1/*-
2 * Copyright (c) 2007 David Schultz
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD$
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/* digittoint is in the FreeBSD C library, but not Bionic at this point */
39static int
40digittoint(char ch)
41{
42    int d;
43
44    d = ch - '0';
45    if ((unsigned)d < 10) {
46        return d;
47    }
48    d = ch - 'a';
49    if ((unsigned)d < 6) {
50        return d + 10;
51    }
52    d = ch - 'A';
53    if ((unsigned)d < 6) {
54        return d + 10;
55    }
56    return -1;
57}
58
59/*
60 * Scan a string of hexadecimal digits (the format nan(3) expects) and
61 * make a bit array (using the local endianness). We stop when we
62 * encounter an invalid character, NUL, etc.  If we overflow, we do
63 * the same as gcc's __builtin_nan(), namely, discard the high order bits.
64 *
65 * The format this routine accepts needs to be compatible with what is used
66 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in
67 * __builtin_nan(). In fact, we're only 100% compatible for strings we
68 * consider valid, so we might be violating the C standard. But it's
69 * impossible to use nan(3) portably anyway, so this seems good enough.
70 */
71void
72_scan_nan(uint32_t *words, int num_words, const char *s)
73{
74	int si;		/* index into s */
75	int bitpos;	/* index into words (in bits) */
76
77	bzero(words, num_words * sizeof(uint32_t));
78
79	/* Allow a leading '0x'. (It's expected, but redundant.) */
80	if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X'))
81		s += 2;
82
83	/* Scan forwards in the string, looking for the end of the sequence. */
84	for (si = 0; isxdigit(s[si]); si++)
85		;
86
87	/* Scan backwards, filling in the bits in words[] as we go. */
88#if _BYTE_ORDER == _LITTLE_ENDIAN
89	for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) {
90#else
91	for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) {
92#endif
93		if (--si < 0)
94			break;
95		words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32);
96	}
97}
98
99double
100nan(const char *s)
101{
102	union {
103		double d;
104		uint32_t bits[2];
105	} u;
106
107	_scan_nan(u.bits, 2, s);
108#if _BYTE_ORDER == _LITTLE_ENDIAN
109	u.bits[1] |= 0x7ff80000;
110#else
111	u.bits[0] |= 0x7ff80000;
112#endif
113	return (u.d);
114}
115
116float
117nanf(const char *s)
118{
119	union {
120		float f;
121		uint32_t bits[1];
122	} u;
123
124	_scan_nan(u.bits, 1, s);
125	u.bits[0] |= 0x7fc00000;
126	return (u.f);
127}
128
129#if (LDBL_MANT_DIG == 53)
130__weak_alias(nanl, nan);
131#endif
132