gnu/dist/gettext/gettext-tools/lib/stpncpy.c

   1 /* Copyright (C) 1993, 1995-1997, 2002-2003, 2005 Free Software Foundation, Inc.
   2
   3    NOTE: The canonical source of this file is maintained with the GNU C Library.
   4    Bugs can be reported to bug-glibc@gnu.org.
   5
   6    This program is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by the
   8    Free Software Foundation; either version 2, or (at your option) any
   9    later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  19    USA.  */
  20
  21 /* This is almost copied from strncpy.c, written by Torbjorn Granlund.  */
  22
  23 #ifdef HAVE_CONFIG_H
  24 # include <config.h>
  25 #endif
  26
  27 /* Specification.  */
  28 #include "stpncpy.h"
  29
  30 #ifndef weak_alias
  31 # define __stpncpy stpncpy
  32 #endif
  33
  34 /* Copy no more than N bytes of SRC to DST, returning a pointer past the
  35    last non-NUL byte written into DST.  */
  36 char *
  37 __stpncpy (char *dest, const char *src, size_t n)
  38 {
  39   char c;
  40   char *s = dest;
  41
  42   if (n >= 4)
  43     {
  44       size_t n4 = n >> 2;
  45
  46       for (;;)
  47         {
  48           c = *src++;
  49           *dest++ = c;
  50           if (c == '\0')
  51             break;
  52           c = *src++;
  53           *dest++ = c;
  54           if (c == '\0')
  55             break;
  56           c = *src++;
  57           *dest++ = c;
  58           if (c == '\0')
  59             break;
  60           c = *src++;
  61           *dest++ = c;
  62           if (c == '\0')
  63             break;
  64           if (--n4 == 0)
  65             goto last_chars;
  66         }
  67       n -= dest - s;
  68       goto zero_fill;
  69     }
  70
  71  last_chars:
  72   n &= 3;
  73   if (n == 0)
  74     return dest;
  75
  76   for (;;)
  77     {
  78       c = *src++;
  79       --n;
  80       *dest++ = c;
  81       if (c == '\0')
  82         break;
  83       if (n == 0)
  84         return dest;
  85     }
  86
  87  zero_fill:
  88   while (n-- > 0)
  89     dest[n] = '\0';
  90
  91   return dest - 1;
  92 }
  93 #ifdef weak_alias
  94 weak_alias (__stpncpy, stpncpy)
  95 #endif