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 #include <string.h>
  24
  25 #include "config.h"
  26
  27 #ifndef HAVE_STRLCPY
  28 #undef strlcpy
  29
  30 size_t strlcpy(char *__restrict dest,
  31                const char *__restrict src, size_t destsize);
  32
  33 size_t strlcpy(char *__restrict dest,
  34                const char *__restrict src, size_t destsize)
  35 {
  36         size_t src_length = strlen(src);
  37
  38         if (__builtin_expect(src_length >= destsize, 0)) {
  39                 if (destsize > 0) {
  40                         /*
  41                          * Copy the leading portion of the string.  The last
  42                          * character is subsequently overwritten with the NUL
  43                          * terminator, but the destination destsize is usually
  44                          * a multiple of a small power of two, so writing it
  45                          * twice should be more efficient than copying an odd
  46                          * number of bytes.
  47                          */
  48                         memcpy(dest, src, destsize);
  49                         dest[destsize - 1] = '\0';
  50                 }
  51         } else
  52                 /* Copy the string and its terminating NUL character.  */
  53                 memcpy(dest, src, src_length + 1);
  54         return src_length;
  55 }
  56 #endif /* HAVE_STRLCPY */