A pointer delimma (requesting help from pointer/dynamic array gurus) - C / C++ / MFC Discussion Boards

Re: Non-Blocking I/O From Within a Dialog

David Crow9-Jul-04 8:40

David Crow

9-Jul-04 8:40

Put the serial port stuff in a separate thread and the GUI will remain responsive.

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Re: Non-Blocking I/O From Within a Dialog

pHaze4269-Jul-04 9:06

pHaze426

9-Jul-04 9:06

I could do that, but I'd still have to have the function launching the thread wait until the serial read completed before continuing with its tasks. Otherwise, I'd have to hook a callback function or something to handle a state machine that's called after each read. I just wondered if there was any other option as far as a function I could call to do processing while I'm waiting.

Best Regards,

Phaze426

Re: Non-Blocking I/O From Within a Dialog

David Crow9-Jul-04 9:12

David Crow

9-Jul-04 9:12

pHaze426 wrote:
I could do that, but I'd still have to have the function launching the thread wait until the serial read completed before continuing with its tasks.

Nothing wrong with that (except for the "wait" part). Once the secondary thread has completed, it would post a message to the primary thread indicating it is done. At that point, the primary thread could do what it needed with the serial port data. No waiting is necessary. Make sense?

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Re: Non-Blocking I/O From Within a Dialog

palbano9-Jul-04 8:46

palbano

9-Jul-04 8:46

pHaze426 wrote:
I'm using WaitForSingleObject() with a short timeout to check whether the event has been set or I've timed out.

How are you doing that continuously without multiple threads and without blocking the UI thread? In a mesasge loop?

pHaze426 wrote:
What I want to do is cause my dialog to perform message handling (specifically redrawing) whenever WaitForSingleObject times out

Then use SendMessage() or PostMessage()

"No matter where you go, there your are." - Buckaroo Banzai

-pete

Re: Non-Blocking I/O From Within a Dialog

pHaze4269-Jul-04 9:30

pHaze426

9-Jul-04 9:30

I guess I am using threads in a roundabout sort of way. When I call CreateFile to open the serial port, I specify the OVERLAPPED I/O flag. Then, when I call ReadFile() I pass it an overlapped structure with an event handle. When it's done, it sets that event handle. (I guess this means that internally, Windows is spawning another thread for ReadFile). Anyhow. WaitForSingleObject just waits until the event handle is set, or its own timeout has expired. So... if I give the call to ReadFile a timeout of 10 seconds and the call to WaitForSingleObject a timeout of 100ms, I will get a chance to do something every 100ms until the serial I/O completes, or readfile times out after 10s.

Along the SendMessage lines, I've used:
this->SendMessage(WM_PAINT, 0, 0); from within this wait loop to no avail. Is there another message I should be sending?

Re: Non-Blocking I/O From Within a Dialog

palbano10-Jul-04 8:17

palbano

10-Jul-04 8:17

Well if you don't need to send any data the just call CWnd::Invalidate() that will cause a Paint to occur.

"No matter where you go, there your are." - Buckaroo Banzai

-pete

Re: Non-Blocking I/O From Within a Dialog

pHaze42612-Jul-04 2:30

pHaze426

12-Jul-04 2:30

Just for everyone's reference, I figured out a way to do this (granted, this way isn't all that clean and is probably more of a 16-bit windows style of doing things, but it works). Rather than using WaitForSingleObject to wait for the I/O to complete, I stuck in this:

while (MsgWaitForMultipleObjects(1,
&ol.hEvent,
FALSE,
10,
QS_ALLINPUT) !=
WAIT_OBJECT_0) {
while ( PeekMessage ( &msg, NULL, 0, 0, PM_REMOVE)) {
DispatchMessage ( &msg);
}
}

So... I just keep dispatching all the messages I received until the serial even becomes signalled. This seems to work well.

