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/* $OpenBSD: gcvt.c,v 1.12 2010/09/25 13:19:19 millert Exp $ */
/*
* Copyright (c) 2002, 2003, 2006, 2010
* Todd C. Miller <Todd.Miller@courtesan.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* Sponsored in part by the Defense Advanced Research Projects
* Agency (DARPA) and Air Force Research Laboratory, Air Force
* Materiel Command, USAF, under agreement number F39502-99-1-0512.
*/
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
extern char *__dtoa(double, int, int, int *, int *, char **);
extern void __freedtoa(char *);
#define DEFPREC 6
char *
gcvt(double value, int ndigit, char *buf)
{
char *digits, *dst, *src;
int i, decpt, sign;
struct lconv *lconv;
lconv = localeconv();
if (ndigit <= 0) {
/* Match printf(3) behavior. */
ndigit = ndigit ? DEFPREC : 1;
}
digits = __dtoa(value, 2, ndigit, &decpt, &sign, NULL);
if (digits == NULL)
return (NULL);
if (decpt == 9999) {
/*
* Infinity or NaN, convert to inf or nan with sign.
* We can't infer buffer size based on ndigit.
* We have to assume it is at least 5 chars.
*/
snprintf(buf, 5, "%s%s", sign ? "-" : "",
*digits == 'I' ? "inf" : "nan");
__freedtoa(digits);
return (buf);
}
dst = buf;
if (sign)
*dst++ = '-';
/* Match printf(3) behavior for exponential vs. regular fomatting. */
if (decpt <= -4 || decpt > ndigit) {
/* exponential format (e.g. 1.2345e+13) */
if (--decpt < 0) {
sign = 1;
decpt = -decpt;
} else
sign = 0;
src = digits;
*dst++ = *src++;
if (*src != '\0') {
*dst++ = *lconv->decimal_point;
do {
*dst++ = *src++;
} while (*src != '\0');
}
*dst++ = 'e';
if (sign)
*dst++ = '-';
else
*dst++ = '+';
if (decpt < 10) {
*dst++ = '0';
*dst++ = '0' + decpt;
*dst = '\0';
} else {
/* XXX - optimize */
for (sign = decpt, i = 0; (sign /= 10) != 0; i++)
continue;
dst[i + 1] = '\0';
while (decpt != 0) {
dst[i--] = '0' + decpt % 10;
decpt /= 10;
}
}
} else {
/* standard format */
for (i = 0, src = digits; i < decpt; i++) {
if (*src != '\0')
*dst++ = *src++;
else
*dst++ = '0';
}
if (*src != '\0') {
if (src == digits)
*dst++ = '0'; /* zero before decimal point */
*dst++ = *lconv->decimal_point;
while (decpt < 0) {
*dst++ = '0';
decpt++;
}
for (i = decpt; digits[i] != '\0'; i++) {
*dst++ = digits[i];
}
}
*dst = '\0';
}
__freedtoa(digits);
return (buf);
}
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