_ldtoa.c revision 331722 
1/*-
2 * Copyright (c) 2003 David Schultz <das@FreeBSD.ORG>
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 THE 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 THE 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
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: stable/11/lib/libc/gdtoa/_ldtoa.c 331722 2018-03-29 02:50:57Z eadler $");
29
30#include <float.h>
31#include <inttypes.h>
32#include <limits.h>
33#include <math.h>
34#include <stdlib.h>
35#include "../stdio/floatio.h"
36#include "fpmath.h"
37#include "gdtoaimp.h"
38
39/*
40 * ldtoa() is a wrapper for gdtoa() that makes it smell like dtoa(),
41 * except that the floating point argument is passed by reference.
42 * When dtoa() is passed a NaN or infinity, it sets expt to 9999.
43 * However, a long double could have a valid exponent of 9999, so we
44 * use INT_MAX in ldtoa() instead.
45 */
46char *
47__ldtoa(long double *ld, int mode, int ndigits, int *decpt, int *sign,
48    char **rve)
49{
50	FPI fpi = {
51		LDBL_MANT_DIG,			/* nbits */
52		LDBL_MIN_EXP - LDBL_MANT_DIG,	/* emin */
53		LDBL_MAX_EXP - LDBL_MANT_DIG,	/* emax */
54		FLT_ROUNDS,	       		/* rounding */
55#ifdef Sudden_Underflow	/* unused, but correct anyway */
56		1
57#else
58		0
59#endif
60	};
61	int be, kind;
62	char *ret;
63	union IEEEl2bits u;
64	uint32_t bits[(LDBL_MANT_DIG + 31) / 32];
65	void *vbits = bits;
66
67	u.e = *ld;
68
69	/*
70	 * gdtoa doesn't know anything about the sign of the number, so
71	 * if the number is negative, we need to swap rounding modes of
72	 * 2 (upwards) and 3 (downwards).
73	 */
74	*sign = u.bits.sign;
75	fpi.rounding ^= (fpi.rounding >> 1) & u.bits.sign;
76
77	be = u.bits.exp - (LDBL_MAX_EXP - 1) - (LDBL_MANT_DIG - 1);
78	LDBL_TO_ARRAY32(u, bits);
79
80	switch (fpclassify(u.e)) {
81	case FP_NORMAL:
82		kind = STRTOG_Normal;
83#ifdef	LDBL_IMPLICIT_NBIT
84		bits[LDBL_MANT_DIG / 32] |= 1 << ((LDBL_MANT_DIG - 1) % 32);
85#endif /* LDBL_IMPLICIT_NBIT */
86		break;
87	case FP_ZERO:
88		kind = STRTOG_Zero;
89		break;
90	case FP_SUBNORMAL:
91		kind = STRTOG_Denormal;
92		be++;
93		break;
94	case FP_INFINITE:
95		kind = STRTOG_Infinite;
96		break;
97	case FP_NAN:
98		kind = STRTOG_NaN;
99		break;
100	default:
101		abort();
102	}
103
104	ret = gdtoa(&fpi, be, vbits, &kind, mode, ndigits, decpt, rve);
105	if (*decpt == -32768)
106		*decpt = INT_MAX;
107	return ret;
108}
109