// Queue implementation -*- C++ -*-

// Copyright (C) 2001, 2002 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
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// any later version.

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// GNU General Public License for more details.

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// USA.

// As a special exception, you may use this file as part of a free software
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// invalidate any other reasons why the executable file might be covered by
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/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 * Copyright (c) 1996,1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/** @file stl_queue.h
 *  This is an internal header file, included by other library headers.
 *  You should not attempt to use it directly.
 */

#ifndef __GLIBCPP_INTERNAL_QUEUE_H
#define __GLIBCPP_INTERNAL_QUEUE_H

#include <bits/concept_check.h>

// Since this entire file is within namespace std, there's no reason to
// waste two spaces along the left column.  Thus the leading indentation is
// slightly violated from here on.
namespace std
{

// Forward declarations of operators < and ==, needed for friend declaration.

template <typename _Tp, typename _Sequence = deque<_Tp> >
class queue;

template <typename _Tp, typename _Seq>
inline bool operator==(const queue<_Tp,_Seq>&, const queue<_Tp,_Seq>&);

template <typename _Tp, typename _Seq>
inline bool operator<(const queue<_Tp,_Seq>&, const queue<_Tp,_Seq>&);


/**
 *  @brief  A standard container giving FIFO behavior.
 *
 *  @ingroup Containers
 *  @ingroup Sequences
 *
 *  Meets many of the requirements of a <a href="tables.html#65">container</a>,
 *  but does not define anything to do with iterators.  Very few of the
 *  other standard container interfaces are defined.
 *
 *  This is not a true container, but an @e adaptor.  It holds another
 *  container, and provides a wrapper interface to that container.  The
 *  wrapper is what enforces strict first-in-first-out %queue behavior.
 *
 *  The second template parameter defines the type of the underlying
 *  sequence/container.  It defaults to std::deque, but it can be any type
 *  that supports @c front, @c back, @c push_back, and @c pop_front,
 *  such as std::list or an appropriate user-defined type.
 *
 *  Members not found in "normal" containers are @c container_type,
 *  which is a typedef for the second Sequence parameter, and @c push and
 *  @c pop, which are standard %queue/FIFO operations.
*/
template <typename _Tp, typename _Sequence>
  class queue
{
  // concept requirements
  typedef typename _Sequence::value_type _Sequence_value_type;
  __glibcpp_class_requires(_Tp, _SGIAssignableConcept)
  __glibcpp_class_requires(_Sequence, _FrontInsertionSequenceConcept)
  __glibcpp_class_requires(_Sequence, _BackInsertionSequenceConcept)
  __glibcpp_class_requires2(_Tp, _Sequence_value_type, _SameTypeConcept)

  template <typename _Tp1, typename _Seq1>
  friend bool operator== (const queue<_Tp1, _Seq1>&,
                          const queue<_Tp1, _Seq1>&);
  template <typename _Tp1, typename _Seq1>
  friend bool operator< (const queue<_Tp1, _Seq1>&,
                         const queue<_Tp1, _Seq1>&);

public:
  typedef typename _Sequence::value_type                value_type;
  typedef typename _Sequence::reference                 reference;
  typedef typename _Sequence::const_reference           const_reference;
  typedef typename _Sequence::size_type                 size_type;
  typedef          _Sequence                            container_type;

protected:
  /**
   *  'c' is the underlying container.  Maintainers wondering why this isn't
   *  uglified as per style guidelines should note that this name is
   *  specified in the standard, [23.2.3.1].  (Why?  Presumably for the same
   *  reason that it's protected instead of private:  to allow derivation.
   *  But none of the other containers allow for derivation.  Odd.)
  */
  _Sequence c;

public:
  /**
   *  @brief  Default constructor creates no elements.
  */
  explicit
  queue(const _Sequence& __c = _Sequence())
  : c(__c) {}

  /**
   *  Returns true if the %queue is empty.
  */
  bool
  empty() const { return c.empty(); }

  /**  Returns the number of elements in the %queue.  */
  size_type
  size() const { return c.size(); }

  /**
   *  Returns a read/write reference to the data at the first element of the
   *  %queue.
  */
  reference
  front() { return c.front(); }

  /**
   *  Returns a read-only (constant) reference to the data at the first
   *  element of the %queue.
  */
  const_reference
  front() const { return c.front(); }

