Re: str_repeat() patch

On Fri, 11 Jun 2004 17:00:03 +0200 (CEST), Derick Rethans <derick@php.net> wrote:

On Fri, 11 Jun 2004, Alexander Valyalkin wrote:

Read it: void *memmove(void *s1, const void *s2, size_t n); If s1 and s2 overlap, all bytes are copied in a preserving manner (unlike memcpy()) And anwer the question: are s1 and s2 overlap in the str_repeat() ? Why don't use memcpy() instead of memmove() ?

Because it's slower and we're copying to newly allocated memory anyway so things CAN not overlap. Also, your patch is the wrong way around.

Mybe I'm mistaken, but I think, that memmove() looks like that (without any error checks): void *memmove(void *dst, void *src, size_t len) { /* check overlapping of src & dst */ size_t distance = (char *)dst > (char *)src ? (char *)dst - (char *)src : (char *)src - (char *)dst; if (distance < len) { /* overlap. Use temporary buffer & memcpy(). Here could be used byte-to-byte copying or any oher tricks

            */

char *tmp = malloc(len); memcpy(tmp, src, len); memcpy(dst, tmp, len); free(tmp); } else { /* not overlap. Use memcpy() */ memcpy(dst, src, len); } return dst; } Are you still think that memcpy() is slower than memmove() ? I would tell that memcpy() at least not more slowly than memmove(). -- Using Opera's revolutionary e-mail client: http://www.opera.com/m2/