Difference:
If there is an overlap, use memmove in place of memcpy
Q: Could you provide a practical scenario of any C lib function where an overlap happens so memmove is used in place of memcpy?
Add a comment
|
2 Answers
Here's one:
// len => array length, idx => index where we want to remove
void removeAt(int* array, size_t* len, size_t idx)
{
// copy next values to replace current
// example: {1, 2, 3, 4} => {1, 3, 4}
// ^ remove
memmove(&array[idx], &array[idx+1], (--(*len) - idx) * sizeof(int));
}
Edit: Regarding this appearing in the implementation of a C stdlib function, that would be a bit more difficult to find, since each implementation can do their own thing, and most stdlib functions require that the arguments do not overlap.
Comments
For example you need to insert an element in the middle of an array (in-place). This requires shifting the elements from the insertion points onwards by one place. This can be done with memmove() but not with memcpy().
3 Comments
codey modey
that is an acceptable, general scenario, but do you remember any from a library function?
NPE
@codeymodey: Have a browse of code.ohloh.net/… -- there's a ton of real-world examples there.
NPE
@codeymodey: Here's an example from the Linux kernel: code.ohloh.net/…