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/**
* @file ListManager.h
* Template class that manages items in a double-linked list.
* If C++ could do it, this would just be a class that worked on an interface.
*
* @author Ben Gardner
* @license GPL v2+
*/
#ifndef LIST_MANAGER_H_INCLUDED
#define LIST_MANAGER_H_INCLUDED
/*
* TODO: why do we provide this template class? can't we use
* a double linked list std::deque from the standard library ?
*/
/**
* A simple list manager for a double-linked list.
* Class T must define 'next' and 'prev', which must be pointers to type T.
*/
template<class T>
class ListManager
{
protected:
T *first; //! pointer to the head of list
T *last; //! pointer to tail of list
private:
// Hide copy constructor
ListManager(const ListManager &ref)
{
first = nullptr;
last = nullptr;
}
public:
ListManager()
{
first = nullptr;
last = nullptr;
}
/**
* @brief return the first element of the linked list
*
* @return pointer to first element or nullptr if list is empty
*/
T *GetHead() const
{
return(first);
}
/**
* @brief return the last element of the linked list
*
* @return pointer to last element or nullptr if list is empty
*/
T *GetTail() const
{
return(last);
}
/**
* @brief return the next element of the linked list
*
* @param[in] ref pointer to current list element
*
* @return pointer to next element or nullptr if no next element exists
*/
T *GetNext(const T *ref) const
{
return((ref != nullptr) ? ref->next : nullptr);
}
/**
* @brief return the previous element of the linked list
*
* @param[in] ref pointer to current list element
*
* @return pointer to previous element or nullptr if no previous element exists
*/
T *GetPrev(const T *ref) const
{
return((ref != nullptr) ? ref->prev : nullptr);
}
/**
* @brief remove an element from a linked list
*
* @param[in] obj list element to remove
*/
void Pop(T *obj)
{
if (obj != nullptr)
{
if (first == obj)
{
first = obj->next;
}
if (last == obj)
{
last = obj->prev;
}
if (obj->next != nullptr)
{
obj->next->prev = obj->prev;
}
if (obj->prev != nullptr)
{
obj->prev->next = obj->next;
}
obj->next = nullptr;
obj->prev = nullptr;
}
}
//! swap two elements of a list
void Swap(T *obj1, T *obj2)
{
if ( obj1 != nullptr
&& obj2 != nullptr)
{
if (obj1->prev == obj2)
{
Pop(obj1);
AddBefore(obj1, obj2);
}
else if (obj2->prev == obj1)
{
Pop(obj2);
AddBefore(obj2, obj1);
}
else
{
T *prev1 = obj1->prev;
Pop(obj1);
T *prev2 = obj2->prev;
Pop(obj2);
AddAfter(obj1, prev2);
AddAfter(obj2, prev1);
}
}
}
/**
* @brief add a new element after a reference position in a list
*
* @param obj new element to add to list
* @param ref chunk after which to insert new object
*/
void AddAfter(T *obj, T *ref)
{
if ( obj != nullptr
&& ref != nullptr)
{
Pop(obj); // TODO: is this necessary?
obj->next = ref->next;
obj->prev = ref;
if (ref->next != nullptr)
{
ref->next->prev = obj;
}
else
{
last = obj;
}
ref->next = obj;
}
}
/**
* @brief add a new element before a reference position in a list
*
* @param obj new element to add to list
* @param ref chunk before to insert new object
*/
void AddBefore(T *obj, T *ref)
{
if ( obj != nullptr
&& ref != nullptr)
{
Pop(obj);
obj->next = ref;
obj->prev = ref->prev;
if (ref->prev != nullptr)
{
ref->prev->next = obj;
}
else
{
first = obj;
}
ref->prev = obj;
}
}
/**
* @brief add a new element to the tail of a lis
*
* @param obj new element to add to the list
*/
void AddTail(T *obj)
{
obj->next = nullptr;
obj->prev = last;
if (last == nullptr)
{
last = obj;
first = obj;
}
else
{
last->next = obj;
}
last = obj;
}
/**
* @brief add a new element to the head of a list
*
* @param obj new element to add to the list
*/
void AddHead(T *obj)
{
obj->next = first;
obj->prev = nullptr;
if (first == nullptr)
{
last = obj;
first = obj;
}
else
{
first->prev = obj;
}
first = obj;
}
};
#endif /* LIST_MANAGER_H_INCLUDED */
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