1 /* mpz_com(MP_INT *dst, MP_INT *src) -- Assign the bit-complemented value of
4 Copyright (C) 1991 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 General Public License as published by
10 the Free Software Foundation; either version 2, or (at your option)
13 The GNU MP Library is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with the GNU MP Library; see the file COPYING. If not, write to
20 the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
27 mpz_com (MP_INT *dst, const MP_INT *src)
34 mp_size size = src->size;
40 /* As with infinite precision: one's complement, two's complement.
41 But this can be simplified using the identity -x = ~x + 1.
42 So we're going to compute (~~x) + 1 = x + 1! */
44 if (dst->alloc < size + 1)
45 _mpz_realloc (dst, size + 1);
52 /* Special case, as mpn_add wants the first arg's size >= the
63 cy = mpn_add (dst_ptr, src_ptr, size, &one, 1);
71 /* Store a negative size, to indicate ones-extension. */
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->alloc < size)
82 _mpz_realloc (dst, size);
90 size += mpn_sub (dst_ptr, src_ptr, size, &one, 1);
93 /* Store a positive size, to indicate zero-extension. */