stl_queue.h

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// 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
// Free Software Foundation; either version 2, 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 General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/*
 *
 * 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>

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.
   *