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Since the base class is protected, none of the members of the base class can be accessed using its object or pointer.
All access will only be possible withing the class itself.
So you will not be able to access any members of the class using the x pointer.
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I know, but that doesn't really answer my question. I'm not looking to access any members (except the constructor, which i'm guessing is called when the compiler tries to solve the cast). The question was whether I can change this without changing the protected to public (i.e. make ONLY the constructor public).
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If you do not want to access any members, you really don't need an object.
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We're only accessing members of the sub-class that are overwritten and declared public in the super-class, so it does work. For the implicit cast, the constructor of the base class has to be public. Can this be changed?
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Not really. The protected keyword is doing what it's supposed to do by disallowing the cast.
Steve
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Try it with explicit conversion, like:
...
B* y;
f((A *)y);
> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Computers don't kill programs, users kill programs <
> "It doesn't work, fix it" does not qualify as a bug report. <
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This does work but it's exactly the thing i'm trying to avoid.
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An ugly solution but you could write "wrapper" methods that do the explicit conversations and call the originals, so if you have:
int f(A *pA) {}
then you could create
int f(B *pB) { return f((A *)pB); }
Of course i do not know what exactly you are trying to achieve so this might or might not solve your problem. And even if it does, you'd have to do this kind of crap for every method you want to use so i supose it's not a comfortable solution at all...
> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> Computers don't kill programs, users kill programs <
> "It doesn't work, fix it" does not qualify as a bug report. <
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No, no way without an explicit cast or maybe a using statement in the derived class. What you're saying is that B is a class that can use A's public members but no one else can. There's no safe reason why you'd want to convert a B * to an A* - the two aren't type compatible.
I'm not trying to be (too) judgemental here, but have you ever considered you're programming in the wrong language? In both your recent posts you've wanted a duck-typed language, one that really doesn't give two hoots what you do with objects - they'll make up their minds at run time whether they want to play or not. If that's the case then use something like Smalltalk or Python that explicitly allows what you want to do - C++ is always going to frustrate you with its stronger typing and lack of emphasis on allowing programmers to use arbitrary runtime type conversions.
Cheers,
Ash
PS: I've think I've finally grokked what your problem is - have a look at the post I've just made in the other thread on this subject.
modified on Thursday, June 17, 2010 4:37 AM
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Yet you are being judgemental. I'm merely trying to take code that is already written for quite some time and adapt it. It wasn't me who wrote it, just trying to make it easier to use. If it were up to me I would have also taken a totally different approach. But it's not.
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You're not actually trying to make it easier to use, what you're trying to do is subvert the type system and turn off all the alarm bells. That's fairly unfriendly for the poor mug that comes after you - the poor sod who finds that things aren't behaving the way any sane and experienced C++ programmer expected it to.
So if you don't want to change any existing code (e.g. to convert it to use template functions) then keep the casts. It signals to future maintainers that there's something a bit weird here and they should watch their nuts.
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Basically, you want to break the rules of C++ and then complain about having to use an explicit cast to inform the compiler you really do want to break the rules and you don't care about the consequences. Why are you so resistive to the casts? And if this is a production environment, you need to inform future maintainers that you at least thought about the consequences of breaking the rules.
Once you agree to clans, tribes, governments...you've opted for socialism. The rest is just details.
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Does anyone know if it's possible to print graphics using Direct2D together with a printer-based HDC (i.e. CPrintInfo, DoPreparePrinting(), etc)?
Using the ID2D1DCRenderTarget interface and the BindDC method works just fine when drawing to a screen-based DC (or to a bitmap, which is blitted to screen later), but when the DC represents a printer the BindDC method returns E_INVALIDARG.
D2D1_RENDER_TARGET_PROPERTIES props = D2D1::RenderTargetProperties(
D2D1_RENDER_TARGET_TYPE_HARDWARE,
D2D1::PixelFormat(DXGI_FORMAT_B8G8R8A8_UNORM, D2D1_ALPHA_MODE_IGNORE),
0,
0,
D2D1_RENDER_TARGET_USAGE_NONE,
D2D1_FEATURE_LEVEL_DEFAULT);
ID2D1DCRenderTargetPtr pRT;
Globals::g_D2DFactory->CreateDCRenderTarget(&props, &pRT);
int sizeX=pDC->GetDeviceCaps(HORZSIZE);
int sizeY=pDC->GetDeviceCaps(VERTSIZE);
CRect rect(0, 0, sizeX, sizeY);
hr = pRT->BindDC(pDC->m_hDC, rect);
if (FAILED(hr))
{
const char* szErr = DXGetErrorStringA(hr);
const char* szDesc = DXGetErrorDescriptionA(hr);
ATLTRACE("BindDC: %s - %s\n", szErr, szDesc);
}
pDC->MoveTo(10,10);
pDC->LineTo(200,200);
The same thing happens if the DC is a CMetaFileDC.
The DC seems to be OK, because it works just fine to draw GDI onto that DC.
Is the ID2D1RenderTarget created with incompatible parameters? Should I pass a different pixel format?
Please help.
Thanks.
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D2D does not support rendering to a printer DC. You can render to a WIC bitmat target and then bitblit to the printer DC.
Salvador Patuel
MSFT
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Hi,
Anyone know how to write text to a pdf file using vc++?
Thanks,
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Or here , or you can use this library , is good one !
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Hi
I need to encrypt the plan text using AES algorithm in java and decrypt the encrypted text using C.Any please give solution ASAP.
Thanks
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Some suggestions:
1. Don't cross post in multiple forums.
2. Don't for the full code ASAP. Members here are not paid to help people, so if you want somebody to provide you with the code ASAP, you'll need to hire somebody.
3. Explain precisely where you are stuck, people here won't provide a fully working solution (for the same reason as point 3).
4. Read the posting guidelines at the top of this message board.
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Is your third point some kind of recursive definition? 
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Nice trick there from Cedric! 
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Yeah, took me about 15 minutes before I realized I was reading the same row over and over... (cheeky bastard) 
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Have a look at OpenSSL. It supports AES and you should be able to use if from Java and C. If you have problems using it from C then feel free to ask questions about how to use it. I believe there's a JNI wrapper for it as well to save you rolling your own but I've never used it.
Oh, and if you do a search for "Gladman" and "AES" you might find another open source implementation of AES. I've never used it but one of my co-workers does in a product. It's lighter weight than OpenSSL and you should be able to compile and link it with your C code.
Cheers,
Ash
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Murugan k wrote: I need to encrypt the plan text using AES algorithm in java and decrypt the encrypted text using C.Any please give solution ASAP.
do you know how to write AES alogorithm in C and Java
"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
Never mind - my own stupidity is the source of every "problem" - Mixture
cheers,
Alok Gupta
VC Forum Q&A :- I/ IV
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