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 #pragma ident "%Z%%M% %I% %E% SMI"
31
32 /*
33 * ecvt converts to decimal
34 * the number of digits is specified by ndigit
35 * decpt is set to the position of the decimal point
36 * sign is set to 0 for positive, 1 for negative
37 *
38 */
39
40 #pragma weak _ecvt = ecvt
41 #pragma weak _fcvt = fcvt
42
43 #include "lint.h"
44 #include <sys/types.h>
45 #include <values.h>
46 #include <nan.h>
47 #include <string.h>
48 #include "tsd.h"
49
50 #define NMAX ((DSIGNIF * 3 + 19)/10) /* restrict max precision */
51 #define NDIG 80
52
53 static char *cvt(double, int, int *, int *, int);
54
55 char *
ecvt(double value,int ndigit,int * decpt,int * sign)56 ecvt(double value, int ndigit, int *decpt, int *sign)
57 {
58 return (cvt(value, ndigit, decpt, sign, 0));
59 }
60
61 char *
fcvt(double value,int ndigit,int * decpt,int * sign)62 fcvt(double value, int ndigit, int *decpt, int *sign)
63 {
64 return (cvt(value, ndigit, decpt, sign, 1));
65 }
66
67 static char *
cvt(double value,int ndigit,int * decpt,int * sign,int f_flag)68 cvt(double value, int ndigit, int *decpt, int *sign, int f_flag)
69 {
70 char *buf = tsdalloc(_T_ECVT, NDIG, NULL);
71 char *p = &buf[0], *p_last = &buf[ndigit];
72
73 buf[0] = '\0';
74
75 if (IsNANorINF(value)) {
76 if (IsINF(value)) /* value is an INF, return "inf" */
77 (void) strncpy(buf, "inf", NDIG);
78 else /* value is a NaN, return "NaN" */
79 (void) strncpy(buf, "nan", NDIG);
80
81 return (buf);
82 }
83
84 if ((*sign = (value < 0.0)) != 0)
85 value = -value;
86 *decpt = 0;
87 if (value != 0.0) {
88 /*
89 * rescale to range [1.0, 10.0)
90 * in binary for speed and to minimize error build-up
91 * even for the IEEE standard with its high exponents,
92 * it's probably better for speed to just loop on them
93 */
94 static const struct s { double p10; int n; } s[] = {
95 1e32, 32,
96 1e16, 16,
97 1e8, 8,
98 1e4, 4,
99 1e2, 2,
100 1e1, 1,
101 };
102 const struct s *sp = s;
103
104 ++*decpt;
105 if (value >= 2.0 * MAXPOWTWO) /* can't be precisely integral */
106 do {
107 for (; value >= sp->p10; *decpt += sp->n)
108 value /= sp->p10;
109 } while (sp++->n > 1);
110 else if (value >= 10.0) { /* convert integer part separately */
111 double pow10 = 10.0, powtemp;
112
113 while ((powtemp = 10.0 * pow10) <= value)
114 pow10 = powtemp;
115 for (; ; pow10 /= 10.0) {
116 int digit = value/pow10;
117 *p++ = digit + '0';
118 value -= digit * pow10;
119 ++*decpt;
120 if (pow10 <= 10.0)
121 break;
122 }
123 } else if (value < 1.0)
124 do {
125 for (; value * sp->p10 < 10.0; *decpt -= sp->n)
126 value *= sp->p10;
127 } while (sp++->n > 1);
128 }
129 if (f_flag)
130 p_last += *decpt;
131 if (p_last >= buf) {
132 if (p_last > &buf[NDIG - 2])
133 p_last = &buf[NDIG - 2];
134 for (; ; ++p) {
135 if (value == 0 || p >= &buf[NMAX])
136 *p = '0';
137 else {
138 int intx; /* intx in [0, 9] */
139 *p = (intx = (int)value) + '0';
140 value = 10.0 * (value - (double)intx);
141 }
142 if (p >= p_last) {
143 p = p_last;
144 break;
145 }
146 }
147 if (*p >= '5') /* check rounding in last place + 1 */
148 do {
149 if (p == buf) { /* rollover from 99999... */
150 buf[0] = '1'; /* later digits are 0 */
151 ++*decpt;
152 if (f_flag)
153 ++p_last;
154 break;
155 }
156 *p = '0';
157 } while (++*--p > '9'); /* propagate carries left */
158 *p_last = '\0';
159 }
160 return (buf);
161 }
162