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