freebsd-dev/contrib/libgmp/mpf/set_prc.c

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/* mpf_set_prec(x) -- Change the precision of x.
Copyright (C) 1993, 1994, 1995 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 Library General Public License as published by
the Free Software Foundation; either version 2 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 Library General Public
License for more details.
You should have received a copy of the GNU Library General Public License
along with the GNU MP Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include "gmp.h"
#include "gmp-impl.h"
void
#if __STDC__
mpf_set_prec (mpf_ptr x, unsigned long int prec_in_bits)
#else
mpf_set_prec (x, prec_in_bits)
mpf_ptr x;
unsigned long int prec_in_bits;
#endif
{
mp_size_t prec;
mp_size_t size = ABS (x->_mp_size);
prec = (MAX (53, prec_in_bits) + 2 * BITS_PER_MP_LIMB - 1)/BITS_PER_MP_LIMB;
/* We want the most significant limbs, so move the limbs down if we are
about to truncate the value. */
if (size > prec + 1)
{
mp_size_t offset = size - (prec + 1);
mp_ptr xp = x->_mp_d;
MPN_COPY (xp, xp + offset, prec + 1);
}
x->_mp_d = (mp_ptr) (*_mp_reallocate_func)
(x->_mp_d,
(x->_mp_prec + 1) * BYTES_PER_MP_LIMB, (prec + 1) * BYTES_PER_MP_LIMB);
x->_mp_prec = prec;
/* If the precision decreased, truncate the number. */
if (size > prec + 1)
x->_mp_size = x->_mp_size >= 0 ? (prec + 1) : -(prec + 1);
}