string/strnlen.c

   1 /* Find the length of STRING, but scan at most MAXLEN characters.
   2    Copyright (C) 1991-2023 Free Software Foundation, Inc.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If
  16    not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <string.h>
  19
  20 /* Find the length of S, but scan at most MAXLEN characters.  If no
  21    '\0' terminator is found in that many characters, return MAXLEN.  */
  22
  23 #ifdef STRNLEN
  24 # define __strnlen STRNLEN
  25 #endif
  26
  27 size_t
  28 __strnlen (const char *str, size_t maxlen)
  29 {
  30   const char *found = memchr (str, '\0', maxlen);
  31   return found ? found - str : maxlen;
  32 }
  33
  34 #ifndef STRNLEN
  35 weak_alias (__strnlen, strnlen)
  36 libc_hidden_def (__strnlen)
  37 libc_hidden_def (strnlen)
  38 #endif