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#ifndef CYGONCE_INFRA_CLIST_HXX

#define CYGONCE_INFRA_CLIST_HXX

//==========================================================================

//

//      clist.hxx

//

//      Standard types, and some useful coding macros.

//

//==========================================================================

// ####ECOSGPLCOPYRIGHTBEGIN####

// -------------------------------------------

// This file is part of eCos, the Embedded Configurable Operating System.

// Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.

//

// eCos 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.

//

// eCos 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 eCos; if not, write to the Free Software Foundation, Inc.,

// 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

//

// As a special exception, if other files instantiate templates or use

// macros or inline functions from this file, or you compile this file

// and link it with other works to produce a work based on this file,

// this file does not by itself cause the resulting work to be covered by

// the GNU General Public License. However the source code for this file

// must still be made available in accordance with section (3) of the GNU

// General Public License v2.

//

// This exception does not invalidate any other reasons why a work based

// on this file might be covered by the GNU General Public License.

// -------------------------------------------

// ####ECOSGPLCOPYRIGHTEND####

//==========================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):     nickg

// Contributors:  nickg

// Date:        2000-11-08

// Purpose:     Simple circular list implementation

// Description: A simple implementation of circular lists.

// Usage:       #include "cyg/infra/clist.hxx"

//              ...

//

//####DESCRIPTIONEND####

//

//==========================================================================

#include 

// -------------------------------------------------------------------------

// Class and structure conversion macros.

// CYG_CLASSFROMFIELD translates a pointer to a field of a struct or

// class into a pointer to the class.

// CYG_OFFSETOFBASE yields the offset of a base class of a derived

// class.

// CYG_CLASSFROMBASE translates a pointer to a base class into a pointer

// to a selected derived class. The base class object _must_ be part of

// the specified derived class. This is essentially a poor mans version

// of the RTTI dynamic_cast operator.

// Caveat: These macros do not work for virtual base classes.

// Note: These definitions are exact duplicates of definitions in

// ktypes.h. If either definition is changed, the other should be too

// to avoid compiler messages.

#define CYG_CLASSFROMFIELD(_type_,_member_,_ptr_)\

    ((_type_ *)((char *)(_ptr_)-((char *)&(((_type_ *)0)->_member_))))

#define CYG_OFFSETOFBASE(_type_,_base_)\

    ((char *)((_base_ *)((_type_ *)4)) - (char *)4)

# define CYG_CLASSFROMBASE(_class_,_base_,_ptr_)\

    ((_class_ *)((char *)(_ptr_) - CYG_OFFSETOFBASE(_class_,_base_)))

// -------------------------------------------------------------------------

// Cyg_DNode class.

// This simply represents a double linked node that is intended to

// be a base member of the class that is being managed.

class Cyg_DNode

{

    friend class Cyg_CList;

    Cyg_DNode   *next;

    Cyg_DNode   *prev;

public:

    Cyg_DNode()

    {

        // Initialize pointers to point here

        next = prev = this;

    };

    // Accessor and test functions

    Cyg_DNode *get_next() { return next; };

    Cyg_DNode *get_prev() { return prev; };

    cyg_bool  in_list() { return next != this; };

    // Insert a node into the list before this one,

    // so that it becomes this nodes predecessor in

    // the list.

    void insert( Cyg_DNode *node )

    {

        node->next = this;

        node->prev = prev;

        prev->next = node;

        prev = node;

    };

    // Append a node after this one so that it become

    // this nodes sucessor in the list.

    void append( Cyg_DNode *node )

    {

        node->prev = this;

        node->next = next;

        next->prev = node;

        next = node;

    };

    // Unlink this node from it's list. It is safe to apply this to an

    // already unlinked node.

    void unlink()

    {

        next->prev = prev;

        prev->next = next;

        next = prev = this;

    };

    ~Cyg_DNode()

    {

        // If this node is still linked, unlink it.

        if( next != this )

            unlink();

    };

};

// -------------------------------------------------------------------------

// Cyg_CList class.

