how use memset()?

[Cambalinho]

how i use memset()?
heres my actual code:

if(Pixels==NULL)VirtualFree(Pixels, 0,MEM_RELEASE);;
            unsigned int PixelsCount =SizeWidth*SizeHeight*sizeof(unsigned int);
            Pixels = (unsigned int*) VirtualAlloc(0, PixelsCount,MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
memset(Pixels,NewColor, PixelsCount );

on these sample the 'NewColor' is 'RGB(0,255,0)'...
but why all arrays elements don't recive the same value?

[ne555]

> on these sample the 'NewColor' is 'RGB(0,255,0)'...
¿how do you represent that with only one byte?

man wrote:

void *memset(void *s, int c, size_t n);
The memset() function fills the first n bytes of the memory area pointed to by s with the constant byte c.

also, keep in mind that the function will fill the array byte by byte (it seems that you are storing integers, which may be a little bigger than one byte)

[DizzyDon]

Use std::fill (in <algorithm>) instead.

    std::fill(Pixels, Pixels + SizeWidth * SizeHeight, NewColor);

Is there a good reason you're using VirtualAlloc instead of new?

[keskiverto]

In the previous topic http://www.cplusplus.com/forum/general/283026/ Cambalinho did show intent to use malloc() and free() ... and had no destructor to clean up ...

We did offer std::vector too (which would handle memory management automatically). In vain.

[helios]

if(Pixels==NULL)VirtualFree(Pixels, 0,MEM_RELEASE);;
            unsigned int PixelsCount =SizeWidth*SizeHeight*sizeof(unsigned int);
            Pixels = (unsigned int*) VirtualAlloc(0, PixelsCount,MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
memset(Pixels,NewColor, PixelsCount );

Dude, you've been posting here for more than nine years. How is it possible you're writing code like this after using C++ for so long?

[Cambalinho]

1st i'm sorry something.. nothing was in vain... i'm learning what i can for what i need.. .sorry something.

"Dude, you've been posting here for more than nine years. How is it possible you're writing code like this after using C++ for so long?"
i'm sorry, but what you mean?

[jonnin]

memset is a crude tool.
but I think your issue is that it tells you the second parameter is an int. OK, it is, but its 0-255. You can't use it with an RGB.
like if you want a black image:
memset(pixels, 0, height*width*rgb_is_3_or_rgba_is_4_etc);
or a white image.. (pixels, 255,
or a sickly grey: (pixels, 128,
and so on. Most of the time with images those 3 constants are all you want.
all the mem*** family functions came from C and are a wee bit dangerous. Like serialization, they can't handle internal pointers in objects, and like anything C about arrays/pointers you can go out of bounds and all. I would avoid it unless you need the extra speed, they are fast, if nothing else.

As for your code, you are trying to deal with microsoftisms while also struggling with a lot of pointer basics. This is a recipe for disaster; if you are going down this road you need to go brush up on pointers before trying to use that pointer heavy, messy library.

[DizzyDon]

i'm sorry, but what you mean?

*sigh*

[Cambalinho]

the best shot was realy:

std::fill(Pixels, Pixels + SizeWidth * SizeHeight, BackColor);

thank you so much for all to all.