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: src/lib/msun/src/s_nan.c,v 1.2 2007/12/18 23:46:32 das Exp $ 27 */ 28 29 //VBS 30 //#include <sys/endian.h> 31 #include <ctype.h> 32 #include <float.h> 33 #include <openlibm.h> 34 #include <stdint.h> 35 #include <strings.h> 36 37 #include "math_private.h" 38 39 /* 40 * Scan a string of hexadecimal digits (the format nan(3) expects) and 41 * make a bit array (using the local endianness). We stop when we 42 * encounter an invalid character, NUL, etc. If we overflow, we do 43 * the same as gcc's __builtin_nan(), namely, discard the high order bits. 44 * 45 * The format this routine accepts needs to be compatible with what is used 46 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in 47 * __builtin_nan(). In fact, we're only 100% compatible for strings we 48 * consider valid, so we might be violating the C standard. But it's 49 * impossible to use nan(3) portably anyway, so this seems good enough. 50 */ 51 void 52 _scan_nan(u_int32_t *words, int num_words, const char *s) 53 { 54 int si; /* index into s */ 55 int bitpos; /* index into words (in bits) */ 56 57 bzero(words, num_words * sizeof(u_int32_t)); 58 59 /* Allow a leading '0x'. (It's expected, but redundant.) */ 60 if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X')) 61 s += 2; 62 63 /* Scan forwards in the string, looking for the end of the sequence. */ 64 for (si = 0; isxdigit(s[si]); si++) 65 ; 66 67 /* Scan backwards, filling in the bits in words[] as we go. */ 68 #if _BYTE_ORDER == _LITTLE_ENDIAN 69 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) { 70 #else 71 for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) { 72 #endif 73 if (--si < 0) 74 break; 75 words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32); 76 } 77 } 78 79 double 80 nan(const char *s) 81 { 82 union { 83 double d; 84 u_int32_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 u_int32_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