/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2004-2008 David Schultz <das@FreeBSD.ORG>
* 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 THE 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 THE 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.
*/
#include <sys/cdefs.h>
#include <float.h>
#include <limits.h>
#include <math.h>
#include "../stdio/floatio.h"
#include "fpmath.h"
#include "gdtoaimp.h"
/* Strings values used by dtoa() */
#define INFSTR "Infinity"
#define NANSTR "NaN"
#define DBL_ADJ (DBL_MAX_EXP - 2)
#define SIGFIGS ((DBL_MANT_DIG + 3) / 4 + 1)
static const float one[] = { 1.0f, -1.0f };
/*
* This procedure converts a double-precision number in IEEE format
* into a string of hexadecimal digits and an exponent of 2. Its
* behavior is bug-for-bug compatible with dtoa() in mode 2, with the
* following exceptions:
*
* - An ndigits < 0 causes it to use as many digits as necessary to
* represent the number exactly.
* - The additional xdigs argument should point to either the string
* "0123456789ABCDEF" or the string "0123456789abcdef", depending on
* which case is desired.
* - This routine does not repeat dtoa's mistake of setting decpt
* to 9999 in the case of an infinity or NaN. INT_MAX is used
* for this purpose instead.
*
* Note that the C99 standard does not specify what the leading digit
* should be for non-zero numbers. For instance, 0x1.3p3 is the same
* as 0x2.6p2 is the same as 0x4.cp3. This implementation always makes
* the leading digit a 1. This ensures that the exponent printed is the
* actual base-2 exponent, i.e., ilogb(d).
*
* Inputs: d, xdigs, ndigits
* Outputs: decpt, sign, rve
*/
char *
__hdtoa(double d, const char *xdigs, int ndigits, int *decpt, int *sign,
char **rve)
{
union IEEEd2bits u;
char *s, *s0;
int bufsize;
uint32_t manh, manl;
u.d = d;
*sign = u.bits.sign;
switch (fpclassify(d)) {
case FP_NORMAL:
*decpt = u.bits.exp - DBL_ADJ;
break;
case FP_ZERO:
*decpt = 1;
return (nrv_alloc("0", rve, 1));
case FP_SUBNORMAL:
u.d *= 0x1p514;
*decpt = u.bits.exp - (514 + DBL_ADJ);
break;
case FP_INFINITE:
*decpt = INT_MAX;
return (nrv_alloc(INFSTR, rve, sizeof(INFSTR) - 1));
default: /* FP_NAN or unrecognized */
*decpt = INT_MAX;
return (nrv_alloc(NANSTR, rve, sizeof(NANSTR) - 1));
}
/* FP_NORMAL or FP_SUBNORMAL */
if (ndigits == 0) /* dtoa() compatibility */
ndigits = 1;
/*
* If ndigits < 0, we are expected to auto-size, so we allocate
* enough space for all the digits.
*/
bufsize = (ndigits > 0) ? ndigits : SIGFIGS;
s0 = rv_alloc(bufsize);
/* Round to the desired number of digits. */
if (SIGFIGS > ndigits && ndigits > 0) {
float redux = one[u.bits.sign];
int offset = 4 * ndigits + DBL_MAX_EXP - 4 - DBL_MANT_DIG;
u.bits.exp = offset;
u.d += redux;
u.d -= redux;
*decpt += u.bits.exp - offset;
}
manh = u.bits.manh;
manl = u.bits.manl;
*s0 = '1';
for (s = s0 + 1; s < s0 + bufsize; s++) {
*s = xdigs[(manh >> (DBL_MANH_SIZE - 4)) & 0xf];
manh = (manh << 4) | (manl >> (DBL_MANL_SIZE - 4));
manl <<= 4;
}
/* If ndigits < 0, we are expected to auto-size the precision. */
if (ndigits < 0) {
for (ndigits = SIGFIGS; s0[ndigits - 1] == '0'; ndigits--)
;
}
s = s0 + ndigits;
*s = '\0';
if (rve != NULL)
*rve = s;
return (s0);
}
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