C / C++ / MFC

Re: The difference between VERIFIY() and ASSERT()...

25-Sep-02 21:58

Unless AdamUK beats me to it again...

ASSERT disappears in a release build, while VERIFY doesn't.

For example,

ASSERT( ( p = somefunction() ) != 0)

VERIFY( ( p = somefunction() ) != 0)

In the first case, the code is =eliminated= and will more than likely cause some hapless (or should that be witless) developer to tear out their hair trying to figure what's gone wrong. In the second case, the code is retained, but no test is actually performed.

At least, that's how they used to work...

Steve S
[This signature space available for rent]

yourbuddy7726-Sep-02 1:17

yourbuddy77

26-Sep-02 1:17

check out this link for more info:
http://gamedev.net/reference/articles/article1846.asp

Can somebody explain these lines for me?

Mazdak25-Sep-02 21:29

25-Sep-02 21:29

	if (remaining & pAccess->dwValue)
	{
		remaining &= ~pAccess->dwValue;
//		DoSomething(pAccess->szName);
	}

remaining is a typedef DWORD structure and pAccess is a structure and dwValue is DWORD type.
What does one & mean?And what does its next line means?:remaining &= ~pAccess->dwValue;

Mazy

"If I go crazy then will you still
Call me Superman
If I’m alive and well, will you be
There holding my hand
I’ll keep you by my side with
My superhuman might
Kryptonite"Kryptonite-3 Doors Down

adamUK25-Sep-02 21:45

adamUK

25-Sep-02 21:45

Mazy,

The & operator is the bitwise 'AND' operator. Your code takes dwValue and performs a bitwise and operation with remaining. Eg if remaining = 0000101011 and dwValue = 0100011001 then the result is 0000001001 (in binary)

If the if statement is nonzero, it executes the remaining code.

x&=y is equivalent to x=x & y (the bitwise operator again)

~ is the bitwise ones complement (or NOT operator) i.e. 010101 becomes 101010 in binary.

So, remaining &=~pAccess->dwValue is equivalent to
remaining=remaining & ~pAccess->dwValue

Hence the bits in dwValue are complemented (ie. all the 1s turn to 0s and the 0s turn to 1s) it is then 'AND'ed with remaining and the result stored in remaining.

Hope this clears things up
Adam.

www.beachwizard.com/travelogue[^]

"I spent a lot of my money on booze, birds and fast cars. The rest I just squandered"
George Best.

Mazdak25-Sep-02 22:21

25-Sep-02 22:21

Thank you very much. Smile | :)

Mazy

"If I go crazy then will you still
Call me Superman
If I’m alive and well, will you be
There holding my hand
I’ll keep you by my side with
My superhuman might
Kryptonite"Kryptonite-3 Doors Down

Steve S25-Sep-02 21:46

25-Sep-02 21:46

Relatively simple, & is a binary AND, while ~ is a binary NOT.

For instance, if "remaining" contains 127 (0x7F, or 01111111 binary),
and pAccess->dwValue contains 6 (0x6, 0110 binary), the ~ flips the bits
in pAccess->dwValue, so it contains 0xFFFFFF9, and then it's ANDed with
the "remaining" value

0111 1111 (remaining)
1111 1001 (dwValue)
---------
0111 1001

which is then stored in remaining.

It's a common technique used to turn off bits in one value that are set in another.

Steve S
[This signature space available for rent]

Mazdak25-Sep-02 22:20

25-Sep-02 22:20

Thanks.I got the point. Smile | :)

listbox question

Mazdak25-Sep-02 20:59

25-Sep-02 20:59

I have list box.When I fill it for second time I want previous items deleted and new ones shown.I use ResetContent but items do not deleted.I use this code:

m_listgrowp.ResetContent();
for(int i=0;i<(int)strSidArray.GetCount();i++)
    m_listgrowp.AddString(strSidArray.GetAt(i));
strSidArray.RemoveAll();

Re: listbox question

Roman Fadeyev25-Sep-02 23:35

Roman Fadeyev

25-Sep-02 23:35

Set breakpoint to line "m_listgrowp.ResetContent()", Type "ERR,hr" in watch window. You will see the GetLastError() string message. May be, it will help you.