  /**
   *  Returns a read/write reference to the data at the last element of the
   *  %queue.
  */
  reference
  back() { return c.back(); }

  /**
   *  Returns a read-only (constant) reference to the data at the last
   *  element of the %queue.
  */
  const_reference
  back() const { return c.back(); }

  /**
   *  @brief  Add data to the end of the %queue.
   *  @param  x  Data to be added.
   *
   *  This is a typical %queue operation.  The function creates an element at
   *  the end of the %queue and assigns the given data to it.
   *  The time complexity of the operation depends on the underlying
   *  sequence.
  */
  void
  push(const value_type& __x) { c.push_back(__x); }

  /**
   *  @brief  Removes first element.
   *
   *  This is a typical %queue operation.  It shrinks the %queue by one.
   *  The time complexity of the operation depends on the underlying
   *  sequence.
   *
   *  Note that no data is returned, and if the first element's data is
   *  needed, it should be retrieved before pop() is called.
  */
  void
  pop() { c.pop_front(); }
};


/**
 *  @brief  Queue equality comparison.
 *  @param  x  A %queue.
 *  @param  y  A %queue of the same type as @a x.
 *  @return  True iff the size and elements of the queues are equal.
 *
 *  This is an equivalence relation.  Complexity and semantics depend on the
 *  underlying sequence type, but the expected rules are:  this relation is
 *  linear in the size of the sequences, and queues are considered equivalent
 *  if their sequences compare equal.
*/
template <typename _Tp, typename _Sequence>
  inline bool 
  operator==(const queue<_Tp, _Sequence>& __x, const queue<_Tp, _Sequence>& __y)
  { return __x.c == __y.c; }

/**
 *  @brief  Queue ordering relation.
 *  @param  x  A %queue.
 *  @param  y  A %queue of the same type as @a x.
 *  @return  True iff @a x is lexographically less than @a y.
 *
 *  This is an total ordering relation.  Complexity and semantics depend on the
 *  underlying sequence type, but the expected rules are:  this relation is
 *  linear in the size of the sequences, the elements must be comparable
 *  with @c <, and std::lexographical_compare() is usually used to make the
 *  determination.
*/
template <typename _Tp, typename _Sequence>
  inline bool
  operator<(const queue<_Tp, _Sequence>& __x, const queue<_Tp, _Sequence>& __y)
  { return __x.c < __y.c; }

/// Based on operator==
template <typename _Tp, typename _Sequence>
  inline bool
  operator!=(const queue<_Tp, _Sequence>& __x, const queue<_Tp, _Sequence>& __y)
  { return !(__x == __y); }

/// Based on operator<
template <typename _Tp, typename _Sequence>
  inline bool 
  operator>(const queue<_Tp, _Sequence>& __x, const queue<_Tp, _Sequence>& __y)
  { return __y < __x; }

/// Based on operator<
template <typename _Tp, typename _Sequence>
  inline bool 
  operator<=(const queue<_Tp, _Sequence>& __x, const queue<_Tp, _Sequence>& __y)
  { return !(__y < __x); }

/// Based on operator<
template <typename _Tp, typename _Sequence>
  inline bool 
  operator>=(const queue<_Tp, _Sequence>& __x, const queue<_Tp, _Sequence>& __y)
  { return !(__x < __y); }


