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   s = cvtbuf = (char*)malloc(ndigits + NUMBER_EFMT);
  22   d = ecvtbuf;
  23
  24   *sign = 0;
  25   *decpt = 0;
  26
  27   if (cvtbuf == NULL)
  28   {
  29     return NULL;
  30   }
  31
  32   sprintf(cvtbuf, "%-+.*E", ndigits, value);
  33   /* Treat special values */
  34   if (strncmp(s, "NaN", 3) == 0)
  35   {
  36     memcpy(ecvtbuf, s, 4);
  37   }
  38   else if (strncmp(s + 1, "Inf", 3) == 0)
  39   {
  40     memcpy(ecvtbuf, s, 5);
  41   }
  42   else
  43   {
  44     /* Set the sign */
  45     if (*s && *s == '-')
  46     {
  47       *sign = 1;
  48     }
  49     s++;
  50     /* Copy the first digit */
  51     if (*s && *s != '.')
  52     {
  53       if (d - ecvtbuf < ndigits)
  54       {
  55         *d++ = *s++;
  56       }
  57       else
  58       {
  59         s++;
  60       }
  61     }
  62     /* Skip the decimal point */
  63     if (*s && *s == '.')
  64     {
  65       s++;
  66     }
  67     /* Copy fractional digits */
  68     while (*s && *s != 'E')
  69     {
  70       if (d - ecvtbuf < ndigits)
  71       {
  72         *d++ = *s++;
  73       }
  74       else
  75       {
  76         s++;
  77       }
  78     }
  79     /* Skip the exponent */
  80     if (*s && *s == 'E')
  81     {
  82       s++;
  83     }
  84     /* Set the decimal point to the exponent value plus the one digit we copied */
  85     *decpt = atoi(s) + 1;
  86     /* Handle special decimal point cases */
  87     if (cvtbuf[1] == '0')
  88     {
  89       *decpt = 0;
  90     }
  91     if (ndigits < 1)
  92     {
  93       /* Need enhanced precision*/
  94       char* tbuf = (char*)malloc(NUMBER_EFMT);
  95       if (tbuf == NULL)
  96       {
  97         free(cvtbuf);
  98         return NULL;
  99       }
 100       sprintf(tbuf, "%-+.*E", ndigits + 2, value);
 101       if (tbuf[1] >= '5')
 102       {
 103         (*decpt)++;
 104       }
 105       free(tbuf);
 106     }
 107     /* Pad with zeroes */
 108     while (d - ecvtbuf < ndigits)
 109     {
 110       *d++ = '0';
 111     }
 112     /* Terminate */
 113     *d = '\0';
 114   }
 115   free(cvtbuf);
 116   return ecvtbuf;
 117 }