ldtoa.c revision 1.5 
1/*	$NetBSD: ldtoa.c,v 1.5 2016/03/13 19:44:58 christos Exp $	*/
2
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#if 0
31__FBSDID("$FreeBSD: src/lib/libc/gdtoa/_ldtoa.c,v 1.2 2004/01/18 07:53:49 das Exp $");
32#else
33__RCSID("$NetBSD: ldtoa.c,v 1.5 2016/03/13 19:44:58 christos Exp $");
34#endif
35
36#include <float.h>
37#include <inttypes.h>
38#include <limits.h>
39#include <math.h>
40#include <stdlib.h>
41#ifndef __vax__
42#include <machine/ieee.h>
43#endif
44#include "gdtoaimp.h"
45
46/*
47 * ldtoa() is a wrapper for gdtoa() that makes it smell like dtoa(),
48 * except that the floating point argument is passed by reference.
49 * When dtoa() is passed a NaN or infinity, it sets expt to 9999.
50 * However, a long double could have a valid exponent of 9999, so we
51 * use INT_MAX in ldtoa() instead.
52 */
53char *
54ldtoa(long double *ld, int mode, int ndigits, int *decpt, int *sign, char **rve)
55{
56#ifdef EXT_EXPBITS
57	static FPI fpi = {
58		LDBL_MANT_DIG,			/* nbits */
59		LDBL_MIN_EXP - LDBL_MANT_DIG,	/* emin */
60		LDBL_MAX_EXP - LDBL_MANT_DIG,	/* emax */
61		FPI_Round_near,	       		/* rounding */
62#ifdef Sudden_Underflow	/* unused, but correct anyway */
63		1
64#else
65		0
66#endif
67	};
68	int be, kind;
69	char *ret;
70	union ieee_ext_u u;
71	uint32_t bits[(LDBL_MANT_DIG + 31) / 32];
72
73	u.extu_ld = *ld;
74	*sign = u.extu_ext.ext_sign;
75	be = u.extu_ext.ext_exp - (LDBL_MAX_EXP - 1) - (LDBL_MANT_DIG - 1);
76	EXT_TO_ARRAY32(u, bits);
77
78	switch (fpclassify(u.extu_ld)) {
79	case FP_NORMAL:
80		kind = STRTOG_Normal;
81#ifdef	LDBL_IMPLICIT_NBIT
82		bits[LDBL_MANT_DIG / 32] |= 1 << ((LDBL_MANT_DIG - 1) % 32);
83#endif /* LDBL_IMPLICIT_NBIT */
84		break;
85	case FP_ZERO:
86		kind = STRTOG_Zero;
87		break;
88	case FP_SUBNORMAL:
89		kind = STRTOG_Denormal;
90		be++;
91		break;
92	case FP_INFINITE:
93		kind = STRTOG_Infinite;
94		break;
95	case FP_NAN:
96		kind = STRTOG_NaN;
97		break;
98	default:
99		abort();
100	}
101
102	ret = gdtoa(&fpi, be, (ULong *)bits, &kind, mode, ndigits, decpt, rve);
103	if (*decpt == -32768)
104		*decpt = INT_MAX;
105	return ret;
106#else
107	return dtoa((double)*ld, mode, ndigits, decpt, sign, rve);
108#endif
109}
110