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Copy pathfilter.hpp
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177 lines (143 loc) · 5.64 KB
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#ifndef ITER_FILTER_H_
#define ITER_FILTER_H_
#include "iterbase.hpp"
#include <utility>
#include <iterator>
#include <initializer_list>
namespace iter {
//Forward declarations of Filter and filter
template <typename FilterFunc, typename Container>
class Filter;
template <typename FilterFunc, typename Container>
Filter<FilterFunc, Container> filter(FilterFunc, Container&&);
template <typename FilterFunc, typename T>
Filter<FilterFunc, std::initializer_list<T>> filter(
FilterFunc, std::initializer_list<T>);
template <typename FilterFunc, typename Container>
class Filter {
private:
Container container;
FilterFunc filter_func;
// The filter function is the only thing allowed to create a Filter
friend Filter filter<FilterFunc, Container>(
FilterFunc, Container&&);
template <typename FF, typename T>
friend Filter<FF, std::initializer_list<T>> filter(
FF, std::initializer_list<T>);
// Value constructor for use only in the filter function
Filter(FilterFunc in_filter_func, Container&& in_container)
: container(std::forward<Container>(in_container)),
filter_func(in_filter_func)
{ }
public:
class Iterator
: public std::iterator<std::input_iterator_tag,
iterator_traits_deref<Container>>
{
protected:
using Holder = DerefHolder<iterator_deref<Container>>;
iterator_type<Container> sub_iter;
iterator_type<Container> sub_end;
Holder item;
FilterFunc *filter_func;
void inc_sub_iter() {
++this->sub_iter;
if (this->sub_iter != this->sub_end) {
this->item.reset(*this->sub_iter);
}
}
// increment until the iterator points to is true on the
// predicate. Called by constructor and operator++
void skip_failures() {
while (this->sub_iter != this->sub_end
&& !(*this->filter_func)(this->item.get())) {
this->inc_sub_iter();
}
}
public:
Iterator (iterator_type<Container> iter,
iterator_type<Container> end,
FilterFunc& in_filter_func)
: sub_iter{iter},
sub_end{end},
filter_func(&in_filter_func)
{
if (this->sub_iter != this->sub_end) {
this->item.reset(*this->sub_iter);
}
this->skip_failures();
}
typename Holder::reference operator*() {
return this->item.get();
}
typename Holder::pointer operator->() {
return this->item.get_ptr();
}
Iterator& operator++() {
this->inc_sub_iter();
this->skip_failures();
return *this;
}
Iterator operator++(int) {
auto ret = *this;
++*this;
return ret;
}
bool operator!=(const Iterator& other) const {
return this->sub_iter != other.sub_iter;
}
bool operator==(const Iterator& other) const {
return !(*this != other);
}
};
Iterator begin() {
return {std::begin(this->container),
std::end(this->container),
this->filter_func};
}
Iterator end() {
return {std::end(this->container),
std::end(this->container),
this->filter_func};
}
};
// Helper function to instantiate a Filter
template <typename FilterFunc, typename Container>
Filter<FilterFunc, Container> filter(
FilterFunc filter_func, Container&& container) {
return {filter_func, std::forward<Container>(container)};
}
template <typename FilterFunc, typename T>
Filter<FilterFunc, std::initializer_list<T>> filter(
FilterFunc filter_func,
std::initializer_list<T> il)
{
return {filter_func, std::move(il)};
}
namespace detail {
template <typename T>
bool boolean_cast(const T& t) {
return bool(t);
}
template <typename Container>
class BoolTester {
public:
bool operator() (const iterator_deref<Container> item) const {
return bool(item);
}
};
}
template <typename Container>
auto filter(Container&& container) {
return filter(
detail::BoolTester<Container>(),
std::forward<Container>(container));
}
template <typename T>
auto filter(std::initializer_list<T> il) {
return filter(
detail::BoolTester<std::initializer_list<T>>(),
std::move(il));
}
}
#endif