Re: searching web - automated - C / C++ / MFC Discussion Boards

_NielsB12-Jan-08 10:55

12-Jan-08 10:55

Hello,

I try to understand memory management and pointers in C on a simple level right now.
Here is the task: concatenate 2 buffers (in this case buffA & buffB to buffAB). The values of the following code-snipets are small for debugging purposes ... imagine the size of each source buffer is much larger: how can I propper clean up the "mess" after creating buffAB?

<br />
// buffA<br />
char buffA[] = {'a'};<br />
char* p_buffA = &buffA[0];<br />
<br />
// buffB<br />
char buffB[] = {'b','b'};<br />
char* p_buffB = &buffB[0];<br />
<br />
// buffAB<br />
char buffAB[] = {'x','x','x'};<br />
char* p_buffAB = &buffAB[0];<br />
<br />
// cpy<br />
memcpy(p_buffAB, p_buffA, 1); // copy buffA to buffAB<br />
memcpy(p_buffAB+1, p_buffB, 2); // copy buffB to buffAB<br />
<br />
// buffAB is the only thing we want ... how to clean up the rest?<br />
<br />

I am thankfull for all suggesting to improve the code.

Re: Newbie Question on C Pointers

C^hris L^osinger12-Jan-08 11:03

C^hris L^osinger

12-Jan-08 11:03

since you didn't dynamically allocate anything (with new or malloc, etc), there's nothing to clean up.

image processing toolkits | batch image processing

Re: Newbie Question on C Pointers

CPallini12-Jan-08 11:58

CPallini

12-Jan-08 11:58

_NielsB wrote:
// buffAB is the only thing we want ... how to clean up the rest?

clean up is called free in C language and works on dynamic allocated memory, i.e. it should pair a previous call to malloc (or another allocation function, like calloc).
For instance:

char * pB = malloc(2);
pB[0]='b';
pB[1]='b';
/* or *pb='b'; *(pb+1)='b'; */
/* or memset(b, (int)'b', 2); */
char * pA = malloc(1);
pA[0]='a'; /* same options b has */
char * PAB = malloc(3);
memcpy(pAB, pA, 1 );
memcpy(pAB+1, pB, 2);
free(pA);
free(pB);

Note that I've omitted (to keep code compact) malloc return value check, but you must always do it in real programming, i.e.

char *p=malloc(10);
if ( ! p )
{
  /* handle error */
}
/* allocation was fine, go on

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.

[my articles]

Re: Newbie Question on C Pointers

_NielsB12-Jan-08 21:29

_NielsB

12-Jan-08 21:29

Hello again!
Thank you for your adwises Smile | :)

The real task I want to test is to append buffB to buffA. Asume there is a function-call that gives me 2 pointers to buffers (p_buffA and p_buffB) and the size of each of them (n_A and n_B). The function should retur the new pointer to buffA and the new size (f.e. saved in a struct).

Now I am using c++ new / delete to allocate and free memory.

<br />
// buffA<br />
int n_A = 30; <br />
char* p_buffA = new char[n_A];<br />
memset(p_buffA, (int)'a', n_A);<br />
<br />
// buffB<br />
int n_B = 50;<br />
char* p_buffB = new char[n_B];<br />
memset(p_buffB, (int)'b', n_B);<br />
	<br />
// append buffB to buffA, use temp buffAB<br />
int n_AB = n_A + n_B;<br />
char* p_buffAB = new char[n_AB];<br />
	<br />
// cpy<br />
memcpy(p_buffAB, p_buffA, n_A); // copy buffA to buffAB<br />
memcpy(p_buffAB+n_A, p_buffB, n_B); // copy buffB to buffAB<br />
<br />
// buffA and buffB are no longer neaded -> delete<br />
delete [] p_buffA;<br />
delete [] p_buffB;<br />
<br />
// set buffA to buffAB<br />
p_buffA = p_buffAB;<br />
n_A = n_AB;<br />
<br />

Is this snipet ok?
Are there better ways to solve this issue?

Re: Newbie Question on C Pointers

CPallini12-Jan-08 23:19

CPallini

12-Jan-08 23:19

It is ok. But you have always check for pointer validity, for instance

char* p_buffA = new char[n_A];
if ( !p_buffA )
{
  // handle error
}
// go on with program
...

You have also the option to use realloc:

// buffA
int n_A = 30; 
char* p_buffA = (char*) malloc(n_A);
memset(p_buffA, (int)'a', n_A);

// buffB
int n_B = 50;
char* p_buffB = (char*) malloc(n_B);
memset(p_buffB, (int)'b', n_B);

// append buffB to buffA, without use temporary
char* p_buffA = realloc[p_BuffA, n_A + n_B];

// cpy
memcpy(p_buffA + n_A, p_buffB, n_B); // copy buffB to new buffA

// buffB is no longer neaded, delete
free(p_buffB);

(as stated above you've always to check return value of allocation function)

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.

