1 /* mpz_com(mpz_ptr dst, mpz_ptr src) -- Assign the bit-complemented value of
4 Copyright (C) 1991, 1993, 1994, 1996 Free Software Foundation, Inc.
6 This file is part of the GNU MP Library.
8 The GNU MP Library is free software; you can redistribute it and/or modify
9 it under the terms of the GNU Library General Public License as published by
10 the Free Software Foundation; either version 2 of the License, or (at your
11 option) any later version.
13 The GNU MP Library is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
16 License for more details.
18 You should have received a copy of the GNU Library General Public License
19 along with the GNU MP Library; see the file COPYING.LIB. If not, write to
20 the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
21 MA 02111-1307, USA. */
28 mpz_com (mpz_ptr dst, mpz_srcptr src)
35 mp_size_t size = src->_mp_size;
41 /* As with infinite precision: one's complement, two's complement.
42 But this can be simplified using the identity -x = ~x + 1.
43 So we're going to compute (~~x) + 1 = x + 1! */
45 if (dst->_mp_alloc < size + 1)
46 _mpz_realloc (dst, size + 1);
53 /* Special case, as mpn_add wants the first arg's size >= the
63 cy = mpn_add_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
71 /* Store a negative size, to indicate ones-extension. */
72 dst->_mp_size = -size;
76 /* As with infinite precision: two's complement, then one's complement.
77 But that can be simplified using the identity -x = ~(x - 1).
78 So we're going to compute ~~(x - 1) = x - 1! */
81 if (dst->_mp_alloc < size)
82 _mpz_realloc (dst, size);
87 mpn_sub_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
88 size -= dst_ptr[size - 1] == 0;
90 /* Store a positive size, to indicate zero-extension. */