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A huge difference is that for an object the constructor is not guaranteed to be called when using ::malloc(), but it's guaranteed to be called when using new.
The same goes for ::free() and delete.
Read Stroustrup's FAQ for more info: clickety[^].
"It's supposed to be hard, otherwise anybody could do it!" - selfquote
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I know what the difference is between the two, but I would like to know why he thinks using malloc is worse than using new. Granted, using new has become the standard in c++ code, but there are instances where using malloc has proved to be better, take the resizing of dynamic arrays for example or needing to allocatate an instance without calling the c'tor ( not that I can think of a valid reason for doing this ).
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WalderMort wrote: but there are instances where using malloc has proved to be better
Sorry, WalderMort, I don't know what you're referring to by this statement.
If you follow the link I provided in my previous post and scroll up a few lines, you will find this:
Stroustrup wrote: There is no performance difference between malloc() and new when you take initialization into account.
In my humble opinion, if you find yourself in a situation where you think you benefit from the use of ::malloc() in C++, you're probably not using the language in the way Stroustrup intended.
This is also how I interpret his statement a little bit further down:
Stroustrup wrote: If you feel the need for realloc() - and many do - then consider using a standard library vector.
WalderMort wrote: needing to allocatate an instance without calling the c'tor
I cannot possibly think that I will find myself in a situation where I actually want to use uninitalized data, the compiler would also complain about it. If you want to create a copy of an existing object, you don't use ::memcpy() but you would rather use the copy constructor or the assignment operator.
But that may be just me...:-> ...but I think not...
"It's supposed to be hard, otherwise anybody could do it!" - selfquote
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voorugonda prashanth wrote:
when it reaches maximum of virtual memory client application crashes.
i believe we cannot be much use for you as you urself have to debug the application to find cause of memory leaks
"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
Support CRY- Child Relief and you
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I run the program by Microsoft Visual Studio 2005 on the Windows® XP
operating system.
I try to run the basic program of RTC.
There is no compile error, but there is a run-time error.
==> hr = pIDispatch->QueryInterface
(IID_IRTCSessionStateChangeEvent,reinterpret_cast<void**> (&pISessionState));
The error message is __vfptr = CXX0030: Error: expression cannot be
evaluated.
The code is followed.
Can somebody tell me where is the problem?
#include "stdafx.h"<br />
#define _WIN32_DCOM<br />
#include <windows.h><br />
#include <Winuser.h><br />
#include <malloc.h><br />
#include <objbase.h><br />
#include <Rtccore.h><br />
#include <oleauto.h><br />
#include <iostream><br />
#include <unknwn.h><br />
#pragma comment(lib, "ole32.lib")<br />
#pragma comment(lib, "Uuid.lib")<br />
using namespace std; <br />
int _tmain(int argc, _TCHAR* argv[])<br />
{ <br />
HRESULT hr = S_OK; <br />
CoInitializeEx(NULL,COINIT_APARTMENTTHREADED);<br />
IRTCClient *pIRTCClient;<br />
hr = CoCreateInstance( CLSID_RTCClient, NULL, CLSCTX_INPROC_SERVER, IID_IRTCClient,<br />
reinterpret_cast<void **> (&pIRTCClient) );<br />
hr = pIRTCClient->Initialize();<br />
long lEventMask;<br />
lEventMask = RTCEF_ALL; <br />
hr = pIRTCClient->put_EventFilter(lEventMask);<br />
DWORD dwEventCookie;<br />
IUnknown *pUnknown = NULL;<br />
IConnectionPointContainer *pCPC = NULL;<br />
IConnectionPoint *pCP = NULL;<br />
hr = pIRTCClient->QueryInterface( IID_IUnknown, reinterpret_cast<void**> (&pUnknown) );<br />
hr = pIRTCClient->QueryInterface( IID_IConnectionPointContainer, reinterpret_cast<void**> (&pCPC) );<br />
hr = pCPC->FindConnectionPoint( IID_IRTCEventNotification, &pCP );<br />
hr = pCP->Advise( pUnknown, &dwEventCookie ); <br />
pCP->Release();<br />
pCPC->Release();<br />
pUnknown->Release(); <br />
hr = pIRTCClient->put_ListenForIncomingSessions( RTCLM_BOTH ); <br />
BSTR bstrLocalURI = NULL;<br />
BSTR bstrDestURI = NULL;<br />
RTC_SESSION_TYPE SessionType;<br />
IRTCSession *pIRTCSession = NULL;<br />
IRTCProfile *pIRTCProfile = NULL; <br />
SessionType = RTCST_PC_TO_PC ;
if(SessionType == RTCST_PHONE_TO_PHONE){bstrLocalURI = SysAllocString(_T("tel:+14255550123"));}<br />
bstrDestURI = SysAllocString(_T("sip:22500@163.22.20.154")); <br />
hr = pIRTCClient->CreateSession( SessionType, bstrLocalURI, pIRTCProfile,RTCCS_FORCE_PROFILE,&pIRTCSession );<br />
IRTCParticipant *pIRTCParticipant;<br />
hr = pIRTCSession->AddParticipant( bstrDestURI, NULL, &pIRTCParticipant );<br />
hr = pIRTCSession->Terminate(RTCTR_NORMAL);<br />
IRTCSessionStateChangeEvent *pISessionState = NULL;<br />
RTC_SESSION_STATE SessionState;<br />
IDispatch *pIDispatch = NULL; <br />
hr = pIDispatch->QueryInterface(IID_IRTCSessionStateChangeEvent,reinterpret_cast<void**> (&pISessionState));<br />
hr = pISessionState->get_State(&SessionState);<br />
switch(SessionState)<br />
{<br />
case RTCSS_DISCONNECTED:<br />
{<br />
pIRTCSession->Release();<br />
pIRTCSession = NULL;<br />
break;<br />
}<br />
}<br />
return 0;<br />
}<br />
<br />
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what can i do , i have this error when i try to open the recordset : "dynamic cursors not supported by odbc driver"!
