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() ?
===========cut=============
--- string.c Thu May 13 20:44:32 2004
+++ string_str_repeat.c Fri Jun 11 17:40:47 2004
@@ -3581,7 +3581,7 @@
while (e<ee) {
l = (e-s) < (ee-e) ? (e-s) : (ee-e);
-
memmove(e, s, l);
-
}memcpy(e, s, l); e += l; }
===========cut=============
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Read your memcpy manpages
"The memcpy() function copies n bytes from memory area src to memory
area dest. The memory areas may not overlap."
Ilia
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() ?===========cut=============
--- string.c Thu May 13 20:44:32 2004
+++ string_str_repeat.c Fri Jun 11 17:40:47 2004
@@ -3581,7 +3581,7 @@while (e<ee) { l = (e-s) < (ee-e) ? (e-s) : (ee-e);
memmove(e, s, l);
memcpy(e, s, l); e += l; }===========cut=============
--
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On Fri, 11 Jun 2004 10:55:20 -0400, Ilia Alshanetsky ilia@prohost.org
wrote:
Read your memcpy manpages
"The memcpy() function copies n bytes from memory area src to memory
area dest. The memory areas may not overlap."
Well, I've read my manpages:
The memcpy() function copies n bytes from memory area src
to memory area dest. The memory areas may not overlap.
Use memmove() if the memory areas do overlap.
Pay attention on the LAST sentence.
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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.
Please stop wasting our time with those silly patches that fix nothing;
there is plenty of other good things to do to help with PHP development
(like translations as Antony mentioned).
regards,
Derick
On Fri, 11 Jun 2004 17:00:03 +0200 (CEST), Derick Rethans derick@php.net
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().
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On Fri, 11 Jun 2004 17:00:03 +0200 (CEST), Derick Rethans
derick@php.net 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):
That's not what my glibc sources look like.
George
Well, surely memmove() needs an additional branch to check for
overlapping, though (the OP was wrong in that memmove() would need a
temporary buffer, though - it doesn't, it usually copies from high
addres to low in the overlapping case).
Cheers,
Michael
George Schlossnagle wrote:
On Fri, 11 Jun 2004 17:00:03 +0200 (CEST), Derick Rethans
derick@php.net 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):That's not what my glibc sources look like.
George
Michael Walter wrote:
Well, surely memmove() needs an additional branch to check for
overlapping, though (the OP was wrong in that memmove() would need a
temporary buffer, though - it doesn't, it usually copies from high
addres to low in the overlapping case).
The whole discussion about memcpy beeing faster than memmove is
completely pointless. It is obvious that copying without checking is
faster than coyping with checking. But the performance impact is
minimal, otherwise it would not be fact that the BSD's all have
memcpy==memmove.
Stefan
Stefan Esser wrote:
The whole discussion about memcpy beeing faster than memmove is
completely pointless. [..]
Agreed.
Cheers,
Michael