string/bits/string2.h

   1 /* Machine-independant string function optimizations.
   2    Copyright (C) 1997-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef _STRING_H
  21 # error "Never use <bits/string2.h> directly; include <string.h> instead."
  22 #endif
  23
  24 #ifndef __NO_STRING_INLINES
  25
  26 /* Unlike the definitions in the header <bits/string.h> the
  27    definitions contained here are not optimized down to assembler
  28    level.  Those optimizations are not always a good idea since this
  29    means the code size increases a lot.  Instead the definitions here
  30    optimize some functions in a way which do not dramatically
  31    increase the code size and which do not use assembler.  The main
  32    trick is to use GCC's `__builtin_constant_p' function.
  33
  34    Every function XXX which has a defined version in
  35    <bits/string.h> must be accompanied by a symbol _HAVE_STRING_ARCH_XXX
  36    to make sure we don't get redefinitions.
  37
  38    We must use here macros instead of inline functions since the
  39    trick won't work with the latter.  */
  40
  41 #ifndef __STRING_INLINE
  42 # ifdef __cplusplus
  43 #  define __STRING_INLINE inline
  44 # else
  45 #  define __STRING_INLINE __extern_inline
  46 # endif
  47 #endif
  48
  49 /* Dereferencing a pointer arg to run sizeof on it fails for the void
  50    pointer case, so we use this instead.
  51    Note that __x is evaluated twice. */
  52 #define __string2_1bptr_p(__x) \
  53   ((size_t)(const void *)((__x) + 1) - (size_t)(const void *)(__x) == 1)
  54
  55 /* Set N bytes of S to 0.  */
  56 #if !defined _HAVE_STRING_ARCH_memset
  57 # define __bzero(s, n) __builtin_memset (s, '\0', n)
  58 #endif
  59
  60
  61 /* Copy SRC to DEST, returning pointer to final NUL byte.  */
  62 #ifdef __USE_GNU
  63 # ifndef _HAVE_STRING_ARCH_stpcpy
  64 #  define __stpcpy(dest, src) __builtin_stpcpy (dest, src)
  65 /* In glibc we use this function frequently but for namespace reasons
  66    we have to use the name `__stpcpy'.  */
  67 #  define stpcpy(dest, src) __stpcpy (dest, src)
  68 # endif
  69 #endif
  70
  71
  72 /* Copy no more than N characters of SRC to DEST.  */
  73 #ifndef _HAVE_STRING_ARCH_strncpy
  74 # define strncpy(dest, src, n) __builtin_strncpy (dest, src, n)
  75 #endif
  76
  77
  78 /* Append no more than N characters from SRC onto DEST.  */
  79 #ifndef _HAVE_STRING_ARCH_strncat
  80 # ifdef _USE_STRING_ARCH_strchr
  81 #  define strncat(dest, src, n) \
  82   (__extension__ ({ char *__dest = (dest);                                    \
  83                     __builtin_constant_p (src) && __builtin_constant_p (n)    \
  84                     ? (strlen (src) < ((size_t) (n))                          \
  85                        ? strcat (__dest, src)                                 \
  86                        : (*((char *) __mempcpy (strchr (__dest, '\0'),        \
  87                                                 src, n)) = '\0', __dest))     \
  88                     : strncat (dest, src, n); }))
  89 # else
  90 #  define strncat(dest, src, n) __builtin_strncat (dest, src, n)
  91 # endif
  92 #endif
  93
  94
  95 /* Return the length of the initial segment of S which
  96    consists entirely of characters not in REJECT.  */
  97 #ifndef _HAVE_STRING_ARCH_strcspn
  98 # define strcspn(s, reject) __builtin_strcspn (s, reject)
  99 #endif
 100
 101
 102 /* Return the length of the initial segment of S which
 103    consists entirely of characters in ACCEPT.  */
 104 #ifndef _HAVE_STRING_ARCH_strspn
 105 # define strspn(s, accept) __builtin_strspn (s, accept)
 106 #endif
 107
 108
 109 /* Find the first occurrence in S of any character in ACCEPT.  */
 110 #ifndef _HAVE_STRING_ARCH_strpbrk
 111 # define strpbrk(s, accept) __builtin_strpbrk (s, accept)
 112 #endif
 113
 114
 115 #ifndef _FORCE_INLINES
 116 # undef __STRING_INLINE
 117 #endif
 118
 119 #endif /* No string inlines.  */