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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 #ifdef SDCC_mcs51
  27         bit sign;
  28 #else
  29         char sign;
  30 #endif
  31
  32         //Skip leading blanks
  33         while (isspace(*s)) s++;
  34
  35         //Get the sign
  36         if (*s == '-')
  37         {
  38                 sign=1;
  39                 s++;
  40         }
  41         else
  42         {
  43                 sign=0;
  44                 if (*s == '+') s++;
  45         }
  46
  47         //Get the integer part
  48         for (value=0.0; isdigit(*s); s++)
  49         {
  50                 value=10.0*value+(*s-'0');
  51         }
  52
  53         //Get the fraction
  54         if (*s=='.')
  55         {
  56                 s++;
  57                 for (fraction=10.0; isdigit(*s); s++)
  58                 {
  59                         value+=(*s-'0')/fraction;
  60                         fraction*=10.0;
  61                 }
  62         }
  63
  64         //Finally, the exponent (not very efficient, but enough for now*/
  65         if (toupper(*s)=='E')
  66         {
  67                 s++;
  68                 while(*s=='0') s++;//So atoi doesn't return an octal number
  69                 iexp=(char)atoi(s);
  70                 {
  71                         while(iexp!=0)
  72                         {
  73                                 if(iexp<0)
  74                                 {
  75                                         value/=10.0;
  76                                         iexp++;
  77                                 }
  78                                 else
  79                                 {
  80                                         value*=10.0;
  81                                         iexp--;
  82                                 }
  83                         }
  84                 }
  85         }
  86
  87         if(sign) value*=-1.0;
  88         return (value);
  89 }