blocking_iterator.hpp

// Copyright (C) 2020-2025 Andrei Avram
 
#ifndef MSD_CHANNEL_BLOCKING_ITERATOR_HPP_
#define MSD_CHANNEL_BLOCKING_ITERATOR_HPP_
 
#include <cstddef>
#include <iterator>
#include <mutex>
 
namespace msd {
 
template <typename Channel>
class blocking_iterator {
   public:
    using value_type = typename Channel::value_type;
 
    using reference = const typename Channel::value_type&;
 
    using iterator_category = std::input_iterator_tag;
 
    using difference_type = std::ptrdiff_t;
 
    using pointer = const value_type*;
 
    explicit blocking_iterator(Channel& chan) : chan_{chan} {}
 
    blocking_iterator<Channel> operator++() const noexcept { return *this; }
 
    reference operator*()
    {
        chan_ >> value_;
 
        return value_;
    }
 
    bool operator!=(blocking_iterator<Channel>) const
    {
        std::unique_lock<std::mutex> lock{chan_.mtx_};
        chan_.waitBeforeRead(lock);
 
        return !(chan_.closed() && chan_.empty());
    }
 
   private:
    Channel& chan_;
    value_type value_{};
};
 
}  // namespace msd
 
#endif  // MSD_CHANNEL_BLOCKING_ITERATOR_HPP_