1 /* $OpenBSD: gcvt.c,v 1.14 2019/01/25 00:19:25 millert Exp $ */
2
3 /*
4 * Copyright (c) 2002, 2003, 2006, 2010
5 * Todd C. Miller <millert@openbsd.org>
6 *
7 * Permission to use, copy, modify, and distribute this software for any
8 * purpose with or without fee is hereby granted, provided that the above
9 * copyright notice and this permission notice appear in all copies.
10 *
11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
18 *
19 * Sponsored in part by the Defense Advanced Research Projects
20 * Agency (DARPA) and Air Force Research Laboratory, Air Force
21 * Materiel Command, USAF, under agreement number F39502-99-1-0512.
22 */
23
24 #include <locale.h>
25 #include <stdio.h>
26 #include <stdlib.h>
27 #include <string.h>
28 #include "gdtoa.h"
29
30 #define DEFPREC 6
31
32 char *
gcvt(double value,int ndigit,char * buf)33 gcvt(double value, int ndigit, char *buf)
34 {
35 char *digits, *dst, *src;
36 int i, decpt, sign;
37 struct lconv *lconv;
38
39 lconv = localeconv();
40 if (ndigit <= 0) {
41 /* Match printf(3) behavior. */
42 ndigit = ndigit ? DEFPREC : 1;
43 }
44
45 digits = __dtoa(value, 2, ndigit, &decpt, &sign, NULL);
46 if (digits == NULL)
47 return (NULL);
48 if (decpt == 9999) {
49 /*
50 * Infinity or NaN, convert to inf or nan with sign.
51 * We can't infer buffer size based on ndigit.
52 * We have to assume it is at least 5 chars.
53 */
54 snprintf(buf, 5, "%s%s", sign ? "-" : "",
55 *digits == 'I' ? "inf" : "nan");
56 __freedtoa(digits);
57 return (buf);
58 }
59
60 dst = buf;
61 if (sign)
62 *dst++ = '-';
63
64 /* Match printf(3) behavior for exponential vs. regular fomatting. */
65 if (decpt <= -4 || decpt > ndigit) {
66 /* exponential format (e.g. 1.2345e+13) */
67 if (--decpt < 0) {
68 sign = 1;
69 decpt = -decpt;
70 } else
71 sign = 0;
72 src = digits;
73 *dst++ = *src++;
74 if (*src != '\0') {
75 *dst++ = *lconv->decimal_point;
76 do {
77 *dst++ = *src++;
78 } while (*src != '\0');
79 }
80 *dst++ = 'e';
81 if (sign)
82 *dst++ = '-';
83 else
84 *dst++ = '+';
85 if (decpt < 10) {
86 *dst++ = '0';
87 *dst++ = '0' + decpt;
88 *dst = '\0';
89 } else {
90 /* XXX - optimize */
91 for (sign = decpt, i = 0; (sign /= 10) != 0; i++)
92 continue;
93 dst[i + 1] = '\0';
94 while (decpt != 0) {
95 dst[i--] = '0' + decpt % 10;
96 decpt /= 10;
97 }
98 }
99 } else {
100 /* standard format */
101 for (i = 0, src = digits; i < decpt; i++) {
102 if (*src != '\0')
103 *dst++ = *src++;
104 else
105 *dst++ = '0';
106 }
107 if (*src != '\0') {
108 if (src == digits)
109 *dst++ = '0'; /* zero before decimal point */
110 *dst++ = *lconv->decimal_point;
111 while (decpt < 0) {
112 *dst++ = '0';
113 decpt++;
114 }
115 for (i = decpt; digits[i] != '\0'; i++) {
116 *dst++ = digits[i];
117 }
118 }
119 *dst = '\0';
120 }
121 __freedtoa(digits);
122 return (buf);
123 }
124