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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Assertions.h>
#include <AK/Error.h>
#include <AK/Find.h>
#include <AK/StdLibExtras.h>
namespace AK {
template<typename ListType, typename ElementType>
class DoublyLinkedListIterator {
public:
bool operator!=(DoublyLinkedListIterator const& other) const { return m_node != other.m_node; }
bool operator==(DoublyLinkedListIterator const& other) const { return m_node == other.m_node; }
DoublyLinkedListIterator& operator++()
{
m_node = m_node->next;
return *this;
}
ElementType& operator*() { return m_node->value; }
ElementType* operator->() { return &m_node->value; }
[[nodiscard]] bool is_end() const { return !m_node; }
static DoublyLinkedListIterator universal_end() { return DoublyLinkedListIterator(nullptr); }
private:
friend ListType;
explicit DoublyLinkedListIterator(typename ListType::Node* node)
: m_node(node)
{
}
typename ListType::Node* m_node;
};
template<typename T>
class DoublyLinkedList {
private:
struct Node {
template<typename U>
explicit Node(U&& v)
: value(forward<U>(v))
{
static_assert(
requires { T(v); }, "Conversion operator is missing.");
}
T value;
Node* next { nullptr };
Node* prev { nullptr };
};
public:
DoublyLinkedList() = default;
~DoublyLinkedList() { clear(); }
[[nodiscard]] bool is_empty() const { return !m_head; }
void clear()
{
for (auto* node = m_head; node;) {
auto* next = node->next;
delete node;
node = next;
}
m_head = nullptr;
m_tail = nullptr;
}
[[nodiscard]] T& first()
{
VERIFY(m_head);
return m_head->value;
}
[[nodiscard]] const T& first() const
{
VERIFY(m_head);
return m_head->value;
}
[[nodiscard]] T& last()
{
VERIFY(m_head);
return m_tail->value;
}
[[nodiscard]] const T& last() const
{
VERIFY(m_head);
return m_tail->value;
}
template<typename U>
ErrorOr<void> try_append(U&& value)
{
static_assert(
requires { T(value); }, "Conversion operator is missing.");
auto* node = new (nothrow) Node(forward<U>(value));
if (!node)
return Error::from_errno(ENOMEM);
if (!m_head) {
VERIFY(!m_tail);
m_head = node;
m_tail = node;
return {};
}
VERIFY(m_tail);
VERIFY(!node->next);
m_tail->next = node;
node->prev = m_tail;
m_tail = node;
return {};
}
template<typename U>
ErrorOr<void> try_prepend(U&& value)
{
static_assert(IsSame<T, U>);
auto* node = new (nothrow) Node(forward<U>(value));
if (!node)
return Error::from_errno(ENOMEM);
if (!m_head) {
VERIFY(!m_tail);
m_head = node;
m_tail = node;
return {};
}
VERIFY(m_tail);
VERIFY(!node->prev);
m_head->prev = node;
node->next = m_head;
m_head = node;
return {};
}
#ifndef KERNEL
template<typename U>
void append(U&& value)
{
MUST(try_append(forward<U>(value)));
}
template<typename U>
void prepend(U&& value)
{
MUST(try_prepend(forward<U>(value)));
}
#endif
[[nodiscard]] bool contains_slow(const T& value) const
{
return find(value) != end();
}
using Iterator = DoublyLinkedListIterator<DoublyLinkedList, T>;
friend Iterator;
Iterator begin() { return Iterator(m_head); }
Iterator end() { return Iterator::universal_end(); }
using ConstIterator = DoublyLinkedListIterator<const DoublyLinkedList, const T>;
friend ConstIterator;
ConstIterator begin() const { return ConstIterator(m_head); }
ConstIterator end() const { return ConstIterator::universal_end(); }
ConstIterator find(const T& value) const
{
return AK::find(begin(), end(), value);
}
Iterator find(const T& value)
{
return AK::find(begin(), end(), value);
}
void remove(Iterator it)
{
VERIFY(it.m_node);
auto* node = it.m_node;
if (node->prev) {
VERIFY(node != m_head);
node->prev->next = node->next;
} else {
VERIFY(node == m_head);
m_head = node->next;
}
if (node->next) {
VERIFY(node != m_tail);
node->next->prev = node->prev;
} else {
VERIFY(node == m_tail);
m_tail = node->prev;
}
delete node;
}
private:
Node* m_head { nullptr };
Node* m_tail { nullptr };
};
}
using AK::DoublyLinkedList;
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