reactos/lib/crtdll/stdlib/ecvtbuf.c

   1 /* Copyright (C) 1998 DJ Delorie, see COPYING.DJ for details */
   2 #include <msvcrt/stdlib.h>
   3 #include <msvcrt/stdio.h>
   4 #include <msvcrt/string.h>
   5 #include <msvcrt/float.h>
   6 #include <msvcrt/alloc.h>
   7 // #include <msvcrt/locale.h>
   8
   9 void __ecvround (char *, char *, const char *, int *);
  10
  11 void
  12 __ecvround (char *numbuf, char *last_digit, const char *after_last, int *decpt)
  13 {
  14   char *p;
  15   int carry = 0;
  16
  17   /* Do we have at all to round the last digit?  */
  18   if (*after_last > '4')
  19     {
  20       p = last_digit;
  21       carry = 1;
  22
  23       /* Propagate the rounding through trailing '9' digits.  */
  24       do {
  25         int sum = *p + carry;
  26         carry = sum > '9';
  27         *p-- = sum - carry * 10;
  28       } while (carry && p >= numbuf);
  29
  30       /* We have 9999999... which needs to be rounded to 100000..  */
  31       if (carry && p == numbuf)
  32         {
  33           *p = '1';
  34           *decpt += 1;
  35         }
  36     }
  37 }
  38
  39 char *
  40 ecvtbuf (double value, int ndigits, int *decpt, int *sign, char *buf)
  41 {
  42   static char INFINITY[] = "Infinity";
  43   char decimal = '.' /* localeconv()->decimal_point[0] */;
  44   char *cvtbuf = (char *)alloca (ndigits + 20); /* +3 for sign, dot, null; */
  45                                                 /* two extra for rounding */
  46                                                 /* 15 extra for alignment */
  47   char *s = cvtbuf, *d = buf;
  48
  49   /* Produce two extra digits, so we could round properly.  */
  50   sprintf (cvtbuf, "%-+.*E", ndigits + 2, value);
  51   *decpt = 0;
  52
  53   /* The sign.  */
  54   if (*s++ == '-')
  55     *sign = 1;
  56   else
  57     *sign = 0;
  58
  59   /* Special values get special treatment.  */
  60   if (strncmp (s, "Inf", 3) == 0)
  61     {
  62       /* SunOS docs says we have return "Infinity" for NDIGITS >= 8.  */
  63       memcpy (buf, INFINITY, ndigits >= 8 ? 9 : 3);
  64       if (ndigits < 8)
  65         buf[3] = '\0';
  66     }
  67   else if (strcmp (s, "NaN") == 0)
  68     memcpy (buf, s, 4);
  69   else
  70     {
  71       char *last_digit, *digit_after_last;
  72
  73       /* Copy (the single) digit before the decimal.  */
  74       while (*s && *s != decimal && d - buf < ndigits)
  75         *d++ = *s++;
  76
  77       /* If we don't see any exponent, here's our decimal point.  */
  78       *decpt = d - buf;
  79       if (*s)
  80         s++;
  81
  82       /* Copy the fraction digits.  */
  83       while (*s && *s != 'E' && d - buf < ndigits)
  84         *d++ = *s++;
  85
  86       /* Remember the last digit copied and the one after it.  */
  87       last_digit = d > buf ? d - 1 : d;
  88       digit_after_last = s;
  89
  90       /* Get past the E in exponent field.  */
  91       while (*s && *s++ != 'E')
  92         ;
  93
  94       /* Adjust the decimal point by the exponent value.  */
  95       *decpt += atoi (s);
  96
  97       /* Pad with zeroes if needed.  */
  98       while (d - buf < ndigits)
  99         *d++ = '0';
 100
 101       /* Zero-terminate.  */
 102       *d = '\0';
 103
 104       /* Round if necessary.  */
 105       __ecvround (buf, last_digit, digit_after_last, decpt);
 106     }
 107   return buf;
 108 }