1 /*- 2 * Copyright (c) 2007 David Schultz 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 * 26 * $FreeBSD$ 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 #if _BYTE_ORDER == _LITTLE_ENDIAN 68 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) { 69 #else 70 for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) { 71 #endif 72 if (--si < 0) 73 break; 74 words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32); 75 } 76 } 77 78 double 79 nan(const char *s) 80 { 81 union { 82 double d; 83 uint32_t bits[2]; 84 } u; 85 86 _scan_nan(u.bits, 2, s); 87 #if _BYTE_ORDER == _LITTLE_ENDIAN 88 u.bits[1] |= 0x7ff80000; 89 #else 90 u.bits[0] |= 0x7ff80000; 91 #endif 92 return (u.d); 93 } 94 95 float 96 nanf(const char *s) 97 { 98 union { 99 float f; 100 uint32_t bits[1]; 101 } u; 102 103 _scan_nan(u.bits, 1, s); 104 u.bits[0] |= 0x7fc00000; 105 return (u.f); 106 } 107 108 #if (LDBL_MANT_DIG == 53) 109 __weak_reference(nan, nanl); 110 #endif 111