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Import gmp 2.0.2

/* 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);
}