C / C++ / MFC

Pass class member function as paramter?

27-Mar-02 8:24

By your use of clrscr(), you're compiling on a possibly 16 bit platform/compiler? If so, it may be that you need to scanf(%u,...) to input an unsigned integer.

Todd Smith27-Mar-02 7:22

Todd Smith

27-Mar-02 7:22

How do I create a template that takes a member function as a parameter?

Here's what I'm trying to do

<pre>
void MyClass::DoSomething(int x)
{
}

MyClass::blah()
{
foo<MyClass>(DoSomething);
}
</pre>

<pre>
????

template <class C>
void foo(FunctionPointer fp)
{
int x = 0;

for (int i=0; i<10; i++)
{
fp(x);
}
}
</pre>

<b>Todd Smith
CPUA 0x007 ... shaken not stirred</b>

Tim Deveaux27-Mar-02 8:27

27-Mar-02 8:27

Google for 'functors' and you should hit it.

(Boy, hows that for a detailed response! Smile | :)

)

Todd Smith28-Mar-02 8:02

Todd Smith

28-Mar-02 8:02

That landed me in boost territory. It was a little daunting at first but here's what I came up with.

#include "stdafx.h"
#include <boost bind.hpp="">

#include "debugstr.h"

class CTest
{
public:
void Test(const char* str)
{
printf("member function: %s", str);
}
};

template <class f="">
void foo(F f)
{
for (int i=0; i<10; i++)
{
char buf[128] = {0};

sprintf(buf, "test %i\n", i);

f(buf);
}
}

void Test(const char* str)
{
printf("global function: %s", str);
}

int main(int argc, char* argv[])
{
CTest test;

foo(boost::bind(&CTest::Test, boost::ref(test), _1));
foo(boost::bind(Test, _1));

return 0;
}

Todd Smith
CPUA 0x007 ... shaken not stirred

soptest27-Mar-02 8:51

soptest

27-Mar-02 8:51

It is doable, but it is not correct unless your member function is a staic one. Why do not pass pointer to that class as a parameter to foo() and inside foo() call p->DoSomething()

soptest

History list in browser window

Jim Crafton27-Mar-02 10:50

Jim Crafton

27-Mar-02 10:50

Well if you can keep the same parameters for the function then this might work

template <typename T>
class FunctionPointer {

typedef void (T::*FuncPtr)(int);

FunctionPointer( T* src, FuncPtr func ):m_source( src ), m_func(func) {};

void doit( int x ) {
(m_source->*m_func)(x)
}
FuncPtr m_func;
T* m_source;
};

template <typename T>
void foo(FunctionPointer<T> fp )
{
int x = 0;
for (int i=0; i<10; i++) {
fp.doit(x);
}
}

MyClass::blah()
{
foo( FunctionPointer<MyClass>(this, DoSomething) );
}

would this work ?

Aaron Schaefer27-Mar-02 6:24

Aaron Schaefer

27-Mar-02 6:24

Hi All,

I'm deriving a view class from the CHtmlView, and sticking this in a child frame window of an MDI app. Anyway, I've got a toolbar with a forward and backward arrow for going forward and backward through the CHtmlView's history list. Going forward and back is simple enough (through CHtmlView::GoForward, and CHtmlView::GoBack), but how can I determine if there are previous entries or next entries in the history list of the browser from the current page? What I need is something like a CanGoBack or a CanGoForward method so I can update the buttons on the toolbar in the CmdUI handler.

Thanks,

Aaron

sending keystrokes to window

vins27-Mar-02 5:14

vins

27-Mar-02 5:14

keybord event can generate a keystroke ,but how do you direct this keystroke to a particular window or its message queue.

Tim Deveaux27-Mar-02 6:12

27-Mar-02 6:12

I posted this a while back, and have been meaning to clean it up and offer it to the god of FAQ - maybe it will help.

vins27-Mar-02 6:22

vins

27-Mar-02 6:22

I am sorry,I could not locate anything on 'this' link.

Tim Deveaux27-Mar-02 7:41

27-Mar-02 7:41

Ok - here is the example I posted, which should be made into a SendKeys type function. Here I hardcoded a known window handle - (Calculator).

Basically, the trick is to post messages for keydown and keyup, and its nice to format the lparam properly.

// Console.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "crtdbg.h"
#include "conio.h"
#include "windows.h"
#include "winbase.h"
 
 
int main(int argc, char* argv[])
{
    HWND    hwnd = (HWND)  0x025c;
     
    INT Vk;
    INT Scan;
    CHAR character[2];
    CHAR oemchar[2];
    CHAR ch;
    do {
        while(!_kbhit());
        ch = getch();
        
        character[0]=ch;
        character[1]='\0';
        
        // Get the virtual key code for this character
        Vk = VkKeyScan(character[0]) & 0xFF;  
        CharToOem(character, oemchar);
        
        // Get the scan code for this key
        Scan = OemKeyScan(oemchar[0]) & 0xFF;
        
        // show the key:
        printf("Key = %c, VK code = %d, scan = %d\n", ch, Vk, Scan);
        
        UINT    lKeydata = 0;
 
        UINT    mask = 1;
        lKeydata |= mask;         // repeat count of 1;
        lKeydata |= Scan << 15;   // not really necessary for most apps
         
        ::PostMessage(hwnd, WM_KEYDOWN, Vk, lKeydata);
         
        lKeydata |= mask;         // repeat count of 1;
        lKeydata |= Scan << 15;
        lKeydata |= mask << 31;   // transition (fUp) is 1 for key up.
         
