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
38static int digittoint(char ch) {
39  int d = ch - '0';
40  if ((unsigned) d < 10) {
41    return d;
42  }
43  d = ch - 'a';
44  if ((unsigned) d < 6) {
45    return d + 10;
46  }
47  d = ch - 'A';
48  if ((unsigned) d < 6) {
49    return d + 10;
50  }
51  return -1;
52}
53
54/*
55 * Scan a string of hexadecimal digits (the format nan(3) expects) and
56 * make a bit array (using the local endianness). We stop when we
57 * encounter an invalid character, NUL, etc.  If we overflow, we do
58 * the same as gcc's __builtin_nan(), namely, discard the high order bits.
59 *
60 * The format this routine accepts needs to be compatible with what is used
61 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in
62 * __builtin_nan(). In fact, we're only 100% compatible for strings we
63 * consider valid, so we might be violating the C standard. But it's
64 * impossible to use nan(3) portably anyway, so this seems good enough.
65 */
66void
67_scan_nan(uint32_t *words, int num_words, const char *s)
68{
69	int si;		/* index into s */
70	int bitpos;	/* index into words (in bits) */
71
72	bzero(words, num_words * sizeof(uint32_t));
73
74	/* Allow a leading '0x'. (It's expected, but redundant.) */
75	if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X'))
76		s += 2;
77
78	/* Scan forwards in the string, looking for the end of the sequence. */
79	for (si = 0; isxdigit(s[si]); si++)
80		;
81
82	/* Scan backwards, filling in the bits in words[] as we go. */
83#if _BYTE_ORDER == _LITTLE_ENDIAN
84	for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) {
85#else
86	for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) {
87#endif
88		if (--si < 0)
89			break;
90		words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32);
91	}
92}
93
94double
95nan(const char *s)
96{
97	union {
98		double d;
99		uint32_t bits[2];
100	} u;
101
102	_scan_nan(u.bits, 2, s);
103#if _BYTE_ORDER == _LITTLE_ENDIAN
104	u.bits[1] |= 0x7ff80000;
105#else
106	u.bits[0] |= 0x7ff80000;
107#endif
108	return (u.d);
109}
110
111float
112nanf(const char *s)
113{
114	union {
115		float f;
116		uint32_t bits[1];
117	} u;
118
119	_scan_nan(u.bits, 1, s);
120	u.bits[0] |= 0x7fc00000;
121	return (u.f);
122}
123
124#if (LDBL_MANT_DIG == 53)
125#define __weak_reference(sym,alias) \
126    __asm__(".weak " #alias); \
127    __asm__(".equ "  #alias ", " #sym)
128__weak_reference(nan, nanl);
129#endif
130