stdlib/strtod_nan_main.c

   1 /* Convert string for NaN payload to corresponding NaN.
   2    Copyright (C) 1997-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C 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    The GNU C 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 the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <ieee754.h>
  20 #include <locale.h>
  21 #include <math.h>
  22 #include <stdlib.h>
  23 #include <wchar.h>
  24
  25
  26 /* If STR starts with an optional n-char-sequence as defined by ISO C
  27    (a sequence of ASCII letters, digits and underscores), followed by
  28    ENDC, return a NaN whose payload is set based on STR.  Otherwise,
  29    return a default NAN.  If ENDPTR is not NULL, set *ENDPTR to point
  30    to the character after the initial n-char-sequence.  */
  31
  32 FLOAT
  33 STRTOD_NAN (const STRING_TYPE *str, STRING_TYPE **endptr, STRING_TYPE endc)
  34 {
  35   const STRING_TYPE *cp = str;
  36
  37   while ((*cp >= L_('0') && *cp <= L_('9'))
  38          || (*cp >= L_('A') && *cp <= L_('Z'))
  39          || (*cp >= L_('a') && *cp <= L_('z'))
  40          || *cp == L_('_'))
  41     ++cp;
  42
  43   FLOAT retval = NAN;
  44   if (*cp != endc)
  45     goto out;
  46
  47   /* This is a system-dependent way to specify the bitmask used for
  48      the NaN.  We expect it to be a number which is put in the
  49      mantissa of the number.  */
  50   STRING_TYPE *endp;
  51   unsigned long long int mant;
  52
  53   mant = STRTOULL (str, &endp, 0);
  54   if (endp == cp)
  55     SET_NAN_PAYLOAD (retval, mant);
  56
  57  out:
  58   if (endptr != NULL)
  59     *endptr = (STRING_TYPE *) cp;
  60   return retval;
  61 }
  62 libc_hidden_def (STRTOD_NAN)