/* mpfr_set_f -- set a MPFR number from a GNU MPF number

Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
Contributed by the Arenaire and Cacao projects, INRIA.

This file is part of the GNU MPFR Library.

The GNU MPFR 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 2.1 of the License, or (at your
option) any later version.

The GNU MPFR 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 MPFR Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
MA 02110-1301, USA. */

#define MPFR_NEED_LONGLONG_H
#include "mpfr-impl.h"

int
mpfr_set_f (mpfr_ptr y, mpf_srcptr x, mp_rnd_t rnd_mode)
{
  mp_limb_t *my, *mx, *tmp;
  unsigned long cnt, sx, sy;
  int inexact, carry = 0;
  MPFR_TMP_DECL(marker);

  sx = ABS(SIZ(x)); /* number of limbs of the mantissa of x */

  if (sx == 0) /* x is zero */
    {
      MPFR_CLEAR_FLAGS (y);
      MPFR_SET_ZERO(y);
      MPFR_SET_POS(y);
      return 0; /* 0 is exact */
    }

  if (SIZ(x) * MPFR_FROM_SIGN_TO_INT(MPFR_SIGN(y)) < 0)
    MPFR_CHANGE_SIGN (y);

  MPFR_CLEAR_FLAGS (y);

  sy = 1 + (MPFR_PREC(y) - 1) / BITS_PER_MP_LIMB;
  my = MPFR_MANT(y);
  mx = PTR(x);

  count_leading_zeros(cnt, mx[sx - 1]);

  if (sy <= sx) /* we may have to round even when sy = sx */
    {
      unsigned long xprec = sx * BITS_PER_MP_LIMB;

      MPFR_TMP_MARK(marker);
      tmp = (mp_limb_t*) MPFR_TMP_ALLOC(sx * BYTES_PER_MP_LIMB);
      if (cnt)
        mpn_lshift (tmp, mx, sx, cnt);
      else
        /* FIXME: we may avoid the copy here, and directly call mpfr_round_raw
           on mx instead of tmp */
        MPN_COPY (tmp, mx, sx);
      carry = mpfr_round_raw (my, tmp, xprec, (SIZ(x) < 0), MPFR_PREC(y),
                              rnd_mode, &inexact);
      if (MPFR_UNLIKELY(carry)) /* result is a power of two */
        my[sy - 1] = MPFR_LIMB_HIGHBIT;
      MPFR_TMP_FREE(marker);
    }
  else
    {
      if (cnt)
        mpn_lshift (my + sy - sx, mx, sx, cnt);
      else
        MPN_COPY (my + sy - sx, mx, sx);
      MPN_ZERO(my, sy - sx);
      /* no rounding necessary, since y has a larger mantissa */
      inexact = 0;
    }

  /* warning: EXP(x) * BITS_PER_MP_LIMB may exceed the maximal exponent */
  if (EXP(x) > 1 + (__gmpfr_emax - 1) / BITS_PER_MP_LIMB)
    {
      /* EXP(x) >= 2 + floor((__gmpfr_emax-1)/BITS_PER_MP_LIMB)
         EXP(x) >= 2 + (__gmpfr_emax - BITS_PER_MP_LIMB) / BITS_PER_MP_LIMB
                >= 1 + __gmpfr_emax / BITS_PER_MP_LIMB
         EXP(x) * BITS_PER_MP_LIMB >= __gmpfr_emax + BITS_PER_MP_LIMB
         Since 0 <= cnt <= BITS_PER_MP_LIMB-1, and 0 <= carry <= 1,
         we have then EXP(x) * BITS_PER_MP_LIMB - cnt + carry > __gmpfr_emax */
      return mpfr_overflow (y, rnd_mode, MPFR_SIGN (y));
    }
  else
    {
      /* Do not use MPFR_SET_EXP as the exponent may be out of range. */
      MPFR_EXP (y) = EXP (x) * BITS_PER_MP_LIMB - (mp_exp_t) cnt + carry;
    }

  return mpfr_check_range (y, inexact, rnd_mode);
}
