Dynamic Dispatch - C / C++ / MFC Discussion Boards

Re: SMS Sending programme

Garth J Lancaster10-Dec-09 1:03

Garth J Lancaster

10-Dec-09 1:03

yes - you need to look at purchasing a GSM/GPRS modem

'g'

Is STL string can be used in multithreading application ?

Member 67757439-Dec-09 1:01

Member 6775743

9-Dec-09 1:01

HI,
I want to write c++ String Functions using STL string class on Linux OS.
Is this string class error free ?
I read some where these below lines.
" The Standard Template Library (STL) that is included with Microsoft Visual C++ 6.0 is not safe for multi-threaded applications."
http://support.microsoft.com/kb/813810[^]

is it Safe in Linux multi threaded applications ?

Thanks,
Rayalu.

Re: Is STL string can be used in multithreading application ?

mav@octaval9-Dec-09 1:05

mav@octaval

9-Dec-09 1:05

STL collections are not thread-safe. You can synchronize them with a mutex when you are accessing them from more than one thread.

--

Si dos montan un caballo, uno debe ir detrás.

Re: Is STL string can be used in multithreading application ?

Member 67757439-Dec-09 1:37

Member 6775743

9-Dec-09 1:37

Thank you.

Re: Is STL string can be used in multithreading application ?

Nemanja Trifunovic9-Dec-09 5:26

Nemanja Trifunovic

9-Dec-09 5:26

Member 6775743 wrote:
The Standard Template Library (STL) that is included with Microsoft Visual C++ 6.0 is not safe for multi-threaded applications

That means the library that comes with MSVC 6.0 was not to safe to use in multi-threaded applications even if the containers were not shared among threads. If you use a more recent version of MSVC (or even MSVC 6 with STLPort), that should not be a problem. Of course, you should still need to synchronize access to container objects that are shared between threads.

utf8-cpp

How could I add print facility to Analogmeter Control

ganesh.dp9-Dec-09 0:56

ganesh.dp

9-Dec-09 0:56

Hi,

I have the "Analog Meter Control" class by Mark C. Malburg.

I downloaded this from code project only.

Now I want to add the print facility to that control.

how could I make this, any suggestion and directions are welcome.

Thanks in advance.

Re: How could I add print facility to Analogmeter Control

CPallini9-Dec-09 1:54

CPallini

9-Dec-09 1:54

I would say:"Why don't you post it in the right place?", but you've already done so. Hence I say:"Good luck!".
Smile | :)

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]

Dynamic Dispatch

hrishiS8-Dec-09 23:16

hrishiS

8-Dec-09 23:16

Hi to All,

Could you please clear my following doubt.
I have 3 class with multilevel inheritance as follows,,...

class A
{
public:
     A()
     {
          s();
     }
     virtual void s()
     {
          printf("\nIn A");
     }
};
class B:public A
{
     public:
};
class C:public B
{
     public:
          void s()
          {
               printf("\nIn C");
          }
};

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

A *ptr     =     new C();
}

when i create an object of C,...by theory it should call always the method S of C....am I correct?...but when I called C from A's constructor Its calling S() of C....Why so?...Could anyone please explain me the reason and some points on it??

thanks in advance

-----------------------------
I am a beginner

Re: Dynamic Dispatch

Cedric Moonen8-Dec-09 23:24

Cedric Moonen

8-Dec-09 23:24

hrishiS wrote:
but when I called C from A's constructor Its calling S() of C....

You mean it is calling s() of A, right ?
That's normal because when A is being constructed, it's virtual table is not create yet, which means that the call can't be redirected properly. So, the rule is simple: never call a virtual function from within a constructor.

Read this[^] for instance.

