stdlib/OpenBSD/gcvt.c

   1 /*      $OpenBSD: gcvt.c,v 1.11 2009/10/16 12:15:03 martynas Exp $      */
   2
   3 /*
   4  * Copyright (c) 2002, 2003, 2006 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 #include <locale.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27
  28 extern char *__dtoa(double, int, int, int *, int *, char **);
  29 extern void  __freedtoa(char *);
  30
  31 char *
  32 gcvt(double value, int ndigit, char *buf)
  33 {
  34         char *digits, *dst, *src;
  35         int i, decpt, sign;
  36         struct lconv *lconv;
  37
  38         lconv = localeconv();
  39         if (ndigit == 0) {
  40                 buf[0] = '\0';
  41                 return (buf);
  42         }
  43
  44         digits = __dtoa(value, 2, ndigit, &decpt, &sign, NULL);
  45         if (digits == NULL)
  46                 return (NULL);
  47         if (decpt == 9999) {
  48                 /*
  49                  * Infinity or NaN, convert to inf or nan with sign.
  50                  * We assume the buffer is at least ndigit long.
  51                  */
  52                 snprintf(buf, ndigit + 1, "%s%s", sign ? "-" : "",
  53                     *digits == 'I' ? "inf" : "nan");
  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 (e.g. 1.2345e+13) */
  64                 if (--decpt < 0) {
  65                         sign = 1;
  66                         decpt = -decpt;
  67                 } else
  68                         sign = 0;
  69                 src = digits;
  70                 *dst++ = *src++;
  71                 *dst++ = *lconv->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                                 continue;
  87                         dst[i + 1] = '\0';
  88                         while (decpt != 0) {
  89                                 dst[i--] = '0' + decpt % 10;
  90                                 decpt /= 10;
  91                         }
  92                 }
  93         } else {
  94                 /* standard format */
  95                 for (i = 0, src = digits; i < decpt; i++) {
  96                         if (*src != '\0')
  97                                 *dst++ = *src++;
  98                         else
  99                                 *dst++ = '0';
 100                 }
 101                 if (*src != '\0') {
 102                         if (src == digits)
 103                                 *dst++ = '0';   /* zero before decimal point */
 104                         *dst++ = *lconv->decimal_point;
 105                         for (i = decpt; digits[i] != '\0'; i++) {
 106                                 *dst++ = digits[i];
 107                         }
 108                 }
 109                 *dst = '\0';
 110         }
 111         __freedtoa(digits);
 112         return (buf);
 113 }