num2long.c

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/* num2long.c: bcmath library file. */
/*
    Copyright (C) 1991, 1992, 1993, 1994, 1997 Free Software Foundation, Inc.
    Copyright (C) 2000 Philip A. Nelson
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.
 
    This library 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
    Lesser General Public License for more details.  (LICENSE)
 
    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to:
 
      The Free Software Foundation, Inc.
      59 Temple Place, Suite 330
      Boston, MA 02111-1307 USA.
 
    You may contact the author by:
       e-mail:  philnelson@acm.org
      us-mail:  Philip A. Nelson
                Computer Science Department, 9062
                Western Washington University
                Bellingham, WA 98226-9062
 
*************************************************************************/
 
#include "bcmath.h"
#include <stddef.h>
 
/* Convert a number NUM to a long.  The function returns only the integer
   part of the number.  For numbers that are too large to represent as
   a long, this function returns a zero.  This can be detected by checking
   the NUM for zero after having a zero returned. */
 
long bc_num2long(bc_num num)
{
    /* Extract the int value, ignore the fraction. */
    long val = 0;
    const char *nptr = num->n_value;
    for (size_t index = num->n_len; index > 0; index--) {
        char n = *nptr++;
 
        if (val > LONG_MAX / BASE) {
            return 0;
        }
        val *= BASE;
 
        if (val > LONG_MAX - n) {
            return 0;
        }
        val += n;
    }
 
    /* Return the value. */
    if (num->n_sign == PLUS) {
        return (val);
    } else {
        return (-val);
    }
}