1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2003 David Schultz <das@FreeBSD.ORG>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
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.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30__FBSDID("$FreeBSD$");
31
32#include <float.h>
33#include <inttypes.h>
34#include <limits.h>
35#include <math.h>
36#include <stdlib.h>
37#include "../stdio/floatio.h"
38#include "fpmath.h"
39#include "gdtoaimp.h"
40
41/*
42 * ldtoa() is a wrapper for gdtoa() that makes it smell like dtoa(),
43 * except that the floating point argument is passed by reference.
44 * When dtoa() is passed a NaN or infinity, it sets expt to 9999.
45 * However, a long double could have a valid exponent of 9999, so we
46 * use INT_MAX in ldtoa() instead.
47 */
48char *
49__ldtoa(long double *ld, int mode, int ndigits, int *decpt, int *sign,
50    char **rve)
51{
52	FPI fpi = {
53		LDBL_MANT_DIG,			/* nbits */
54		LDBL_MIN_EXP - LDBL_MANT_DIG,	/* emin */
55		LDBL_MAX_EXP - LDBL_MANT_DIG,	/* emax */
56		FLT_ROUNDS,	       		/* rounding */
57#ifdef Sudden_Underflow	/* unused, but correct anyway */
58		1
59#else
60		0
61#endif
62	};
63	int be, kind;
64	char *ret;
65	union IEEEl2bits u;
66	uint32_t bits[(LDBL_MANT_DIG + 31) / 32];
67	void *vbits = bits;
68
69	u.e = *ld;
70
71	/*
72	 * gdtoa doesn't know anything about the sign of the number, so
73	 * if the number is negative, we need to swap rounding modes of
74	 * 2 (upwards) and 3 (downwards).
75	 */
76	*sign = u.bits.sign;
77	fpi.rounding ^= (fpi.rounding >> 1) & u.bits.sign;
78
79	be = u.bits.exp - (LDBL_MAX_EXP - 1) - (LDBL_MANT_DIG - 1);
80	LDBL_TO_ARRAY32(u, bits);
81
82	switch (fpclassify(u.e)) {
83	case FP_NORMAL:
84		kind = STRTOG_Normal;
85#ifdef	LDBL_IMPLICIT_NBIT
86		bits[LDBL_MANT_DIG / 32] |= 1 << ((LDBL_MANT_DIG - 1) % 32);
87#endif /* LDBL_IMPLICIT_NBIT */
88		break;
89	case FP_ZERO:
90		kind = STRTOG_Zero;
91		break;
92	case FP_SUBNORMAL:
93		kind = STRTOG_Denormal;
94		be++;
95		break;
96	case FP_INFINITE:
97		kind = STRTOG_Infinite;
98		break;
99	case FP_NAN:
100		kind = STRTOG_NaN;
101		break;
102	default:
103		abort();
104	}
105
106	ret = gdtoa(&fpi, be, vbits, &kind, mode, ndigits, decpt, rve);
107	if (*decpt == -32768)
108		*decpt = INT_MAX;
109	return ret;
110}
111