1 /* $OpenBSD: s_nan.c,v 1.14 2016/09/12 19:47:02 guenther 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/types.h> 31 #include <ctype.h> 32 #include <endian.h> 33 #include <float.h> 34 #include <math.h> 35 #include <stdint.h> 36 #include <strings.h> 37 38 #include "math_private.h" 39 40 /* 41 * OpenBSD's ctype doesn't have digittoint, so we define it here. 42 */ 43 static int 44 _digittoint(int c) 45 { 46 if (!isxdigit(c)) 47 return 0; 48 49 if (isdigit(c)) 50 return c - '0'; 51 else 52 return isupper(c) ? c - 'A' + 10 : c - 'a' + 10; 53 } 54 55 /* 56 * Scan a string of hexadecimal digits (the format nan(3) expects) and 57 * make a bit array (using the local endianness). We stop when we 58 * encounter an invalid character, NUL, etc. If we overflow, we do 59 * the same as gcc's __builtin_nan(), namely, discard the high order bits. 60 * 61 * The format this routine accepts needs to be compatible with what is used 62 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in 63 * __builtin_nan(). In fact, we're only 100% compatible for strings we 64 * consider valid, so we might be violating the C standard. But it's 65 * impossible to use nan(3) portably anyway, so this seems good enough. 66 */ 67 void 68 _scan_nan(uint32_t *words, int num_words, const char *s) 69 { 70 int si; /* index into s */ 71 int bitpos; /* index into words (in bits) */ 72 73 bzero(words, num_words * sizeof(uint32_t)); 74 75 /* Allow a leading '0x'. (It's expected, but redundant.) */ 76 if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X')) 77 s += 2; 78 79 /* Scan forwards in the string, looking for the end of the sequence. */ 80 for (si = 0; isxdigit((unsigned char)s[si]); si++) 81 ; 82 83 /* Scan backwards, filling in the bits in words[] as we go. */ 84 #if BYTE_ORDER == LITTLE_ENDIAN 85 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) { 86 #else 87 for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) { 88 #endif 89 if (--si < 0) 90 break; 91 words[bitpos / 32] |= _digittoint((unsigned char)s[si]) << (bitpos % 32); 92 } 93 } 94 95 double 96 nan(const char *s) 97 { 98 union { 99 double d; 100 uint32_t bits[2]; 101 } u; 102 103 _scan_nan(u.bits, 2, s); 104 #if BYTE_ORDER == LITTLE_ENDIAN 105 u.bits[1] |= 0x7ff80000; 106 #else 107 u.bits[0] |= 0x7ff80000; 108 #endif 109 return (u.d); 110 } 111 DEF_STD(nan); 112 LDBL_MAYBE_UNUSED_CLONE(nan); 113 114 float 115 nanf(const char *s) 116 { 117 union { 118 float f; 119 uint32_t bits[1]; 120 } u; 121 122 _scan_nan(u.bits, 1, s); 123 u.bits[0] |= 0x7fc00000; 124 return (u.f); 125 } 126