1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 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 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 38 /* 39 * Scan a string of hexadecimal digits (the format nan(3) expects) and 40 * make a bit array (using the local endianness). We stop when we 41 * encounter an invalid character, NUL, etc. If we overflow, we do 42 * the same as gcc's __builtin_nan(), namely, discard the high order bits. 43 * 44 * The format this routine accepts needs to be compatible with what is used 45 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in 46 * __builtin_nan(). In fact, we're only 100% compatible for strings we 47 * consider valid, so we might be violating the C standard. But it's 48 * impossible to use nan(3) portably anyway, so this seems good enough. 49 */ 50 void 51 _scan_nan(uint32_t *words, int num_words, const char *s) 52 { 53 int si; /* index into s */ 54 int bitpos; /* index into words (in bits) */ 55 56 bzero(words, num_words * sizeof(uint32_t)); 57 58 /* Allow a leading '0x'. (It's expected, but redundant.) */ 59 if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X')) 60 s += 2; 61 62 /* Scan forwards in the string, looking for the end of the sequence. */ 63 for (si = 0; isxdigit(s[si]); si++) 64 ; 65 66 /* Scan backwards, filling in the bits in words[] as we go. */ 67 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) { 68 if (--si < 0) 69 break; 70 #if _BYTE_ORDER == _LITTLE_ENDIAN 71 words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32); 72 #else 73 words[num_words - 1 - bitpos / 32] |= 74 digittoint(s[si]) << (bitpos % 32); 75 #endif 76 } 77 } 78 79 double 80 nan(const char *s) 81 { 82 union { 83 double d; 84 uint32_t bits[2]; 85 } u; 86 87 _scan_nan(u.bits, 2, s); 88 #if _BYTE_ORDER == _LITTLE_ENDIAN 89 u.bits[1] |= 0x7ff80000; 90 #else 91 u.bits[0] |= 0x7ff80000; 92 #endif 93 return (u.d); 94 } 95 96 float 97 nanf(const char *s) 98 { 99 union { 100 float f; 101 uint32_t bits[1]; 102 } u; 103 104 _scan_nan(u.bits, 1, s); 105 u.bits[0] |= 0x7fc00000; 106 return (u.f); 107 } 108 109 #if (LDBL_MANT_DIG == 53) 110 __weak_reference(nan, nanl); 111 #endif 112