gcc/gmp/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 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 http://www.gnu.org/licenses/.  */

#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;
    }
}