xstrtod.c   [plain text]


/* error-checking interface to strtod-like functions

   Copyright (C) 1996, 1999, 2000, 2003, 2004 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

/* Written by Jim Meyering.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include "xstrtod.h"

#include <errno.h>
#include <limits.h>
#include <stdio.h>

/* Tell the compiler that non-default rounding modes are used.  */
#if 199901 <= __STDC_VERSION__
 #pragma STDC FENV_ACCESS ON
#endif

/* An interface to strtod that encapsulates all the error checking
   one should usually perform.  Like strtod, but upon successful
   conversion put the result in *RESULT and return true.  Return
   false and don't modify *RESULT upon any failure.  CONVERT
   specifies the conversion function, e.g., strtod itself.  */

bool
xstrtod (char const *str, char const **ptr, double *result,
	 double (*convert) (char const *, char **))
{
  double val;
  char *terminator;
  bool ok = true;

  errno = 0;
  val = convert (str, &terminator);

  /* Having a non-zero terminator is an error only when PTR is NULL. */
  if (terminator == str || (ptr == NULL && *terminator != '\0'))
    ok = false;
  else
    {
      /* Allow underflow (in which case strtod returns zero),
	 but flag overflow as an error. */
      if (val != 0.0 && errno == ERANGE)
	ok = false;
    }

  if (ptr != NULL)
    *ptr = terminator;

  *result = val;
  return ok;
}