com.c
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上传日期:2022-08-06
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- /* 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 3 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. If not, see http://www.gnu.org/licenses/. */
- #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;
- }
- }