1 /* mpz_com(mpz_ptr dst, mpz_ptr src) -- Assign the bit-complemented value of
4 Copyright 1991, 1993, 1994, 1996, 2001, 2003 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 Lesser General Public License as published by
10 the Free Software Foundation; either version 3 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 Lesser General Public
16 License for more details.
18 You should have received a copy of the GNU Lesser General Public License
19 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
25 mpz_com (mpz_ptr dst, mpz_srcptr src)
27 mp_size_t size = src->_mp_size;
33 /* As with infinite precision: one's complement, two's complement.
34 But this can be simplified using the identity -x = ~x + 1.
35 So we're going to compute (~~x) + 1 = x + 1! */
37 if (dst->_mp_alloc < size + 1)
38 _mpz_realloc (dst, size + 1);
43 if (UNLIKELY (size == 0))
45 /* special case, as mpn_add_1 wants size!=0 */
54 cy = mpn_add_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
62 /* Store a negative size, to indicate ones-extension. */
63 dst->_mp_size = -size;
67 /* As with infinite precision: two's complement, then one's complement.
68 But that can be simplified using the identity -x = ~(x - 1).
69 So we're going to compute ~~(x - 1) = x - 1! */
72 if (dst->_mp_alloc < size)
73 _mpz_realloc (dst, size);
78 mpn_sub_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
79 size -= dst_ptr[size - 1] == 0;
81 /* Store a positive size, to indicate zero-extension. */