stdlib/OpenBSD/gcvt.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
  31 extern char *__dtoa(double, int, int, int *, int *, char **);
  32
  33 char *
  34 gcvt(double value, int ndigit, char *buf)
  35 {
  36         char *digits, *dst, *src;
  37         int i, decpt, sign;
  38
  39         if (ndigit == 0) {
  40                 buf[0] = '\0';
  41                 return (buf);
  42         }
  43
  44         digits = __dtoa(value, 2, ndigit, &decpt, &sign, NULL);
  45         if (decpt == 9999) {
  46                 /* Infinity or NaN, assume buffer is at least ndigit long. */
  47                 strlcpy(buf, digits, ndigit + 1);
  48                 return (buf);
  49         }
  50
  51         dst = buf;
  52         if (sign)
  53                 *dst++ = '-';
  54
  55         if (decpt < 0 || decpt > ndigit) {
  56                 /* exponential format */
  57                 if (--decpt < 0) {
  58                         sign = 1;
  59                         decpt = -decpt;
  60                 } else
  61                         sign = 0;
  62                 for (src = digits; *src != '\0'; )
  63                         *dst++ = *src++;
  64                 *dst++ = 'e';
  65                 if (sign)
  66                         *dst++ = '-';
  67                 else
  68                         *dst++ = '+';
  69                 if (decpt < 10) {
  70                         *dst++ = '0';
  71                         *dst++ = '0' + decpt;
  72                         *dst = '\0';
  73                 } else {
  74                         /* XXX - optimize */
  75                         for (sign = decpt, i = 0; (sign /= 10) != 0; i++)
  76                                 sign /= 10;
  77                         while (decpt != 0) {
  78                                 dst[i--] = '0' + decpt % 10;
  79                                 decpt /= 10;
  80                         }
  81                 }
  82         } else {
  83                 /* standard format */
  84                 for (i = 0, src = digits; i < decpt; i++) {
  85                         if (*src != '\0')
  86                                 *dst++ = *src++;
  87                         else
  88                                 *dst++ = '0';
  89                 }
  90                 if (*src != '\0') {
  91                         *dst++ = '.';           /* XXX - locale-specific (LC_NUMERIC) */
  92                         for (i = decpt; digits[i] != '\0'; i++) {
  93                                 *dst++ = digits[i];
  94                         }
  95                 }
  96                 *dst = '\0';
  97         }
  98         return (buf);
  99 }