C / C++ / MFC

16-Sep-07 20:03

I wonder if somebody could remind me the method of defining a struct where you can set the bits of a member directly, without using the bitwise OR or bitshift operators. ie. I have a struct with 2 members

struct foo
{
BYTE Repaint;
BYTE Offset;
};

The offset member requires only 4 bits, and the repaint only 1. Idealy they could be combined so that the Repaint member uses the high order bit of the same BYTE. I remember seeing a way to do this, possibly using a union, but I cannot remember how or where I saw it.

Waldermort

Michael Dunn16-Sep-07 20:20

Michael Dunn

16-Sep-07 20:20

Add the number of bits after the member names:

struct foo
{
  BYTE Repaint:1;
  BYTE Offset:4;
};

--Mike--
Visual C++ MVP Cool | :cool:

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Waldermort17-Sep-07 2:03

17-Sep-07 2:03

Thanks Mike, that's exactly what I was looking for. Can't think why I thought a union had something to do with it, possibly one of MS's wierd structs...

Waldermort

Iain Clarke, Warrior Programmer

Iain Clarke, Warrior Programmer17-Sep-07 4:20

17-Sep-07 4:20

There is usefulness in using a union as well.

Below is a code snippet from my software:

union __ChannelsOn
{
    BYTE    Mask;
    struct {
        BYTE    On1 : 1;
        BYTE    On2 : 1;
        BYTE    On3 : 1;
        BYTE    On4 : 1;
        BYTE    OnTOF   : 1;
        BYTE    Unused  : 1;
        BYTE    MasterOn: 1;
        BYTE    ScanOn  : 1;
    } Bits;
} ChannelsOn;

This is mirroring a register in some hardware I talk to. I can set the variable by twiddling individual bits:

ChannelsOn.Bits.MasterOn = 1<code>, and also use it as a whole byte...   <code>SendStuffToHardware (...., ChannelsOn.Mask, ....);

So, while its not a linked language construct, it's often handy.

Unions can also be usedto ensure the overall variable ends up the correct size.

Iain.

Randor 16-Sep-07 21:58

Randor

16-Sep-07 21:58

I am having trouble understanding what it is your trying to accomplish, however I believe you want to manipulate the bits in these bytes indirectly without accessing struct members, although I can't imagine why you would want to do this. Perhaps you have a high performance application and are attempting to shave off a few operations in a critical function.

If speed is your goal, then you should work with the fastest datatype on a 32 bit operating system, sizeof(int). On a modern Intel Core 2 Duo the following function is the fastest, you should define bit masks in your application. The function does not generate any branching op codes, quite fast.

unsigned int bitset(unsigned int bits,unsigned int mask,bool flag)
{
	bits = (bits & ~mask) | (-flag & mask);
}

Best Wishes,
-Randor (David Delaune)

help

john563216-Sep-07 19:50

john5632

16-Sep-07 19:50

void CDisplayBody::OnNavigateComplete2(LPCTSTR strURL)<br />
{	<br />
CString pszText="<html><head><body>Hi How r u</body></head></html>";<br />
	if (GetBusy())                          // See if it's busy with something else<br />
		Stop();        <br />
<br />
	// Get a pointer to the HTML Document Object Model's interface<br />
	IDispatch * pDisp = GetHtmlDocument();<br />
	if (!pDisp)<br />
		return;<br />
<br />
	IHTMLDocument2* pDoc;<br />
	if (SUCCEEDED(pDisp->QueryInterface( IID_IHTMLDocument2, (void**)&pDoc )))<br />
	{<br />
		// Empty URL and parameters opens the current document<br />
		CComBSTR    bstrURL;<br />
		CComVariant varDummy;<br />
		pDoc->open(bstrURL, varDummy, varDummy, varDummy, NULL);<br />
<br />
		// Create a safearray to store the HTML text<br />
		SAFEARRAY      *pSA;<br />
		SAFEARRAYBOUND  saBound = {1, 0};<br />
		pSA = SafeArrayCreate(VT_VARIANT, 1, &saBound);<br />
<br />
		// Copy the HTML into the one and only element<br />
		VARIANT   *pVar;<br />
		CComBSTR   bstrHTML = pszText;              // Load the text<br />
		varDummy = bstrHTML;                        // .. into a variant<br />
<br />
		SafeArrayAccessData(pSA, (void**)&pVar);    // Access safearray data<br />
		pVar[0] = varDummy;                         // Set the text data<br />
		SafeArrayUnaccessData(pSA);                 // Release access<br />
<br />
		// Write the HTML as the document's new text<br />
		pDoc->write(pSA);                           // Overwrite HTML<br />
		pDoc->close();                              // Update browser<br />
<br />
		SafeArrayDestroy(pSA);                      // Finished with the safearray<br />
		pDoc->Release();                            // Don't forget to release the reference<br />
<br />
	}<br />
	<br />
}<br />

This code is to display html in html view But the statement (IDispatch * pDisp = GetHtmlDocument();)return Null .Why ? plz help

Re: help

Hamid_RT16-Sep-07 21:56

Hamid_RT

16-Sep-07 21:56

Where do you use of strURL and do you want to show a html file?

