/* mpf_get_si -- mpf to long conversion

Copyright 2001, 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 either:

  * 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.

or

  * the GNU General Public License as published by the Free Software

    Foundation; either version 2 of the License, or (at your option) any

    later version.

or both in parallel, as here.

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 General Public License

for more details.

You should have received copies of the GNU General Public License and 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"

/* Any fraction bits are truncated, meaning simply discarded.

   For values bigger than a long, the low bits are returned, like

   mpz_get_si, but this isn't documented.

   Notice this is equivalent to mpz_set_f + mpz_get_si.

   Implementation:

   fl is established in basically the same way as for mpf_get_ui, see that

   code for explanations of the conditions.

   However unlike mpf_get_ui we need an explicit return 0 for exp<=0.  When

   f is a negative fraction (ie. size<0 and exp<=0) we can't let fl==0 go

   through to the zany final "~ ((fl - 1) & LONG_MAX)", that would give

   -0x80000000 instead of the desired 0.  */

long

mpf_get_si (mpf_srcptr f) __GMP_NOTHROW

{

  mp_exp_t exp;

  mp_size_t size, abs_size;

  mp_srcptr fp;

  mp_limb_t fl;

  exp = EXP (f);

  size = SIZ (f);

  fp = PTR (f);

  /* fraction alone truncates to zero

     this also covers zero, since we have exp==0 for zero */

  if (exp <= 0)

    return 0L;

  /* there are some limbs above the radix point */

  fl = 0;

  abs_size = ABS (size);

  if (abs_size >= exp)

    fl = fp[abs_size-exp];

#if BITS_PER_ULONG > GMP_NUMB_BITS

  if (exp > 1 && abs_size+1 >= exp)

    fl |= fp[abs_size - exp + 1] << GMP_NUMB_BITS;

#endif

  if (size > 0)

    return fl & LONG_MAX;

  else

    /* this form necessary to correctly handle -0x80..00 */

    return -1 - (long) ((fl - 1) & LONG_MAX);

}