List.h

//------------------------------------------------------------------------------
/*
    This file is part of Beast: https://github.com/vinniefalco/Beast
    Copyright 2013, Vinnie Falco <vinnie.falco@gmail.com>
 
    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.
 
    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
 
#ifndef BEAST_INTRUSIVE_LIST_H_INCLUDED
#define BEAST_INTRUSIVE_LIST_H_INCLUDED
 
#include <iterator>
 
namespace beast {
 
template <typename, typename>
class List;
 
namespace detail {
 
template <typename T, typename U>
struct CopyConst
{
    explicit CopyConst() = default;
 
    using type = typename std::remove_const<U>::type;
};
 
template <typename T, typename U>
struct CopyConst<T const, U>
{
    explicit CopyConst() = default;
 
    using type = typename std::remove_const<U>::type const;
};
// This is the intrusive portion of the doubly linked list.
// One derivation per list that the object may appear on
// concurrently is required.
//
template <typename T, typename Tag>
class ListNode
{
private:
    using value_type = T;
 
    friend class List<T, Tag>;
 
    template <typename>
    friend class ListIterator;
 
    ListNode* m_next;
    ListNode* m_prev;
};
 
//------------------------------------------------------------------------------
 
template <typename N>
class ListIterator
{
public:
    using iterator_category = std::bidirectional_iterator_tag;
    using value_type =
        typename beast::detail::CopyConst<N, typename N::value_type>::type;
    using difference_type = std::ptrdiff_t;
    using pointer = value_type*;
    using reference = value_type&;
    using size_type = std::size_t;
 
    ListIterator(N* node = nullptr) noexcept : m_node(node)
    {
    }
 
    template <typename M>
    ListIterator(ListIterator<M> const& other) noexcept : m_node(other.m_node)
    {
    }
 
    template <typename M>
    bool
    operator==(ListIterator<M> const& other) const noexcept
    {
        return m_node == other.m_node;
    }
 
    template <typename M>
    bool
    operator!=(ListIterator<M> const& other) const noexcept
    {
        return !((*this) == other);
    }
 
    reference
    operator*() const noexcept
    {
        return dereference();
    }
 
    pointer
    operator->() const noexcept
    {
        return &dereference();
    }
 
    ListIterator&
    operator++() noexcept
    {
        increment();
        return *this;
    }
 
    ListIterator
    operator++(int) noexcept
    {
        ListIterator result(*this);
        increment();
        return result;
    }
 
    ListIterator&
    operator--() noexcept
    {
        decrement();
        return *this;
    }
 
    ListIterator
    operator--(int) noexcept
    {
        ListIterator result(*this);
        decrement();
        return result;
    }
 
private:
    reference
    dereference() const noexcept
    {
        return static_cast<reference>(*m_node);
    }
 
    void
    increment() noexcept
    {
        m_node = m_node->m_next;
    }
 
    void
    decrement() noexcept
    {
        m_node = m_node->m_prev;
    }
 
    N* m_node;
};
 
}  // namespace detail
 
template <typename T, typename Tag = void>
class List
{
public:
    using Node = typename detail::ListNode<T, Tag>;
 
    using value_type = T;
    using pointer = value_type*;
    using reference = value_type&;
    using const_pointer = value_type const*;
    using const_reference = value_type const&;
    using size_type = std::size_t;
    using difference_type = std::ptrdiff_t;
 
    using iterator = detail::ListIterator<Node>;
    using const_iterator = detail::ListIterator<Node const>;
 
    List()
    {
        m_head.m_prev = nullptr;  // identifies the head
        m_tail.m_next = nullptr;  // identifies the tail
        clear();
    }
 
    List(List const&) = delete;
    List&
    operator=(List const&) = delete;
 
    bool
    empty() const noexcept
    {
        return size() == 0;
    }
 
    size_type
    size() const noexcept
    {
        return m_size;
    }
 
    reference
    front() noexcept
    {
        return element_from(m_head.m_next);
    }
 
    const_reference
    front() const noexcept
    {
        return element_from(m_head.m_next);
    }
 
    reference
    back() noexcept
    {
        return element_from(m_tail.m_prev);
    }
 
    const_reference
    back() const noexcept
    {
        return element_from(m_tail.m_prev);
    }
 
    iterator
    begin() noexcept
    {
        return iterator(m_head.m_next);
    }
 
    const_iterator
    begin() const noexcept
    {
        return const_iterator(m_head.m_next);
    }
 
    const_iterator
    cbegin() const noexcept
    {
        return const_iterator(m_head.m_next);
    }
 
    iterator
    end() noexcept
    {
        return iterator(&m_tail);
    }
 
    const_iterator
    end() const noexcept
    {
        return const_iterator(&m_tail);
    }
 
    const_iterator
    cend() const noexcept
    {
        return const_iterator(&m_tail);
    }
 
    void
    clear() noexcept
    {
        m_head.m_next = &m_tail;
        m_tail.m_prev = &m_head;
        m_size = 0;
    }
 
    iterator
    insert(iterator pos, T& element) noexcept
    {
        Node* node = static_cast<Node*>(&element);
        node->m_next = &*pos;
        node->m_prev = node->m_next->m_prev;
        node->m_next->m_prev = node;
        node->m_prev->m_next = node;
        ++m_size;
        return iterator(node);
    }
 
    void
    insert(iterator pos, List& other) noexcept
    {
        if (!other.empty())
        {
            Node* before = &*pos;
            other.m_head.m_next->m_prev = before->m_prev;
            before->m_prev->m_next = other.m_head.m_next;
            other.m_tail.m_prev->m_next = before;
            before->m_prev = other.m_tail.m_prev;
            m_size += other.m_size;
            other.clear();
        }
    }
 
    iterator
    erase(iterator pos) noexcept
    {
        Node* node = &*pos;
        ++pos;
        node->m_next->m_prev = node->m_prev;
        node->m_prev->m_next = node->m_next;
        --m_size;
        return pos;
    }
 
    iterator
    push_front(T& element) noexcept
    {
        return insert(begin(), element);
    }
 
    T&
    pop_front() noexcept
    {
        T& element(front());
        erase(begin());
        return element;
    }
 
    iterator
    push_back(T& element) noexcept
    {
        return insert(end(), element);
    }
 
    T&
    pop_back() noexcept
    {
        T& element(back());
        erase(--end());
        return element;
    }
 
    void
    swap(List& other) noexcept
    {
        List temp;
        temp.append(other);
        other.append(*this);
        append(temp);
    }
 
    iterator
    prepend(List& list) noexcept
    {
        return insert(begin(), list);
    }
 
    iterator
    append(List& list) noexcept
    {
        return insert(end(), list);
    }
 
    iterator
    iterator_to(T& element) const noexcept
    {
        return iterator(static_cast<Node*>(&element));
    }
 
    const_iterator
    const_iterator_to(T const& element) const noexcept
    {
        return const_iterator(static_cast<Node const*>(&element));
    }
 
private:
    reference
    element_from(Node* node) noexcept
    {
        return *(static_cast<pointer>(node));
    }
 
    const_reference
    element_from(Node const* node) const noexcept
    {
        return *(static_cast<const_pointer>(node));
    }
 
private:
    size_type m_size;
    Node m_head;
    Node m_tail;
};
 
}  // namespace beast
 
#endif