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glibc/string/bits/string2.h

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/* Machine-independant string function optimizations.
Copyright (C) 1997-2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#ifndef _STRING_H
# error "Never use <bits/string2.h> directly; include <string.h> instead."
#endif
#ifndef __NO_STRING_INLINES
/* Unlike the definitions in the header <bits/string.h> the
definitions contained here are not optimized down to assembler
level. Those optimizations are not always a good idea since this
means the code size increases a lot. Instead the definitions here
optimize some functions in a way which do not dramatically
increase the code size and which do not use assembler. The main
trick is to use GCC's `__builtin_constant_p' function.
Every function XXX which has a defined version in
<bits/string.h> must be accompanied by a symbol _HAVE_STRING_ARCH_XXX
to make sure we don't get redefinitions.
We must use here macros instead of inline functions since the
trick won't work with the latter. */
#ifndef __STRING_INLINE
# ifdef __cplusplus
# define __STRING_INLINE inline
# else
# define __STRING_INLINE __extern_inline
# endif
#endif
/* Dereferencing a pointer arg to run sizeof on it fails for the void
pointer case, so we use this instead.
Note that __x is evaluated twice. */
#define __string2_1bptr_p(__x) \
((size_t)(const void *)((__x) + 1) - (size_t)(const void *)(__x) == 1)
/* Set N bytes of S to 0. */
#if !defined _HAVE_STRING_ARCH_memset
# define __bzero(s, n) __builtin_memset (s, '\0', n)
#endif
#ifndef _HAVE_STRING_ARCH_strchr
extern void *__rawmemchr (const void *__s, int __c);
# define strchr(s, c) \
(__extension__ (__builtin_constant_p (c) && !__builtin_constant_p (s) \
&& (c) == '\0' \
? (char *) __rawmemchr (s, c) \
: __builtin_strchr (s, c)))
#endif
/* Copy SRC to DEST, returning pointer to final NUL byte. */
#ifdef __USE_GNU
# ifndef _HAVE_STRING_ARCH_stpcpy
# define __stpcpy(dest, src) __builtin_stpcpy (dest, src)
/* In glibc we use this function frequently but for namespace reasons
we have to use the name `__stpcpy'. */
# define stpcpy(dest, src) __stpcpy (dest, src)
# endif
#endif
/* Copy no more than N characters of SRC to DEST. */
#ifndef _HAVE_STRING_ARCH_strncpy
# define strncpy(dest, src, n) __builtin_strncpy (dest, src, n)
#endif
/* Append no more than N characters from SRC onto DEST. */
#ifndef _HAVE_STRING_ARCH_strncat
# ifdef _USE_STRING_ARCH_strchr
# define strncat(dest, src, n) \
(__extension__ ({ char *__dest = (dest); \
__builtin_constant_p (src) && __builtin_constant_p (n) \
? (strlen (src) < ((size_t) (n)) \
? strcat (__dest, src) \
: (*((char *) __mempcpy (strchr (__dest, '\0'), \
src, n)) = '\0', __dest)) \
: strncat (dest, src, n); }))
# else
# define strncat(dest, src, n) __builtin_strncat (dest, src, n)
# endif
#endif
/* Compare characters of S1 and S2. */
#ifndef _HAVE_STRING_ARCH_strcmp
# define strcmp(s1, s2) \
__extension__ \
({ size_t __s1_len, __s2_len; \
(__builtin_constant_p (s1) && __builtin_constant_p (s2) \
&& (__s1_len = strlen (s1), __s2_len = strlen (s2), \
(!__string2_1bptr_p (s1) || __s1_len >= 4) \
&& (!__string2_1bptr_p (s2) || __s2_len >= 4)) \
? __builtin_strcmp (s1, s2) \
: (__builtin_constant_p (s1) && __string2_1bptr_p (s1) \
&& (__s1_len = strlen (s1), __s1_len < 4) \
? (__builtin_constant_p (s2) && __string2_1bptr_p (s2) \
? __builtin_strcmp (s1, s2) \
: __strcmp_cg (s1, s2, __s1_len)) \
