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#pragma once
#include "asl/base/meta.hpp"
#include "asl/base/assert.hpp"
namespace asl
{
template<typename T>
struct intrusive_list_node
{
T* prev{};
T* next{};
};
template<typename T>
concept is_intrusive_list_node = convertible_from<intrusive_list_node<T>*, T*>;
template<is_intrusive_list_node T>
class IntrusiveList
{
struct sentinel: public intrusive_list_node<T> {};
sentinel m_sentinel{};
T* sentinel() { return reinterpret_cast<T*>(&m_sentinel); }
const T* sentinel() const { return reinterpret_cast<const T*>(&m_sentinel); }
constexpr T* head_inner() const { return m_sentinel.next; }
constexpr T* tail_inner() const { return m_sentinel.prev; }
void insert_after(T* before, T* after)
{
after->prev = before;
after->next = before->next;
before->next = after;
after->next->prev = after;
}
public:
constexpr IntrusiveList() : m_sentinel{ sentinel(), sentinel() } {}
constexpr bool is_empty() const { return head_inner() == sentinel(); }
void push_front(T* node)
{
ASL_ASSERT(node->next == nullptr && node->prev == nullptr);
insert_after(head_inner()->prev, node);
}
void push_back(T* node)
{
ASL_ASSERT(node->next == nullptr && node->prev == nullptr);
insert_after(tail_inner(), node);
}
T* head() const
{
T* h = head_inner();
return (h == sentinel()) ? nullptr : h;
}
T* tail() const
{
T* t = tail_inner();
return (t == sentinel()) ? nullptr : t;
}
void detach(T* node)
{
ASL_ASSERT(node->next != nullptr && node->prev != nullptr);
node->prev->next = node->next;
node->next->prev = node->prev;
node->next = nullptr;
node->prev = nullptr;
}
T* pop_front()
{
if (T* h = head_inner(); h != sentinel())
{
detach(h);
return h;
}
return nullptr;
}
T* pop_back()
{
if (T* t = tail_inner(); t != sentinel())
{
detach(t);
return t;
}
return nullptr;
}
template<typename TT>
struct generic_iterator
{
TT* m_node;
public:
constexpr explicit generic_iterator(TT* node) : m_node{node} {}
constexpr bool operator==(const generic_iterator& other) const = default;
constexpr generic_iterator& operator++()
{
m_node = m_node->next;
return *this;
}
constexpr generic_iterator operator++(int)
{
return iterator{ exchange(m_node, m_node->next) };
}
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>;
// @Todo(C++23) Deduplicate with deducing-this maybe
const_iterator begin() const { return const_iterator{ head_inner() }; }
const_iterator end() const { return const_iterator{ sentinel() }; }
iterator begin() { return iterator{ head_inner() }; }
iterator end() { return iterator{ sentinel() }; }
};
}
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