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tdesktop/Telegram/lib_rpl/rpl/take.h
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2026-02-16 15:50:16 +03:00

123 lines
2.8 KiB
C++

// This file is part of Desktop App Toolkit,
// a set of libraries for developing nice desktop applications.
//
// For license and copyright information please follow this link:
// https://github.com/desktop-app/legal/blob/master/LEGAL
//
#pragma once
namespace rpl {
namespace details {
class take_helper {
public:
take_helper(int count) : _count(count) {
}
template <
typename Value,
typename Error,
typename Generator>
auto operator()(producer<Value, Error, Generator> &&initial) {
return make_producer<Value, Error>([
initial = std::move(initial),
limit = _count
](const auto &consumer) mutable {
auto count = consumer.template make_state<int>(limit);
auto initial_consumer = make_consumer<Value, Error>(
[consumer, count](auto &&value) {
auto left = (*count)--;
if (left) {
consumer.put_next_forward(
std::forward<decltype(value)>(value));
--left;
}
if (!left) {
consumer.put_done();
}
}, [consumer](auto &&error) {
consumer.put_error_forward(
std::forward<decltype(error)>(error));
}, [consumer] {
consumer.put_done();
});
consumer.add_lifetime(initial_consumer.terminator());
return std::move(initial).start_existing(initial_consumer);
});
}
private:
int _count = 0;
};
} // namespace details
inline auto take(int count)
-> details::take_helper {
Expects(count >= 0);
return details::take_helper(count);
}
namespace details {
template <typename Predicate>
class take_while_helper {
public:
template <typename OtherPredicate>
take_while_helper(OtherPredicate &&predicate)
: _predicate(std::forward<OtherPredicate>(predicate)) {
}
template <
typename Value,
typename Error,
typename Generator,
typename = std::enable_if_t<
details::is_callable_v<Predicate, Value>>>
auto operator()(producer<Value, Error, Generator> &&initial) {
return make_producer<Value, Error>([
initial = std::move(initial),
predicate = std::move(_predicate)
](const auto &consumer) mutable {
return std::move(initial).start(
[
consumer,
predicate = std::move(predicate)
](auto &&value) {
const auto &immutable = value;
if (details::callable_invoke(
predicate,
immutable)
) {
consumer.put_next_forward(
std::forward<decltype(value)>(value));
} else {
consumer.put_done();
}
}, [consumer](auto &&error) {
consumer.put_error_forward(
std::forward<decltype(error)>(error));
}, [consumer] {
consumer.put_done();
});
});
}
private:
Predicate _predicate;
};
} // namespace details
template <typename Predicate>
inline auto take_while(Predicate &&predicate)
-> details::take_while_helper<std::decay_t<Predicate>> {
return details::take_while_helper<std::decay_t<Predicate>>(
std::forward<Predicate>(predicate));
}
} // namespace rpl