buildtools/gcc/gmp/mpz/com.c

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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, 2012, 2015 Free Software
Foundation, Inc.
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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 either:
* 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.
or
* the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any
later version.
or both in parallel, as here.
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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 General Public License
for more details.
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You should have received copies of the GNU General Public License and the
GNU Lesser General Public License along with the GNU MP Library. If not,
see https://www.gnu.org/licenses/. */
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#include "gmp-impl.h"
void
mpz_com (mpz_ptr dst, mpz_srcptr src)
{
mp_size_t size = SIZ (src);
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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 (UNLIKELY (size == 0))
{
/* special case, as mpn_add_1 wants size!=0 */
MPZ_NEWALLOC (dst, 1)[0] = 1;
SIZ (dst) = -1;
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}
else
{
mp_limb_t cy;
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dst_ptr = MPZ_REALLOC (dst, size + 1);
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src_ptr = PTR (src);
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cy = mpn_add_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);
dst_ptr[size] = cy;
size += cy;
/* Store a negative size, to indicate ones-extension. */
SIZ (dst) = -size;
}
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}
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;
dst_ptr = MPZ_REALLOC (dst, size);
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src_ptr = PTR (src);
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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. */
SIZ (dst) = size;
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}
}