87 lines
2.4 KiB
C
87 lines
2.4 KiB
C
/* mpz_com(mpz_ptr dst, mpz_ptr src) -- Assign the bit-complemented value of
|
|
SRC to DST.
|
|
|
|
Copyright 1991, 1993, 1994, 1996, 2001, 2003 Free Software Foundation, Inc.
|
|
|
|
This file is part of the GNU MP Library.
|
|
|
|
The GNU MP 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 2.1 of the License, or (at your
|
|
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
|
|
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
|
|
License for more details.
|
|
|
|
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, write to
|
|
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
|
|
MA 02110-1301, USA. */
|
|
|
|
#include "gmp.h"
|
|
#include "gmp-impl.h"
|
|
|
|
void
|
|
mpz_com (mpz_ptr dst, mpz_srcptr src)
|
|
{
|
|
mp_size_t size = src->_mp_size;
|
|
mp_srcptr src_ptr;
|
|
mp_ptr dst_ptr;
|
|
|
|
if (size >= 0)
|
|
{
|
|
/* As with infinite precision: one's complement, two's complement.
|
|
But this can be simplified using the identity -x = ~x + 1.
|
|
So we're going to compute (~~x) + 1 = x + 1! */
|
|
|
|
if (dst->_mp_alloc < size + 1)
|
|
_mpz_realloc (dst, size + 1);
|
|
|
|
src_ptr = src->_mp_d;
|
|
dst_ptr = dst->_mp_d;
|
|
|
|
if (UNLIKELY (size == 0))
|
|
{
|
|
/* special case, as mpn_add_1 wants size!=0 */
|
|
dst_ptr[0] = 1;
|
|
dst->_mp_size = -1;
|
|
return;
|
|
}
|
|
|
|
{
|
|
mp_limb_t cy;
|
|
|
|
cy = mpn_add_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
|
|
if (cy)
|
|
{
|
|
dst_ptr[size] = cy;
|
|
size++;
|
|
}
|
|
}
|
|
|
|
/* Store a negative size, to indicate ones-extension. */
|
|
dst->_mp_size = -size;
|
|
}
|
|
else
|
|
{
|
|
/* As with infinite precision: two's complement, then one's complement.
|
|
But that can be simplified using the identity -x = ~(x - 1).
|
|
So we're going to compute ~~(x - 1) = x - 1! */
|
|
size = -size;
|
|
|
|
if (dst->_mp_alloc < size)
|
|
_mpz_realloc (dst, size);
|
|
|
|
src_ptr = src->_mp_d;
|
|
dst_ptr = dst->_mp_d;
|
|
|
|
mpn_sub_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
|
|
size -= dst_ptr[size - 1] == 0;
|
|
|
|
/* Store a positive size, to indicate zero-extension. */
|
|
dst->_mp_size = size;
|
|
}
|
|
}
|