1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 /* Copyright (c) 1988 AT&T */
28 /* All Rights Reserved */
29
30 /*
31 * ecvt converts to decimal
32 * the number of digits is specified by ndigit
33 * decpt is set to the position of the decimal point
34 * sign is set to 0 for positive, 1 for negative
35 *
36 */
37
38 #pragma weak _ecvt = ecvt
39 #pragma weak _fcvt = fcvt
40
41 #include "lint.h"
42 #include <sys/types.h>
43 #include <values.h>
44 #include <nan.h>
45 #include <string.h>
46 #include "tsd.h"
47
48 #define NMAX ((DSIGNIF * 3 + 19)/10) /* restrict max precision */
49 #define NDIG 80
50
51 static char *cvt(double, int, int *, int *, int);
52
53 char *
ecvt(double value,int ndigit,int * decpt,int * sign)54 ecvt(double value, int ndigit, int *decpt, int *sign)
55 {
56 return (cvt(value, ndigit, decpt, sign, 0));
57 }
58
59 char *
fcvt(double value,int ndigit,int * decpt,int * sign)60 fcvt(double value, int ndigit, int *decpt, int *sign)
61 {
62 return (cvt(value, ndigit, decpt, sign, 1));
63 }
64
65 static char *
cvt(double value,int ndigit,int * decpt,int * sign,int f_flag)66 cvt(double value, int ndigit, int *decpt, int *sign, int f_flag)
67 {
68 char *buf = tsdalloc(_T_ECVT, NDIG, NULL);
69 char *p = &buf[0], *p_last = &buf[ndigit];
70
71 buf[0] = '\0';
72
73 if (IsNANorINF(value)) {
74 if (IsINF(value)) /* value is an INF, return "inf" */
75 (void) strncpy(buf, "inf", NDIG);
76 else /* value is a NaN, return "NaN" */
77 (void) strncpy(buf, "nan", NDIG);
78
79 return (buf);
80 }
81
82 if ((*sign = (value < 0.0)) != 0)
83 value = -value;
84 *decpt = 0;
85 if (value != 0.0) {
86 /*
87 * rescale to range [1.0, 10.0)
88 * in binary for speed and to minimize error build-up
89 * even for the IEEE standard with its high exponents,
90 * it's probably better for speed to just loop on them
91 */
92 static const struct s { double p10; int n; } s[] = {
93 1e32, 32,
94 1e16, 16,
95 1e8, 8,
96 1e4, 4,
97 1e2, 2,
98 1e1, 1,
99 };
100 const struct s *sp = s;
101
102 ++*decpt;
103 if (value >= 2.0 * MAXPOWTWO) /* can't be precisely integral */
104 do {
105 for (; value >= sp->p10; *decpt += sp->n)
106 value /= sp->p10;
107 } while (sp++->n > 1);
108 else if (value >= 10.0) { /* convert integer part separately */
109 double pow10 = 10.0, powtemp;
110
111 while ((powtemp = 10.0 * pow10) <= value)
112 pow10 = powtemp;
113 for (; ; pow10 /= 10.0) {
114 int digit = value/pow10;
115 *p++ = digit + '0';
116 value -= digit * pow10;
117 ++*decpt;
118 if (pow10 <= 10.0)
119 break;
120 }
121 } else if (value < 1.0)
122 do {
123 for (; value * sp->p10 < 10.0; *decpt -= sp->n)
124 value *= sp->p10;
125 } while (sp++->n > 1);
126 }
127 if (f_flag)
128 p_last += *decpt;
129 if (p_last >= buf) {
130 if (p_last > &buf[NDIG - 2])
131 p_last = &buf[NDIG - 2];
132 for (; ; ++p) {
133 if (value == 0 || p >= &buf[NMAX])
134 *p = '0';
135 else {
136 int intx; /* intx in [0, 9] */
137 *p = (intx = (int)value) + '0';
138 value = 10.0 * (value - (double)intx);
139 }
140 if (p >= p_last) {
141 p = p_last;
142 break;
143 }
144 }
145 if (*p >= '5') /* check rounding in last place + 1 */
146 do {
147 if (p == buf) { /* rollover from 99999... */
148 buf[0] = '1'; /* later digits are 0 */
149 ++*decpt;
150 if (f_flag)
151 ++p_last;
152 break;
153 }
154 *p = '0';
155 } while (++*--p > '9'); /* propagate carries left */
156 *p_last = '\0';
157 }
158 return (buf);
159 }
160