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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/Forward.h>
#include <AK/StdLibExtras.h>
namespace AK {
template<typename T, size_t Capacity>
class CircularQueue {
friend CircularDuplexStream<Capacity>;
public:
CircularQueue() = default;
~CircularQueue()
{
clear();
}
void clear()
{
for (size_t i = 0; i < m_size; ++i)
elements()[(m_head + i) % Capacity].~T();
m_head = 0;
m_size = 0;
}
bool is_empty() const { return !m_size; }
size_t size() const { return m_size; }
size_t capacity() const { return Capacity; }
template<typename U = T>
void enqueue(U&& value)
{
auto& slot = elements()[(m_head + m_size) % Capacity];
if (m_size == Capacity)
slot.~T();
new (&slot) T(forward<U>(value));
if (m_size == Capacity)
m_head = (m_head + 1) % Capacity;
else
++m_size;
}
T dequeue()
{
VERIFY(!is_empty());
auto& slot = elements()[m_head];
T value = move(slot);
slot.~T();
m_head = (m_head + 1) % Capacity;
--m_size;
return value;
}
const T& at(size_t index) const { return elements()[(m_head + index) % Capacity]; }
const T& first() const { return at(0); }
const T& last() const { return at(size() - 1); }
class ConstIterator {
public:
bool operator!=(const ConstIterator& other) { return m_index != other.m_index; }
ConstIterator& operator++()
{
m_index = (m_index + 1) % Capacity;
if (m_index == m_queue.m_head)
m_index = m_queue.m_size;
return *this;
}
const T& operator*() const { return m_queue.elements()[m_index]; }
private:
friend class CircularQueue;
ConstIterator(const CircularQueue& queue, const size_t index)
: m_queue(queue)
, m_index(index)
{
}
const CircularQueue& m_queue;
size_t m_index { 0 };
};
ConstIterator begin() const { return ConstIterator(*this, m_head); }
ConstIterator end() const { return ConstIterator(*this, size()); }
size_t head_index() const { return m_head; }
protected:
T* elements() { return reinterpret_cast<T*>(m_storage); }
const T* elements() const { return reinterpret_cast<const T*>(m_storage); }
friend class ConstIterator;
alignas(T) u8 m_storage[sizeof(T) * Capacity];
size_t m_size { 0 };
size_t m_head { 0 };
};
}
using AK::CircularQueue;
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