reactos/lib/sdk/crt/stdlib/ecvt.c

   1 /*
   2  * PROJECT:         ReactOS CRT
   3  * LICENSE:         See COPYING in the top level directory
   4  * PURPOSE:         CRT's ecvt
   5  * FILE:            lib/sdk/crt/stdlib/ecvt.c
   6  * PROGRAMERS:      Gregor Schneider (parts based on ecvtbuf.c by DJ Delorie)
   7  */
   8
   9 #include <precomp.h>
  10 #define NUMBER_EFMT 18 /* sign, dot, null, 15 for alignment */
  11
  12 /*
  13  * @implemented
  14  */
  15 char *
  16 _ecvt (double value, int ndigits, int *decpt, int *sign)
  17 {
  18   static char ecvtbuf[DBL_MAX_10_EXP + 10];
  19   char *cvtbuf, *s, *d;
  20
  21   if (ndigits < 0) ndigits = 0;
  22   s = cvtbuf = (char*)malloc(ndigits + NUMBER_EFMT);
  23   d = ecvtbuf;
  24
  25   *sign = 0;
  26   *decpt = 0;
  27
  28   if (cvtbuf == NULL)
  29   {
  30     return NULL;
  31   }
  32
  33   sprintf(cvtbuf, "%-+.*E", ndigits, value);
  34   /* Treat special values */
  35   if (strncmp(s, "NaN", 3) == 0)
  36   {
  37     memcpy(ecvtbuf, s, 4);
  38   }
  39   else if (strncmp(s + 1, "Inf", 3) == 0)
  40   {
  41     memcpy(ecvtbuf, s, 5);
  42   }
  43   else
  44   {
  45     /* Set the sign */
  46     if (*s && *s == '-')
  47     {
  48       *sign = 1;
  49     }
  50     s++;
  51     /* Copy the first digit */
  52     if (*s && *s != '.')
  53     {
  54       if (d - ecvtbuf < ndigits)
  55       {
  56         *d++ = *s++;
  57       }
  58       else
  59       {
  60         s++;
  61       }
  62     }
  63     /* Skip the decimal point */
  64     if (*s && *s == '.')
  65     {
  66       s++;
  67     }
  68     /* Copy fractional digits */
  69     while (*s && *s != 'E')
  70     {
  71       if (d - ecvtbuf < ndigits)
  72       {
  73         *d++ = *s++;
  74       }
  75       else
  76       {
  77         s++;
  78       }
  79     }
  80     /* Skip the exponent */
  81     if (*s && *s == 'E')
  82     {
  83       s++;
  84     }
  85     /* Set the decimal point to the exponent value plus the one digit we copied */
  86     *decpt = atoi(s) + 1;
  87     /* Handle special decimal point cases */
  88     if (cvtbuf[1] == '0')
  89     {
  90       *decpt = 0;
  91     }
  92     if (ndigits < 1)
  93     {
  94       /* Need enhanced precision*/
  95       char* tbuf = (char*)malloc(NUMBER_EFMT);
  96       if (tbuf == NULL)
  97       {
  98         free(cvtbuf);
  99         return NULL;
 100       }
 101       sprintf(tbuf, "%-+.*E", ndigits + 2, value);
 102       if (tbuf[1] >= '5')
 103       {
 104         (*decpt)++;
 105       }
 106       free(tbuf);
 107     }
 108     /* Pad with zeroes */
 109     while (d - ecvtbuf < ndigits)
 110     {
 111       *d++ = '0';
 112     }
 113     /* Terminate */
 114     *d = '\0';
 115   }
 116   free(cvtbuf);
 117   return ecvtbuf;
 118 }