A pointer delimma (requesting help from pointer/dynamic array gurus)

NTense9-Jul-04 7:45

NTense

9-Jul-04 7:45

Ok, I have a CArray container like so:

<br />
CArray <myObject, myObject> objectList;<br />

and I declared a dynamic array in a separate class like so:

<br />
class SelectionBox<br />
{<br />
public:<br />
   //constructor , destructor, etc...<br />
   void AddContent(myObject *); // <-- this is what's I can't figure out<br />
<br />
protected:<br />
   myObject *content;    // to be used as dynamic array<br />
   unsigned long numContents;  // counter that contains the number<br />
                               // of contents in the selection box<br />
}<br />

So now I built my AddContent() function like this:

<br />
void SelectionBox::AddContent(myObject *c)<br />
{<br />
   unsigned long counter;<br />
   myObject *tempObject;<br />
   tempObject = new myObject[numContents];<br />
<br />
   tempObject = content;<br />
<br />
   content = new myObject[numContents + 1];<br />
<br />
   for(counter = 0; counter < numContents; counter++)<br />
   {<br />
      content[counter] = tempObject[counter];<br />
   }<br />
<br />
   //c->IsSelected = true;  //<- this gives me the illusion that it's working<br />
   content[numContents] = c;<br />
   //content[numContents].IsSelected = true;  // <- this is what I need to work<br />
   <br />
   <br />
   numContents++;<br />
   delete [] tempObject;<br />
} <br />

Finally, in another part of the program, I shoot the address of one of the objects stored in the CArray to the AddContent function.

At first the function appeared to be working.. That is until I later tried to manipulate the original objects in the CArray by manipulating what I thought was the pointer to them in my SelectionBox class. Then I found out that I had copies of data stored and not a pointer to the CArray data. I can't for the life of me figure out how to declare the function and pass the data so that I can store an array of pointers/addresses to the data in the CArray container. Can someone show me an example, or maybe a link to a relevant tutorial?

Re: A pointer delimma (requesting help from pointer/dynamic array gurus)

palbano9-Jul-04 8:13

palbano

9-Jul-04 8:13

I recommend you use CTypedPtrArray in your class rather than try to manage your own array. There are other options to be sure but that should suffice.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore/html/_core_Collections_Topics.asp[^]

"No matter where you go, there your are." - Buckaroo Banzai

-pete

Re: A pointer delimma (requesting help from pointer/dynamic array gurus)

NTense10-Jul-04 7:22

NTense

10-Jul-04 7:22

That worked perfectly!!!! Thanks Pete.. I didn't even know that container existed, .. which will help a quite a few more problems I've been facing. Thanks Again Smile | :)

Testing which OS I'm on

Timothy Grabrian9-Jul-04 6:15

Timothy Grabrian

9-Jul-04 6:15

Hello,
I am writing a program that needs to do diffrent stuff depending on which OS it's running.
How can I do this?
Can I do it without GetVersionEx?
Can I do it with #if(WINVER >= #)? If so what values are for which OS?

Thanks.

wWw.KruncherInc.cOm - My cool programs

Re: Testing which OS I'm on

David Crow9-Jul-04 7:01

David Crow

9-Jul-04 7:01

KingKruncher wrote:
Can I do it without GetVersionEx?

Why would you want to?

KingKruncher wrote:
Can I do it with #if(WINVER >= #)? If so what values are for which OS?

See here for values.

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Re: Testing which OS I'm on

palbano9-Jul-04 7:04

palbano

9-Jul-04 7:04

KingKruncher wrote:
Can I do it with #if(WINVER >= #)?

No, that is a compile time directive not a runtime evaluation.

