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// Copyright 2025 Steven Le Rouzic
//
// SPDX-License-Identifier: BSD-3-Clause
#pragma once
#include "asl/base/meta.hpp"
#include "asl/base/assert.hpp"
#include "asl/base/utility.hpp"
namespace asl
{
template<typename T>
struct intrusive_list_node
{
T* m_prev{};
T* m_next{};
};
template<typename T>
concept is_intrusive_list_node = convertible_from<intrusive_list_node<T>*, T*>;
template<is_intrusive_list_node T>
class IntrusiveList
{
T* m_head{};
static void insert_after(T* before, T* after)
{
after->m_prev = before;
after->m_next = before->m_next;
before->m_next = after;
after->m_next->m_prev = after;
}
public:
constexpr IntrusiveList() = default;
explicit IntrusiveList(T* head)
{
push_front(head);
}
ASL_DELETE_COPY(IntrusiveList)
ASL_DEFAULT_MOVE(IntrusiveList)
~IntrusiveList() = default;
constexpr bool is_empty() const { return m_head == nullptr; }
void push_front(T* node)
{
ASL_ASSERT(node->m_next == nullptr && node->m_prev == nullptr);
if (is_empty())
{
m_head = node;
node->m_prev = node;
node->m_next = node;
}
else
{
insert_after(m_head->m_prev, node);
m_head = node;
}
}
void push_back(T* node)
{
ASL_ASSERT(node->m_next == nullptr && node->m_prev == nullptr);
if (is_empty())
{
m_head = node;
node->m_prev = node;
node->m_next = node;
}
else
{
insert_after(m_head->m_prev, node);
}
}
constexpr auto front(this auto&& self)
{
using return_type = un_ref_t<copy_cref_t<decltype(self), T>>*;
return return_type{ self.m_head };
}
constexpr auto back(this auto&& self)
{
using return_type = un_ref_t<copy_cref_t<decltype(self), T>>*;
return return_type{ self.m_head != nullptr ? self.m_head->m_prev : nullptr };
}
void detach(T* node)
{
ASL_ASSERT(node->m_next != nullptr && node->m_prev != nullptr);
if (m_head->m_next == m_head)
{
ASL_ASSERT(m_head->m_prev == m_head);
ASL_ASSERT(m_head == node);
m_head = nullptr;
}
else
{
if (m_head == node)
{
m_head = node->m_next;
}
node->m_prev->m_next = node->m_next;
node->m_next->m_prev = node->m_prev;
}
node->m_next = nullptr;
node->m_prev = nullptr;
}
T* pop_front()
{
if (!is_empty())
{
T* node = m_head;
detach(node);
return node;
}
return nullptr;
}
T* pop_back()
{
if (!is_empty())
{
T* node = m_head->m_prev;
detach(node);
return node;
}
return nullptr;
}
template<typename TT>
struct generic_iterator
{
TT* m_node;
bool m_advanced = false;
public:
constexpr explicit generic_iterator(TT* node, bool end = false)
: m_node{node}
, m_advanced{end}
{}
constexpr bool operator==(const generic_iterator& other) const = default;
constexpr generic_iterator& operator++()
{
m_node = m_node->m_next;
m_advanced = true;
return *this;
}
constexpr generic_iterator operator++(int)
{
return iterator{
exchange(m_node, m_node->m_next), exchange(m_advanced, true)
};
}
constexpr TT& operator*() const { return *m_node; }
constexpr TT* operator->() const { return m_node; }
};
using iterator = generic_iterator<T>;
using const_iterator = generic_iterator<const T>;
auto begin(this auto&& self)
{
using iterator_type = select_t<is_const<un_ref_t<decltype(self)>>, const_iterator, iterator>;
return iterator_type{ self.front(), self.is_empty() };
}
auto end(this auto&& self)
{
using iterator_type = select_t<is_const<un_ref_t<decltype(self)>>, const_iterator, iterator>;
return iterator_type{ self.front(), true };
}
};
}
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