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[glibc.git] / sysdeps / generic / stpncpy.c
blob8303f6e5fce1972e415b82e4c5e13bc234fe2974
1 /* Copyright (C) 1993, 1995, 1996, 1997 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Library General Public License as
6 published by the Free Software Foundation; either version 2 of the
7 License, or (at your option) any later version.
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 Library General Public License for more details.
14 You should have received a copy of the GNU Library General Public
15 License along with the GNU C Library; see the file COPYING.LIB. If not,
16 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 Boston, MA 02111-1307, USA. */
19 /* This is almost copied from strncpy.c, written by Torbjorn Granlund. */
21 #ifdef HAVE_CONFIG_H
22 # include <config.h>
23 #endif
25 #ifdef _LIBC
26 # include <string.h>
27 #else
28 # include <sys/types.h>
29 #endif
31 #ifndef weak_alias
32 # define __stpncpy stpncpy
33 #endif
35 /* Copy no more than N characters of SRC to DEST, returning the address of
36 the terminating '\0' in DEST, if any, or else DEST + N. */
37 char *
38 __stpncpy (dest, src, n)
39 char *dest;
40 const char *src;
41 size_t n;
43 char c;
44 char *s = dest;
46 if (n >= 4)
48 size_t n4 = n >> 2;
50 for (;;)
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 c = *src++;
65 *dest++ = c;
66 if (c == '\0')
67 break;
68 if (--n4 == 0)
69 goto last_chars;
71 n -= dest - s;
72 goto zero_fill;
75 last_chars:
76 n &= 3;
77 if (n == 0)
78 return dest;
80 for (;;)
82 c = *src++;
83 --n;
84 *dest++ = c;
85 if (c == '\0')
86 break;
87 if (n == 0)
88 return dest;
91 zero_fill:
92 while (n-- > 0)
93 dest[n] = '\0';
95 return dest - 1;
97 #ifdef weak_alias
98 weak_alias (__stpncpy, stpncpy)
99 #endif