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 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) { 70 if (--si < 0) 71 break; 72 #if _BYTE_ORDER == _LITTLE_ENDIAN 73 words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32); 74 #else 75 words[num_words - 1 - bitpos / 32] |= 76 digittoint(s[si]) << (bitpos % 32); 77 #endif 78 } 79 } 80 81 double 82 nan(const char *s) 83 { 84 union { 85 double d; 86 uint32_t bits[2]; 87 } u; 88 89 _scan_nan(u.bits, 2, s); 90 #if _BYTE_ORDER == _LITTLE_ENDIAN 91 u.bits[1] |= 0x7ff80000; 92 #else 93 u.bits[0] |= 0x7ff80000; 94 #endif 95 return (u.d); 96 } 97 98 float 99 nanf(const char *s) 100 { 101 union { 102 float f; 103 uint32_t bits[1]; 104 } u; 105 106 _scan_nan(u.bits, 1, s); 107 u.bits[0] |= 0x7fc00000; 108 return (u.f); 109 } 110 111 #if (LDBL_MANT_DIG == 53) 112 __weak_reference(nan, nanl); 113 #endif 114