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/*-
* Copyright (c) 2007 David Schultz
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD: src/lib/msun/src/s_nan.c,v 1.2.2.1.2.1 2009/10/25 01:10:29 kensmith Exp $
*/
#include <sys/endian.h>
#include <ctype.h>
#include <float.h>
#include <math.h>
#include <stdint.h>
#include <strings.h>
#include "math_private.h"
/*
* Scan a string of hexadecimal digits (the format nan(3) expects) and
* make a bit array (using the local endianness). We stop when we
* encounter an invalid character, NUL, etc. If we overflow, we do
* the same as gcc's __builtin_nan(), namely, discard the high order bits.
*
* The format this routine accepts needs to be compatible with what is used
* in contrib/gdtoa/hexnan.c (for strtod/scanf) and what is used in
* __builtin_nan(). In fact, we're only 100% compatible for strings we
* consider valid, so we might be violating the C standard. But it's
* impossible to use nan(3) portably anyway, so this seems good enough.
*/
void
_scan_nan(uint32_t *words, int num_words, const char *s)
{
int si; /* index into s */
int bitpos; /* index into words (in bits) */
bzero(words, num_words * sizeof(uint32_t));
/* Allow a leading '0x'. (It's expected, but redundant.) */
if (s[0] == '0' && (s[1] == 'x' || s[1] == 'X'))
s += 2;
/* Scan forwards in the string, looking for the end of the sequence. */
for (si = 0; isxdigit(s[si]); si++)
;
/* Scan backwards, filling in the bits in words[] as we go. */
#if _BYTE_ORDER == _LITTLE_ENDIAN
for (bitpos = 0; bitpos < 32 * num_words; bitpos += 4) {
#else
for (bitpos = 32 * num_words - 4; bitpos >= 0; bitpos -= 4) {
#endif
if (--si < 0)
break;
words[bitpos / 32] |= digittoint(s[si]) << (bitpos % 32);
}
}
double
nan(const char *s)
{
union {
double d;
uint32_t bits[2];
} u;
_scan_nan(u.bits, 2, s);
#if _BYTE_ORDER == _LITTLE_ENDIAN
u.bits[1] |= 0x7ff80000;
#else
u.bits[0] |= 0x7ff80000;
#endif
return (u.d);
}
float
nanf(const char *s)
{
union {
float f;
uint32_t bits[1];
} u;
_scan_nan(u.bits, 1, s);
u.bits[0] |= 0x7fc00000;
return (u.f);
}
#if (LDBL_MANT_DIG == 53)
__weak_reference(nan, nanl);
#endif
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