1 /*
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright © 2021 Keith Packard
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above
14 * copyright notice, this list of conditions and the following
15 * disclaimer in the documentation and/or other materials provided
16 * with the distribution.
17 *
18 * 3. Neither the name of the copyright holder nor the names of its
19 * contributors may be used to endorse or promote products derived
20 * from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
23 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
24 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
25 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
26 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
27 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
28 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
29 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
31 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
32 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
33 * OF THE POSSIBILITY OF SUCH DAMAGE.
34 */
35
36 #define _NEED_IO_LONG_DOUBLE
37
38 #include "dtoa.h"
39
40 #ifdef _NEED_IO_FLOAT_LARGE
41
42 #define max(a, b) ({\
43 __typeof(a) _a = a;\
44 __typeof(b) _b = b;\
45 _a > _b ? _a : _b; })
46
47 #define min(a, b) ({\
48 __typeof(a) _a = a;\
49 __typeof(b) _b = b;\
50 _a < _b ? _a : _b; })
51
52 int
__ldtoa_engine(long double x,struct dtoa * dtoa,int max_digits,bool fmode,int max_decimals)53 __ldtoa_engine(long double x, struct dtoa *dtoa, int max_digits, bool fmode, int max_decimals)
54 {
55 int i;
56
57 dtoa->flags = 0;
58
59 if (signbit(x)) {
60 dtoa->flags |= DTOA_MINUS;
61 x = -x;
62 }
63 if (isnan(x)) {
64 dtoa->flags |= DTOA_NAN;
65 return max_digits;
66 } else if (isinf(x)) {
67 dtoa->flags |= DTOA_INF;
68 return max_digits;
69 }
70
71 int expo;
72 int decexp = 0;
73
74 x = frexpl(x, &expo);
75
76 /* move into [1-2) range */
77 x *= 2.0l;
78 expo--;
79
80 while (expo <= -2) {
81
82 /* Make room to allow multiplication by 5 without overflow */
83 do {
84 expo++;
85 x *= 0.5l;
86 } while (x >= 2.0l);
87
88 x *= 5.0l;
89 expo++;
90 decexp--;
91 }
92
93 while (expo > 0) {
94 /* divide by 10 */
95 x *= 0.2l;
96 expo--;
97 decexp++;
98
99 /* get the value back in range */
100 do {
101 x *= 2.0l;
102 expo--;
103 } while (x < 1.0l);
104 }
105
106 while (expo < 0) {
107 x *= 0.5l;
108 expo++;
109 }
110
111 if (x < 1.0l) {
112 x *= 10.0l;
113 decexp--;
114 }
115
116 /* x is now in the range 1 <= x < 10 */
117
118 int save_max_digits = max_digits;
119
120 if (fmode)
121 max_digits = min(max_digits, max(1, max_decimals + decexp + 1));
122
123 int decimals = max_digits;
124
125 long double round = 0.5l;
126 while (decimals--) {
127 round *= 0.1l;
128 }
129 x += round;
130
131 if (x >= 10.0l) {
132 x *= 0.1l;
133 decexp++;
134 max_digits = min(save_max_digits, max(1, max_decimals + decexp + 1));
135 }
136
137 /* convert to decimal */
138
139 for (i = 0; i < max_digits; i++) {
140 int digit = (int) x;
141 dtoa->digits[i] = '0' + digit;
142 x -= digit;
143 x *= 10.0l;
144 }
145
146 dtoa->exp = decexp;
147
148 return max_digits;
149 }
150
151 #endif
152
