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 */
39 static int
digittoint(char ch)40 digittoint(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 */
71 void
_scan_nan(uint32_t * words,int num_words,const char * s)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
99 double
100 nan(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
116 float
117 nanf(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