1 /*
2 Copyright (c) 1994 Cygnus Support.
3 All rights reserved.
4
5 Redistribution and use in source and binary forms are permitted
6 provided that the above copyright notice and this paragraph are
7 duplicated in all such forms and that any documentation,
8 and/or other materials related to such
9 distribution and use acknowledge that the software was developed
10 at Cygnus Support, Inc. Cygnus Support, Inc. may not be used to
11 endorse or promote products derived from this software without
12 specific prior written permission.
13 THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
14 IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
15 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
16 */
17 /*
18 FUNCTION
19 <<strncpy>>---counted copy string
20
21 INDEX
22 strncpy
23
24 SYNOPSIS
25 #include <string.h>
26 char *strncpy(char *restrict <[dst]>, const char *restrict <[src]>,
27 size_t <[length]>);
28
29 DESCRIPTION
30 <<strncpy>> copies not more than <[length]> characters from
31 the string pointed to by <[src]> (including the terminating
32 null character) to the array pointed to by <[dst]>. If the
33 string pointed to by <[src]> is shorter than <[length]>
34 characters, null characters are appended to the destination
35 array until a total of <[length]> characters have been
36 written.
37
38 RETURNS
39 This function returns the initial value of <[dst]>.
40
41 PORTABILITY
42 <<strncpy>> is ANSI C.
43
44 <<strncpy>> requires no supporting OS subroutines.
45
46 QUICKREF
47 strncpy ansi pure
48 */
49
50 #include <string.h>
51 #include <limits.h>
52 #include <stdint.h>
53
54 /*SUPPRESS 560*/
55 /*SUPPRESS 530*/
56
57 /* Nonzero if either X or Y is not aligned on a "long" boundary. */
58 #define UNALIGNED(X, Y) \
59 (((uintptr_t)X & (sizeof (long) - 1)) | ((uintptr_t)Y & (sizeof (long) - 1)))
60
61 #if LONG_MAX == 2147483647L
62 #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
63 #else
64 #if LONG_MAX == 9223372036854775807L
65 /* Nonzero if X (a long int) contains a NULL byte. */
66 #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
67 #else
68 #error long int is not a 32bit or 64bit type.
69 #endif
70 #endif
71
72 #ifndef DETECTNULL
73 #error long int is not a 32bit or 64bit byte
74 #endif
75
76 #define TOO_SMALL(LEN) ((LEN) < sizeof (long))
77
78 #undef strncpy
79
80 char *
strncpy(char * __restrict dst0,const char * __restrict src0,size_t count)81 strncpy (char *__restrict dst0,
82 const char *__restrict src0,
83 size_t count)
84 {
85 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) || \
86 defined(PICOLIBC_NO_OUT_OF_BOUNDS_READS)
87 char *dscan;
88 const char *sscan;
89
90 dscan = dst0;
91 sscan = src0;
92 while (count > 0)
93 {
94 --count;
95 if ((*dscan++ = *sscan++) == '\0')
96 break;
97 }
98 while (count-- > 0)
99 *dscan++ = '\0';
100
101 return dst0;
102 #else
103 char *dst = dst0;
104 const char *src = src0;
105 long *aligned_dst;
106 const long *aligned_src;
107
108 /* If SRC and DEST is aligned and count large enough, then copy words. */
109 if (!UNALIGNED (src, dst) && !TOO_SMALL (count))
110 {
111 aligned_dst = (long*)dst;
112 aligned_src = (long*)src;
113
114 /* SRC and DEST are both "long int" aligned, try to do "long int"
115 sized copies. */
116 while (count >= sizeof (long int) && !DETECTNULL(*aligned_src))
117 {
118 count -= sizeof (long int);
119 *aligned_dst++ = *aligned_src++;
120 }
121
122 dst = (char*)aligned_dst;
123 src = (char*)aligned_src;
124 }
125
126 while (count > 0)
127 {
128 --count;
129 if ((*dst++ = *src++) == '\0')
130 break;
131 }
132
133 while (count-- > 0)
134 *dst++ = '\0';
135
136 return dst0;
137 #endif /* not PREFER_SIZE_OVER_SPEED */
138 }
139
