glibc/stdlib/sub_n.c

54 lines
1.6 KiB
C
Raw Normal View History

/* mpn_sub_n -- Subtract two limb vectors of equal, non-zero length.
1995-02-18 01:27:10 +00:00
Copyright (C) 1992-2017 Free Software Foundation, Inc.
1995-02-18 01:27:10 +00:00
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
2001-07-07 10:13:33 +00:00
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at your
1995-02-18 01:27:10 +00:00
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
2001-07-07 10:13:33 +00:00
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
1995-02-18 01:27:10 +00:00
License for more details.
2001-07-07 10:13:33 +00:00
You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library; see the file COPYING.LIB. If not, see
<http://www.gnu.org/licenses/>. */
1995-02-18 01:27:10 +00:00
2005-12-14 15:06:39 +00:00
#include <gmp.h>
1995-02-18 01:27:10 +00:00
#include "gmp-impl.h"
1996-05-07 21:04:52 +00:00
mp_limb_t
mpn_sub_n (mp_ptr res_ptr, mp_srcptr s1_ptr, mp_srcptr s2_ptr, mp_size_t size)
1995-02-18 01:27:10 +00:00
{
1996-05-07 21:04:52 +00:00
register mp_limb_t x, y, cy;
1995-02-18 01:27:10 +00:00
register mp_size_t j;
/* The loop counter and index J goes from -SIZE to -1. This way
the loop becomes faster. */
j = -size;
/* Offset the base pointers to compensate for the negative indices. */
s1_ptr -= j;
s2_ptr -= j;
res_ptr -= j;
cy = 0;
do
{
y = s2_ptr[j];
x = s1_ptr[j];
y += cy; /* add previous carry to subtrahend */
cy = (y < cy); /* get out carry from that addition */
y = x - y; /* main subtract */
cy = (y > x) + cy; /* get out carry from the subtract, combine */
res_ptr[j] = y;
}
while (++j != 0);
return cy;
}