lib/xstrtod.c

   1 /* xstrtod.c - error-checking interface to strtod
   2    Copyright (C) 1996, 1999, 2000 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* Written by Jim Meyering.  */
  19
  20 #ifdef HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #ifdef STDC_HEADERS
  25 # include <stdlib.h>
  26 #else
  27 double strtod ();
  28 #endif
  29
  30 #include <errno.h>
  31 #include <stdio.h>
  32 #include <limits.h>
  33 #include "xstrtod.h"
  34
  35 /* Tell the compiler that non-default rounding modes are used.  */
  36 #if 199901 <= __STDC_VERSION__
  37  #pragma STDC FENV_ACCESS ON
  38 #endif
  39
  40 /* An interface to strtod that encapsulates all the error checking
  41    one should usually perform.  Like strtod, but upon successful
  42    conversion put the result in *RESULT and return zero.  Return
  43    non-zero and don't modify *RESULT upon any failure.  */
  44
  45 int
  46 xstrtod (str, ptr, result)
  47      const char *str;
  48      const char **ptr;
  49      double *result;
  50 {
  51   double val;
  52   char *terminator;
  53   int fail;
  54
  55   fail = 0;
  56   errno = 0;
  57   val = strtod (str, &terminator);
  58
  59   /* Having a non-zero terminator is an error only when PTR is NULL. */
  60   if (terminator == str || (ptr == NULL && *terminator != '\0'))
  61     fail = 1;
  62   else
  63     {
  64       /* Allow underflow (in which case strtod returns zero),
  65          but flag overflow as an error. */
  66       if (val != 0.0 && errno == ERANGE)
  67         fail = 1;
  68     }
  69
  70   if (ptr != NULL)
  71     *ptr = terminator;
  72
  73   *result = val;
  74   return fail;
  75 }