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