/**
 *  @brief  A standard container automatically sorting its contents.
 *
 *  @ingroup Containers
 *  @ingroup Sequences
 *
 *  This is not a true container, but an @e adaptor.  It holds another
 *  container, and provides a wrapper interface to that container.  The
 *  wrapper is what enforces sorting and first-in-first-out %queue behavior.
 *  Very few of the standard container/sequence interface requirements are
 *  met (e.g., iterators).
 *
 *  The second template parameter defines the type of the underlying
 *  sequence/container.  It defaults to std::vector, but it can be any type
 *  that supports @c front(), @c push_back, @c pop_back, and random-access
 *  iterators, such as std::deque or an appropriate user-defined type.
 *
 *  The third template parameter supplies the means of making priority
 *  comparisons.  It defaults to @c less<value_type> but can be anything
 *  defining a strict weak ordering.
 *
 *  Members not found in "normal" containers are @c container_type,
 *  which is a typedef for the second Sequence parameter, and @c push,
 *  @c pop, and @c top, which are standard %queue/FIFO operations.
 *
 *  @note  No equality/comparison operators are provided for %priority_queue.
 *
 *  @note  Sorting of the elements takes place as they are added to, and
 *         removed from, the %priority_queue using the %priority_queue's
 *         member functions.  If you access the elements by other means, and
 *         change their data such that the sorting order would be different,
 *         the %priority_queue will not re-sort the elements for you.  (How
 *         could it know to do so?)
*/
template <typename _Tp, typename _Sequence = vector<_Tp>,
          typename _Compare  = less<typename _Sequence::value_type> >
  class priority_queue
{
  // concept requirements
  typedef typename _Sequence::value_type _Sequence_value_type;
  __glibcpp_class_requires(_Tp, _SGIAssignableConcept)
  __glibcpp_class_requires(_Sequence, _SequenceConcept)
  __glibcpp_class_requires(_Sequence, _RandomAccessContainerConcept)
  __glibcpp_class_requires2(_Tp, _Sequence_value_type, _SameTypeConcept)
  __glibcpp_class_requires4(_Compare, bool, _Tp, _Tp, _BinaryFunctionConcept)

public:
  typedef typename _Sequence::value_type                value_type;
  typedef typename _Sequence::reference                 reference;
  typedef typename _Sequence::const_reference           const_reference;
  typedef typename _Sequence::size_type                 size_type;
  typedef          _Sequence                            container_type;

protected:
  //  See queue::c for notes on these names.
  _Sequence  c;
  _Compare   comp;

public:
  /**
   *  @brief  Default constructor creates no elements.
  */
  explicit
  priority_queue(const _Compare& __x = _Compare(),
                 const _Sequence& __s = _Sequence()) 
  : c(__s), comp(__x) 
  { make_heap(c.begin(), c.end(), comp); }

  /**
   *  @brief  Builds a %queue from a range.
   *  @param  first  An input iterator.
   *  @param  last  An input iterator.
   *  @param  x  A comparison functor describing a strict weak ordering.
   *  @param  s  An initial sequence with which to start.
   * 
   *  Begins by copying @a s, inserting a copy of the elements from
   *  @a [first,last) into the copy of @a s, then ordering the copy
   *  according to @a x.
   *
   *  For more information on function objects, see the documentation on
   *  @link s20_3_1_base functor base classes@endlink.
  */
  template <typename _InputIterator>
    priority_queue(_InputIterator __first, _InputIterator __last,
                   const _Compare& __x = _Compare(),
                   const _Sequence& __s = _Sequence())
    : c(__s), comp(__x)
    { 
      c.insert(c.end(), __first, __last);
      make_heap(c.begin(), c.end(), comp);
    }

  /**
   *  Returns true if the %queue is empty.
  */
  bool
  empty() const { return c.empty(); }

  /**  Returns the number of elements in the %queue.  */
  size_type
  size() const { return c.size(); }

  /**
   *  Returns a read-only (constant) reference to the data at the first
   *  element of the %queue.
  */
  const_reference
  top() const { return c.front(); }

  /**
   *  @brief  Add data to the %queue.
   *  @param  x  Data to be added.
   *
   *  This is a typical %queue operation.
   *  The time complexity of the operation depends on the underlying
   *  sequence.
  */
  void 
  push(const value_type& __x) 
  {
    try 
      {
        c.push_back(__x); 
        push_heap(c.begin(), c.end(), comp);
      }
    catch(...)
      {
        c.clear();
        __throw_exception_again; 
      }
  }

  /**
   *  @brief  Removes first element.
   *
   *  This is a typical %queue operation.  It shrinks the %queue by one.
   *  The time complexity of the operation depends on the underlying
   *  sequence.
   *
   *  Note that no data is returned, and if the first element's data is
   *  needed, it should be retrieved before pop() is called.
  */
  void 
  pop() 
  {
    try 
      {
        pop_heap(c.begin(), c.end(), comp);
        c.pop_back();
      }
    catch(...)
      {
        c.clear();
        __throw_exception_again; 
      }
  }
};

// No equality/comparison operators are provided for priority_queue.

} // namespace std

#endif /* __GLIBCPP_INTERNAL_QUEUE_H */