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

Re: Dynamic Dispatch

Stuart Dootson8-Dec-09 23:59

Stuart Dootson

8-Dec-09 23:59

Not quite, Cedric - in A's constructor, the object has A's v-table. See the C++ 98 Standard, Section 12.7-3.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: Dynamic Dispatch

hema_soft8-Dec-09 23:30

hema_soft

8-Dec-09 23:30

When u create base class pointer as derived class using new, it first allocate memory for base class one by one, call their constructors, initialize their member variables , finally it call declared class constructor(here it is Class C). since fn s() is called in class A's Constructor, it invoke its own fn even though u declared it as virtual.
A *ptr = new C();

if you define like this ,
A *ptr = new C();
ptr->s();

Class C's fn of s() will be invoked!

hemmalatha.g

Re: Dynamic Dispatch

Stuart Dootson9-Dec-09 0:04

Stuart Dootson

9-Dec-09 0:04

When constructing an object, base class constructors use that base classes virtual function table. So, when you call C's constructor, the first thing it does is call B's (implicitly defined) constructor, which call's A's constructor. Within A's constructor, only virtual functions defined in A can be called. Within B's constructor, only virtual functions defined in A or B can be called. Within C's constructor, virtual functions defined in A, B or C could be called.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Twain endorse text

sujtha8-Dec-09 22:26

sujtha

8-Dec-09 22:26

Kindly let me know, how to use endorsement option in the scanner using twain

Re: Twain endorse text

Rajesh R Subramanian8-Dec-09 22:36

Rajesh R Subramanian

8-Dec-09 22:36

This is the C++ forum.

“Follow your bliss.” – Joseph Campbell

Twain endorse text [modified]

hema_soft8-Dec-09 23:02

hema_soft

8-Dec-09 23:02

I use twain.h in vc++ application for scanner operation. twain.h file contains n number of capabilities (like CAP_DUPLEXENABLED,ICAP_XRESOLUTION,ICAP_AUTOMATICROTATE etc) which are supported by scanner. kindly help me how to use CAP_ENDORSER and TWEI_ENDORSEDTEXT capabilities to do endorsement in the scanner.

sujtha

modified on Wednesday, December 9, 2009 5:13 AM

SetDIBitsToDevice problem

sashoalm8-Dec-09 21:12

sashoalm

8-Dec-09 21:12

I have this code that loads a DIB bitmap from a file and passes it to SetDIBitsToDevice.

This code works:

FILE* f = fopen(".\\bitmap1.bmp", "rb");

vector<BYTE> buffer;
buffer.resize(_filelength(f->_file));
fread(&buffer[0], buffer.size(), 1, f);
BITMAPINFO* bminfo = (BITMAPINFO*) &buffer[14];
BITMAPFILEHEADER* bmh = (BITMAPFILEHEADER*) &buffer[0];
LPVOID bits = &buffer[bmh->bfOffBits];

SetDIBitsToDevice(
    pDC->GetSafeHdc(),              // handle to device context
    0,                              // x-coordinate of upper-left corner of
                                    // dest. rect.
    0,                              // y-coordinate of upper-left corner of
                                    // dest. rect.
    bminfo->bmiHeader.biWidth,       // source rectangle width
    bminfo->bmiHeader.biHeight,      // source rectangle height
    0,                              // x-coordinate of lower-left corner of
                                    // source rect.
    0,                              // y-coordinate of lower-left corner of
                                    // source rect.
    0,                              // first scan line in array
    bminfo->bmiHeader.biHeight,      // number of scan lines
    bits,                           // address of array with DIB bits
    bminfo,                         // address of structure with bitmap info.
    DIB_RGB_COLORS                  // RGB or palette indexes
    );

But this doesn't. The only differences are in the source origins and width/height/number of scanlines. I'm trying to pass a smaller rectangle that starts at (100,100) and has the same lower-right corner (hence smaller width/height).

