Re: How to Convert vector::reference to vector::iterator ? - C / C++ / MFC Discussion Boards

Re: what is the result(union & structure)?

CPallini14-Dec-11 2:33

CPallini

14-Dec-11 2:33

Your code is utterly broken. A more compiler-friendly one could be:

C++

#include <iostream>
using namespace std;

union U
{
  struct S
  {
    short int x;
    short int y;
  }s;
  float f;
  long l;
} u1;

int main()
{
  u1.s.x=3;
  u1.s.y=4;

  cout << u1.f << endl;
  cout << u1.l << endl; 

}

Now let's have a look at the u1 memory layout (at least on my 32 bit machine):

ADDR      00 01 02 03
VALUE     03 00 04 00

where addresses are relative to &u1.
Since the (my) machine is little endian, we have the following bit configuration

BYTES   0    0    0    4    0    0    0    3
BITS  0000 0000 0000 0100 0000 0000 0000 0011

That is, for the float member,

SIGN     0
EXP      0
MANTISSA 00001000000000000000011

That is a denormalized float (see here[^]) with value

(2^-5 + 2^-22 + 2^-23) * 2^-126 = 3.6735039242275079514265571025945 * 10^-40

that looks similar to the program output: 3.67346E-040

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[My articles]

Re: what is the result(union & structure)?

Richard MacCutchan14-Dec-11 2:40

Richard MacCutchan

14-Dec-11 2:40

Excellent answer.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Re: what is the result(union & structure)?

CPallini14-Dec-11 2:42

CPallini

14-Dec-11 2:42

Thank you, Richard. Smile | :)

Re: what is the result(union & structure)?

Stefan_Lang14-Dec-11 5:34

Stefan_Lang

14-Dec-11 5:34

While C.Pallini's response may be correct, there is no guarantee, as the internal format of float is not defined by the standard and therefore compiler-specific! There may even be compiler options to use a specific representation, so the result may change depending on those options.

Also the standard does not specify that long is a 32 bit type, only that it must be at least 32 bit. While I know of no compiler that does this*, any compiler is free to use more than 32 bits, especially when the OS is not 32 bit! If for instance long were a 64 bit type, the value of l would be 3*2^48+4*2^32, which is a lot bigger than 3*2^16+4 in case of a 32 bit long type.

*compilers that support bigger than 32 bit integer types usually provide them by different names, such as 'long long' or '__int64', rather than just 'long'

Re: what is the result(union & structure)?

CPallini15-Dec-11 10:10

CPallini

15-Dec-11 10:10

As you correctly note, the particular memory layout I considered is not assured (this is why I specified 'on my 32 bit', 'little endian' machine and so on). My aim was to give him a method for investigating such matter.
Smile | :)

How to Convert vector::reference to vector::iterator ?

002comp13-Dec-11 20:21

002comp

13-Dec-11 20:21

Hello Friends

I am using vector and I used vector::iterator to iterate over the elements.
And after that I am using vector::reference = vector.back() to access last element.

Now,i want to assign all these refernce value to iterator one.

Any Ideas ?

Thanks & Regards
Yogesh

Re: How to Convert vector::reference to vector::iterator ?

C^hris L^osinger14-Dec-11 2:22

C^hris L^osinger

14-Dec-11 2:22

C++

for (int i=1;i<vec.size();i++) vec[i] = vec[0];

image processing toolkits | batch image processing

Re: How to Convert vector::reference to vector::iterator ?

Stefan_Lang14-Dec-11 5:40

Stefan_Lang

14-Dec-11 5:40

You can't. The type of vector<T>::reference is T&, and has no reference to the original vector object, only to one element of type T.

The only way to assign an iterator is either through one of the methods of vector, or by assigning another iterator.

If you want an iterator to the last element, you can do this:

C++

std::vector<int> myvector(5); // 5 elements
std::vector::iterator last = myvector.end(); // points past the last element
--last; // now points at the last element

P.S.: after rereading your question I think I may have misinterpreted your question. If this isn't what you wanted and need more help, please clarify.

Re: How to Convert vector::reference to vector::iterator ?

002comp14-Dec-11 17:30

002comp

14-Dec-11 17:30

Thanks For your Answers.
I also proceed with the Stefan Method.

Thanks A Lot.
Regards
Yogesh

how to test a compressed file in MFC?

Le@rner13-Dec-11 20:20

Le@rner

13-Dec-11 20:20

hi all,

i want to test comressed file or Archive in my MFC application.

i want its a valid zip file or not.

i have no idea from where i have to start.

please guide me and help me for this.

thanks in advance.

Re: how to test a compressed file in MFC?

Richard MacCutchan13-Dec-11 22:09

Richard MacCutchan

13-Dec-11 22:09

Use Google to find details on the different types of compressed files and their signatures.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Re: how to test a compressed file in MFC?

Le@rner13-Dec-11 23:52

Le@rner

13-Dec-11 23:52

now how to open these files and decide these are valid archive or not.

Re: how to test a compressed file in MFC?

Richard MacCutchan14-Dec-11 0:08

Richard MacCutchan

14-Dec-11 0:08

I just explained what you need to do; what more information do you need?

