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I am attempting to write a C library of routines for my DVD player. (It talks over a serial port.) I want the library as portable as possible, so I'm attempting to do it in C. I know it'd be alot easier for me to do it with classes, but as far as I'm concerened, C++ is out of the question.
I can successfully compile the header below with it's .c file. The problem comes when other C++ modules (I'm trying to use the C library in an MFC app) #include the header. The compiler chokes on the first paranthesis inside the struct definition. I'm thinking it's something having to do with switching into C++ mode.
The whole reason why I'm doing this is because I don't want the user to have to mess with a buffer. All they need to provide are callbacks for Open, Close, Read, and Write (reguarldess if they are using J.P. Naughter's serial wrappers, raw win32 api, or Unix file i/o) of the serial port library and users can do something simple like: DVDPlayer.Execute(PLAY); and not have to worry themselves with formatting, writing and returning the response to me for parsing. This way, it can all be handled internally. And in C.
[ccode]
#pragma once
int DVF07Error(struct DVF07*);
void DVF07StoreTOC(struct DVF07*, struct toc_type*);
void DVF07StoreTrack(struct DVF07*, struct toc_type*, int);
void DVF07TraceTOC(struct toc_type*);
int DVF07Format(struct DVF07*, int, int);
int DVF07Execute(struct DVF07*, int, int);
int DVF07ReturnedInt(struct DVF07*);
int DVF07SizeofBuf(struct DVF07*);
typedef struct DVF07{
/* in c++ files, when this is #included, the ( of int (*Error is */
/* where the compiler chokes, but it compiles fine when */
/* the .c file #includes it */
int (*Error)(struct DFV07 *this);
void (*StoreTOC)(struct toc_type*, struct *toc_type);
void (*StoreTrack)(struct toc_type*, int i);
void (*TraceTOC)(struct toc_type *toc);
int (*Format)(struct DVF07 *this, int, int);
int (*Execute)(struct DVF07 *this, int, int);
int (*ReturnedInt)(struct DVF07 *this);
int (*SizeOfBuf)(struct DVF07 *this);
/* user provided routines below */
int (*Write)(struct DVF07 *this);
int (*Read) (struct DVF07 *this);
int (*Open) (struct DVF07 *this, int port);
int (*Close)(struct DVF07 *this);
char buf[256];
} DVF07_Type;
[/ccode]
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I see one potential problem with that line: "this" is a C++ keyword. Could that be the problem? What happens if you comment that line?
"Harland Pepper, would you stop naming nuts" - Harland Pepper
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I don't think so. I've compiled code before using 'this' in C. I think it only is a problem when __cplusplus is defined. And in this case, it is not -
I hope
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#ifdef __cplusplus<br />
extern "C" {<br />
#endif<br />
<br />
<br />
#ifdef __cplusplus<br />
}<br />
#endif
-Ben
---------
On the topic of code with no error handling -- It's not poor coding, it's "optimistic" 
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Thanks! this worked after I cleaned up a a few issues...
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Anyone know how I can find what the path to the "My Documents" directory is please?
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Use the SHGetSpecialFolderLocation function with the CSIDL_PERSONAL option.
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Thanks! 
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hi!!!
can you help me???I've a matter with my MFC because when I press a button "New",which is already in a MFC,it doesn't get on...Debugger of Visual C++ send me to the line:
"ASSERT(::GetWindowLong(hWnd Ctrl,GWL_STYLE & WS_STYLE));"
and it stop to a line of my programm which is:
if(mListX.FindString(0,lNewExplosif->NameX()) EQ LB_ERR))
Do you know what does it mean????
foed in france
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I am going through some code, and I noticed the following:
{snip}
double x[SIZE];
//x[] is filled
foo(x-1);
//where foo takes double data[] as argument
{snip}
What exactly is being passed here? What does subtracting an integer from an array do?
Thanks,
Ryan
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When u reduce n from an array address (here x), the address will reduce to x - (n * sizeof(the type of x))
In this case u r reducing 1 from the double array address x. So, the new address will be educed by 8 bytes, since size of double is 8 bytes.
Go through the below given sample.
void foo(double* x)
{
printf("%f", *x);
}
void main()
{
double x[] = {1,2,3};
foo(x+1);
}
See the output to convince urself.
