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/* mpz_ui_sub -- Subtract an unsigned one-word integer and an mpz_t.
Copyright 2002, 2004 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 https://www.gnu.org/licenses/. */
#include "gmp.h"
#include "gmp-impl.h"
void
mpz_ui_sub (mpz_ptr w, unsigned long int uval, mpz_srcptr v)
{
mp_ptr vp, wp;
mp_size_t vn, wn;
mp_limb_t cy;
#if BITS_PER_ULONG > GMP_NUMB_BITS /* avoid warnings about shift amount */
if (uval > GMP_NUMB_MAX)
{
mpz_t u;
mp_limb_t ul[2];
PTR(u) = ul;
ul[0] = uval & GMP_NUMB_MASK;
ul[1] = uval >> GMP_NUMB_BITS;
SIZ(u) = 2;
mpz_sub (w, u, v);
return;
}
#endif
vp = PTR(v);
vn = SIZ(v);
wp = PTR(w);
if (vn > 1)
{
wp = MPZ_REALLOC (w, vn);
vp = PTR(v);
mpn_sub_1 (wp, vp, vn, (mp_limb_t) uval);
wn = -(vn - (wp[vn - 1] == 0));
}
else if (vn == 1)
{
if (uval >= vp[0])
{
wp[0] = uval - vp[0];
wn = wp[0] != 0;
}
else
{
wp[0] = vp[0] - uval;
wn = -1;
}
}
else if (vn == 0)
{
wp[0] = uval;
wn = uval != 0;
}
else /* (vn < 0) */
{
vn = -vn;
wp = MPZ_REALLOC (w, vn + 1);
vp = PTR(v);
cy = mpn_add_1 (wp, vp, vn, (mp_limb_t) uval);
wp[vn] = cy;
wn = vn + (cy != 0);
}
SIZ(w) = wn;
}
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