"No matter where you go, there your are." - Buckaroo Banzai

-pete

Re: Testing which OS I'm on

jmkhael9-Jul-04 7:05

jmkhael

9-Jul-04 7:05

You'll eventually need to compile an exe for each version if you'll use #if(WINVER >= # method

It wont be the same exe

Papa

while (TRUE)
Papa.WillLove ( Bebe ) ;

Re: Testing which OS I'm on

Michael Dunn9-Jul-04 10:05

Michael Dunn

9-Jul-04 10:05

The purpose of GetVersionEx() is to tell you the OS version, why wouldn't you use it? There are also GetVersion() and the CRT variables _winmajor and _winminor.

--Mike--
Personal stuff:: Ericahist | Homepage
Shareware stuff:: 1ClickPicGrabber | RightClick-Encrypt
CP stuff:: CP SearchBar v2.0.2 | C++ Forum FAQ
----

Re: Testing which OS I'm on

ThatsAlok9-Jul-04 19:25

ThatsAlok

9-Jul-04 19:25

here you can use my code for this
//structure
struct NmpWindowVersion
{
public:
CString WindowName;//name of windows
int Plateform;//0 stand for single user and 1 stand for multi user
CString WindowsVersion;// contain the iformation abbt service pack etc
CString BuildNumber;
};
////function
int MeCheckVersionInfo(NmpWindowVersion &StructVar)
{
OSVERSIONINFO info;
info.dwOSVersionInfoSize=sizeof(OSVERSIONINFO);
GetVersionEx(&info);
int nMajor,nMinor;
CString BuildStr;

//getting Verion nme
switch (info.dwMajorVersion)
{
case 3: StructVar.WindowName="Windows NT 3.51";
nMajor=3;
nMinor=51;

break;
case 4: switch(info.dwMinorVersion)
{
case 0:
if(info.dwPlatformId==VER_PLATFORM_WIN32_WINDOWS)
StructVar.WindowName="Windows 95";
else
StructVar.WindowName="Windows NT 4.0";

nMajor=4;
nMinor=0;

break;

case 10: StructVar.WindowName="Windows 98 ";
nMajor=4;
nMinor=10;

break;

case 90: StructVar.WindowName="Windows Me ";
nMajor=4;
nMinor=90;

break;
}
break;

case 5: switch(info.dwMinorVersion)
{
case 0: StructVar.WindowName="Windows 2000";
nMajor=5;
nMinor=0;

break;
case 1: StructVar.WindowName="Windows XP";
nMajor=5;
nMinor=1;

break;
case 2: StructVar.WindowName="Windows Server 2003 family 2";

nMajor=5;
nMinor=2;

break;

}
break;

}

////getting Plateform ID
switch(info.dwPlatformId)
{
case VER_PLATFORM_WIN32_WINDOWS:StructVar.Plateform=0; break;
case VER_PLATFORM_WIN32_NT :StructVar.Plateform=1; break;
}

///getting Platform version

StructVar.WindowsVersion=(CString)info.szCSDVersion;

////getting the build number
BuildStr.Format("%d.%d.%d",nMajor,nMinor,LOWORD(info.dwBuildNumber));
StructVar.BuildNumber=BuildStr;
return 0;
}

-----------------------------
"I Think It will Work"
-----------------------------
Alok Gupta
visit me at http://www.thisisalok.tk

adding help to application

BlackDice9-Jul-04 6:10

BlackDice

9-Jul-04 6:10

I forgot (like I often do) to add help to my app's settings when creating my project. I'm pretty far along in the project now, so I don't want to start over, so what do I need to do to add help now since the project is already created?

If it's broken, I probably did it

bdiamond

Re: adding help to application

David Crow9-Jul-04 7:03

David Crow

9-Jul-04 7:03

Anytime you forget to do something with AppWizard, it's usually best to create a temp project using the desired settings, and then compare to see what items your project is missing.

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Re: adding help to application

BlackDice9-Jul-04 7:11

BlackDice

9-Jul-04 7:11

yeah, I thought about doing that, but I was hoping there was an easier way!! (just lazy Smile | :)

) thanks!

