookup through a file, and this file can be wery large.
I dont know if the CString functions like CString::Find() or CString::FindFirst() are the quickest for this!
Also, the source is an stream, file stream!

That is the cause why i ask about!

with best regards!
break;

Displaying continous values

Zac Howland15-Sep-06 9:08

Zac Howland

15-Sep-06 9:08

Consider using OpenFile or ofstream to open the file instead of fopen. Also, if you use ofstream, you can use the string class instead of CString. It has similar functions to CString, and you also gain the ability to use some of the more complex STL algorithms if you need them.

I'm assuming this is an actual file you are opening (that is, it isn't a serial port) so if you wanted to, you could easily load the entire file into memory to parse it.

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

Pratheep Kenny14-Sep-06 22:56

Pratheep Kenny

14-Sep-06 22:56

Hi all,

I have designed a MFC based Dialog application. I have a parent dialog and a corresponding child dialog.

My requirement is this. My parent dialog has a edit box. Which should display value form 0 to n without stopping although the child window is opened or closed.

Just like a clock it should be incrementing the value by itself. Which function do u suppose can be used to achieve this?

I tried WM_TIMER but to no avail. It increments once and then stops.

Please some one tell me as to which function or handle can accomplish this.

Thanks and Regards in Advance
Kenny

Re: Displaying continous values

Rinu_Raj14-Sep-06 23:01

Rinu_Raj

14-Sep-06 23:01

Use a thread function to implement the edit box updation.

Threadproc()
{
m_edit = 1; // edit box member variable
while( 1 )
{
m_edit++
UpdateData(FALSE);
sleep( 10 )
if( m_edit == n ) // return if n is reached
{
return;
}
}

Rinu Raj

Problem with fonts in DC ?

Vinod Sankaranarayanan14-Sep-06 22:49

Vinod Sankaranarayanan

14-Sep-06 22:49

Hi all,

I want to draw some diagrams (rectangles ...etc) and put text in to it..

I have used TextOut() function to write the text...

But I want to reduce the font size ....

Now it takes current font settings of Device Context...

How do I make it ?

Thanks in advance....

vinsankar

Re: Problem with fonts in DC ?

kk.tvm14-Sep-06 22:52

kk.tvm

14-Sep-06 22:52

Hi
Use CreateFont to set font size.

Attach font object to dc using SelectObject

Re: Problem with fonts in DC ?

Steve S14-Sep-06 22:52

Steve S

14-Sep-06 22:52

Are you using the original (default) font in the DC, or have you selected your own in? I'm guessing the former, since if you were selecting them in, you'd just create a smaller one.

Steve S
Developer for hire

Re: Problem with fonts in DC ?

Hamid_RT15-Sep-06 7:26

Hamid_RT

15-Sep-06 7:26

You can use of CreateFontand SelectObject but in the end use CFont::DeleteObject and also you can use of CreateFontIndirect

WhiteSky

Linking Error when use Class Template in VC6 [modified]

Andy Rama14-Sep-06 20:42

Andy Rama

14-Sep-06 20:42

I create an 'Win32 Console Application' "Program01" in VC6 as follows,

//Program01.cpp File<br />
#include "stdafx.h"    #include "Class.h"<br />
int main(int argc, char* argv[]){<br />
	Class<int> a;<br />
	int b = a.GetValue(1729);<br />
	printf("\n\t");<br />
	return 0;<br />
}<br />
<br />
//Class.cpp File<br />
#include "stdafx.h"   #include "Class.h"<br />
template <class T><br />
Class<T>::Class(){<br />
}<br />
template <class T><br />
Class<T>::~Class(){<br />
}<br />
template <class T><br />
int Class<T>::GetValue(int value){<br />
	return value;<br />
}<br />
<br />
//Class.h File<br />
template <class T> class Class{<br />
public:<br />
	Class();<br />
	virtual ~Class();<br />
	int GetValue(int value);<br />
};

It shows Linking error for the member functions of class. But when I remove template from Class the program runs well; even when I write all code (Class with template) in single "Program01.cpp" File then also it runs well.
Then what might be the problem in the above code?

-- modified at 4:03 Friday 15th September, 2006

Re: Linking Error when use Class Template in VC6 [modified]

Mr.Brainley14-Sep-06 21:48

Mr.Brainley

14-Sep-06 21:48

This article should awnser you question :

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccelng/htm/tions_35.asp[^]

(pay special attention to the second scentence)

-- modified at 3:53 Friday 15th September, 2006

Re: Linking Error when use Class Template in VC6

Nibu babu thomas14-Sep-06 21:56

Re: Linking Error when use Class Template in VC6

14-Sep-06 21:56

Aniket Salunkhe wrote:
It shows Linking error for the member functions of class. But when I remove template from Class the program runs well; even when I write all code (Class with template) in single "Program01.cpp" File then also it runs well.
Then what might be the problem in the above code?

Template classes should be defined and declared in .h files so that the compiler can generate code for these classes when an instantiation is required.

Because templates are compiled when required, this forces a restriction for multi-file projects: the implementation (definition) of a template class or function must be in the same file as its declaration. That means that we cannot separate the interface in a separate header file, and that we must include both interface and implementation in any file that uses the templates.

Remove definitions from .cpp file to .h file.

These days compilers do allow you to forward declare template types, but some compilers don't yet support them.

// In AClass.h
template < class T >
class AClass
{
    int ATemplateFunction( T aObj );
};
 
// Don't define this function in AClass.cpp but in AClass.h
template< class T >
int AClass< T >::ATemplateFunction( T aObj )
{
   // Have fun
   return 1;
}

Nibu thomas
A Developer

Programming tips[^] My site[^]

Andy Rama14-Sep-06 22:09

Andy Rama

14-Sep-06 22:09

Nibu babu thomas wrote:
Template classes should be defined and declared in .h files

But I am creating Library ('Wind32 Static Library') using that code, so i can't write implementation of class in .h file.
So what should i do?

Re: Linking Error when use Class Template in VC6

Nibu babu thomas14-Sep-06 22:19