        ::PostMessage(hwnd, WM_KEYUP, Vk, lKeydata);
    }
    while(1);
    return 0;
}

How do I determine what functions a dll are exporting?

vins27-Mar-02 8:16

vins

27-Mar-02 8:16

thanks!! it is a great help

Tommy Svensson27-Mar-02 5:03

Re: How do I determine what functions a dll are exporting?

27-Mar-02 5:03

Hi everybody,

Is ther a way [read: a program] to find out what functions a dll is exporting? Is there a tool with MVS that can do this?

To learn more about this I chose the default implementation of a sample dll in VC++: New->Projects->Win32 dynamic link-library.

Now, there's a test function called fnDllTest (my project is called DllTest) which is exported like this:

__declspec(dllexport) int fnDllTest(void)
{
  return 42;
}

Now, I created a simple console application which should call this dll function. I loaded the dll using LoadLibrary and that works fine... BUT, now I wish to get the function fnDllTest through the use of GetProcAddress but I can't seem to get it working!

If the dll and the console app loading the dll are residing in the same place then the call to GetProcAddress should look like this right?

blabla = (blabla)GetProcAddress(libPtr, "fnDllTest");

where libPtr is the return value of LoadLibrary... What kind of type should blabla be of?
I haven't found any documentation on how to call dll exported functions...

Thx for all your help,

/Tommy

C^hris L^osinger27-Mar-02 5:27

C^hris L^osinger

27-Mar-02 5:27

find the tool called DUMPBIN. it will tell you the function names. i'm not sure if it can tell you the params, tho.

-c

Smaller Animals Software, Inc.
Few things are harder to put up with than the annoyance of a good example.
_{Mark Twain}

Re: How do I determine what functions a dll are exporting?

Tommy Svensson27-Mar-02 6:08

Re: How do I determine what functions a dll are exporting?

27-Mar-02 6:08

Thx!

I tried and this was the result:

...

ordinal   hint    RVA         name

1         0       0000100A    ?fnDllTest@@YAHXZ

...

What does this tell me? I can't very likely do like this, or...?

... GetProcAddress(libPtr, "?fnDllTest@@YAHXZ");

I mean, there must be a way for me to know what the exporting function name will look like when it is me writing them...?

THx for your help!

/Tommy

Paul M Watt27-Mar-02 5:48

Paul M Watt

27-Mar-02 5:48

blabla will be a function pointer that is the same type as the function that you are loading. This is why it is hard to use functions in a dll without a header file or good documentation.

In the example that you have given, here would be the function pointer that you would declare:

int (fnDllTestPtr*)(void);

fnDllTestPtr becomes the name of the function pointer type. To use this you would now call this:

fnDllTestPtr fnDllTest = (fnDllTestPtr)GetProcAddress(libPtr, "fnDllTest);

As far as determining which functions are exported pragmatically, you will need to traverse the PE file structure of the DLL in order to read the exports section. Lookup Mike Peitrics article on the PE file format. He created a smaple program called PEDump.

Re: How do I determine what functions a dll are exporting?

Tommy Svensson27-Mar-02 6:16

Re: How do I determine what functions a dll are exporting?

27-Mar-02 6:16

No, that can't be right...

It crashed when I tried to do that... I mean, shouldn't there be a typedef somewhere?

Tommy Svensson27-Mar-02 6:36

Re: How do I determine what functions a dll are exporting?

27-Mar-02 6:36

Hi again,

Shouldn't it be:

int (*fnDllTestPtr)(void);

and then

fnDllTestPtr = (???)GetProcAddress(libPtr, "fnDllTest");

but I don't know what to put in '???'...

/Tommy

Paul M Watt27-Mar-02 9:03

Paul M Watt

27-Mar-02 9:03

I am sorry, this is the correct declaration for the function pointer. Typedef it so that you can use it later.

typedef int(*fnDllTestPtr)(void);

Also, if you do not encapsulate the function that you are exporting with extern "c"{ }, then the function will be name mangled, and you will have to include the mangled name in order to load it. So for the function that you have sent in, it should be managled like this:

?fnDllTest@@YAHXZ

Before you attempt to call the function, you should check the return value from GetProcAddress to insure that the function was found and properly pointed to. If the function fails, it will return NULL.

Here is the code that you should use.

typedef int(*fnDllTestPtr)(void);
fnDllTestPtr fp = (fnDllTestPtr)::GetProcAddress(libPtr, "?fnDllTest@@YAHXZ");
if (NULL == fp)
{
MessageBox(NULL, "an error has occurred. The function did not load.", "error", MB_OK);
}
else
{
int i = fp();
}

Re: How do I determine what functions a dll are exporting?

Tommy Svensson1-Apr-02 21:49