FILE* f = fopen(".\\bitmap1.bmp", "rb");

vector<BYTE> buffer;
buffer.resize(_filelength(f->_file));
fread(&buffer[0], buffer.size(), 1, f);
BITMAPINFO* bminfo = (BITMAPINFO*) &buffer[14];
BITMAPFILEHEADER* bmh = (BITMAPFILEHEADER*) &buffer[0];
LPVOID bits = &buffer[bmh->bfOffBits];

SetDIBitsToDevice(
    pDC->GetSafeHdc(),              // handle to device context
    0,                              // x-coordinate of upper-left corner of
                                    // dest. rect.
    0,                              // y-coordinate of upper-left corner of
                                    // dest. rect.
    bminfo->bmiHeader.biWidth-100,   // source rectangle width
    bminfo->bmiHeader.biHeight-100,  // source rectangle height
    100,                            // x-coordinate of lower-left corner of
                                    // source rect.
    100,                            // y-coordinate of lower-left corner of
                                    // source rect.
    0,                              // first scan line in array
    bminfo->bmiHeader.biHeight-100,  // number of scan lines
    bits,                           // address of array with DIB bits
    bminfo,                         // address of structure with bitmap info.
    DIB_RGB_COLORS                  // RGB or palette indexes
    );

What can be the problem with the second code?

There is sufficient light for those who desire to see, and there is sufficient darkness for those of a contrary disposition.
Blaise Pascal

Re: SetDIBitsToDevice problem

C^hris L^osinger9-Dec-09 9:36

C^hris L^osinger

9-Dec-09 9:36

are you sure SetDIBitsToDevice lets you draw sub-sections of a DIB ?

image processing toolkits | batch image processing

Re: SetDIBitsToDevice problem

Rozis9-Dec-09 11:34

Rozis

9-Dec-09 11:34

I never have used SetDIBitsToDevice() myself. I would suggest you to use Stretchblt(), it's almost the same. I'm sure that one does the job...

My experience is that problems with these functions mostly are caused by:
- wrong coordinate system (try negative values)
- pending clipping areas

So if you try Stretchblt() and it doesn't work either you know its not in the coordinates..

And, as someone on CP a few days before suggested, there seems to be a 'DCviewer' somewhere on CP.

Good luck

Rozis

Conneting to a computer using socket

bubuzzz8-Dec-09 20:21

bubuzzz

8-Dec-09 20:21

Hi,

I am writing a small app to connect 2 computers. When i test the server side right from my computer, it 's ok. But because i am using a shared network with a router, my friends cannot connect to my computer by using my IP (because it is a local ip). Can anyone suggest a way to overcome this problem, please?

Re: Conneting to a computer using socket

CPallini8-Dec-09 21:11

CPallini

8-Dec-09 21:11

You may configure your router for NAT [^], [^].
Smile | :)

Re: Conneting to a computer using socket

bubuzzz8-Dec-09 22:07

bubuzzz

8-Dec-09 22:07

so, that 's means i have to configure something "manually". Is there any solution by using code? I just wonder how p2p apps can work when 2 comps connected directly to each other and one comp is under a shared network OMG | :OMG:

Re: Conneting to a computer using socket

CPallini8-Dec-09 22:13

CPallini

8-Dec-09 22:13

bubuzzz wrote:
I just wonder how p2p apps can work when 2 comps connected directly to each other and one comp is under a shared network

When one of the two peer-to-peer appliacations is inside a private network, you've to configure (manually) the router for NAT.
Smile | :)

Re: Conneting to a computer using socket

Moak12-Dec-09 4:27

Moak

12-Dec-09 4:27

bubuzzz wrote:
so, that 's means i have to configure something "manually". Is there any solution by using code? I just wonder how p2p apps can work when 2 comps connected directly to each other and one comp is under a shared network OMG

As long as one of the two peers is not firewalled (incoming connections are not blocked), they can make a connection. If both are in a local network without port forwarding it gets much more trickier, but there are still possibilities (as Skype shows).

/M

Webchat in Europe Java | [Coffee]

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Re: Conneting to a computer using socket

Moak9-Dec-09 2:31

Moak

9-Dec-09 2:31

Port forwarding is not possible (see router configuration)?

Webchat in Europe Java | [Coffee]

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Re: Conneting to a computer using socket

bubuzzz10-Dec-09 21:51

bubuzzz

10-Dec-09 21:51

yup. That is what i am trying these day. Thanks all for replying me

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