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Can any one help me to truncate the string based on the buffer size, for the below show scenario.
main()
{
int size = 50;
char errmsg [size];
get_last_error( errmsg, size );
cout<<errmsg;
}
get_last_error( char *errmsg, int bufsize )
{
string sErrMsg;
if ( sErrMsg.capacity() > bufsize )
{
// here i want to truncate the string, so that the size of string will fit into "bufsize". Then copy the string to errmsg
// strcpy( errmsg, sErrMsg.c_str() );
// how to truncate the string based on given buffersize
// so that we can atlest copy the possible string to errmsg if not the whole string
}
else
{
strcpy( errmsg, sErrMsg.c_str() );
*errcode = nErrCode;
}
}
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Nandu_77b wrote: // how to truncate the string based on given buffersize
How about the substr() method?
"Love people and use things, not love things and use people." - Unknown
"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne
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Nandu_77b wrote:
// how to truncate the string based on given buffersize
How about the substr() method?
substr() this fun will not take buffer size, it takes length of characters. I need to truncate based on buffer size. Please see my code which will give you clear idea.
-Nandu
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If the size of your buffer is 50, then you would extract characters 0-49.
"Love people and use things, not love things and use people." - Unknown
"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne
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What about strncpy [^]?
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke
[My articles]
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strncpy() will also take char length not the buffersize.
- Nandu
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--strncpy() will also take char length not the buffersize.
- Nandu
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Are you aware that, for ANSI strings, the char length and the buffer size (bytes) are basically the same?
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke
[My articles]
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Yes you are correct,
Thanks
Nandu
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lstrcpynA(errmsg, bufsize);
If using TCHAR, do:
<br />
lstrcpyn(errmsg, bufsize / sizeof(TCHAR));
(lstrcpyn is a tiny bit more efficient than strncpy since it doesn't fill the rest of the buffer with zeros after completing the copy. With large buffers, this is generally a waste of cycles.)
Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke
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Hi,
I have created an SDI application with tabbed view. I have used view class derived from CTabView (class from MFC Feature Pack). I want to show different toolbars on the MainFrame for each tab and alternately change the toolbars when the tab selection is changed. But i have problems with swithching the toolbars. Is there any way to switch the toolbars or associate a custom toolbar for each tab of the view?
Thanks
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Dear All,
I have two classes Test and Test1. I have a static variable in the class Test and I have to access it in another class Test1 from a funtion. When I access it, I got linker error. The error is :
1>Test1.obj : error LNK2001: unresolved external symbol "public: static int Test::cnt" (?cnt@Test@@2HA)
1>Test.obj : error LNK2001: unresolved external symbol "public: static int Test::cnt" (?cnt@Test@@2HA)
Code snippet :
class Test : public CDialog,public CDemux
{
DECLARE_DYNAMIC(DecodeTS)
Public
static int cnt;
.......
void Test1::GetData()
{
int cnt =Test::cnt;
}
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This is a known quirk in C++: For static variables in a class, you need to repeat the declaration in the .cpp file.
So add this:
int Test1::cnt;
to your .cpp file and it will stop this linker error.
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I have the static variable in Test class. When I declare again in Test.cpp it shows redefinition error. I do like this in Test.cpp file.
int Test::cnt;
Linker error gone but another error occur as redefinition.
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Hello Alan,
Now I have fixed it, the problem is that I give the int Test::cnt; in the constructor and thats why the error I got. Now I give the line at the top of the cpp file and it is working fine.
Thank you very much.
Many thanks.
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Alan Balkany wrote: This is a known quirk in C++: For static variables in a class, you need to repeat the declaration in the .cpp file.
It's not a quirk, and you're not re-declaring the variable.
The one-and-only static member variable instance needs to exist
somewhere, so you have to define that instance.
Mark
Mark Salsbery
Microsoft MVP - Visual C++
![Java | [Coffee]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/coffee.gif)
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But this is counterintuitive; you don't have to redeclare the non-static class members.
I got burned by this quirk years ago. I've seen several other people run into this same problem on this forum over the years. There's no good reason for this behavior.
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Alan Balkany wrote: you don't have to redeclare the non-static class members.
A declaration is not an instance. You are NOT declaring static member variables twice.
You declare the variable once, and you also must provide an instance of the variable.
Non-static members are not the same - every existing object (instance) of the type gets its
own instance of the variable.
Alan Balkany wrote: There's no good reason for this behavior.
You'll have to ask Bjarne for the good reason
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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Yet people continue to get burned by this "feature".
I see bad design every day.
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"burned"? How so? It's just a simple linker error - a LOT easier
than tracking down a runtime error
Mark Salsbery
Microsoft MVP - Visual C++
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Burned: You write code that the compiler accepts, but it doesn't work. You waste hours or days until you (somehow) learn the gimmick that gets by the quirk.
Good language design minimizes instances of this. Stroustrup isn't infallible, and the fact that he implemented this doesn't automatically make it good.
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Right. I never said it was good. Every language has its trade-offs.
This particular case has always been the case. Had the C++ designer(s) let the
compiler choose where to create the instance, there's would be a whole lot
of us whining because we don't have control over the storage of our variables.
I use C++ for the low level control. I understand how objects exist and where, and
I take advantage of the control I have over that. So to me it is not counter-intuitive
to have to explicitly state where an object is stored. For times I don't care, I'll use
a higher level language - C# works just fine
The whole "static" thing in itself is kind of an abomination itself - mixing linkage with compilation.
Cheers,
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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Since there's only one instance of a static variable, it doesn't matter where it's stored.
It's counterintuitive because neither instance variables NOR "ordinary" static variables require two declarations, and the thousands of people who have had their time wasted by this quirk support this assertion.
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Alan Balkany wrote: and the thousands of people who have had their time wasted by this
Thousands? I thought EVERYONE went through it at least once
I get where you're coming from - I just do not agree that there's two declarations. There's
a distinct difference between declaration and an actual instance of an object.
Mark Salsbery
Microsoft MVP - Visual C++
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This linked fine for me:
class Test : public CDialog
{
DECLARE_DYNAMIC(Test)
public:
static int cnt;
};
class Test1
{
void GetData()
{
int cnt = Test::cnt;
}
};Can you compare it to what you have?
"Love people and use things, not love things and use people." - Unknown
"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne
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