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lib/libc/amd64/string: implement strnlen(3) trough memchr(3)

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Now that we have an optimised memchr(3), we can use it to implement
strnlen(3) with better perofrmance.

Sponsored by:	The FreeBSD Foundation
Approved by:	mjg
MFC after:	1 week
MFC to:		stable/14
Differential Revision:	https://reviews.freebsd.org/D41598
This commit is contained in:
Robert Clausecker 2023-09-08 17:11:55 -04:00
parent de12a689fa
commit 331737281c
2 changed files with 44 additions and 1 deletions
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3
lib/libc/amd64/string/Makefile.inc
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@ -11,7 +11,8 @@ MDSRCS+= \
strcat.S \
strchrnul.S \
strcmp.S \
strcpy.c \
strcspn.S \
strlen.S \
strcpy.c \
strnlen.c \
strspn.S

42
lib/libc/amd64/string/strnlen.c Normal file
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@ -0,0 +1,42 @@
/*-
* Copyright (c) 2023 The FreeBSD Foundation
*
* This software was developed by Robert Clausecker <fuz@FreeBSD.org>
* under sponsorship from the FreeBSD Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ''AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE
*/
#include <sys/cdefs.h>
#include <string.h>
char *__memchr(const void *, int, size_t);
size_t
strnlen(const char *s, size_t maxlen)
{
const char *loc;
loc = __memchr(s, '\0', maxlen);
return (loc == NULL ? maxlen : (size_t)(loc - s));
}