lib/strlcpy.c

   1 /* Copy a null-terminated string to a fixed-size buffer, with length checking.
   2  * Copyright (C) 2016 Free Software Foundation, Inc.
   3  * This file is part of the GNU C Library.
   4  *
   5  * The GNU C Library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2.1 of the License, or (at your option) any later version.
   9  *
  10  * The GNU C Library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with the GNU C Library; if not, see
  17  * <http://www.gnu.org/licenses/>.
  18  */
  19
  20 /* adapted for Quagga from glibc patch submission originally from
  21  * Florian Weimer <fweimer@redhat.com>, 2016-05-18 */
  22
  23 #ifdef HAVE_CONFIG_H
  24 #include "config.h"
  25 #endif
  26
  27 #include <string.h>
  28
  29 #ifndef HAVE_STRLCPY
  30 #undef strlcpy
  31
  32 size_t strlcpy(char *__restrict dest,
  33                const char *__restrict src, size_t destsize);
  34
  35 size_t strlcpy(char *__restrict dest,
  36                const char *__restrict src, size_t destsize)
  37 {
  38         size_t src_length = strlen(src);
  39
  40         if (__builtin_expect(src_length >= destsize, 0)) {
  41                 if (destsize > 0) {
  42                         /*
  43                          * Copy the leading portion of the string.  The last
  44                          * character is subsequently overwritten with the NUL
  45                          * terminator, but the destination destsize is usually
  46                          * a multiple of a small power of two, so writing it
  47                          * twice should be more efficient than copying an odd
  48                          * number of bytes.
  49                          */
  50                         memcpy(dest, src, destsize);
  51                         dest[destsize - 1] = '\0';
  52                 }
  53         } else
  54                 /* Copy the string and its terminating NUL character.  */
  55                 memcpy(dest, src, src_length + 1);
  56         return src_length;
  57 }
  58 #endif /* HAVE_STRLCPY */