debug/stpncpy_chk.c

   1 /* Copyright (C) 1993,1995,1996,1997,2002,2005 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 /* This is almost copied from strncpy.c, written by Torbjorn Granlund.  */
  20
  21 #include <string.h>
  22
  23
  24 /* Copy no more than N characters of SRC to DEST, returning the address of
  25    the terminating '\0' in DEST, if any, or else DEST + N.  */
  26 char *
  27 __stpncpy_chk (char *dest, const char *src, size_t n, size_t destlen)
  28 {
  29   char c;
  30   char *s = dest;
  31
  32   if (__builtin_expect (destlen < n, 0))
  33     __chk_fail ();
  34
  35   if (n >= 4)
  36     {
  37       size_t n4 = n >> 2;
  38
  39       for (;;)
  40         {
  41           c = *src++;
  42           *dest++ = c;
  43           if (c == '\0')
  44             break;
  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           if (--n4 == 0)
  58             goto last_chars;
  59         }
  60       n -= dest - s;
  61       goto zero_fill;
  62     }
  63
  64  last_chars:
  65   n &= 3;
  66   if (n == 0)
  67     return dest;
  68
  69   for (;;)
  70     {
  71       c = *src++;
  72       --n;
  73       *dest++ = c;
  74       if (c == '\0')
  75         break;
  76       if (n == 0)
  77         return dest;
  78     }
  79
  80  zero_fill:
  81   while (n-- > 0)
  82     dest[n] = '\0';
  83
  84   return dest - 1;
  85 }