As far as I could understand, memcpy just iterate through the memory( byte
by byte or word by word) and blindly copies 'n' number of bytes from source
to destination without considering whether source and destination memory
overlaps. While memmove first copies n number of bytes to intermediate
buffer and then copies the buffer content to destination address.
consider the following example:
#include <cstdio>
#include <memory.h>
#include <iostream>
using namespace std;
int main()
{
char a[20] = "weather is good";
memcpy(a+1, a, strlen(a) );
cout << a;
return 0;
}
it produces the o/p: wweather is good
But as per definition of memcpy, o/p should be : wwwwwwwwwwwwwww. Its
because, after writing 'w' at a[1], memcpy tries to copy a[1] to a[2] , but
now we have 'w' at a[1]. so effectively w should be copied on subsequent
locations (from a[2] onwards) strlen(a) times.
can anybody explain the o/p "wweather is good" to me? Can you give me an
example when just replacing memmove by memcpy produces different output?
--
Vipin
Delhi College of Engineering
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