stl_queue.h

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

// Copyright (C) 2001, 2002, 2003, 2004 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 _QUEUE_H
#define _QUEUE_H 1

#include <bits/concept_check.h>
#include <debug/debug.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;
            __glibcxx_class_requires(_Tp, _SGIAssignableConcept)
                __glibcxx_class_requires(_Sequence, _FrontInsertionSequenceConcept)
                __glibcxx_class_requires(_Sequence, _BackInsertionSequenceConcept)
                __glibcxx_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()
                {
                    __glibcxx_requires_nonempty();
                    return c.front();
                }

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

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

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


    /**