1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2007 David Schultz
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * $FreeBSD: head/lib/msun/src/s_nan.c 326219 2017-11-26 02:00:33Z pfg $
29 */
30
31 #include <sys/endian.h>
32 #include <ctype.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 * Scan a string of hexadecimal digits (the format nan(3) expects) and
42 * make a bit array (using the local endianness). We stop when we
43 * encounter an invalid character, NUL, etc. If we overflow, we do
44 * the same as gcc's __builtin_nan(), namely, discard the high order bits.
45 *
46 * The format this routine accepts needs to be compatible with what is used
47 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in
48 * __builtin_nan(). In fact, we're only 100% compatible for strings we
49 * consider valid, so we might be violating the C standard. But it's
50 * impossible to use nan(3) portably anyway, so this seems good enough.
51 */
52 void
_scan_nan(uint32_t * words,int num_words,const char * s)53 _scan_nan(uint32_t *words, int num_words, const char *s)
54 {
55 int si; /* index into s */
56 int bitpos; /* index into words (in bits) */
57
58 bzero(words, num_words * sizeof(uint32_t));
59
60 /* Allow a leading '0x'. (It's expected, but redundant.) */
61 if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X'))
62 s += 2;
63
64 /* Scan forwards in the string, looking for the end of the sequence. */
65 for (si = 0; isxdigit(s[si]); si++)
66 ;
67
68 /* Scan backwards, filling in the bits in words[] as we go. */
69 #if _BYTE_ORDER == _LITTLE_ENDIAN
70 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) {
71 #else
72 for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) {
73 #endif
74 if (--si < 0)
75 break;
76 words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32);
77 }
78 }
79
80 double
81 nan(const char *s)
82 {
83 union {
84 double d;
85 uint32_t bits[2];
86 } u;
87
88 _scan_nan(u.bits, 2, s);
89 #if _BYTE_ORDER == _LITTLE_ENDIAN
90 u.bits[1] |= 0x7ff80000;
91 #else
92 u.bits[0] |= 0x7ff80000;
93 #endif
94 return (u.d);
95 }
96
97 float
98 nanf(const char *s)
99 {
100 union {
101 float f;
102 uint32_t bits[1];
103 } u;
104
105 _scan_nan(u.bits, 1, s);
106 u.bits[0] |= 0x7fc00000;
107 return (u.f);
108 }
109
110 #if (LDBL_MANT_DIG == 53)
111 __weak_reference(nan, nanl);
112 #endif
113