StartService in vista

samira forooghi16-Sep-07 19:39

Re: StartService in vista

16-Sep-07 19:39

hi every one
i wrote one mfc project and called StartService Api .
it work in windows xp correctly but in vista this Api returned 0;
please help me.

Hamid_RT16-Sep-07 21:59

Hamid_RT

16-Sep-07 21:59

Did you use of GetLastError for see error information?

Re: StartService in vista

sudarshan12416-Sep-07 22:21

sudarshan124

16-Sep-07 22:21

hi ,
first tell me did u start u r service under system or admin. context. i think if u start under admin context then in vista u need to give Manifest.

Re: StartService in vista

samira forooghi16-Sep-07 23:21

16-Sep-07 23:21

thanks of my dear friends

i fined my problem.it was in registery .
when i deleted some key in Windows registry ,my program worked correctly.

Good Luck

\\\\.\\

samira forooghi16-Sep-07 19:31

16-Sep-07 19:31

hi every one
whats the means of \\\\.\\ in path?
current directory or system directory?

please help me.

Re: \\\\.\\

Michael Dunn16-Sep-07 19:34

Michael Dunn

16-Sep-07 19:34

\\.\ is used when opening a device or device driver on the local computer. The dot is used in place of a computer name.

--Mike--
Visual C++ MVP Cool | :cool:

LINKS~! Ericahist | PimpFish | CP SearchBar v3.0 | C++ Forum FAQ

I work for Keyser Söze

Re: \\\\.\\

samira forooghi16-Sep-07 19:46

Problem with RegEnumValue()

16-Sep-07 19:46

thanks dear Michal

in all windows?
(vista????)

Re: \\\\.\\

Hamid_RT16-Sep-07 22:24

Hamid_RT

16-Sep-07 22:24

I guess maybe you want to see some about localsystem account so see LocalSystem Account[^]

GauranG Shah16-Sep-07 19:20

GauranG Shah

16-Sep-07 19:20

Hello Friends.

I am Using RegEnumValue() to Obtain the Names of the Values in the Specified Registry. But Its Not Working correctly. I dont know where I am doing the mistake. According to me the code is perfectly OK. But see if u can Find any Bug and can HELP me.

When I debug the Following in Code it just Show me the Last Value Name int he Registry MyApplication while there is eight Values. I get Other Values as Empty String.(String Values).

HKEY hKey;<br />
DWORD dValue;<br />
RegOpenKey(HKEY_CURRENT_USER,L"Software\\MyApplication",&hKey);<br />
RegQueryInfoKey(hKey,NULL,NULL,NULL,NULL,NULL,NULL,&dValue,0,0,0,0);<br />
 for(int i=0;i<dValue;i++)<br />
	 {<br />
	RegEnumValue(hKey,i+0,ValueName,&size,0,0,0,0);<br />
	SendMessage(hCombo,CB_ADDSTRING,(WPARAM)0,(LPARAM)ValueName);<br />
	 }

Re: Problem with RegEnumValue()

Roger Broomfield16-Sep-07 19:48

Roger Broomfield

16-Sep-07 19:48

The 4th parameter to RegEnumValue() ?
lpcValueName [in/out] should be the size of the buffer before the call, after the call its the number of characters returned, being in a for loop you should be setting that before the call everytime.

Re: Problem with RegEnumValue()

GauranG Shah16-Sep-07 19:57

GauranG Shah

16-Sep-07 19:57

Thnx a lot for Your Help. Now Its Woking Correctly.

Big Grin | :-D

Is there any way to let a process write some bytes to itself's PE file?

samfromcn16-Sep-07 19:08

samfromcn

16-Sep-07 19:08

I have a PE file a.exe, I hope that during a.exe is running, it can write some bytes to a.exe's .rdata block. If you have any idea helpful to me, please tell me, thanks a lot. Blush | :O

Re: Is there any way to let a process write some bytes to itself's PE file?

Waldermort16-Sep-07 20:11

Re: Is there any way to let a process write some bytes to itself's PE file?

16-Sep-07 20:11

Why would you want to do that? The PE header is only used for the initialization of the process, once the main thread has started execution it is not used anymore.

What are you trying to do exactly, perhaps there is another method?

Waldermort

samfromcn16-Sep-07 22:45

samfromcn

16-Sep-07 22:45

I am writting register part of my software. When user enter the right register code, I want to modify some Bytes in the a.exe file's to remember this. And it means I need write some bytes to the a.exe file when it is running.

Re: Is there any way to let a process write some bytes to itself's PE file?

Waldermort17-Sep-07 4:06