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 static int digittoint(char ch) { 39 int d = ch - '0'; 40 if ((unsigned) d < 10) { 41 return d; 42 } 43 d = ch - 'a'; 44 if ((unsigned) d < 6) { 45 return d + 10; 46 } 47 d = ch - 'A'; 48 if ((unsigned) d < 6) { 49 return d + 10; 50 } 51 return -1; 52 } 53 54 /* 55 * Scan a string of hexadecimal digits (the format nan(3) expects) and 56 * make a bit array (using the local endianness). We stop when we 57 * encounter an invalid character, NUL, etc. If we overflow, we do 58 * the same as gcc's __builtin_nan(), namely, discard the high order bits. 59 * 60 * The format this routine accepts needs to be compatible with what is used 61 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in 62 * __builtin_nan(). In fact, we're only 100% compatible for strings we 63 * consider valid, so we might be violating the C standard. But it's 64 * impossible to use nan(3) portably anyway, so this seems good enough. 65 */ 66 void 67 _scan_nan(uint32_t *words, int num_words, const char *s) 68 { 69 int si; /* index into s */ 70 int bitpos; /* index into words (in bits) */ 71 72 bzero(words, num_words * sizeof(uint32_t)); 73 74 /* Allow a leading '0x'. (It's expected, but redundant.) */ 75 if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X')) 76 s += 2; 77 78 /* Scan forwards in the string, looking for the end of the sequence. */ 79 for (si = 0; isxdigit(s[si]); si++) 80 ; 81 82 /* Scan backwards, filling in the bits in words[] as we go. */ 83 #if _BYTE_ORDER == _LITTLE_ENDIAN 84 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) { 85 #else 86 for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) { 87 #endif 88 if (--si < 0) 89 break; 90 words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32); 91 } 92 } 93 94 double 95 nan(const char *s) 96 { 97 union { 98 double d; 99 uint32_t bits[2]; 100 } u; 101 102 _scan_nan(u.bits, 2, s); 103 #if _BYTE_ORDER == _LITTLE_ENDIAN 104 u.bits[1] |= 0x7ff80000; 105 #else 106 u.bits[0] |= 0x7ff80000; 107 #endif 108 return (u.d); 109 } 110 111 float 112 nanf(const char *s) 113 { 114 union { 115 float f; 116 uint32_t bits[1]; 117 } u; 118 119 _scan_nan(u.bits, 1, s); 120 u.bits[0] |= 0x7fc00000; 121 return (u.f); 122 } 123 124 #if (LDBL_MANT_DIG == 53) 125 #define __weak_reference(sym,alias) \ 126 __asm__(".weak " #alias); \ 127 __asm__(".equ " #alias ", " #sym) 128 __weak_reference(nan, nanl); 129 #endif 130
