/* mpf_set_prec(x) -- Change the precision of x.

Copyright 1993-1995, 2000, 2001 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"


/* A full new_prec+1 limbs are always retained, even though just new_prec
   would satisfy the requested precision.  If size==new_prec+1 then
   certainly new_prec+1 should be kept since no copying is needed in that
   case.  If just new_prec was kept for size>new_prec+1 it'd be a bit
   inconsistent.  */

void
mpf_set_prec (mpf_ptr x, mp_bitcnt_t new_prec_in_bits)
{
  mp_size_t  old_prec, new_prec, new_prec_plus1;
  mp_size_t  size, sign;
  mp_ptr     xp;

  new_prec = __GMPF_BITS_TO_PREC (new_prec_in_bits);
  old_prec = PREC(x);

  /* do nothing if already the right precision */
  if (new_prec == old_prec)
    return;

  PREC(x) = new_prec;
  new_prec_plus1 = new_prec + 1;

  /* retain most significant limbs */
  sign = SIZ(x);
  size = ABS (sign);
  xp = PTR(x);
  if (size > new_prec_plus1)
    {
      SIZ(x) = (sign >= 0 ? new_prec_plus1 : -new_prec_plus1);
      MPN_COPY_INCR (xp, xp + size - new_prec_plus1, new_prec_plus1);
    }

  PTR(x) = __GMP_REALLOCATE_FUNC_LIMBS (xp, old_prec+1, new_prec_plus1);
}