lib/xstrtod.c

   1 /* error-checking interface to strtod-like functions
   2
   3    Copyright (C) 1996, 1999-2000, 2003-2006, 2009-2017 Free Software
   4    Foundation, Inc.
   5
   6    This program is free software: you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 /* Written by Jim Meyering.  */
  20
  21 #include <config.h>
  22
  23 #include "xstrtod.h"
  24
  25 #include <errno.h>
  26 #include <limits.h>
  27 #include <stdio.h>
  28
  29 #if LONG
  30 # define XSTRTOD xstrtold
  31 # define DOUBLE long double
  32 #else
  33 # define XSTRTOD xstrtod
  34 # define DOUBLE double
  35 #endif
  36
  37 /* An interface to a string-to-floating-point conversion function that
  38    encapsulates all the error checking one should usually perform.
  39    Like strtod/strtold, but stores the conversion in *RESULT,
  40    and returns true upon successful conversion.
  41    CONVERT specifies the conversion function, e.g., strtod itself.  */
  42
  43 bool
  44 XSTRTOD (char const *str, char const **ptr, DOUBLE *result,
  45          DOUBLE (*convert) (char const *, char **))
  46 {
  47   DOUBLE val;
  48   char *terminator;
  49   bool ok = true;
  50
  51   errno = 0;
  52   val = convert (str, &terminator);
  53
  54   /* Having a non-zero terminator is an error only when PTR is NULL. */
  55   if (terminator == str || (ptr == NULL && *terminator != '\0'))
  56     ok = false;
  57   else
  58     {
  59       /* Allow underflow (in which case CONVERT returns zero),
  60          but flag overflow as an error.  The user can decide
  61          to use the limits in RESULT upon ERANGE.  */
  62       if (val != 0 && errno == ERANGE)
  63         ok = false;
  64     }
  65
  66   if (ptr != NULL)
  67     *ptr = terminator;
  68
  69   *result = val;
  70   return ok;
  71 }