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