345 lines
11 KiB
C++
345 lines
11 KiB
C++
// Copyright 2019 TuxSH
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// Licensed under GPLv2 or any later version
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// Refer to the license.txt file included.
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#pragma once
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#include <array>
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#include <iterator>
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#include <list>
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#include <utility>
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#include "common/bit_util.h"
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#include "common/common_types.h"
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namespace Common {
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/**
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* A MultiLevelQueue is a type of priority queue which has the following characteristics:
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* - iteratable through each of its elements.
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* - back can be obtained.
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* - O(1) add, lookup (both front and back)
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* - discrete priorities and a max of 64 priorities (limited domain)
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* This type of priority queue is normaly used for managing threads within an scheduler
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*/
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template <typename T, std::size_t Depth>
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class MultiLevelQueue {
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public:
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using value_type = T;
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using reference = value_type&;
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using const_reference = const value_type&;
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using pointer = value_type*;
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using const_pointer = const value_type*;
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using difference_type = typename std::pointer_traits<pointer>::difference_type;
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using size_type = std::size_t;
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template <bool is_constant>
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class iterator_impl {
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public:
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using iterator_category = std::bidirectional_iterator_tag;
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using value_type = T;
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using pointer = std::conditional_t<is_constant, T*, const T*>;
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using reference = std::conditional_t<is_constant, const T&, T&>;
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using difference_type = typename std::pointer_traits<pointer>::difference_type;
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friend bool operator==(const iterator_impl& lhs, const iterator_impl& rhs) {
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if (lhs.IsEnd() && rhs.IsEnd())
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return true;
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return std::tie(lhs.current_priority, lhs.it) == std::tie(rhs.current_priority, rhs.it);
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}
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friend bool operator!=(const iterator_impl& lhs, const iterator_impl& rhs) {
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return !operator==(lhs, rhs);
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}
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reference operator*() const {
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return *it;
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}
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pointer operator->() const {
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return it.operator->();
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}
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iterator_impl& operator++() {
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if (IsEnd()) {
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return *this;
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}
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++it;
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if (it == GetEndItForPrio()) {
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u64 prios = mlq.used_priorities;
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prios &= ~((1ULL << (current_priority + 1)) - 1);
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if (prios == 0) {
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current_priority = static_cast<u32>(mlq.depth());
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} else {
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current_priority = CountTrailingZeroes64(prios);
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it = GetBeginItForPrio();
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}
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}
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return *this;
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}
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iterator_impl& operator--() {
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if (IsEnd()) {
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if (mlq.used_priorities != 0) {
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current_priority = 63 - CountLeadingZeroes64(mlq.used_priorities);
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it = GetEndItForPrio();
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--it;
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}
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} else if (it == GetBeginItForPrio()) {
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u64 prios = mlq.used_priorities;
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prios &= (1ULL << current_priority) - 1;
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if (prios != 0) {
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current_priority = CountTrailingZeroes64(prios);
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it = GetEndItForPrio();
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--it;
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}
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} else {
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--it;
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}
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return *this;
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}
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iterator_impl operator++(int) {
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const iterator_impl v{*this};
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++(*this);
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return v;
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}
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iterator_impl operator--(int) {
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const iterator_impl v{*this};
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--(*this);
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return v;
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}
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// allow implicit const->non-const
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iterator_impl(const iterator_impl<false>& other)
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: mlq(other.mlq), it(other.it), current_priority(other.current_priority) {}
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iterator_impl(const iterator_impl<true>& other)
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: mlq(other.mlq), it(other.it), current_priority(other.current_priority) {}
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iterator_impl& operator=(const iterator_impl<false>& other) {
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mlq = other.mlq;
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it = other.it;
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current_priority = other.current_priority;
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return *this;
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}
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friend class iterator_impl<true>;
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iterator_impl() = default;
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private:
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friend class MultiLevelQueue;
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using container_ref =
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std::conditional_t<is_constant, const MultiLevelQueue&, MultiLevelQueue&>;
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using list_iterator = std::conditional_t<is_constant, typename std::list<T>::const_iterator,
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typename std::list<T>::iterator>;
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explicit iterator_impl(container_ref mlq, list_iterator it, u32 current_priority)
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: mlq(mlq), it(it), current_priority(current_priority) {}
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explicit iterator_impl(container_ref mlq, u32 current_priority)
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: mlq(mlq), it(), current_priority(current_priority) {}
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bool IsEnd() const {
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return current_priority == mlq.depth();
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}
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list_iterator GetBeginItForPrio() const {
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return mlq.levels[current_priority].begin();
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}
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list_iterator GetEndItForPrio() const {
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return mlq.levels[current_priority].end();
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}
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container_ref mlq;
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list_iterator it;
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u32 current_priority;
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};
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using iterator = iterator_impl<false>;
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using const_iterator = iterator_impl<true>;
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void add(const T& element, u32 priority, bool send_back = true) {
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if (send_back)
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levels[priority].push_back(element);
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else
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levels[priority].push_front(element);
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used_priorities |= 1ULL << priority;
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}
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void remove(const T& element, u32 priority) {
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auto it = ListIterateTo(levels[priority], element);
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if (it == levels[priority].end())
