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memory copying

Started by CProgrammer Dec 29, 2002 at 4:31 AM 4 replies 150+ views

Original Post

113

Dec 29, 2002 at 4:31 AM

i have two pointers: int *x; int *y; now i want to copy the content of y into x BUT i want the content of y(lets say size 10) to be copied from x''s 5th slot on. At the end the following should be the case: x[5] = y[0] x[6] = y[1] and so on.(y will be deleted after the process. Please can anyone help me. Thanks in advance -CProgrammer

civguy

Dec 29, 2002 at 4:42 AM

Reading these could be helpful:
http://www.gametutorials.com/Tutorials/C/C_Pg1.htm

Oh and a bit more specifically on the subject, try this:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore98/html/_crt_memcpy.aspp. It has some examples too

[edited by - civguy on December 29, 2002 5:48:01 AM]

CWizard

Dec 29, 2002 at 7:07 AM

I don't really see what is problematic about it. Wouldn't something like this suffice, or am I missing something?

    void weird_copy(int *x, int *y, int size, int offset)
{
    while(size--)
        x[offset++] = *y++;
}
 
// or a perhaps faster way

void weird_copy(int *x, int *y, int size, int offset)
{
    memcpy((void)(x + offset), (void)y, size * sizeof(int));
}

[edited by - CWizard on December 29, 2002 8:08:34 AM]

CProgrammer

Author

113

CProgrammer

Dec 29, 2002 at 7:08 AM

Thanks for your help the problem is solved. For those interested:
Use "memmove"

memmove(x+5, y, size);

That works. +5 specifies how much to skip in x. Weird that i never needed this earlier.

CWizard

Dec 29, 2002 at 7:11 AM

quote:
Original post by CProgrammer
memmove(x+5, y, size);

Note that size is in bytes, so you must multiply it with the size of the type (as in my example).

Fruny

203

Fruny

Dec 29, 2002 at 7:19 AM

#include <algorithm>
std::copy( y, y + 10, x + 5 );

Make sure x is large enough.
This will work regardless of the type of the array elements.

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