Re: listbox question

Mazdak25-Sep-02 23:50

Re: CString Unicode Problem!

25-Sep-02 23:50

Thanks.I'll do it. Smile | :)

CString Unicode Problem!

Daniel Strigl25-Sep-02 20:49

Daniel Strigl

25-Sep-02 20:49

I have written some code to save a CString to a file with the WriteFile API function (I prever to use the API function and not the CFile member functions).

CString str = _T("HI");

if (!WriteFile(hFile, str, str.GetLength(), &dwWrittenBytes, NULL) || 
        dwWrittenBytes != (DWORD) str.GetLength())
{
    AfxMessageBox(_T("Could not write to file."), MB_OK | MB_ICONEXCLAMATION);   
    return FALSE;
}

On Windows XP (or other Windows Systems) it works fine, but when I use the code in Embedded Visual C++ 3.0 in the Emulator I have to change the code like the following, to get the same result as under WinXP.

CString str = _T("HI");

if (!WriteFile(hFile, str, str.GetLength() * 2, &dwWrittenBytes, NULL) || 
        dwWrittenBytes != (DWORD) str.GetLength() * 2)
{
    AfxMessageBox(_T("Could not write to file."), MB_OK | MB_ICONEXCLAMATION);   
    return FALSE;
}

I have to write twice as much characters (str.GetLength() * 2) to get the same result! Is that something with Unicode? Can anyone explane me that? And, how I have to write this function that it works under both systems (XP and CE)?

(When I debug the code in Embedded VC++ 3.0 and I look the memory where the string in CString is saved, every second character is 0, like 'H|I|' --> | is for 0.)

--
Nice greets, Daniel.

567890123425-Sep-02 20:54

5678901234

25-Sep-02 20:54

Third parameter of WriteFile is buffer size in bytes. sizeof(char) in UNICODE is 2. In both cases you should write:
WriteFile(hFile, str, str.GetLength() * sizeof(TCHAR), ...

Re: CString Unicode Problem!

Daniel Strigl25-Sep-02 21:08

Daniel Strigl

25-Sep-02 21:08

Thanks!

--
Nice greets, Daniel.

Recent File List help

Chou25-Sep-02 19:18

Chou

25-Sep-02 19:18

Putting a recent file list into my MFC-based app was a no-brainer, but there's something I'm having trouble with.

If I select a file from the Recent list that's currently open, MFC magically avoids calling OnOpenDocument() in my doc class. While this is desirable behavior in most cases, for my particular app I need to reopen the file instead.

Any ideas on how to tweak the behavior?

Steve S25-Sep-02 22:04

25-Sep-02 22:04

Override the CWinApp::OpenDocumentFile ?

Steve S
[This signature space available for rent]

Chou25-Sep-02 22:43

Chou

25-Sep-02 22:43

Sounds good, except I can't figure out how to access the doc class from scope of the app. Is there a good way to do this?

Steve S25-Sep-02 23:00

25-Sep-02 23:00

Generally in situations like this, I use the "Star Wars" approach.

Use the source, Luke.;)

Without looking, I'd guess that the CWinApp version trawls through the registered document templates, and asks each of them to do it. So what you'd probably want to do is create an overridden version in a CxxxxDocTemplate derived class, that instead of activating the window, closes then reloads the document. Of course, you don't want to do that if it's an SDI app.

Steve S
[This signature space available for rent]

Chou25-Sep-02 23:35

Chou

25-Sep-02 23:35

Duh, it never occurred to me to look into overriding the doc template. Maybe that's a sign I should go to sleep. Smile | :)

Looks like I could override CDocTemplate::MatchDocType to lie in its return value about a document being open, but that sounds kind of dangerous.

Unfortunately for me, the actual decision whether or not to open a file lies in a CDocManager class, which sits out reach in the MFC dll. Sounds like I might have to look into another solution after all. Maybe maintain the Recent list myself?

Steve S25-Sep-02 23:37