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
digittoint(char ch)38 static 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 */
66 void
_scan_nan(uint32_t * words,int num_words,const char * s)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
94 double
95 nan(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
111 float
112 nanf(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