2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2007 David Schultz
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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.
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19 * ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
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21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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31 #include <sys/endian.h>
38 #include "math_private.h"
41 * Scan a string of hexadecimal digits (the format nan(3) expects) and
42 * make a bit array (using the local endianness). We stop when we
43 * encounter an invalid character, NUL, etc. If we overflow, we do
44 * the same as gcc's __builtin_nan(), namely, discard the high order bits.
46 * The format this routine accepts needs to be compatible with what is used
47 * in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in
48 * __builtin_nan(). In fact, we're only 100% compatible for strings we
49 * consider valid, so we might be violating the C standard. But it's
50 * impossible to use nan(3) portably anyway, so this seems good enough.
53 _scan_nan(uint32_t *words, int num_words, const char *s)
55 int si; /* index into s */
56 int bitpos; /* index into words (in bits) */
58 bzero(words, num_words * sizeof(uint32_t));
60 /* Allow a leading '0x'. (It's expected, but redundant.) */
61 if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X'))
64 /* Scan forwards in the string, looking for the end of the sequence. */
65 for (si = 0; isxdigit(s[si]); si++)
68 /* Scan backwards, filling in the bits in words[] as we go. */
69 #if _BYTE_ORDER == _LITTLE_ENDIAN
70 for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) {
72 for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) {
76 words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32);
88 _scan_nan(u.bits, 2, s);
89 #if _BYTE_ORDER == _LITTLE_ENDIAN
90 u.bits[1] |= 0x7ff80000;
92 u.bits[0] |= 0x7ff80000;
105 _scan_nan(u.bits, 1, s);
106 u.bits[0] |= 0x7fc00000;
110 #if (LDBL_MANT_DIG == 53)
111 __weak_reference(nan, nanl);