1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2003 David Schultz <[email protected]>
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 */
48 char *
__ldtoa(long double * ld,int mode,int ndigits,int * decpt,int * sign,char ** rve)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