1 /* Copyright (C) 1991, 1997 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, see
16 <http://www.gnu.org/licenses/>. */
17
18 #include <string.h>
19
20 #include "memcopy.h"
21
strncat(char * s1,const char * s2,size_t n)22 char *strncat (char *s1, const char *s2, size_t n)
23 {
24 reg_char c;
25 char *s = s1;
26
27 /* Find the end of S1. */
28 do
29 c = *s1++;
30 while (c != '\0');
31
32 /* Make S1 point before next character, so we can increment
33 it while memory is read (wins on pipelined cpus). */
34 s1 -= 2;
35
36 if (n >= 4)
37 {
38 size_t n4 = n >> 2;
39 do
40 {
41 c = *s2++;
42 *++s1 = c;
43 if (c == '\0')
44 return s;
45 c = *s2++;
46 *++s1 = c;
47 if (c == '\0')
48 return s;
49 c = *s2++;
50 *++s1 = c;
51 if (c == '\0')
52 return s;
53 c = *s2++;
54 *++s1 = c;
55 if (c == '\0')
56 return s;
57 } while (--n4 > 0);
58 n &= 3;
59 }
60
61 while (n > 0)
62 {
63 c = *s2++;
64 *++s1 = c;
65 if (c == '\0')
66 return s;
67 n--;
68 }
69
70 if (c != '\0')
71 *++s1 = '\0';
72
73 return s;
74 }
75 libc_hidden_def(strncat)
76