compiler/stdc/strtod.c

   1 /*
   2     Copyright © 1995-2012, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     C99 function strtod().
   6 */
   7
   8 #ifndef AROS_NOFPU
   9
  10 #include <ctype.h>
  11 #include <limits.h>
  12
  13 /*****************************************************************************
  14
  15     NAME */
  16 #include <stdlib.h>
  17 #include <math.h>
  18
  19         double strtod (
  20
  21 /*  SYNOPSIS */
  22         const char * str,
  23         char      ** endptr)
  24
  25 /*  FUNCTION
  26         Convert a string of digits into a double.
  27
  28     INPUTS
  29         str - The string which should be converted. Leading
  30                 whitespace are ignored. The number may be prefixed
  31                 by a '+' or '-'. An 'e' or 'E' introduces the exponent.
  32                 Komma is only allowed before exponent.
  33         endptr - If this is non-NULL, then the address of the first
  34                 character after the number in the string is stored
  35                 here.
  36
  37     RESULT
  38         The value of the string. The first character after the number
  39         is returned in *endptr, if endptr is non-NULL. If no digits can
  40         be converted, *endptr contains str (if non-NULL) and 0 is
  41         returned.
  42
  43     NOTES
  44
  45     EXAMPLE
  46
  47     BUGS
  48         NAN is not handled at the moment
  49
  50     SEE ALSO
  51         atof(), atoi(), atol(), strtol(), strtoul()
  52
  53     INTERNALS
  54
  55 ******************************************************************************/
  56 {
  57     /* Unit tests available in : tests/clib/strtod.c */
  58     /* FIXME: implement NAN handling */
  59     double  val = 0, precision;
  60     int     exp = 0;
  61     char    c = 0, c2 = 0;
  62     int     digits = 0;
  63
  64     /* assign initial value in case nothing will be found */
  65     if (endptr)
  66         *endptr = (char *)str;
  67
  68     /* skip all leading spaces */
  69     while (isspace (*str))
  70         str ++;
  71
  72     /* start with scanning the floting point number */
  73     if (*str)
  74     {
  75         /* Is there a sign? */
  76         if (*str == '+' || *str == '-')
  77             c = *str ++;
  78
  79         /* scan numbers before the dot */
  80         while (isdigit(*str))
  81         {
  82             digits++;
  83             val = val * 10 + (*str - '0');
  84             str ++;
  85         }
  86
  87         /* see if there is the dot and there were digits before it or there is
  88             at least one digit after it */
  89         if ((*str == '.') && ((digits > 0) || (isdigit(*(str + 1)))))
  90         {
  91             str++;
  92             /* scan the numbers behind the dot */
  93             precision = 0.1;
  94             while (isdigit (*str))
  95             {
  96                 digits++;
  97                 val += ((*str - '0') * precision) ;
  98                 str ++;
  99                 precision = precision * 0.1;
 100             }
 101         }
 102
 103         /* look for a sequence like "E+10" or "e-22" if there were any digits up to now */
 104         if ((digits > 0) && (tolower(*str) == 'e'))
 105         {
 106             int edigits = 0;
 107             str++;
 108
 109             if (*str == '+' || *str == '-')
 110                 c2 = *str ++;
 111
 112             while (isdigit (*str))
 113             {
 114                 edigits++;
 115                 exp = exp * 10 + (*str - '0');
 116                 str ++;
 117             }
 118
 119             if (c2 == '-')
 120                 exp = -exp;
 121
 122             if (edigits == 0)
 123             {
 124                 /* there were no digits after 'e' - rollback pointer */
 125                 str--; if (c2 != 0) str--;
 126             }
 127
 128             val *= pow (10, exp);
 129         }
 130
 131         if (c == '-')
 132             val = -val;
 133
 134         if ((digits == 0) && (c != 0))
 135         {
 136             /* there were no digits but there was sign - rollback pointer */
 137             str--;
 138         }
 139     }
 140
 141     /* something was found, assign the pointer value */
 142     if (endptr && digits > 0)
 143         *endptr = (char *)str;
 144
 145     return val;
 146 } /* strtod */
 147
 148 #else
 149
 150 void strtod (const char * str,char ** endptr)
 151 {
 152     return;
 153 }
 154
 155 #endif /* AROS_NOFPU */