// This may look like C code, but it is really -*- C++ -*-
/* 
Copyright (C) 1991 Free Software Foundation

This file is part of the GNU C++ Library.  This library is free
software; you can redistribute it and/or modify it under the terms of
the GNU Library General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your
option) any later version.  This 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 Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/*
 * Sets implemented via William Pugh SkipList algorithms.
 * CACM, June 1990, p 668-676.
 *
 */

#ifndef _<T>SkipSet_h
#ifdef __GNUG__
#pragma interface
#endif
#define _<T>SkipSet_h 1

#include "<T>.Set.h"

#include <limits.h>
#include <MLCG.h>

class <T>SkipSet;
class <T>RealSkipSetNode;

class <T>SkipSetNode
{
friend class <T>SkipSet;
  private:
    <T>RealSkipSetNode * * forward;
    <T>SkipSetNode(int size);
};

class <T>RealSkipSetNode : public <T>SkipSetNode
{
friend class <T>SkipSet;
  private:
    <T>             item;
    <T>RealSkipSetNode(<T&> h, int size);
};

typedef <T>RealSkipSetNode* <T>SkipSetNodePtr;

inline <T>SkipSetNode::<T>SkipSetNode(int size)
: forward(new <T>SkipSetNodePtr[size+1])
{
}

inline <T>RealSkipSetNode::<T>RealSkipSetNode(<T&> h, int size)
: item(h),
  <T>SkipSetNode(size)
{
}

class <T>SkipSet : public <T>Set
{
friend class <T>SkipSetinit;
  protected:
    <T>SkipSetNode*   header;
    int               level;
    int               max_levels;
    int               randoms_left;
    long              random_bits;
    
    static MLCG*      gen;
    int               random_level(void);
    
    <T>SkipSetNodePtr leftmost(void);
    <T>SkipSetNodePtr rightmost(void);
    <T>SkipSetNodePtr pred(<T>SkipSetNodePtr t);
    <T>SkipSetNodePtr succ(<T>SkipSetNodePtr t);
    void              _kill(void);
    
  private:
    enum { BITS_IN_RANDOM = LONGBITS-1 };
  public:
    <T>SkipSet(long size=DEFAULT_INITIAL_CAPACITY);
    <T>SkipSet(<T>SkipSet& a);
    ~<T>SkipSet();
    
    Pix             add(<T&> i);
    void            del(<T&> i);
    int             contains(<T&> i);
    
    void            clear(void);
    
    Pix             first(void);
    void            next(Pix& i);
    <T>&            operator () (Pix i);
    Pix             seek(<T&> i);
    
    Pix             last(void);
    void            prev(Pix& i);
    
    void            operator |= (<T>SkipSet& b);
    void            operator -= (<T>SkipSet& b);
    void            operator &= (<T>SkipSet& b);
    
    int             operator == (<T>SkipSet& b);
    int             operator != (<T>SkipSet& b);
    int             operator <= (<T>SkipSet& b); 
    
    int             OK(void);
};

/*
 *  A little overkill on the inlines.
 *
 */

inline <T>SkipSet::~<T>SkipSet(void)
{
  _kill();
  delete header;
}

inline int <T>SkipSet::operator != (<T>SkipSet& b)
{
  return ! (*this == b);
}

inline <T>SkipSetNodePtr <T>SkipSet::leftmost(void)
{
  return header->forward[0];
}

inline <T>SkipSetNodePtr <T>SkipSet::succ(<T>SkipSetNodePtr t)
{
  <T>SkipSetNodePtr result = 0;
  if (t->forward[0]!=header) result = t->forward[0];
  return result;
}

inline Pix <T>SkipSet::first(void)
{
  return Pix(leftmost());
}

inline Pix <T>SkipSet::last(void)
{
  return Pix(rightmost());
}

inline void <T>SkipSet::next(Pix& i)
{
  if (i != 0) i = Pix(succ((<T>SkipSetNodePtr)i));
}

inline void <T>SkipSet::prev(Pix& i)
{
  if (i != 0) i = Pix(pred((<T>SkipSetNodePtr)i));
}

inline <T>& <T>SkipSet::operator () (Pix i)
{
  if (i == 0) error("null Pix");
  return ((<T>SkipSetNodePtr)i)->item;
}


inline int <T>SkipSet::contains(<T&> key)
{
  return seek(key) != 0;
}

static class <T>SkipSetinit
{
  public:
    <T>SkipSetinit();
    ~<T>SkipSetinit();
  private:
    static int count;
} <T>skipSetinit;

#endif