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return;
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levels[priority].erase(it);
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if (levels[priority].empty()) {
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used_priorities &= ~(1ULL << priority);
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}
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}
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void adjust(const T& element, u32 old_priority, u32 new_priority, bool adjust_front = false) {
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remove(element, old_priority);
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add(element, new_priority, !adjust_front);
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}
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void adjust(const_iterator it, u32 old_priority, u32 new_priority, bool adjust_front = false) {
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adjust(*it, old_priority, new_priority, adjust_front);
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}
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void transfer_to_front(const T& element, u32 priority, MultiLevelQueue& other) {
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ListSplice(other.levels[priority], other.levels[priority].begin(), levels[priority],
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ListIterateTo(levels[priority], element));
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other.used_priorities |= 1ULL << priority;
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if (levels[priority].empty()) {
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used_priorities &= ~(1ULL << priority);
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}
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}
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void transfer_to_front(const_iterator it, u32 priority, MultiLevelQueue& other) {
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transfer_to_front(*it, priority, other);
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}
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void transfer_to_back(const T& element, u32 priority, MultiLevelQueue& other) {
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ListSplice(other.levels[priority], other.levels[priority].end(), levels[priority],
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ListIterateTo(levels[priority], element));
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other.used_priorities |= 1ULL << priority;
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if (levels[priority].empty()) {
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used_priorities &= ~(1ULL << priority);
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}
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}
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void transfer_to_back(const_iterator it, u32 priority, MultiLevelQueue& other) {
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transfer_to_back(*it, priority, other);
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}
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void yield(u32 priority, std::size_t n = 1) {
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ListShiftForward(levels[priority], n);
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}
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std::size_t depth() const {
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return Depth;
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}
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std::size_t size(u32 priority) const {
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return levels[priority].size();
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}
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std::size_t size() const {
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u64 priorities = used_priorities;
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std::size_t size = 0;
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while (priorities != 0) {
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const u64 current_priority = CountTrailingZeroes64(priorities);
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size += levels[current_priority].size();
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priorities &= ~(1ULL << current_priority);
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}
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return size;
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}
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bool empty() const {
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return used_priorities == 0;
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}
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bool empty(u32 priority) const {
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return (used_priorities & (1ULL << priority)) == 0;
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}
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u32 highest_priority_set(u32 max_priority = 0) const {
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const u64 priorities =
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max_priority == 0 ? used_priorities : (used_priorities & ~((1ULL << max_priority) - 1));
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return priorities == 0 ? Depth : static_cast<u32>(CountTrailingZeroes64(priorities));
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}
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u32 lowest_priority_set(u32 min_priority = Depth - 1) const {
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const u64 priorities = min_priority >= Depth - 1
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? used_priorities
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: (used_priorities & ((1ULL << (min_priority + 1)) - 1));
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return priorities == 0 ? Depth : 63 - CountLeadingZeroes64(priorities);
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}
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const_iterator cbegin(u32 max_prio = 0) const {
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const u32 priority = highest_priority_set(max_prio);
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return priority == Depth ? cend()
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: const_iterator{*this, levels[priority].cbegin(), priority};
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}
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const_iterator begin(u32 max_prio = 0) const {
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return cbegin(max_prio);
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}
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iterator begin(u32 max_prio = 0) {
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const u32 priority = highest_priority_set(max_prio);
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return priority == Depth ? end() : iterator{*this, levels[priority].begin(), priority};
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}
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const_iterator cend(u32 min_prio = Depth - 1) const {
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return min_prio == Depth - 1 ? const_iterator{*this, Depth} : cbegin(min_prio + 1);
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}
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const_iterator end(u32 min_prio = Depth - 1) const {
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return cend(min_prio);
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}
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iterator end(u32 min_prio = Depth - 1) {
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return min_prio == Depth - 1 ? iterator{*this, Depth} : begin(min_prio + 1);
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}
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T& front(u32 max_priority = 0) {
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const u32 priority = highest_priority_set(max_priority);
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return levels[priority == Depth ? 0 : priority].front();
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}
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const T& front(u32 max_priority = 0) const {
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const u32 priority = highest_priority_set(max_priority);
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return levels[priority == Depth ? 0 : priority].front();
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}
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T back(u32 min_priority = Depth - 1) {
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const u32 priority = lowest_priority_set(min_priority); // intended
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return levels[priority == Depth ? 63 : priority].back();
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}
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const T& back(u32 min_priority = Depth - 1) const {
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const u32 priority = lowest_priority_set(min_priority); // intended
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return levels[priority == Depth ? 63 : priority].back();
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}
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void clear() {
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used_priorities = 0;
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for (std::size_t i = 0; i < Depth; i++) {
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levels[i].clear();
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}
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}
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private:
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using const_list_iterator = typename std::list<T>::const_iterator;
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static void ListShiftForward(std::list<T>& list, const std::size_t shift = 1) {
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if (shift >= list.size()) {
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return;
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}
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const auto begin_range = list.begin();
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const auto end_range = std::next(begin_range, shift);
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list.splice(list.end(), list, begin_range, end_range);
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}
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static void ListSplice(std::list<T>& in_list, const_list_iterator position,
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std::list<T>& out_list, const_list_iterator element) {
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in_list.splice(position, out_list, element);
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}
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static const_list_iterator ListIterateTo(const std::list<T>& list, const T& element) {
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auto it = list.cbegin();
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while (it != list.cend() && *it != element) {
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++it;
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}
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return it;
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}
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std::array<std::list<T>, Depth> levels;
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u64 used_priorities = 0;
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};
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} // namespace Common
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