string/stpncpy.c

   1 /* Copyright (C) 1993, 1995, 1996, 1997, 2002 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 #ifdef HAVE_CONFIG_H
  22 # include <config.h>
  23 #endif
  24
  25 #ifdef _LIBC
  26 # include <string.h>
  27 #else
  28 # include <sys/types.h>
  29 #endif
  30
  31 #ifndef STPNCPY
  32 # ifdef weak_alias
  33 #  define STPNCPY       __stpncpy
  34 weak_alias (__stpncpy, stpncpy)
  35 # else
  36 #  define STPNCPY       stpncpy
  37 # endif
  38 #endif
  39
  40 /* Copy no more than N characters of SRC to DEST, returning the address of
  41    the terminating '\0' in DEST, if any, or else DEST + N.  */
  42 char *
  43 STPNCPY (char *dest, const char *src, size_t n)
  44 {
  45   char c;
  46   char *s = dest;
  47
  48   if (n >= 4)
  49     {
  50       size_t n4 = n >> 2;
  51
  52       for (;;)
  53         {
  54           c = *src++;
  55           *dest++ = c;
  56           if (c == '\0')
  57             break;
  58           c = *src++;
  59           *dest++ = c;
  60           if (c == '\0')
  61             break;
  62           c = *src++;
  63           *dest++ = c;
  64           if (c == '\0')
  65             break;
  66           c = *src++;
  67           *dest++ = c;
  68           if (c == '\0')
  69             break;
  70           if (--n4 == 0)
  71             goto last_chars;
  72         }
  73       n -= dest - s;
  74       goto zero_fill;
  75     }
  76
  77  last_chars:
  78   n &= 3;
  79   if (n == 0)
  80     return dest;
  81
  82   for (;;)
  83     {
  84       c = *src++;
  85       --n;
  86       *dest++ = c;
  87       if (c == '\0')
  88         break;
  89       if (n == 0)
  90         return dest;
  91     }
  92
  93  zero_fill:
  94   while (n-- > 0)
  95     dest[n] = '\0';
  96
  97   return dest - 1;
  98 }
  99 #ifdef weak_alias
 100 libc_hidden_def (__stpncpy)
 101 #endif