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 /* digittoint is in the FreeBSD C library, but not Bionic at this point */ 39 static int 40 digittoint(char ch) 41 { 42 int d; 43 44 d = ch - '0'; 45 if ((unsigned)d < 10) { 46 return d; 47 } 48 d = ch - 'a'; 49 if ((unsigned)d < 6) { 50 return d + 10; 51 } 52 d = ch - 'A'; 53 if ((unsigned)d < 6) { 54 return d + 10; 55 } 56 return -1; 57 } 58 59 /* 60 * Scan a string of hexadecimal digits (the format nan(3) expects) and 61 * make a bit array (using the local endianness). We stop when we 62 * encounter an invalid character, NUL, etc. If we overflow, we do 63 * the same as gcc's __builtin_nan(), namely, discard the high order bits. 64 * 65 * The format this routine accepts needs to be compatible with what is used 66 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in 67 * __builtin_nan(). In fact, we're only 100% compatible for strings we 68 * consider valid, so we might be violating the C standard. But it's 69 * impossible to use nan(3) portably anyway, so this seems good enough. 70 */ 71 void 72 _scan_nan(uint32_t *words, int num_words, const char *s) 73 { 74 int si; /* index into s */ 75 int bitpos; /* index into words (in bits) */ 76 77 bzero(words, num_words * sizeof(uint32_t)); 78 79 /* Allow a leading '0x'. (It's expected, but redundant.) */ 80 if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X')) 81 s += 2; 82 83 /* Scan forwards in the string, looking for the end of the sequence. */ 84 for (si = 0; isxdigit(s[si]); si++) 85 ; 86 87 /* Scan backwards, filling in the bits in words[] as we go. */ 88 #if _BYTE_ORDER == _LITTLE_ENDIAN 89 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) { 90 #else 91 for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) { 92 #endif 93 if (--si < 0) 94 break; 95 words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32); 96 } 97 } 98 99 double 100 nan(const char *s) 101 { 102 union { 103 double d; 104 uint32_t bits[2]; 105 } u; 106 107 _scan_nan(u.bits, 2, s); 108 #if _BYTE_ORDER == _LITTLE_ENDIAN 109 u.bits[1] |= 0x7ff80000; 110 #else 111 u.bits[0] |= 0x7ff80000; 112 #endif 113 return (u.d); 114 } 115 116 float 117 nanf(const char *s) 118 { 119 union { 120 float f; 121 uint32_t bits[1]; 122 } u; 123 124 _scan_nan(u.bits, 1, s); 125 u.bits[0] |= 0x7fc00000; 126 return (u.f); 127 } 128 129 #if (LDBL_MANT_DIG == 53) 130 __weak_alias(nanl, nan); 131 #endif 132