1  /* Copy a null-terminated string to a fixed-size buffer, with length checking.
       2     Copyright (C) 2023 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     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <string.h>
      20  
      21  size_t
      22  __strlcpy (char *__restrict dest, const char *__restrict src, size_t size)
      23  {
      24    size_t src_length = strlen (src);
      25  
      26    if (__glibc_unlikely (src_length >= size))
      27      {
      28        if (size > 0)
      29  	{
      30  	  /* Copy the leading portion of the string.  The last
      31  	     character is subsequently overwritten with the NUL
      32  	     terminator, but the destination size is usually a
      33  	     multiple of a small power of two, so writing it twice
      34  	     should be more efficient than copying an odd number of
      35  	     bytes.  */
      36  	  memcpy (dest, src, size);
      37  	  dest[size - 1] = '\0';
      38  	}
      39      }
      40    else
      41      /* Copy the string and its terminating NUL character.  */
      42      memcpy (dest, src, src_length + 1);
      43    return src_length;
      44  }
      45  libc_hidden_def (__strlcpy)
      46  weak_alias (__strlcpy, strlcpy)