compiler/clib/strtod.c

   1 /*
   2     Copyright © 1995-2011, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     ANSI C function strtod().
   6 */
   7
   8 #ifndef AROS_NOFPU
   9
  10 #include <ctype.h>
  11 #include <errno.h>
  12 #include <limits.h>
  13
  14 /*****************************************************************************
  15
  16     NAME */
  17 #include <stdlib.h>
  18 #include <math.h>
  19
  20         double strtod (
  21
  22 /*  SYNOPSIS */
  23         const char * str,
  24         char      ** endptr)
  25
  26 /*  FUNCTION
  27         Convert a string of digits into a double.
  28
  29     INPUTS
  30         str - The string which should be converted. Leading
  31                 whitespace are ignored. The number may be prefixed
  32                 by a '+' or '-'. An 'e' or 'E' introduces the exponent.
  33                 Komma is only allowed before exponent.
  34         endptr - If this is non-NULL, then the address of the first
  35                 character after the number in the string is stored
  36                 here.
  37
  38     RESULT
  39         The value of the string. The first character after the number
  40         is returned in *endptr, if endptr is non-NULL. If no digits can
  41         be converted, *endptr contains str (if non-NULL) and 0 is
  42         returned.
  43
  44     NOTES
  45
  46     EXAMPLE
  47
  48     BUGS
  49         NAN is not handled at the moment
  50
  51     SEE ALSO
  52         atof(), atoi(), atol(), strtol(), strtoul()
  53
  54     INTERNALS
  55
  56 ******************************************************************************/
  57 {
  58     /* Unit tests available in : tests/clib/strtod.c */
  59     /* FIXME: implement NAN handling */
  60     double  val = 0, precision;
  61     int     exp = 0;
  62     char    c = 0, c2 = 0;
  63     int     digits = 0;
  64
  65     /* assign initial value in case nothing will be found */
  66     if (endptr)
  67         *endptr = (char *)str;
  68
  69     /* skip all leading spaces */
  70     while (isspace (*str))
  71         str ++;
  72
  73     /* start with scanning the floting point number */
  74     if (*str)
  75     {
  76         /* Is there a sign? */
  77         if (*str == '+' || *str == '-')
  78             c = *str ++;
  79
  80         /* scan numbers before the dot */
  81         while (isdigit(*str))
  82         {
  83             digits++;
  84             val = val * 10 + (*str - '0');
  85             str ++;
  86         }
  87
  88         /* see if there is the dot and there were digits before it or there is
  89             at least one digit after it */
  90         if ((*str == '.') && ((digits > 0) || (isdigit(*(str + 1)))))
  91         {
  92             str++;
  93             /* scan the numbers behind the dot */
  94             precision = 0.1;
  95             while (isdigit (*str))
  96             {
  97                 digits++;
  98                 val += ((*str - '0') * precision) ;
  99                 str ++;
 100                 precision = precision * 0.1;
 101             }
 102         }
 103
 104         /* look for a sequence like "E+10" or "e-22" if there were any digits up to now */
 105         if ((digits > 0) && (tolower(*str) == 'e'))
 106         {
 107             int edigits = 0;
 108             str++;
 109
 110             if (*str == '+' || *str == '-')
 111                 c2 = *str ++;
 112
 113             while (isdigit (*str))
 114             {
 115                 edigits++;
 116                 exp = exp * 10 + (*str - '0');
 117                 str ++;
 118             }
 119
 120             if (c2 == '-')
 121                 exp = -exp;
 122
 123             if (edigits == 0)
 124             {
 125                 /* there were no digits after 'e' - rollback pointer */
 126                 str--; if (c2 != 0) str--;
 127             }
 128
 129             val *= pow (10, exp);
 130         }
 131
 132         if (c == '-')
 133             val = -val;
 134
 135         if ((digits == 0) && (c != 0))
 136         {
 137             /* there were no digits but there was sign - rollback pointer */
 138             str--;
 139         }
 140     }
 141
 142     /* something was found, assign the pointer value */
 143     if (endptr && digits > 0)
 144         *endptr = (char *)str;
 145
 146     return val;
 147 } /* strtod */
 148
 149 #else
 150
 151 void strtod (const char * str,char ** endptr)
 152 {
 153         return;
 154 }
 155
 156 #endif /* AROS_NOFPU */