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The value x is treated as a pointer to the start of the array so it is pointer arithmetic that is being used. The code is passing a pointer to one element before the start of array x, i.e. x[-1].
I would guess that one of the algorithms in the function expects the data to be in x[1..N]. This often occurs when the algorithm was originally developed for a different language (e.g. Fortran program where lower bounds are usually 1), rather than C or C++ where the lower bound is zero.
So they may be offsetting the array to use the original algorithm.
void foo(double y[SIZE])
{
// y[1] is now equivalent to x[0]
}
p1514
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VC++ doesn't bother if it is an address pointing to start of an array or not. It knows that x is a pointer to double and size off double is 8 bytes. So, if u increment or decrement the pointer, the address will be recuced as multiple of 8 (for double).
But there is a chance of exception in the case of x[-1], since the location x-1 is not reserved for x and that location may not be free. 
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Hi,
I like to know if anyone knows how to have the child window of an MDI application maximized at the start of the application...
thanks
ehsan
Ehsan Behboudi
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In the OnInitialUpdate() function of your application's View, write the following code
GetParentFrame()->ShowWindow(SW_SHOWMAXIMIZED);
For example, if the view class is CMyView, then do as follows.
void CMyView::OnInitialUpdate()
{
CScrollView::OnInitialUpdate();
GetParentFrame()->ShowWindow(SW_SHOWMAXIMIZED);
}
Happy coding...
Rejeesh
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it didn't work,,
i added the OnInitialUpdate fucntion from the wizard,,but it didn't work???
Ehsan Behboudi
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It must work. I have done it. Do as follows.
1. Make a MDI project.
2. Using class wizard, add a new OnInitialUpdate() function in ur view class.
3. Add as follows,
void CTestView::OnInitialUpdate()
{
CView::OnInitialUpdate(); //Added by wizard
GetParentFrame()->ShowWindow(SW_SHOWMAXIMIZED);//Added by me
}
4. Compile and run the code.
5. It must work.
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Im trying to understand virtual functions but cant see what they do. I presumed this would
be the situation I would use them in where I have two identical functions with same prototypes
which do different things, however this works as expected - outputs the base class cout, and
then the derived class one.
class CBadGuy {
public:
CBadGuy();
virtual ~CBadGuy();
void vfunc() { cout << "Base class vfunc.\n"; };
protected:
unsigned int speed;
unsigned int height;
char* description;
};
class CSoldier : public CBadGuy {
public:
CSoldier();
virtual ~CSoldier();
void vfunc() { cout << "Derived class vfunc.\n"; }
protected:
unsigned int numBullets;
};
int main() {
CBadGuy a;
CSoldier b;
a.vfunc();
b.vfunc();
return 0;
}
I cant understand why this works though, I thought that the funciton vfunc() would be ambigous when
I refered to it through object b as sureley this contains its own vfunc as well as the derived one.
Is it the case that I am simply "overloading" the b.func() function
Thanks,
Mark
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Actually, you are not using virtual functions for vFunc. You are simply re-defining the base class function. To use virtual functions for this, you would need to modify your code to:
class CBadGuy {
public:
CBadGuy();
virtual ~CBadGuy();
virtual void vfunc() { cout << "Base class vfunc.\n"; };
protected:
unsigned int speed;
unsigned int height;
char* description;
};
class CSoldier : public CBadGuy {
public:
CSoldier();
virtual ~CSoldier();
virtual void vfunc() { cout << "Derived class vfunc.\n"; }
protected:
unsigned int numBullets;
};
int main() {
CBadGuy a;
CSoldier b;
a.vfunc();
b.vfunc();
return 0;
}
Even with this change you would get 'Base class vFunc' followed by 'Derived class vFunc'.
Often when using virtual functions it is desirable to not just "overide" a functions functionality, but to augment it. By doing this you can still use the base class implementation and only add what you want.
