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DEFINITIONS
This source file includes following definitions.
- _bc_do_add
- _bc_do_sub
/* doaddsub.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. (COPYING.LIB)
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 <config.h>
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <ctype.h>
#include <stdarg.h>
#include "bcmath.h"
#include "private.h"
/* Perform addition: N1 is added to N2 and the value is
returned. The signs of N1 and N2 are ignored.
SCALE_MIN is to set the minimum scale of the result. */
bc_num
_bc_do_add (n1, n2, scale_min)
bc_num n1, n2;
int scale_min;
{
bc_num sum;
int sum_scale, sum_digits;
char *n1ptr, *n2ptr, *sumptr;
int carry, n1bytes, n2bytes;
int count;
/* Prepare sum. */
sum_scale = MAX (n1->n_scale, n2->n_scale);
sum_digits = MAX (n1->n_len, n2->n_len) + 1;
sum = bc_new_num (sum_digits, MAX(sum_scale, scale_min));
/* Zero extra digits made by scale_min. */
if (scale_min > sum_scale)
{
sumptr = (char *) (sum->n_value + sum_scale + sum_digits);
for (count = scale_min - sum_scale; count > 0; count--)
*sumptr++ = 0;
}
/* Start with the fraction part. Initialize the pointers. */
n1bytes = n1->n_scale;
n2bytes = n2->n_scale;
n1ptr = (char *) (n1->n_value + n1->n_len + n1bytes - 1);
n2ptr = (char *) (n2->n_value + n2->n_len + n2bytes - 1);
sumptr = (char *) (sum->n_value + sum_scale + sum_digits - 1);
/* Add the fraction part. First copy the longer fraction.*/
if (n1bytes != n2bytes)
{
if (n1bytes > n2bytes)
while (n1bytes>n2bytes)
{ *sumptr-- = *n1ptr--; n1bytes--;}
else
while (n2bytes>n1bytes)
{ *sumptr-- = *n2ptr--; n2bytes--;}
}
/* Now add the remaining fraction part and equal size integer parts. */
n1bytes += n1->n_len;
n2bytes += n2->n_len;
carry = 0;
while ((n1bytes > 0) && (n2bytes > 0))
{
*sumptr = *n1ptr-- + *n2ptr-- + carry;
if (*sumptr > (BASE-1))
{
carry = 1;
*sumptr -= BASE;
}
else
carry = 0;
sumptr--;
n1bytes--;
n2bytes--;
}
/* Now add carry the longer integer part. */
if (n1bytes == 0)
{ n1bytes = n2bytes; n1ptr = n2ptr; }
while (n1bytes-- > 0)
{
*sumptr = *n1ptr-- + carry;
if (*sumptr > (BASE-1))
{
carry = 1;
*sumptr -= BASE;
}
else
carry = 0;
sumptr--;
}
/* Set final carry. */
if (carry == 1)
*sumptr += 1;
/* Adjust sum and return. */
_bc_rm_leading_zeros (sum);
return sum;
}
/* Perform subtraction: N2 is subtracted from N1 and the value is
returned. The signs of N1 and N2 are ignored. Also, N1 is
assumed to be larger than N2. SCALE_MIN is the minimum scale
of the result. */
bc_num
_bc_do_sub (n1, n2, scale_min)
bc_num n1, n2;
int scale_min;
{
bc_num diff;
int diff_scale, diff_len;
int min_scale, min_len;
char *n1ptr, *n2ptr, *diffptr;
int borrow, count, val;
/* Allocate temporary storage. */
diff_len = MAX (n1->n_len, n2->n_len);
diff_scale = MAX (n1->n_scale, n2->n_scale);
min_len = MIN (n1->n_len, n2->n_len);
min_scale = MIN (n1->n_scale, n2->n_scale);
diff = bc_new_num (diff_len, MAX(diff_scale, scale_min));
/* Zero extra digits made by scale_min. */
if (scale_min > diff_scale)
{
diffptr = (char *) (diff->n_value + diff_len + diff_scale);
for (count = scale_min - diff_scale; count > 0; count--)
*diffptr++ = 0;
}
/* Initialize the subtract. */
n1ptr = (char *) (n1->n_value + n1->n_len + n1->n_scale -1);
n2ptr = (char *) (n2->n_value + n2->n_len + n2->n_scale -1);
diffptr = (char *) (diff->n_value + diff_len + diff_scale -1);
/* Subtract the numbers. */
borrow = 0;
/* Take care of the longer scaled number. */
if (n1->n_scale != min_scale)
{
/* n1 has the longer scale */
for (count = n1->n_scale - min_scale; count > 0; count--)
*diffptr-- = *n1ptr--;
}
else
{
/* n2 has the longer scale */
for (count = n2->n_scale - min_scale; count > 0; count--)
{
val = - *n2ptr-- - borrow;
if (val < 0)
{
val += BASE;
borrow = 1;
}
else
borrow = 0;
*diffptr-- = val;
}
}
/* Now do the equal length scale and integer parts. */
for (count = 0; count < min_len + min_scale; count++)
{
val = *n1ptr-- - *n2ptr-- - borrow;
if (val < 0)
{
val += BASE;
borrow = 1;
}
else
borrow = 0;
*diffptr-- = val;
}
/* If n1 has more digits then n2, we now do that subtract. */
if (diff_len != min_len)
{
for (count = diff_len - min_len; count > 0; count--)
{
val = *n1ptr-- - borrow;
if (val < 0)
{
val += BASE;
borrow = 1;
}
else
borrow = 0;
*diffptr-- = val;
}
}
/* Clean up and return. */
_bc_rm_leading_zeros (diff);
return diff;
}