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192/**
* @file src/round_robin.h
* @brief Declarations for a round-robin iterator.
*/
#pragma once
// standard includes
#include <iterator>
/**
* @brief A round-robin iterator utility.
* @tparam V The value type.
* @tparam T The iterator type.
*/
namespace round_robin_util {
template<class V, class T>
class it_wrap_t {
public:
using iterator_category = std::random_access_iterator_tag;
using value_type = V;
using difference_type = V;
using pointer = V *;
using const_pointer = V const *;
using reference = V &;
using const_reference = V const &;
typedef T iterator;
typedef std::ptrdiff_t diff_t;
iterator operator+=(diff_t step) {
while (step-- > 0) {
++_this();
}
return _this();
}
iterator operator-=(diff_t step) {
while (step-- > 0) {
--_this();
}
return _this();
}
iterator operator+(diff_t step) {
iterator new_ = _this();
return new_ += step;
}
iterator operator-(diff_t step) {
iterator new_ = _this();
return new_ -= step;
}
diff_t operator-(iterator first) {
diff_t step = 0;
while (first != _this()) {
++step;
++first;
}
return step;
}
iterator operator++() {
_this().inc();
return _this();
}
iterator operator--() {
_this().dec();
return _this();
}
iterator operator++(int) {
iterator new_ = _this();
++_this();
return new_;
}
iterator operator--(int) {
iterator new_ = _this();
--_this();
return new_;
}
reference operator*() {
return *_this().get();
}
const_reference operator*() const {
return *_this().get();
}
pointer operator->() {
return &*_this();
}
const_pointer operator->() const {
return &*_this();
}
bool operator!=(const iterator &other) const {
return !(_this() == other);
}
bool operator<(const iterator &other) const {
return !(_this() >= other);
}
bool operator>=(const iterator &other) const {
return _this() == other || _this() > other;
}
bool operator<=(const iterator &other) const {
return _this() == other || _this() < other;
}
bool operator==(const iterator &other) const {
return _this().eq(other);
};
bool operator>(const iterator &other) const {
return _this().gt(other);
}
private:
iterator &_this() {
return *static_cast<iterator *>(this);
}
const iterator &_this() const {
return *static_cast<const iterator *>(this);
}
};
template<class V, class It>
class round_robin_t: public it_wrap_t<V, round_robin_t<V, It>> {
public:
using iterator = It;
using pointer = V *;
round_robin_t(iterator begin, iterator end):
_begin(begin),
_end(end),
_pos(begin) {
}
void inc() {
++_pos;
if (_pos == _end) {
_pos = _begin;
}
}
void dec() {
if (_pos == _begin) {
_pos = _end;
}
--_pos;
}
bool eq(const round_robin_t &other) const {
return *_pos == *other._pos;
}
pointer get() const {
return &*_pos;
}
private:
It _begin;
It _end;
It _pos;
};
template<class V, class It>
round_robin_t<V, It> make_round_robin(It begin, It end) {
return round_robin_t<V, It>(begin, end);
}
} // namespace round_robin_util