: (__builtin_constant_p (s2) && __string2_1bptr_p (s2) \
&& (__s2_len = strlen (s2), __s2_len < 4) \
? (__builtin_constant_p (s1) && __string2_1bptr_p (s1) \
? __builtin_strcmp (s1, s2) \
: -__strcmp_cg (s2, s1, __s2_len)) \
: __builtin_strcmp (s1, s2)))); })
# define __strcmp_cg(s1, s2, l1) \
(__extension__ ({ const unsigned char *__s2 = \
(const unsigned char *) (const char *) (s2); \
int __result = \
(((const unsigned char *) (const char *) (s1))[0] \
- __s2[0]); \
if (l1 > 0 && __result == 0) \
{ \
__result = (((const unsigned char *) \
(const char *) (s1))[1] - __s2[1]); \
if (l1 > 1 && __result == 0) \
{ \
__result = (((const unsigned char *) \
(const char *) (s1))[2] - __s2[2]); \
if (l1 > 2 && __result == 0) \
__result = (((const unsigned char *) \
(const char *) (s1))[3] \
- __s2[3]); \
} \
} \
__result; }))
#endif
/* Compare N characters of S1 and S2. */
#ifndef _HAVE_STRING_ARCH_strncmp
# define strncmp(s1, s2, n) \
(__extension__ (__builtin_constant_p (n) \
&& ((__builtin_constant_p (s1) \
&& strlen (s1) < ((size_t) (n))) \
|| (__builtin_constant_p (s2) \
&& strlen (s2) < ((size_t) (n)))) \
? strcmp (s1, s2) : strncmp (s1, s2, n)))
#endif
/* Return the length of the initial segment of S which
consists entirely of characters not in REJECT. */
#ifndef _HAVE_STRING_ARCH_strcspn
# define strcspn(s, reject) __builtin_strcspn (s, reject)
#endif
/* Return the length of the initial segment of S which
consists entirely of characters in ACCEPT. */
#ifndef _HAVE_STRING_ARCH_strspn
# define strspn(s, accept) __builtin_strspn (s, accept)
#endif
/* Find the first occurrence in S of any character in ACCEPT. */
#ifndef _HAVE_STRING_ARCH_strpbrk
# define strpbrk(s, accept) __builtin_strpbrk (s, accept)
#endif
/* We need the memory allocation functions for inline strdup().
Referring to stdlib.h (even minimally) is not allowed
in any of the tight standards compliant modes. */
#ifdef __USE_MISC
# if !defined _HAVE_STRING_ARCH_strdup || !defined _HAVE_STRING_ARCH_strndup
# define __need_malloc_and_calloc
# include <stdlib.h>
# endif
# ifndef _HAVE_STRING_ARCH_strdup
extern char *__strdup (const char *__string) __THROW __attribute_malloc__;
# define __strdup(s) \
(__extension__ (__builtin_constant_p (s) && __string2_1bptr_p (s) \
? (((const char *) (s))[0] == '\0' \
? (char *) calloc ((size_t) 1, (size_t) 1) \
: ({ size_t __len = strlen (s) + 1; \
char *__retval = (char *) malloc (__len); \
if (__retval != NULL) \
__retval = (char *) memcpy (__retval, s, __len); \
__retval; })) \
: __strdup (s)))
# if defined __USE_XOPEN_EXTENDED || defined __USE_XOPEN2K8
# define strdup(s) __strdup (s)
# endif
# endif
# ifndef _HAVE_STRING_ARCH_strndup
extern char *__strndup (const char *__string, size_t __n)
__THROW __attribute_malloc__;
# define __strndup(s, n) \
(__extension__ (__builtin_constant_p (s) && __string2_1bptr_p (s) \
? (((const char *) (s))[0] == '\0' \
? (char *) calloc ((size_t) 1, (size_t) 1) \
: ({ size_t __len = strlen (s) + 1; \
size_t __n = (n); \
char *__retval; \
if (__n < __len) \
__len = __n + 1; \
__retval = (char *) malloc (__len); \
if (__retval != NULL) \
{ \
__retval[__len - 1] = '\0'; \
__retval = (char *) memcpy (__retval, s, \
__len - 1); \
} \
__retval; })) \
: __strndup (s, n)))
# ifdef __USE_XOPEN2K8
# define strndup(s, n) __strndup (s, n)
# endif
# endif
#endif /* Use misc. or use GNU. */
#ifndef _FORCE_INLINES
# undef __STRING_INLINE
#endif
#endif /* No string inlines. */
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