// This is a simple class that manages a circular list of DNodes. This

// object points to the head of the list and provides functions to

// manipulate the head and tail of the list.

class Cyg_CList

{

    Cyg_DNode   *head;                  // list head pointer

public:

    Cyg_CList()

    {

        head = NULL;

    };

    // Accessor and test functions

    Cyg_DNode *get_head() { return head; };

    Cyg_DNode *get_tail() { return head?head->prev:NULL; };

    cyg_bool empty() { return head == NULL; };

    // Add a node at the head of the list

    void add_head( Cyg_DNode *node )

    {

        if( head == NULL )

            head = node;

        else

        {

            head->insert( node );

            head = node;

        }

    };

    // Remove the node at the head of the list

    Cyg_DNode *rem_head()

    {

        Cyg_DNode *node = head;

        if( node != NULL )

        {

            // There is a node available

            Cyg_DNode *next = node->next;

            if( next == node )

            {

                // Only node on list

                head = NULL;

            }

            else

            {

                // remove head node and move head to next.

                node->unlink();

                head = next;

            }

        }

        return node;

    };

    // Add a node at the tail of the list

    void add_tail( Cyg_DNode *node )

    {

        if( head == NULL )

            head = node;

        else

            head->insert( node );

    };

    // Remove the node at the tail of the list

    Cyg_DNode *rem_tail()

    {

        if( head == NULL )

            return NULL;

        Cyg_DNode *node = head->prev;

        if( node == head )

            head = NULL;

        else node->unlink();

        return node;

    };

    // Merge the supplied list into this one, at the tail.

    void merge( Cyg_CList& list )

    {

        if( list.head == NULL )

            return;                     // Nothing to do

        else if( head == NULL )

            head = list.head;           // this is empty, just move it

        else

        {

            // We have a real merge to do. Adjust the pointers

            // on the two lists so that they become one.

            Cyg_DNode *lh = list.head;

            Cyg_DNode *lt = lh->prev;

            Cyg_DNode *tail = head->prev;

            head->prev = lt;

            lt->next = head;

            tail->next = lh;

            lh->prev = tail;

        }

        list.head = NULL;

    };

    // General removal. Deals with what happend if this is only

    // object on list, or is the head.

    void remove( Cyg_DNode *node )

    {

        if( node == head )

            rem_head();

        else node->unlink();

    };

    // Rotation - move the head to the next node in the list.

    void rotate()

    {

        if( head )

            head = head->next;

    };

    // Move a node to the head of the list. Assumes that the

    // node is in this list.

    void to_head( Cyg_DNode *node )

    {

        head = node;

    };

    // Insert a node before one in this list, and deal with what

    // happens if the node happens to be at the head of the list.

    void insert( Cyg_DNode *list_node, Cyg_DNode *node )

    {

        if( list_node == head )

        {

            head->insert( node );

            head = node;

        }

        else list_node->insert( node );

    };

    ~Cyg_CList()

    {

        while( head != NULL )

            rem_head();

    };

};

// -------------------------------------------------------------------------

// Cyg_CList_T

// Template class that allows us to make use of the CList class in a

// type-specific way.

template  class Cyg_CList_T

    : public Cyg_CList

{

public:

    Cyg_CList_T() {};

    ~Cyg_CList_T() {};

    T *get_head()

    {

        Cyg_DNode *node = Cyg_CList::get_head();

        if( node ) return CYG_CLASSFROMBASE( T, Cyg_DNode, node );

        return NULL;

    };

    T *get_tail()

    {

        Cyg_DNode *node = Cyg_CList::get_tail();

        if( node ) return CYG_CLASSFROMBASE( T, Cyg_DNode, node );

        return NULL;

    };

    T *rem_head()

    {

        Cyg_DNode *node = Cyg_CList::rem_head();

        if( node ) return CYG_CLASSFROMBASE( T, Cyg_DNode, node );

        return NULL;

    };

    T *rem_tail()

    {

        Cyg_DNode *node = Cyg_CList::rem_tail();

        if( node ) return CYG_CLASSFROMBASE( T, Cyg_DNode, node );

        return NULL;

    };

    // The rest just default to the Cyg_CList class operations.

};

// -------------------------------------------------------------------------

// Cyg_DNode_T

// Template class that allows us to make use of the DNode class in a

// type-specific way.

template  class Cyg_DNode_T

    : public Cyg_DNode

{

public:

    Cyg_DNode_T() {};

    ~Cyg_DNode_T() {};

    T *get_next() { return CYG_CLASSFROMBASE( T, Cyg_DNode, Cyg_DNode::get_next() ); };

    T *get_prev() { return CYG_CLASSFROMBASE( T, Cyg_DNode, Cyg_DNode::get_prev() ); };

    // The rest just default to the Cyg_DNode class operations.

};

// -------------------------------------------------------------------------

#endif // CYGONCE_INFRA_CLIST_HXX multiple inclusion protection

// EOF clist.hxx