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 * $FreeBSD$
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 */
52void
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
80double
81nan(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
97float
98nanf(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