1 /* Copyright (C) 1993, 1995-1997, 2002-2003, 2005-2007, 2009-2018 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 program is free software: you can redistribute it and/or modify it
8    under the terms of the GNU General Public License as published by the
9    Free Software Foundation; either version 3 of the License, or any
10    later version.
11 
12    This program 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 General Public License for more details.
16 
17    You should have received a copy of the GNU 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
93