1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
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
29 #include <sys/endian.h>
30 #include <ctype.h>
31 #include <float.h>
32 #include <math.h>
33 #include <stdint.h>
34 #include <strings.h>
35
36 #include "math_private.h"
37
38 /*
39 * Scan a string of hexadecimal digits (the format nan(3) expects) and
40 * make a bit array (using the local endianness). We stop when we
41 * encounter an invalid character, NUL, etc. If we overflow, we do
42 * the same as gcc's __builtin_nan(), namely, discard the high order bits.
43 *
44 * The format this routine accepts needs to be compatible with what is used
45 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in
46 * __builtin_nan(). In fact, we're only 100% compatible for strings we
47 * consider valid, so we might be violating the C standard. But it's
48 * impossible to use nan(3) portably anyway, so this seems good enough.
49 */
50 void
_scan_nan(uint32_t * words,int num_words,const char * s)51 _scan_nan(uint32_t *words, int num_words, const char *s)
52 {
53 int si; /* index into s */
54 int bitpos; /* index into words (in bits) */
55
56 bzero(words, num_words * sizeof(uint32_t));
57
58 /* Allow a leading '0x'. (It's expected, but redundant.) */
59 if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X'))
60 s += 2;
61
62 /* Scan forwards in the string, looking for the end of the sequence. */
63 for (si = 0; isxdigit(s[si]); si++)
64 ;
65
66 /* Scan backwards, filling in the bits in words[] as we go. */
67 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) {
68 if (--si < 0)
69 break;
70 #if _BYTE_ORDER == _LITTLE_ENDIAN
71 words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32);
72 #else
73 words[num_words - 1 - bitpos / 32] |=
74 digittoint(s[si]) << (bitpos % 32);
75 #endif
76 }
77 }
78
79 double
nan(const char * s)80 nan(const char *s)
81 {
82 union {
83 double d;
84 uint32_t bits[2];
85 } u;
86
87 _scan_nan(u.bits, 2, s);
88 #if _BYTE_ORDER == _LITTLE_ENDIAN
89 u.bits[1] |= 0x7ff80000;
90 #else
91 u.bits[0] |= 0x7ff80000;
92 #endif
93 return (u.d);
94 }
95
96 float
nanf(const char * s)97 nanf(const char *s)
98 {
99 union {
100 float f;
101 uint32_t bits[1];
102 } u;
103
104 _scan_nan(u.bits, 1, s);
105 u.bits[0] |= 0x7fc00000;
106 return (u.f);
107 }
108
109 #if (LDBL_MANT_DIG == 53)
110 __weak_reference(nan, nanl);
111 #endif
112