compiler/clib/strtod.c

   1 /*
   2     Copyright © 1995-2001, 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     /* skip all leading spaces */
  66     while (isspace (*str))
  67         str ++;
  68
  69     /* start with scanning the floting point number */
  70     if (*str)
  71     {
  72         /* Is there a sign? */
  73         if (*str == '+' || *str == '-')
  74             c = *str ++;
  75
  76         /* scan numbers before the dot */
  77         while (isdigit(*str))
  78         {
  79             digits++;
  80             val = val * 10 + (*str - '0');
  81             str ++;
  82         }
  83
  84         /* see if there is the dot and there were digits before it or there is
  85             at least one digit after it */
  86         if ((*str == '.') && ((digits > 0) || (isdigit(*(str + 1)))))
  87         {
  88             str++;
  89             /* scan the numbers behind the dot */
  90             precision = 0.1;
  91             while (isdigit (*str))
  92             {
  93                 digits++;
  94                 val += ((*str - '0') * precision) ;
  95                 str ++;
  96                 precision = precision * 0.1;
  97             }
  98         }
  99
 100         /* look for a sequence like "E+10" or "e-22" if there were any digits up to now */
 101         if ((digits > 0) && (tolower(*str) == 'e'))
 102         {
 103             int edigits = 0;
 104             str++;
 105
 106             if (*str == '+' || *str == '-')
 107                 c2 = *str ++;
 108
 109             while (isdigit (*str))
 110             {
 111                 edigits++;
 112                 exp = exp * 10 + (*str - '0');
 113                 str ++;
 114             }
 115
 116             if (c2 == '-')
 117                 exp = -exp;
 118
 119             if (edigits == 0)
 120             {
 121                 /* there were no digits after 'e' - rollback pointer */
 122                 str--; if (c2 != 0) str--;
 123             }
 124
 125             val *= pow (10, exp);
 126         }
 127
 128         if (c == '-')
 129             val = -val;
 130
 131         if ((digits == 0) && (c != 0))
 132         {
 133             /* there were no digits but there was sign - rollback pointer */
 134             str--;
 135         }
 136     }
 137
 138     if (endptr)
 139         *endptr = (char *)str;
 140
 141     return val;
 142 } /* strtod */
 143
 144 #else
 145
 146 void strtod (const char * str,char ** endptr)
 147 {
 148         return;
 149 }
 150
 151 #endif /* AROS_NOFPU */