If it's broken, I probably did it

bdiamond

fullscreening a dialog

locoone9-Jul-04 4:47

locoone

9-Jul-04 4:47

what message handlers uses the min,max and close button

Re: fullscreening a dialog

Timothy Grabrian9-Jul-04 6:02

Timothy Grabrian

9-Jul-04 6:02

Handle WM_SYSCOMMAND
and these three values of wParam
SC_MINIMIZE
SC_MAXIMIZE
SC_CLOSE

and right before you "return 0;" you should do this:
SetWindowLong(hwnd,DWL_MSGRESULT,0); //For a dialog box

wWw.KruncherInc.com - My cool programs

CPtrList

Mahendra_7869-Jul-04 4:46

Mahendra_786

9-Jul-04 4:46

Hi,
I am trying to iterate and delete the elements (assuming atleast 1 element) in a CptrList with this:

void *pPt = NULL;
POSITION pos = NULL;
for (pos = m_points.GetHeadPosition(); !m_points.IsEmpty(); m_points.GetNext(pos)) {
// TRACE("pos: %d, %d\n", pos, NULL);
pPt = m_points.GetAt(pos);
m_points.RemoveAt(pos);
delete pPt;
}

TRACE shows that pos is not equal to NULL as it should be after the last element has been seen.
So pos != NULL check does not work contrary to the MSDN Library documentation. THIS IS ONE PROBLEM.
The OTHER is even if there are more than 1 elements the second element returned by GetAt is not
"valid" (0xcdcdcdcd) and RemoveAt asserts.
Any clues?

Regards
Mahendra

Re: CPtrList

Navin9-Jul-04 5:10

Navin

9-Jul-04 5:10

As soon as you remove the element, you invalidate the position. Here's a better way of doing it:

{
  void *pPt = NULL;
  POSITION pos = NULL;
  for (pos = m_points.GetHeadPosition(); pos != NULL; m_points.GetNext(pos)) 
  {
    // TRACE("pos: %d, %d\n", pos, NULL);
    pPt = m_points.GetAt(pos);
    delete pPt;
  }
  // Now we have a list full of invalid pointers, so remove them all

  m_points.RemoveAll();
}

"Fish and guests stink in three days." - Benjamin Franlkin

Re: CPtrList

Mahendra_7869-Jul-04 6:12

Mahendra_786

9-Jul-04 6:12

But is this ok - (re)moving from the tail end if a sub-sequence has to be removed and RQUIRES using
RemoveAt. This seems to works:

for (pos = m_points.GetTailPosition(); !m_points.IsEmpty(); m_points.GetPrev(pos)) {
pPt = m_points.GetAt(pos);
delete pPt;
m_points.RemoveAt(pos);
}
pos is still not NULL in the end though!

Or like in the MSDNL RemoveAt help!:
POSITION pos1 = NULL;
POSITION pos2 = NULL;
for (pos1 = m_points.GetHeadPosition(); (pos2 = pos1) != NULL; ) {
m_points.GetNext(pos1);
pPt = m_points.GetAt(pos2);
delete pPt;
m_points.RemoveAt(pos2);
}

Due Regards
Mahendra

Re: CPtrList

Gary R. Wheeler10-Jul-04 2:38

Gary R. Wheeler

10-Jul-04 2:38

One problem I see in your example is the line delete pPt;. This line won't work correctly. Since pPt is a void pointer, the compiler won't know which delete operator and destructor to call. This will lead to memory leaks and possibly heap corruption. A better approach would be:

while (!m_points.IsEmpty()) {
    MyType *pPt = (MyType *)m_points.RemoveHead();
    delete pPt;
}

In this case, MyType is the type of the value pointed to by members of the list.

If you use a CTypedPtrList<>, you can delete the contents of a list more simply as follows:

CTypedPtrList<MyType> m_points;
//...
while (!m_points.IsEmpty()) {
    delete m_points.RemoveHead();
}

Using CTypedPtrList you don't need type casts.

Software Zen: delete this;

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