/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2006 INRIA

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation;

 *

 * This program 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 a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 * Author: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>

 */

#ifndef HIGH_PRECISION_CAIRO_H

#define HIGH_PRECISION_CAIRO_H

#include <stdint.h>

#include <math.h>

#include "cairo-wideint-private.h"

/**

 * This file contains an implementation of the HighPrecision class.

 * Each instance of the Time class also contains an instance of this

 * class which is used to perform all the arithmetic operations of

 * the Time class.

 *

 * This code is a bit ugly with a lot of inline methods for speed:

 * profiling this code on anything but the simplest scenarios shows

 * that it is a big bottleneck if great care in its implementation

 * is not performed. My observations are that what dominates are

 * Division operations (there are really really super costly)

 * and Comparison operations (because there are typically a lot of

 * these in any complex timekeeping code).

 *

 * So, the code tries really hard to perform any of these 128 bit

 * operations by doing all arithmetic on 64 bit integers when possible

 * (i.e., when there is no fractional part. This is a very common case).

 * Hence, the following code has a m_fastValue (64 bits) and a

 * m_slowValue (128 bits). m_fastValue is used by default and the code

 * converts it to a m_slowValue when needed.

 *

 * If you want to monitor the efficiency of this strategy, you can

 * enable the macro HP128INC below and call the HighPrecision::PrintStats

 * method at the end of the simulation.

 *

 *

 * HighPrecision class create a fastValue and a slowValue depending on the

 * input number. If the input is an integer with 0 fractional part, it will

 * use the fastValue which will contain the integer in a 64 bits format. If

 * it has a fractional part, the slowValue will be used. It is represented

 * simply as a high part slowValue.hi which will contain the integer part

 * and the fractional part slowValue.lo which will contain the factional

 * part as an integer (obtained by multiplying the fractional part by 2^64).

 *

 * Explanation of Slow and Fast operations:

 *

 * If both operands are fastValues, we will perform fast operations, i-e

 * simply using integer operations. If we have though one of the value is

 * slowValue we need to convert the fastValue into a slow one. It is simply

 * obtained by putting the slowValue.lo = 0 and slowValue.hi = fastValue.

 * After that we apply the slow operation which will be a 128 bits operation

 * with two 128 bits operands.

 *

 */

namespace ns3 {

class HighPrecision

{

public:

  inline HighPrecision ();

  inline HighPrecision (int64_t value, bool dummy);

  inline HighPrecision (double value);

  inline int64_t GetInteger (void) const;

  inline double GetDouble (void) const;

  inline void Add (HighPrecision const &o);

  inline void Sub (HighPrecision const &o);

  void Mul (HighPrecision const &o);

  void Div (HighPrecision const &o);

  inline int Compare (HighPrecision const &o) const;

  inline static HighPrecision Zero (void);

private:

  cairo_uint128_t  Mul128 (cairo_uint128_t, cairo_uint128_t ) const;

  cairo_int128_t Div128 (cairo_int128_t sa, cairo_int128_t sb) const;

  inline bool IsNegative (void) const;

  cairo_int128_t m_value;

};

} // namespace ns3

namespace ns3 {

HighPrecision::HighPrecision ()

{

  m_value.hi = 0;

  m_value.lo = 0;

}

HighPrecision::HighPrecision (int64_t value, bool dummy)

{

  m_value.hi = value;

  m_value.lo = 0;

}

bool 

HighPrecision::IsNegative (void) const

{

  int64_t hi = m_value.hi;

  return hi < 0;

}

int64_t

HighPrecision::GetInteger (void) const

{

  return m_value.hi;

}

void

HighPrecision::Add (HighPrecision const &o)

{

  m_value.hi += o.m_value.hi;

  m_value.lo += o.m_value.lo;

  if (m_value.lo < o.m_value.lo)

    {

      m_value.hi++;

    }

}

void

HighPrecision::Sub (HighPrecision const &o)

{

  m_value.hi -= o.m_value.hi;

  m_value.lo -= o.m_value.lo;

  if (m_value.lo > o.m_value.lo)

    {

      m_value.hi--;

    }

}

int

HighPrecision::Compare (HighPrecision const &o) const

{

  HighPrecision tmp = *this;

  tmp.Sub (o);

  return tmp.IsNegative ()?-1:(tmp.m_value.hi == 0 && tmp.m_value.lo == 0)?0:1;

}

HighPrecision

HighPrecision::Zero (void)

{

  return HighPrecision ();

}

#define HPCAIRO_MAX_64 18446744073709551615.0

double HighPrecision::GetDouble (void) const

{

  bool is_negative = IsNegative ();

  cairo_int128_t value = is_negative ? _cairo_int128_negate (m_value) : m_value;

  double flo = value.lo;

  flo /= HPCAIRO_MAX_64;

  double retval = value.hi;

  retval += flo;

  retval = is_negative ? -retval: retval;

  return retval;

}

#undef HPCAIRO_MAX_64

#define HPCAIRO_MAX_64 18446744073709551615.0

HighPrecision::HighPrecision (double value)

{

  double fhi = floor (value);

  int64_t hi = fhi;

  uint64_t lo = (uint64_t) ((value - fhi) * HPCAIRO_MAX_64);

  m_value.hi = hi;

  m_value.lo = lo;

}

#undef HPCAIRO_MAX_64

} // namespace ns3

#endif /* HIGH_PRECISION_CAIRO_H */