[my articles]

Re: Newbie Question on C Pointers

_NielsB12-Jan-08 23:45

_NielsB

12-Jan-08 23:45

Looks nice Big Grin | :-D

Thnaks alot.

searching web - automated

Force Code12-Jan-08 10:34

Force Code

12-Jan-08 10:34

Trying to search the web in a loop, hitting the search engine with a new query with each iteration (with thousands of terms for this particular application). Don't know frankly if that's even allowed, as google kicks you off if you try to do it. But the following code below uses the COM IWebBrowser2 interface to an open InternetExplorer. Don't know if that is considered antiquated or there's a faster way to do it, because right now I'm just getting about a page per second. Is there a faster way than the following:

SHDocVw::IWebBrowser2Ptr brwsr = NULL;
.
.
.
brwsr = SHDocVw::IWebBrowser2Ptr(spDisp);

.
.
.

strcpy(srch_engn,"http://www.mysearch.com/search/GGmain.jhtml?searchfor");
sprintf(szURL,"%s=%s+%%22",srch_engn,q_misc);
char* szSrch = szURL+strlen(szURL);

while (1) {

  strcpy(szSrch,getNextSrch(...));

  BSTR bstr = ConvertStringToBSTR(szURL);

  brwsr->Navigate(bstr);

  VARIANT_BOOL busy;
  READYSTATE rs;
  while(1) {
    Sleep(200);
    brwsr->get_Busy(&busy);
    if (!busy) break;
    brwsr->get_ReadyState(&rs);
    if (rs == READYSTATE_LOADED) break;
    if (rs == READYSTATE_COMPLETE) break;
  }

  brwsr->Stop();

  .
  .
  .

}

Re: searching web - automated

Force Code12-Jan-08 10:46

Force Code

12-Jan-08 10:46

After the Stop statement above, here's how I process the returned page (as I guess that might be the bottleneck):

if (rsltDoc = IHTMLDocument2Ptr(brwsr->GetDocument())) {
       HRESULT hr = rsltDoc->get_body(&body);
   if (!FAILED(hr)) {
         BSTR bstr_b;
     hr = body->get_innerText(&bstr_b);
     if (!FAILED(hr)) {
           char* szBody = ConvertBSTRToString(bstr_b);
       if (!strstr(szBody,szNotFound)) {
         pf_fmt(szSrch);
         fprintf(f,"%s\n\n",szSrch);
         printf("%s\n\n",szSrch);
         bMatch = TRUE;
       }
       delete [] szBody;
       SysFreeString(bstr_b);
     }
   }
     }

Switching off hibernation [modified]

tibiz12-Jan-08 8:33

tibiz

12-Jan-08 8:33

Hello

How can I disable/enable hibernation programatically in C++ in VS.NET ?

Or need to change registry values?

Thank you for any help ..will really help

modified on Saturday, January 12, 2008 3:08:48 PM

Re: Switching off hibernation

David Crow12-Jan-08 9:44

David Crow

12-Jan-08 9:44

tibiz wrote:
Or need to change registry values?

You can use RegSetValueEx().

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

Re: Switching off hibernation

tibiz12-Jan-08 9:47

tibiz

12-Jan-08 9:47

Thanx, I know about registry setting.

I'm trying using the GLOBAL_POWER_POLICY and if it will not help, maybe the reg. settings. Can you post me the place where to find the reg. entry ?

Re: Switching off hibernation

David Crow12-Jan-08 10:11

David Crow

12-Jan-08 10:11

tibiz wrote:
Can you post me the place where to find the reg. entry ?

It will be in the following value:

HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Power\Heuristics

Ok, let's have a Working code

tibiz12-Jan-08 11:10

tibiz

12-Jan-08 11:10

<br />
bool SetHibState(BYTE state)<br />
{<br />
	HKEY hKey;<br />
	HKEY hk;<br />
<br />
	if(RegOpenKeyEx(HKEY_LOCAL_MACHINE, SUBKEY, 0, KEY_QUERY_VALUE, &hKey) == ERROR_SUCCESS) {<br />
<br />
		BYTE byteRegData[255];<br />
		DWORD dwBufLen = 255;<br />
<br />
		LONG lRet;<br />
		if((lRet = RegQueryValueEx(hKey, VALNAME, NULL, NULL, byteRegData, &dwBufLen)) == ERROR_SUCCESS) {<br />
			RegCloseKey(hKey);<br />
<br />
			byteRegData[6]=(BYTE)state;<br />
<br />
			//for(int i=0;i<dwbuflen;i++)><br />
			//printf(" %x", byteRegData[i]);<br />
<br />
			if(!RegCreateKey(HKEY_LOCAL_MACHINE, SUBKEY, &hk)) {<br />
<br />
				RegSetValueEx(hk, VALNAME, 0, REG_BINARY, (LPBYTE)byteRegData, (DWORD)dwBufLen);<br />
				RegCloseKey(hk);<br />
			}				<br />
			else return false;<br />
		}<br />
		else {<br />
			RegCloseKey(hKey);<br />
			return false;<br />
		}<br />
	}<br />
<br />
	return true;<br />
}<br />
</dwbuflen;i++)>

.... but the problem is, the system won't give any reaction to the change, in power options is still the old setting

Re: Switching off hibernation

Blake Miller22-Jan-08 11:44

Blake Miller

22-Jan-08 11:44

If you are merely trying to keep a system 'alive' consider investing these coding tips into your application, from the MDSN topic: Using Power Management, instead of disabling the hibernate policy altogether, just keep system awake while your program is running. If user does NOT run your program, then there might be no reason the system should not hibernate. If yu need to perform some task at a scheduled time, then let it hibernate, but consider setting a waitable timer. This will wake system up and your process will resume.

context menu cause flicking

followait12-Jan-08 5:51

followait

12-Jan-08 5:51

I've tested it doesn't flick without popping up the context menu.
With the menu, the backgroup is erase automatically.
Any way to make it flicking free?
Thanks a lot.

Re: context menu cause flicking

Mark Salsbery12-Jan-08 7:34

Mark Salsbery

12-Jan-08 7:34

followait wrote:
With the menu, the backgroup is erase automatically.

backgroup? What's behind/under the menu? One of your windows?

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: context menu cause flicking [modified]

followait12-Jan-08 15:19

followait

12-Jan-08 15:19

Yes, the view.
In OnRButtonDown I draw the memory graphics(GDI+) and call CView::OnRButtonDown.
I have the same code in CView::OnLButtonDown, it doesn't flick with no context menu.

The framework (generated by BCG app wizard) has such a function:

void CMyView::OnContextMenu(CWnd*, CPoint point)
{
	theApp.ShowPopupMenu (IDR_CONTEXT_MENU, point, this);
}

modified on Saturday, January 12, 2008 9:28:51 PM

Re: context menu cause flicking

Mark Salsbery14-Jan-08 6:15

Mark Salsbery

14-Jan-08 6:15

Did you ever solve this?

If not, can you reproduce it in a simple project?

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

difference between stack & heap

raaf12-Jan-08 4:57

raaf

12-Jan-08 4:57

Can anybody tell me the difference between stack & heap? or any relating tutorial.

Re: difference between stack & heap

CPallini12-Jan-08 5:44

CPallini

12-Jan-08 5:44

A quick Google search gave (among others) http://www.cs.jcu.edu.au/Subjects/cp2003/1997/foils/heapAndStack/heapAndStack.html[^].

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.

[my articles]

Re: difference between stack & heap

raaf12-Jan-08 16:13

raaf

12-Jan-08 16:13

thanks for ur help

Re: difference between stack & heap

Maxwell Chen12-Jan-08 8:50

Maxwell Chen

12-Jan-08 8:50

A simple difference is:
1. To declare a variable of size 4G in the stack will usually crash.

struct A {
  unsigned char[0xFFFFFFFE]; // 4GB
} obj;

2. To allocate a variable of size 4G in the heap is OK.

A* p = new A; // 4GB

Maxwell Chen

Re: difference between stack & heap

CPallini12-Jan-08 10:28

CPallini

12-Jan-08 10:28

Hey Max:

(1) There's no hope to compile that code.
(2) 4GB=0x100000000

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.

[my articles]

Re: difference between stack & heap

Maxwell Chen12-Jan-08 10:36

Maxwell Chen

12-Jan-08 10:36

CPallini wrote:
(2) 4GB=0x100000000

Approximately... Poke tongue | ;-P

Maxwell Chen

How Can Create a Project multimedia(video & Sound) Conclave To 3 Computer

vahid akbari12-Jan-08 4:51

vahid akbari

12-Jan-08 4:51

How Can Create a Project multimedia(video & Sound) Conclave To 3 Computer
pc1=server
pc2=station 1
pc3=station 2

pc1 = administrator all computer(pc2,pc3) and veiw both pc and control
pc2 = can see computer pc3 to okey pc3
pc3 = pc2

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.