lib/xstrtod.c

   1 /* error-checking interface to strtod-like functions
   2    Copyright (C) 1996, 1999, 2000, 2003 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 #include "xstrtod.h"
  25
  26 #include <errno.h>
  27 #include <limits.h>
  28 #include <stdio.h>
  29
  30 /* Tell the compiler that non-default rounding modes are used.  */
  31 #if 199901 <= __STDC_VERSION__
  32  #pragma STDC FENV_ACCESS ON
  33 #endif
  34
  35 /* An interface to strtod that encapsulates all the error checking
  36    one should usually perform.  Like strtod, but upon successful
  37    conversion put the result in *RESULT and return zero.  Return
  38    non-zero and don't modify *RESULT upon any failure.  CONVERT
  39    specifies the conversion function, e.g., strtod itself.  */
  40
  41 int
  42 xstrtod (char const *str, char const **ptr, double *result,
  43          double (*convert) (char const *, char **))
  44 {
  45   double val;
  46   char *terminator;
  47   int fail;
  48
  49   fail = 0;
  50   errno = 0;
  51   val = convert (str, &terminator);
  52
  53   /* Having a non-zero terminator is an error only when PTR is NULL. */
  54   if (terminator == str || (ptr == NULL && *terminator != '\0'))
  55     fail = 1;
  56   else
  57     {
  58       /* Allow underflow (in which case strtod returns zero),
  59          but flag overflow as an error. */
  60       if (val != 0.0 && errno == ERANGE)
  61         fail = 1;
  62     }
  63
  64   if (ptr != NULL)
  65     *ptr = terminator;
  66
  67   *result = val;
  68   return fail;
  69 }