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/*
Copyright (c) 2019, 2020, MariaDB
This program 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; version 2 of
the License.
This program 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 program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA
*/
#pragma once
#include <cstddef>
#include <iterator>
namespace intrusive
{
// Derive your class from this struct to insert to a linked list.
template <class Tag= void> struct list_node
{
list_node(list_node *next= NULL, list_node *prev= NULL)
: next(next), prev(prev)
{
}
list_node *next;
list_node *prev;
};
// Modelled after std::list<T>
template <class T, class Tag= void> class list
{
public:
typedef list_node<Tag> ListNode;
class Iterator;
// All containers in C++ should define these types to implement generic
// container interface.
typedef T value_type;
typedef std::size_t size_type;
typedef std::ptrdiff_t difference_type;
typedef value_type &reference;
typedef const value_type &const_reference;
typedef T *pointer;
typedef const T *const_pointer;
typedef Iterator iterator;
typedef Iterator const_iterator; /* FIXME */
typedef std::reverse_iterator<iterator> reverse_iterator;
typedef std::reverse_iterator<const iterator> const_reverse_iterator;
class Iterator
{
public:
// All iterators in C++ should define these types to implement generic
// iterator interface.
typedef std::bidirectional_iterator_tag iterator_category;
typedef T value_type;
typedef std::ptrdiff_t difference_type;
typedef T *pointer;
typedef T &reference;
Iterator(ListNode *node) : node_(node) {}
Iterator &operator++()
{
node_= node_->next;
return *this;
}
Iterator operator++(int)
{
Iterator tmp(*this);
operator++();
return tmp;
}
Iterator &operator--()
{
node_= node_->prev;
return *this;
}
Iterator operator--(int)
{
Iterator tmp(*this);
operator--();
return tmp;
}
reference operator*() { return *static_cast<pointer>(node_); }
pointer operator->() { return static_cast<pointer>(node_); }
bool operator==(const Iterator &rhs) { return node_ == rhs.node_; }
bool operator!=(const Iterator &rhs) { return !(*this == rhs); }
private:
ListNode *node_;
friend class list;
};
list() : sentinel_(&sentinel_, &sentinel_), size_(0) {}
reference front() { return *begin(); }
reference back() { return *--end(); }
const_reference front() const { return *begin(); }
const_reference back() const { return *--end(); }
iterator begin() { return iterator(sentinel_.next); }
const_iterator begin() const
{
return iterator(const_cast<ListNode *>(sentinel_.next));
}
iterator end() { return iterator(&sentinel_); }
const_iterator end() const
{
return iterator(const_cast<ListNode *>(&sentinel_));
}
reverse_iterator rbegin() { return reverse_iterator(end()); }
const_reverse_iterator rbegin() const { return reverse_iterator(end()); }
reverse_iterator rend() { return reverse_iterator(begin()); }
const_reverse_iterator rend() const { return reverse_iterator(begin()); }
bool empty() const { return size_ == 0; }
size_type size() const { return size_; }
void clear()
{
sentinel_.next= &sentinel_;
sentinel_.prev= &sentinel_;
size_= 0;
}
iterator insert(iterator pos, reference value)
{
ListNode *curr= pos.node_;
ListNode *prev= pos.node_->prev;
prev->next= &value;
curr->prev= &value;
static_cast<ListNode &>(value).prev= prev;
static_cast<ListNode &>(value).next= curr;
++size_;
return iterator(&value);
}
iterator erase(iterator pos)
{
ListNode *prev= pos.node_->prev;
ListNode *next= pos.node_->next;
prev->next= next;
next->prev= prev;
// This is not required for list functioning. But maybe it'll prevent bugs
// and ease debugging.
ListNode *curr= pos.node_;
curr->prev= NULL;
curr->next= NULL;
--size_;
return next;
}
void push_back(reference value) { insert(end(), value); }
void pop_back() { erase(end()); }
void push_front(reference value) { insert(begin(), value); }
void pop_front() { erase(begin()); }
// STL version is O(n) but this is O(1) because an element can't be inserted
// several times in the same intrusive list.
void remove(reference value) { erase(iterator(&value)); }
private:
ListNode sentinel_;
size_type size_;
};
} // namespace intrusive
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