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Re: how to test a compressed file in MFC?

Le@rner14-Dec-11 0:35

Le@rner

14-Dec-11 0:35

on signature basis i just found file is which type not that is valid or not.

so i want any class or function using the i can find the file is valid or not.

like test method in 7zip application.

Re: how to test a compressed file in MFC?

Richard MacCutchan14-Dec-11 0:38

Richard MacCutchan

14-Dec-11 0:38

Given the problem you are trying to resolve I would think you will have to write the function yourself. There are lots of resources on the internet concerned with compressed files that will help you.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Re: how to test a compressed file in MFC?

Le@rner14-Dec-11 0:46

Le@rner

14-Dec-11 0:46

can provide any one out of this

thanks.

Re: how to test a compressed file in MFC?

David Crow14-Dec-11 3:34

David Crow

14-Dec-11 3:34

Le@rner wrote:
i want its a valid zip file or not.

Are you using some sort of ZIP library or API?

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Re: how to test a compressed file in MFC?

Le@rner14-Dec-11 17:16

Le@rner

14-Dec-11 17:16

use the LiteZip and LiteUnZip article from code project.

LiteZip and LiteUnzip[^]

i am use its dll in my application.

Re: how to test a compressed file in MFC?

David Crow15-Dec-11 2:07

David Crow

15-Dec-11 2:07

So why not post your question to that article so the author will see it? Surely he has written some sort of "zip test" functionality to that library.

Messure function execution time

columbos1492713-Dec-11 1:40

columbos14927

13-Dec-11 1:40

Hello,
i googled a lot and and dont know what is the best way to messure the time that takes an execution of a function,is there some "stopwatch" in MFC?

Thanks

Re: Messure function execution time

enhzflep13-Dec-11 1:48

enhzflep

13-Dec-11 1:48

Just use QueryPerformanceCounterFrequency and QueryPerformanceCounter.

See here[^]

Re: Messure function execution time

columbos1492713-Dec-11 2:09

columbos14927

13-Dec-11 2:09

Hey,
Just to make sure i understood right

I query the count at the begining and at the end, then i devide it by the frequency and the result is the soconds?

Thanks

Re: Messure function execution time

Stefan_Lang13-Dec-11 2:29

Stefan_Lang

13-Dec-11 2:29

A thing to note: 'to measure' is the act of determining the value of a property. 'to mess (something up)' is somewhat synonym to 'meddle' or 'create chaos'. I'll assume that by 'messure' you mean the former, not the latter. Wink | ;)

Re: Messure function execution time

Code-o-mat13-Dec-11 5:12

Code-o-mat

13-Dec-11 5:12

To 'meddle' with the 'value of a property': messure Smile | :)

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> If it doesn't matter, it's antimatter.<

Problem with owner drawn listbox and double buffering

aangerma13-Dec-11 1:26

aangerma

13-Dec-11 1:26

Hello,

I created owner drawn listbox and I used double buffering
for preventing flickering because I have a lot of data ,
the problem is that its don't present all the items and ,
whan I scroll it down and up its erases part of the items,
the code is:

C++

void HistDlg::OnDrawItem(int nIDCtl, LPDRAWITEMSTRUCT lpDrawItemStruct)
{
	if(IDC_LIST1 ==nIDCtl)
	{
		int width=lpDrawItemStruct->rcItem.right-lpDrawItemStruct->rcItem.left;
		int height=lpDrawItemStruct->rcItem.bottom-lpDrawItemStruct->rcItem.top;
		HDC memDC1 = CreateCompatibleDC(lpDrawItemStruct->hDC);
		HBITMAP hMemBmp = CreateCompatibleBitmap(lpDrawItemStruct->hDC,width , height);
		HBITMAP hOldBmp = (HBITMAP)SelectObject(memDC1, hMemBmp);
		CDC *memDC=CDC::FromHandle(memDC1);
		memDC->FillSolidRect(0,0, width, height,RGB(255,255,255));

		int	 ODI_length =  
		1 + SendDlgItemMessage(IDC_LIST1,
								   LB_GETTEXTLEN,
								   lpDrawItemStruct->itemID,
								   0);

		if (ODI_length)
		{
			wchar_t *ODI_wstr = NULL;
			ODI_wstr = new wchar_t[ODI_length];
			if (ODI_wstr)
			{
				COLORREF ODI_old_text_color;
				//get the string
				SendDlgItemMessage(IDC_LIST1,
								   LB_GETTEXT,
								   lpDrawItemStruct->itemID,
								   (LPARAM)ODI_wstr);
					
					
				memDC->DrawText(ODI_wstr,
							  ODI_length - 1,
							  &lpDrawItemStruct->rcItem,
							  DT_RIGHT);
				
			}

		}
	
		BitBlt(lpDrawItemStruct->hDC, 0, 0, width,height, memDC1, 0, 0, SRCCOPY);
		SelectObject(memDC1, hOldBmp);
		DeleteObject(hMemBmp);
		DeleteDC(memDC1);
	}
}

What doe's I'm doing wrong?

thanks

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