root/maint/gnulib/lib/stpncpy.c

/* */

   1 /* Copyright (C) 1993, 1995-1997, 2002-2003, 2005-2007, 2009-2021 Free Software
   2  * Foundation, Inc.
   3 
   4    NOTE: The canonical source of this file is maintained with the GNU C Library.
   5    Bugs can be reported to bug-glibc@gnu.org.
   6 
   7    This file is free software: you can redistribute it and/or modify
   8    it under the terms of the GNU Lesser General Public License as
   9    published by the Free Software Foundation; either version 2.1 of the
  10    License, or (at your option) any later version.
  11 
  12    This file is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU Lesser General Public License for more details.
  16 
  17    You should have received a copy of the GNU Lesser General Public License
  18    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  19 
  20 /* This is almost copied from strncpy.c, written by Torbjorn Granlund.  */
  21 
  22 #include <config.h>
  23 
  24 /* Specification.  */
  25 #include <string.h>
  26 
  27 #ifndef weak_alias
  28 # define __stpncpy stpncpy
  29 #endif
  30 
  31 /* Copy no more than N bytes of SRC to DST, returning a pointer past the
  32    last non-NUL byte written into DST.  */
  33 char *
  34 (__stpncpy) (char *dest, const char *src, size_t n)
  35 {
  36   char c;
  37   char *s = dest;
  38 
  39   if (n >= 4)
  40     {
  41       size_t n4 = n >> 2;
  42 
  43       for (;;)
  44         {
  45           c = *src++;
  46           *dest++ = c;
  47           if (c == '\0')
  48             break;
  49           c = *src++;
  50           *dest++ = c;
  51           if (c == '\0')
  52             break;
  53           c = *src++;
  54           *dest++ = c;
  55           if (c == '\0')
  56             break;
  57           c = *src++;
  58           *dest++ = c;
  59           if (c == '\0')
  60             break;
  61           if (--n4 == 0)
  62             goto last_chars;
  63         }
  64       n -= dest - s;
  65       goto zero_fill;
  66     }
  67 
  68  last_chars:
  69   n &= 3;
  70   if (n == 0)
  71     return dest;
  72 
  73   for (;;)
  74     {
  75       c = *src++;
  76       --n;
  77       *dest++ = c;
  78       if (c == '\0')
  79         break;
  80       if (n == 0)
  81         return dest;
  82     }
  83 
  84  zero_fill:
  85   while (n-- > 0)
  86     dest[n] = '\0';
  87 
  88   return dest - 1;
  89 }
  90 #ifdef weak_alias
  91 weak_alias (__stpncpy, stpncpy)
  92 #endif

/* */