[PING][PATCH] Improve str(n)cat_chk performance.

[OndÅej BÃlka <neleai at seznam dot cz>]

ping
On Thu, Aug 20, 2015 at 09:35:17AM +0200, OndÅej BÃlka wrote:
> Here we sync implementation with strcat/strncat generic one. That makes
> performance comparable with strcat instead of slow byte-by-byte loop.
> 
> Ok to commit this?
> 
> 
> 	* debug/strcat_chk.c (__strcat_chk): Sync with generic implementation.
> 	* debug/strncat_chk.c (__strncat_chk): Likewise.
> 
> diff --git a/debug/strcat_chk.c b/debug/strcat_chk.c
> index 8d7359f..8f26012 100644
> --- a/debug/strcat_chk.c
> +++ b/debug/strcat_chk.c
> @@ -16,8 +16,6 @@
>     <http://www.gnu.org/licenses/>.  */
>  
>  #include <string.h>
> -#include <memcopy.h>
> -
>  
>  /* Append SRC on the end of DEST.  */
>  char *
> @@ -26,32 +24,12 @@ __strcat_chk (dest, src, destlen)
>       const char *src;
>       size_t destlen;
>  {
> -  char *s1 = dest;
> -  const char *s2 = src;
> -  char c;
> -
> -  /* Find the end of the string.  */
> -  do
> -    {
> -      if (__glibc_unlikely (destlen-- == 0))
> -	__chk_fail ();
> -      c = *s1++;
> -    }
> -  while (c != '\0');
> -
> -  /* Make S1 point before the next character, so we can increment
> -     it while memory is read (wins on pipelined cpus).  */
> -  ++destlen;
> -  s1 -= 2;
> -
> -  do
> -    {
> -      if (__glibc_unlikely (destlen-- == 0))
> -	__chk_fail ();
> -      c = *s2++;
> -      *++s1 = c;
> -    }
> -  while (c != '\0');
> +  size_t len = strlen (dest);
> +  size_t srclen = strlen (src);
>  
> +  if (__glibc_unlikely (len + srclen + 1 > destlen))
> +    __chk_fail ();
> +  
> +  memcpy (dest + len, src, srclen + 1);
>    return dest;
>  }
> diff --git a/debug/strncat_chk.c b/debug/strncat_chk.c
> index 2951d05..c0a68c5 100644
> --- a/debug/strncat_chk.c
> +++ b/debug/strncat_chk.c
> @@ -17,83 +17,16 @@
>  
>  #include <string.h>
>  
> -#include <memcopy.h>
> -
> -
>  char *
> -__strncat_chk (s1, s2, n, s1len)
> -     char *s1;
> -     const char *s2;
> -     size_t n;
> -     size_t s1len;
> +__strncat_chk (char *dest, const char *src, size_t n, size_t destlen)
>  {
> -  char c;
> -  char *s = s1;
> -
> -  /* Find the end of S1.  */
> -  do
> -    {
> -      if (__glibc_unlikely (s1len-- == 0))
> -	__chk_fail ();
> -      c = *s1++;
> -    }
> -  while (c != '\0');
> -
> -  /* Make S1 point before next character, so we can increment
> -     it while memory is read (wins on pipelined cpus).  */
> -  ++s1len;
> -  s1 -= 2;
> -
> -  if (n >= 4)
> -    {
> -      size_t n4 = n >> 2;
> -      do
> -	{
> -	  if (__glibc_unlikely (s1len-- == 0))
> -	    __chk_fail ();
> -	  c = *s2++;
> -	  *++s1 = c;
> -	  if (c == '\0')
> -	    return s;
> -	  if (__glibc_unlikely (s1len-- == 0))
> -	    __chk_fail ();
> -	  c = *s2++;
> -	  *++s1 = c;
> -	  if (c == '\0')
> -	    return s;
> -	  if (__glibc_unlikely (s1len-- == 0))
> -	    __chk_fail ();
> -	  c = *s2++;
> -	  *++s1 = c;
> -	  if (c == '\0')
> -	    return s;
> -	  if (__glibc_unlikely (s1len-- == 0))
> -	    __chk_fail ();
> -	  c = *s2++;
> -	  *++s1 = c;
> -	  if (c == '\0')
> -	    return s;
> -	} while (--n4 > 0);
> -      n &= 3;
> -    }
> -
> -  while (n > 0)
> -    {
> -      if (__glibc_unlikely (s1len-- == 0))
> -	__chk_fail ();
> -      c = *s2++;
> -      *++s1 = c;
> -      if (c == '\0')
> -	return s;
> -      n--;
> -    }
> +  size_t len = strlen (dest);
> +  size_t srclen = __strnlen (src, n);
>  
> -  if (c != '\0')
> -    {
> -      if (__glibc_unlikely (s1len-- == 0))
> -	__chk_fail ();
> -      *++s1 = '\0';
> -    }
> +  if (__glibc_unlikely (len + srclen + 1 > destlen))
> +    __chk_fail ();
>  
> -  return s;
> +  dest[len + srclen] = 0;
> +  memcpy (dest + len, src, srclen);
> +  return dest;
>  }

-- 

LBNC (luser brain not connected)