stdlib/gcvt-obsd.c

   1 /*      $OpenBSD: gcvt.c,v 1.5 2003/06/17 21:56:24 millert Exp $        */
   2
   3 /*
   4  * Copyright (c) 2002, 2003 Todd C. Miller <Todd.Miller@courtesan.com>
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  *
  18  * Sponsored in part by the Defense Advanced Research Projects
  19  * Agency (DARPA) and Air Force Research Laboratory, Air Force
  20  * Materiel Command, USAF, under agreement number F39502-99-1-0512.
  21  */
  22
  23 #if defined(LIBC_SCCS) && !defined(lint)
  24 static char rcsid[] = "$OpenBSD: gcvt.c,v 1.5 2003/06/17 21:56:24 millert Exp $";
  25 #endif /* LIBC_SCCS and not lint */
  26
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include <locale.h>
  31
  32 extern char *__dtoa(double, int, int, int *, int *, char **);
  33 extern void __freedtoa(char *);
  34
  35 char *
  36 gcvt(double value, int ndigit, char *buf)
  37 {
  38         char *digits, *dst, *src;
  39         int i, decpt, sign;
  40         char *decimal_point = localeconv()->decimal_point;
  41
  42         if (ndigit == 0) {
  43                 buf[0] = '\0';
  44                 return (buf);
  45         }
  46
  47         digits = __dtoa(value, 2, ndigit, &decpt, &sign, NULL);
  48         if (decpt == 9999) {
  49                 /* Infinity or NaN, assume buffer is long enough. */
  50                 dst = buf;
  51                 if (sign)
  52                         *dst++ = '-';
  53                 strcpy(dst, (*digits == 'N') ? "nan" : "inf");
  54                 __freedtoa(digits);
  55                 return (buf);
  56         }
  57
  58         dst = buf;
  59         if (sign)
  60                 *dst++ = '-';
  61
  62         if (decpt < 0 || decpt > ndigit) {
  63                 /* exponential format */
  64                 if (--decpt < 0) {
  65                         sign = 1;
  66                         decpt = -decpt;
  67                 } else
  68                         sign = 0;
  69                 src = digits;
  70                 *dst++ = *src++;
  71                 dst = stpcpy(dst, decimal_point);
  72                 while (*src != '\0')
  73                         *dst++ = *src++;
  74                 *dst++ = 'e';
  75                 if (sign)
  76                         *dst++ = '-';
  77                 else
  78                         *dst++ = '+';
  79                 if (decpt < 10) {
  80                         *dst++ = '0';
  81                         *dst++ = '0' + decpt;
  82                         *dst = '\0';
  83                 } else {
  84                         /* XXX - optimize */
  85                         for (sign = decpt, i = 0; (sign /= 10) != 0; i++) {}
  86                         dst[i + 1] = '\0';
  87                         while (decpt != 0) {
  88                                 dst[i--] = '0' + decpt % 10;
  89                                 decpt /= 10;
  90                         }
  91                 }
  92         } else {
  93                 /* standard format */
  94                 for (i = 0, src = digits; i < decpt; i++) {
  95                         if (*src != '\0')
  96                                 *dst++ = *src++;
  97                         else
  98                                 *dst++ = '0';
  99                 }
 100                 if (*src != '\0') {
 101                         if (src == digits) /* need leading zero */
 102                                 *dst++ = '0';
 103                         dst = stpcpy(dst, decimal_point);
 104                         for (i = decpt; digits[i] != '\0'; i++) {
 105                                 *dst++ = digits[i];
 106                         }
 107                 }
 108                 *dst = '\0';
 109         }
 110         __freedtoa(digits);
 111         return (buf);
 112 }