> void *memmove(void *dest, const void *src, size_t count)
> {
> if (dest < src) {
> return memcpy(dest, src, count);
> } else {
> - char *p = dest + count;
> - const char *s = src + count;
> - while (count--)
> - *--p = *--s;
> + return memcpy_backwards(dest, src, count);
> }
> return dest;
> }
Er... presumably, the forward-copy case is somewhat better optimized,
so should be preferred if the areas don't overlap; that is, dest >
src by more than the sount. Assuming that size_t can hold a pointer:
if ((size_t)src - (size_t)dest >= count)
return memcpy(dest, src, count);
else
return memcpy_backwards(dest, src, count);
Or, using GCC's arithmetic on void * extension,
if ((size_t)(src - dest) >= count)
... etc.
If src == dest, it doesn't matter which you use. You could skip the
copy entirely, but presumably that case doesn't arise often enough to
be worth testing for:
if ((size_t)(src - dest) >= count)
return memcpy(dest, src, count);
else if (src - dest != 0)
return memcpy_backwards(dest, src, count);
else
return dest;
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