1 /* $OpenBSD: s_nan.c,v 1.13 2014/07/21 01:51:11 guenther Exp $ */
2 /*-
3 * Copyright (c) 2007 David Schultz
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 * $FreeBSD: src/lib/msun/src/s_nan.c,v 1.2 2007/12/18 23:46:32 das Exp $
28 */
29
30 #include <sys/types.h>
31 #include <ctype.h>
32 #include <sys/endian.h>
33 #include <float.h>
34 #include <math.h>
35 #include <stdint.h>
36 #include <strings.h>
37
38 #include "math_private.h"
39
40 /*
41 * OpenBSD's ctype doesn't have digittoint, so we define it here.
42 */
43 static int
_digittoint(int c)44 _digittoint(int c)
45 {
46 if (!isxdigit(c))
47 return 0;
48
49 if (isdigit(c))
50 return c - '0';
51 else
52 return isupper(c) ? c - 'A' + 10 : c - 'a' + 10;
53 }
54
55 /*
56 * Scan a string of hexadecimal digits (the format nan(3) expects) and
57 * make a bit array (using the local endianness). We stop when we
58 * encounter an invalid character, NUL, etc. If we overflow, we do
59 * the same as gcc's __builtin_nan(), namely, discard the high order bits.
60 *
61 * The format this routine accepts needs to be compatible with what is used
62 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in
63 * __builtin_nan(). In fact, we're only 100% compatible for strings we
64 * consider valid, so we might be violating the C standard. But it's
65 * impossible to use nan(3) portably anyway, so this seems good enough.
66 */
67 void
_scan_nan(uint32_t * words,int num_words,const char * s)68 _scan_nan(uint32_t *words, int num_words, const char *s)
69 {
70 int si; /* index into s */
71 int bitpos; /* index into words (in bits) */
72
73 bzero(words, num_words * sizeof(uint32_t));
74
75 /* Allow a leading '0x'. (It's expected, but redundant.) */
76 if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X'))
77 s += 2;
78
79 /* Scan forwards in the string, looking for the end of the sequence. */
80 for (si = 0; isxdigit((unsigned char)s[si]); si++)
81 ;
82
83 /* Scan backwards, filling in the bits in words[] as we go. */
84 #if BYTE_ORDER == LITTLE_ENDIAN
85 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) {
86 #else
87 for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) {
88 #endif
89 if (--si < 0)
90 break;
91 words[bitpos / 32] |= _digittoint((unsigned char)s[si]) << (bitpos % 32);
92 }
93 }
94
95 double
96 nan(const char *s)
97 {
98 union {
99 double d;
100 uint32_t bits[2];
101 } u;
102
103 _scan_nan(u.bits, 2, s);
104 #if BYTE_ORDER == LITTLE_ENDIAN
105 u.bits[1] |= 0x7ff80000;
106 #else
107 u.bits[0] |= 0x7ff80000;
108 #endif
109 return (u.d);
110 }
111
112 float
113 nanf(const char *s)
114 {
115 union {
116 float f;
117 uint32_t bits[1];
118 } u;
119
120 _scan_nan(u.bits, 1, s);
121 u.bits[0] |= 0x7fc00000;
122 return (u.f);
123 }
124
125 #if LDBL_MANT_DIG == DBL_MANT_DIG
126 __strong_alias(nanl, nan);
127 #endif /* LDBL_MANT_DIG == DBL_MANT_DIG */
128