1 /* $OpenBSD: s_nan.c,v 1.6 2008/12/10 01:08:25 martynas Exp $ */ 2 /*- 3 * Copyright (c) 2007 David Schultz 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE 19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 * 27 * $FreeBSD: src/lib/msun/src/s_nan.c,v 1.2 2007/12/18 23:46:32 das Exp $ 28 */ 29 30 #include <sys/cdefs.h> 31 #include <sys/types.h> 32 #include <sys/endian.h> 33 #include <ctype.h> 34 #include <float.h> 35 #include <math.h> 36 #include <stdint.h> 37 #include <strings.h> 38 39 #include "math_private.h" 40 41 /* 42 * OpenBSD's ctype doesn't have digittoint, so we define it here. 43 */ 44 static int 45 _digittoint(int c) 46 { 47 if (!isxdigit(c)) 48 return 0; 49 50 if (isdigit(c)) 51 return c - '0'; 52 else 53 return isupper(c) ? c - 'A' + 10 : c - 'a' + 10; 54 } 55 56 /* 57 * Scan a string of hexadecimal digits (the format nan(3) expects) and 58 * make a bit array (using the local endianness). We stop when we 59 * encounter an invalid character, NUL, etc. If we overflow, we do 60 * the same as gcc's __builtin_nan(), namely, discard the high order bits. 61 * 62 * The format this routine accepts needs to be compatible with what is used 63 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in 64 * __builtin_nan(). In fact, we're only 100% compatible for strings we 65 * consider valid, so we might be violating the C standard. But it's 66 * impossible to use nan(3) portably anyway, so this seems good enough. 67 */ 68 void 69 _scan_nan(uint32_t *words, int num_words, const char *s) 70 { 71 int si; /* index into s */ 72 int bitpos; /* index into words (in bits) */ 73 74 bzero(words, num_words * sizeof(uint32_t)); 75 76 /* Allow a leading '0x'. (It's expected, but redundant.) */ 77 if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X')) 78 s += 2; 79 80 /* Scan forwards in the string, looking for the end of the sequence. */ 81 for (si = 0; isxdigit(s[si]); si++) 82 ; 83 84 /* Scan backwards, filling in the bits in words[] as we go. */ 85 #if _BYTE_ORDER == _LITTLE_ENDIAN 86 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) { 87 #else 88 for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) { 89 #endif 90 if (--si < 0) 91 break; 92 words[bitpos / 32] |= _digittoint(s[si]) << (bitpos % 32); 93 } 94 } 95 96 double 97 nan(const char *s) 98 { 99 union { 100 double d; 101 uint32_t bits[2]; 102 } u; 103 104 _scan_nan(u.bits, 2, s); 105 #if _BYTE_ORDER == _LITTLE_ENDIAN 106 u.bits[1] |= 0x7ff80000; 107 #else 108 u.bits[0] |= 0x7ff80000; 109 #endif 110 return (u.d); 111 } 112 113 float 114 nanf(const char *s) 115 { 116 union { 117 float f; 118 uint32_t bits[1]; 119 } u; 120 121 _scan_nan(u.bits, 1, s); 122 u.bits[0] |= 0x7fc00000; 123 return (u.f); 124 } 125 126 #if LDBL_MANT_DIG == 53 127 #ifdef __weak_alias 128 __weak_alias(nanl, nan); 129 #endif /* __weak_alias */ 130 #endif /* LDBL_MANT_DIG == 53 */ 131