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   1 /*  atof.c: converts an ASCII string to float
   2
   3     Copyright (C) 2003  Jesus Calvino-Fraga, jesusc@ieee.org
   4
   5     This library is free software; you can redistribute it and/or
   6     modify it under the terms of the GNU Lesser General Public
   7     License as published by the Free Software Foundation; either
   8     version 2.1 of the License, or (at your option) any later version.
   9
  10     This library is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13     Lesser General Public License for more details.
  14
  15     You should have received a copy of the GNU Lesser General Public
  16     License along with this library; if not, write to the Free Software
  17     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA */
  18
  19 #include <ctype.h>
  20 #include <stdlib.h>
  21
  22 float atof(char * s)
  23 {
  24         float value, fraction;
  25         char iexp;
  26         char sign;
  27
  28         //Skip leading blanks
  29         while (isspace(*s)) s++;
  30
  31         //Get the sign
  32         if (*s == '-')
  33         {
  34                 sign=1;
  35                 s++;
  36         }
  37         else
  38         {
  39                 sign=0;
  40                 if (*s == '+') s++;
  41         }
  42
  43         //Get the integer part
  44         for (value=0.0; isdigit(*s); s++)
  45         {
  46                 value=10.0*value+(*s-'0');
  47         }
  48
  49         //Get the fraction
  50         if (*s == '.')
  51         {
  52                 s++;
  53                 for (fraction=0.1; isdigit(*s); s++)
  54                 {
  55                         value+=(*s-'0')*fraction;
  56                         fraction*=0.1;
  57                 }
  58         }
  59
  60         //Finally, the exponent (not very efficient, but enough for now*/
  61         if (toupper(*s)=='E')
  62         {
  63                 s++;
  64                 iexp=(char)atoi(s);
  65                 {
  66                         while(iexp!=0)
  67                         {
  68                                 if(iexp<0)
  69                                 {
  70                                         value*=0.1;
  71                                         iexp++;
  72                                 }
  73                                 else
  74                                 {
  75                                         value*=10.0;
  76                                         iexp--;
  77                                 }
  78                         }
  79                 }
  80         }
  81
  82         if(sign) value*=-1.0;
  83         return (value);
  84 }