mpir/mpq/set_d.c

/* mpq_set_d(mpq_t q, double d) -- Set q to d without rounding.

Copyright 2000, 2002, 2003 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 2.1 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; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301, USA. */

#include "config.h"

#if HAVE_FLOAT_H
#include <float.h>  /* for DBL_MAX */
#endif

#include "gmp.h"
#include "gmp-impl.h"
#include "longlong.h"

#if LIMBS_PER_DOUBLE > 4
  choke me
#endif

void
mpq_set_d (mpq_ptr dest, double d)
{
  int negative;
  mp_exp_t exp;
  mp_limb_t tp[LIMBS_PER_DOUBLE];
  mp_ptr np, dp;
  mp_size_t nn, dn;
  int c;

  DOUBLE_NAN_INF_ACTION (d,
                         __gmp_invalid_operation (),
                         __gmp_invalid_operation ());

  negative = d < 0;
  d = ABS (d);

  exp = __gmp_extract_double (tp, d);

  /* There are two main version of the conversion.  The `then' arm handles
     numbers with a fractional part, while the `else' arm handles integers.  */
#if LIMBS_PER_DOUBLE == 4
  if (exp <= 1 || (exp == 2 && (tp[0] | tp[1]) != 0))
#endif
#if LIMBS_PER_DOUBLE == 3
  if (exp <= 1 || (exp == 2 && tp[0] != 0))
#endif
#if LIMBS_PER_DOUBLE == 2
  if (exp <= 1)
#endif
    {
      if (d == 0.0)
	{
	  SIZ(&(dest->_mp_num)) = 0;
	  SIZ(&(dest->_mp_den)) = 1;
	  PTR(&(dest->_mp_den))[0] = 1;
	  return;
	}

      dn = -exp;
      MPZ_REALLOC (&(dest->_mp_num), 3);
      np = PTR(&(dest->_mp_num));
#if LIMBS_PER_DOUBLE == 4
      if ((tp[0] | tp[1] | tp[2]) == 0)
	np[0] = tp[3], nn = 1;
      else if ((tp[0] | tp[1]) == 0)
	np[1] = tp[3], np[0] = tp[2], nn = 2;
      else if (tp[0] == 0)
	np[2] = tp[3], np[1] = tp[2], np[0] = tp[1], nn = 3;
      else
	np[3] = tp[3], np[2] = tp[2], np[1] = tp[1], np[0] = tp[0], nn = 4;
#endif
#if LIMBS_PER_DOUBLE == 3
      if ((tp[0] | tp[1]) == 0)
	np[0] = tp[2], nn = 1;
      else if (tp[0] == 0)
	np[1] = tp[2], np[0] = tp[1], nn = 2;
      else
	np[2] = tp[2], np[1] = tp[1], np[0] = tp[0], nn = 3;
#endif
#if LIMBS_PER_DOUBLE == 2
      if (tp[0] == 0)
	np[0] = tp[1], nn = 1;
      else
	np[1] = tp[1], np[0] = tp[0], nn = 2;
#endif
      dn += nn + 1;
      ASSERT_ALWAYS (dn > 0);
      MPZ_REALLOC (&(dest->_mp_den), dn);
      dp = PTR(&(dest->_mp_den));
      MPN_ZERO (dp, dn - 1);
      dp[dn - 1] = 1;
      count_trailing_zeros (c, np[0] | dp[0]);
      if (c != 0)
	{
	  mpn_rshift (np, np, nn, c);
	  nn -= np[nn - 1] == 0;
	  mpn_rshift (dp, dp, dn, c);
	  dn -= dp[dn - 1] == 0;
	}
      SIZ(&(dest->_mp_den)) = dn;
      SIZ(&(dest->_mp_num)) = negative ? -nn : nn;
    }
  else
    {
      nn = exp;
      MPZ_REALLOC (&(dest->_mp_num), nn);
      np = PTR(&(dest->_mp_num));
      switch (nn)
        {
	default:
	  MPN_ZERO (np, nn - LIMBS_PER_DOUBLE);
	  np += nn - LIMBS_PER_DOUBLE;
	  /* fall through */
#if LIMBS_PER_DOUBLE == 2
	case 2:
	  np[1] = tp[1], np[0] = tp[0];
	  break;
#endif
#if LIMBS_PER_DOUBLE == 3
	case 3:
	  np[2] = tp[2], np[1] = tp[1], np[0] = tp[0];
	  break;
	case 2:
	  np[1] = tp[2], np[0] = tp[1];
	  break;
#endif
#if LIMBS_PER_DOUBLE == 4
	case 4:
	  np[3] = tp[3], np[2] = tp[2], np[1] = tp[1], np[0] = tp[0];
	  break;
	case 3:
	  np[2] = tp[3], np[1] = tp[2], np[0] = tp[1];
	  break;
	case 2:
	  np[1] = tp[3], np[0] = tp[2];
	  break;
#endif
	}
      dp = PTR(&(dest->_mp_den));
      dp[0] = 1;
      SIZ(&(dest->_mp_den)) = 1;
      SIZ(&(dest->_mp_num)) = negative ? -nn : nn;
    }
}