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/* mpz_com(MP_INT *dst, MP_INT *src) -- Assign the bit-complemented value of
SRC to DST.
Copyright (C) 1991 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 General Public License as published by
the Free Software Foundation; either version 2, 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with the GNU MP Library; see the file COPYING. If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
#include "gmp.h"
#include "gmp-impl.h"
void
#ifdef __STDC__
mpz_com (MP_INT *dst, const MP_INT *src)
#else
mpz_com (dst, src)
MP_INT *dst;
const MP_INT *src;
#endif
{
mp_size size = src->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->alloc < size + 1)
_mpz_realloc (dst, size + 1);
src_ptr = src->d;
dst_ptr = dst->d;
if (size == 0)
{
/* Special case, as mpn_add wants the first arg's size >= the
second arg's size. */
dst_ptr[0] = 1;
dst->size = -1;
return;
}
{
mp_limb one = 1;
int cy;
cy = mpn_add (dst_ptr, src_ptr, size, &one, 1);
if (cy)
{
dst_ptr[size] = cy;
size++;
}
}
/* Store a negative size, to indicate ones-extension. */
dst->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->alloc < size)
_mpz_realloc (dst, size);
src_ptr = src->d;
dst_ptr = dst->d;
{
mp_limb one = 1;
size += mpn_sub (dst_ptr, src_ptr, size, &one, 1);
}
/* Store a positive size, to indicate zero-extension. */
dst->size = size;
}
}
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