My recordset :
-snapshot , .... Open(CRecordset::skipDeletedRecords)
what can i do ? because i want to skip deleted records !
(mark to delete)(i understand)!because i have many records mark for delete and the cursor do not pass over them !
Bravoone
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Without seeing your actual code that is creating/opening the record set, it's hard to offer any sort of answer.
As you are navigating through the result set, you can use the IsDeleted() method before allowing access to the record.
"Approved Workmen Are Not Ashamed" - 2 Timothy 2:15
"Judge not by the eye but by the heart." - Native American Proverb
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The problem may be elsewhere since you haven't shown all the code in your Open() call (if that
IS the entire Open() call it is incorrect) but you can use CRecordset::IsDeleted() when traversing
the recordset.
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Hi All,
I have a problem, its eating lot of time .
i have 24 bit Bitmap file . i want to convert tht file to 8 bit Bitmap file .
can any one know algorithm to convert it . i want to do it in using c-code . NOT USING ANY SOFTWARES OR ANY EDITORS (LIKE PAINT BRUSH)
how can i do it ? can any one suggest me a way .
i will be thank full if you give me any links to do it .
Regards
Vijay
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The easiest way is to create a new bitmap of the same size but with an 8 bit colordepth, then BitBlt your 24-bit bitmap to the new 8-bit bitmap. The OS will take care of the color conversion for you.
Another way is to cteate a DIB from your 24-bit bitmap, loop through the bits and convert each to it's 8-bit equivlent. Doing it this way, you must remember that an 8-bit image has a pallette and each pixel is the index into the pallette, whereas a 24-bit has no pallete and each pixel holds the color.
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Hi Walder ,
Thanks for your time for replying me .
you suggested me 2 ways to me
if i want to use the Another way "Creating DIB " . When i convert 24 bit to 8 bits equivlent wht would be the formula for converstion(24 bit to 8 bit ) and more over how can i get the color platte for that conversion . "Will the OS will do it for me , or i should need to write a code to create a color table "
Regards
Vijay
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There is no direct formula for converting.
Look at the GDI references for bitmaps on MSDN. The BITMAPINFO contains a BITMAPINFO header which details the bitmap, and an array of RGBQUAD structures which is the colors used in the pallette. To convert using a DIB, first create that array of RGBQUAD structures, and use it to create a pallette ( The colors you use depend on you).
Then for each RGB pixel value in the 24-bit bitmap call GetNearestPaletteIndex(), this will give you the index of the color in the pallette you just created. Use this index as the pixel value in your new 8-bit bitmap. Ultimatly you want to build a new array of pixel values.
To save, all you need to do is create a new BITMAPINFO and BITMAPINFOHEADER for the new image, using the new array of RGBQUAD's and the new array of pixel values.
To get you started, look at Chris Maunders DIB wrapper here[^].
If you let the OS do the convertion for you, it will use the standard color pallette. In most case this is not a problem, but the standard pallette contains a range of all the colors from white to black. If your bitmap contains mostly the color green for example, you will lose a lot of colors since the pallette has colors you don't want to use.
Most paint programs will scan the image before doing a bitdepth conversion, and create a pallette that contains only the colors in the bitmap. You will still lose a lot of colors but not as many as with using a standard pallette.
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Thank you very much for your help BOSS. 
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why do you want to do this ? Do you want it to be smaller, or is there another reason ?
I'm asking because if the reason is for a toolbar or similar, you can use 24 bit images, if you set it up right
Christian Graus - C++ MVP
'Why don't we jump on a fad that hasn't already been widely discredited ?' - Dilbert
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Hi Christian,
No i want to convert to PRN format , which i have done for 8 bit.
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OK, then just let BltBlt convert it for you
Christian Graus - C++ MVP
'Why don't we jump on a fad that hasn't already been widely discredited ?' - Dilbert
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Also, if mapping to the system palette doesn't give you the quality you want then try a halftone
palette. Even better, there's the Gervautz-Purgathofer octree color quanitization algorithm.
Check out this MSJ article: Wicked Code [^]
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Hi!
I would like to know whether the value of dmPaperSize in DEVMODE structure for custom papersize varies with the printer used. How is it possible to know the dmPaperSize for custom paper size for a particular printer.
Thanks
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vcpgmr wrote: is it possible to know the dmPaperSize for custom paper size for a particular printer
Hi,
Did you try like this?
pDevModeOutput->dmFormName = NewFormName;
pDevModeOutput->dmPaperSize = DMPAPER_USER;
pDevModeOutput->dmPaperLength = CustomLength;
pDevModeOutput->dmPaperWidth = CustomWidth;
Krishnakumar
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Hi!,
Thank you for the reply.
Yes I had tried the way you said, but its not working. Are there any other variables/properties which we need to set before setting value to DocumentProperties
Thank you
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how to write and read into files using vc++ for smartphones
i am able to write into file.
i am not able to read and append the file.
after reading how do i print that data on smartphones?
please send me the sample code.
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Can you show us the code that you have tried that does not work?
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