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Thanks, but is there any way which just use ANSI C++ standard type rather than BYTE? By using BYTE, we will have problem when we port the code in other platforms. Any idea?
Nacho
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Use unsigned char. (Or use BYTE and on platforms that do not have it defined or typedefed, typedef it yourself.)
Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke
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arey yar
that above one Immpossible.
v.raju
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Why are you using a void pointer? If you want to point to an int why not use an int*? Since void* can point to anything the compiler has no way of knowing the size of the object pointed to. In your code when you done p++ how far did you expect the pointer to be advanced?
Steve
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The arithmetic for void* is not defined, so if you need pointer arithmetic you must do it with a type other than void*. However, the void* is guaranteed to be capable of holding any address on the machine, while other types of pointers do not guarantee it. But, for practical purposes on practical platforms with practical processors you may consider that all pointers are interchangeable.
This means that your code should be re-written to:
int i[10];
void* p = i;
int j = * (((int*)p)+1);
In other words: first cast the void* to int*. On practical systems this conversion does not produce any machine instructions, so it is not really executable code. This means that performance is not an issue.
After the cast the compiler treats the pointer as an int*, so the "+1" arithmetic is well defined (equivalent to "++"). It will be, in fact, equivalent to advancing the pointer to the address where the next int lies. In Win32 this will be an increment of 4 bytes. I've seen SOLARIS implementations where this same code would produce an increment of 8 bytes, to correctly handle its 8 byte int's.
The code I wrote is perfectly legal ANSI, compiles and runs correctly on all platforms, and I wouldn't consider it ugly. Your original code too, except that the precedence is not correct (you increment while the pointer is still void* and at that point it has no arithmetic logic).
Anyway, the second piece of code you propose should not compile. But that can be easilly fixed with "+1" instead of "++". But your reasoning changed in the second example, since you forced the cast from void* (that has no arithmetic logic) to char* (that has arithmetic logic) before incrementing, and so the increment is well defined. However, the increment amount is not correct, because sizeof(char) is 1 and not 4. The char*++ points to the next character (1 byte), instead of the next int (4 bytes). That should have resulted in a bad value for j. Didn't it?
Anyway, below is a piece of code you can test. I initialized "i" to show you that "j" gets a bad value (after fixing from "++" to "+1"). Also, you can see that "k" and "m" get the correct value. As a final note, the code for all 3 integers "j", "k", and "m" as the same instruction type and count, and their efficiency is the same. Of course "j" is wrong, but the compiler doesn't know that (however, some processors may generate exceptions when integers are not aligned, which may result in crashes or slow operating system exception handling).
The "ip" and "n" are not as efficient as the cast versions of "j", "k", and "m" in the debug version. In the release version they should be much more efficient, but the use of the "ip" is most adequate to situations where performance is not an issue, or you intend to do multiple accesses and manipulate the address of the pointer often, or you want the code to be clear. The manipulation could also be done with incrementing indexes in the "m" example, of course.
#include <stdio.h>
void main(void) {
int i[10]={ 1001, 1002, 1003, 1004, 1005, 1006, 1007, 1008, 1009, 1010 };
void* p = i;
int j = *((int*) (((char*)(p))+1) ); // Ugly
int k = *(((int*)p)+1); // Pretty
int m = ((int*)p)[1]; // Also pretty
int* ip=(int*)p;
int n = *++ip; // Even prettier
printf("j=%d, k=%d, m=%d, n=%d\n", j, k, m, n);
}
Rilhas
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hi,
how will you display an icon on a button(CButton MFC VS2005 ), the icon is in say a fil c:\something.ico
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First u have to load the icon using LoadImage() function.. then u will get a handle(HICON) for the icon. Now Pass this handle in the SetIcon function of the CButton
nave
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HICON hicon=(HICON)LoadImage(
AfxGetApp()->m_hInstance, MAKEINTRESOURCE(IDR_AnswerTYPE),IMAGE_ICON, 48, 48, LR_DEFAULTSIZE);
m_Button1.SetIcon(hicon);
and you need to set icon in property window from your button to true.
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thankx a lot guys. Problem solved.
Appreciate the help
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 how comparing similar images to determine how they differ and by how much.? any idea?any code please?
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This is infact not a simple question. I can provide you with hint that try to make Gaussian modal of both images and then compare them. So try to study Gaussian modal first. I hope it helps.
Good luck
We Believe in Excellence
www.aqueelmirza.cjb.net
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The only reliable general purpose image comparison techniques currently available work at a low level. For example, imagine image 1 is a picture of you, and image 2 is a picture of you holding a red ball.
Current gneral purpose comparison techniques don't try to understand that both images contain the same person, and that they are diferent because there is a ball in the second one. Intead, the most reliable techniques today start by subtracting both images and detecting which portions result in a non-zero value. These techniques are the basis for video compression today.
So, your question is not specific enough. What diferences do you which to detect? If you are trying to determine what is diferent in the "meaning" of the pictures then good luck! It is an active area for research, and there is no general solution for it on the horizon. For specific solutions (like detecting that in one image the person has the eyes open and in the next the eyes are closed, or that a room is empty in one picture and not empty in the next) solutions already exist in various domains.
If you intend to determine changes at a lower level then several techniques exist. But be prepared for a very computationally intensive topic, so get yourself a fast processor and be prepared to use C/C++ or even some assembly language!
Rilhas
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im looking for a place where i can find a list/guide of the microsoft standards for a GUI eg how many DU's between radio button etc
thanks
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I have a program which has a total of array size of 94000 float(31 arrays).
When I change 9 of the arrays (73737 size) into double, my program seems not working.
Is the total array size too big ?
How to fix the problem ?
Thanks for any help.
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Typically, when you need an array of more than a few hundred elements, it is best to allocate the array on the heap. This allows you to create arrays bounded only by memory (or 2GB if on w32).
onwards and upwards...
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Thanks for the advice.
You mean I should using pointers ? I am a programer from Fortran/Java. I have not got used to pointers. Give me detailed or further advice please.
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For the array, in order to use the heap memory, you can allocate your array like this
<br />
float* floatArray = NULL;<br />
floatArray = new float[100];<br />
and when you finish using your array, you can
<br />
delete [] floatArray;<br />
floatArray = NULL;<br />
I wish it help!
Nacho
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Thanks Nacho. I have implemented your code suggestion.
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Thanks for the advice.
You mean I should using pointers ? I am a programer from Fortran/Java. I have not got used to pointers. Give me detailed or further advice please.
I particularly use six big arrays a[8200],b[8200],c[8200]
Ideally I need to expand my program to a[16400],b[16400],c[16400]. However, I tried these expansion, the program stopped to work. message says: memery problem.
-- modified at 15:27 Monday 24th April, 2006
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using pointers will not fix all your problems but will help you deal with memory problems.
normally, when allocating memory on the heap ( with new ) you will have a immediate result telling you that the allocation worked or not.
Maximilien Lincourt
Your Head A Splode - Strong Bad
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Thanks
I need to expand the size of the arrays. How can I do this ?
Ideally I should also use "double" instead of "float" to improve the accuracy of the
calculations. However, I tried I can not do it now due to the memery limitations.
Please help me to get a way to deal with this problem
Thanks
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i agree, Use heap instead of stack. If you ar ein C++ now, then you won't be really be able to avoid pointers and dynamic allocation.
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would you please give me some code example segments for using GlobalAlloc()?
Thanks
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