The following example demonstrates this.
class CBadGuy {
public:
CBadGuy();
virtual ~CBadGuy();
virtual void vfunc() { cout << "Base class vfunc.\n"; };
protected:
unsigned int speed;
unsigned int height;
char* description;
};
class CSoldier : public CBadGuy {
public:
CSoldier();
virtual ~CSoldier();
virtual void vfunc() { cout << "Derived class vfunc.\n"; CBadGuy::vFunc();}
protected:
unsigned int numBullets;
};
int main() {
CSoldier b;
b.vfunc();
return 0;
}
This will result in 'Derived class vFunc' followed by 'Base class vFunc'. This can be very useful if you are creating your objects at run-time (ie new CSoldier) and passing them as pointers to CBadGuy); The following example demonstrated this.
class CBadGuy {
public:
CBadGuy();
virtual ~CBadGuy();
virtual void vfunc() { cout << "Base class vfunc.\n"; };
protected:
unsigned int speed;
unsigned int height;
char* description;
};
class CSoldier : public CBadGuy {
public:
CSoldier();
virtual ~CSoldier();
virtual void vfunc() { cout << "Derived class vfunc.\n"; }
protected:
unsigned int numBullets;
};
int main() {
CSoldier* pSolider = new CSoldier;
TestObject(pSoldier);
return 0;
}
void TestObject(CBadGuy* pTest)
{
pTest->vFunc();
}
In this scenario you would get the 'Dervice class vFunc' as output. This can be extremely powerful when you have a "class" of objects which share basic functionality and purpose but need to work in different ways.
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virtual functions are useful when we use base class pointer to access derived class objects.
class CBadGuy {
public:
CBadGuy(){};
virtual ~CBadGuy(){};
virtual void vfunc() { cout << "Base class vfunc.\n"; };
protected:
unsigned int speed;
unsigned int height;
char* description;
};
class CSoldier : public CBadGuy {
public:
CSoldier(){};
virtual ~CSoldier(){};
virtual void vfunc() { cout << "Derived class vfunc.\n"; }
protected:
unsigned int numBullets;
};
int main() {
CBadGuy *pBadGuy;
CSoldier b;
pBadGuy = &b;
pBadGuy->vfunc(); //This will call the derived class vfunc()
//If the vfunc() is not declared as virtual in the base class,
//the above call will call the base class vfunc() function.
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Hi
I have a CListctrl & Iam intersted in creating a tooltip in the form f a PopUp window when I select any item in the CListCtrl . Can anybody explain how I can do this ?? Any Sample code would be very useful.
The ClistCtrl is placed in a dialog box. When I try to implement the OnLButtonDown to know whether the left button of mouse is clicked inside the control, it doesn't respond but actually, the control is being trapped by the parent window ( Dialog Box ). Eventually the HitTest member function of the CListCtrl fails.
Thanks
regards
Sankar
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Handle LVN_ITEMCHANGING (or LVN_ITEMCHANGED) to be notified before (after) the selection changes.
--Mike--
http://home.inreach.com/mdunn/
#include "buffy_sig"
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I have the following code, which looks fine but every time the connection fails... the database is an Access 2000 database in the same directory as the VC project:
void CTest9Dlg::OnButton1()
{
_ConnectionPtr m_pConnection = NULL;
char* m_strConnection = _T("Provider=Microsoft.Jet.OLEDB.4.0; Data Source = db1.mdb");
m_pConnection.CreateInstance(__uuidof(Connection));
try
{
HRESULT hr;
hr = m_pConnection->Open(_bstr_t(m_strConnection), "", "", NULL);
if(hr == S_OK) {
TRACE("Connected");
MessageBox("Connected");
}
}
catch(_com_error &e)
{
TRACE("Connect Failed.");
MessageBox("Failed!");
}
}
Thnaks for your help
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The 2 most common mistakes I make is to not call 'OleInitialize(NULL)' (or some variant ie. AfxOleInit()). Also, is the MDB file in your project directory of your build directory (ie. Debug/Release). If is is your project directory you may need to reference the DB like
char* m_strConnection = _T("Provider=Microsoft.Jet.OLEDB.4.0; Data Source = ../db1.mdb");
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I'm working on an application (let's call it SCONES) which can be used as an OLE server, so that its results can be embedded in Word docs, for example. Now, I know I need to implement the Serialize() function for all my data objects for OLE purposes. On the other hand I don't want to use MS's proprietary file format for saving SCONES files to disk when it's not being an OLE server - I want to use XML. Do I have to write two separate sets of code for file saving and loading, or is there some smart way of doing both tasks in one? I can't be the first to encounter this problem, surely?
Peter Robinson
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