blocking_iterator.hpp

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// Copyright (C) 2020-2025 Andrei Avram
 
#ifndef MSD_CHANNEL_BLOCKING_ITERATOR_HPP_
#define MSD_CHANNEL_BLOCKING_ITERATOR_HPP_
 
#include <cstddef>
#include <iterator>
 
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, bool is_end = false) : chan_{&chan}, is_end_{is_end}
    {
        if (!is_end_ && !chan_->read(value_)) {
            is_end_ = true;
        }
    }
 
    blocking_iterator<Channel>& operator++() noexcept
    {
        if (!chan_->read(value_)) {
            is_end_ = true;
        }
        return *this;
    }
 
    reference operator*() { return value_; }
 
    bool operator!=(const blocking_iterator& other) { return is_end_ != other.is_end_; }
 
   private:
    Channel* chan_;
    value_type value_{};
    bool is_end_{false};
};
 
template <typename Channel>
class blocking_writer_iterator {
   public:
    using value_type = typename Channel::value_type;
 
    using reference = const value_type&;
 
    using iterator_category = std::output_iterator_tag;
 
    using difference_type = std::ptrdiff_t;
 
    using pointer = const value_type*;
 
    explicit blocking_writer_iterator(Channel& chan) : chan_{&chan} {}
 
    blocking_writer_iterator& operator=(reference value)
    {
        chan_->write(value);
        return *this;
    }
 
    blocking_writer_iterator& operator*() { return *this; }
 
    blocking_writer_iterator& operator++() { return *this; }
 
    blocking_writer_iterator operator++(int) { return *this; }
 
   private:
    Channel* chan_;
};
 
template <typename Channel>
blocking_writer_iterator<Channel> back_inserter(Channel& chan)
{
    return blocking_writer_iterator<Channel>{chan};
}
 
}  // namespace msd
 
#endif  // MSD_CHANNEL_BLOCKING_ITERATOR_HPP_