Program Listing for File pool_strategy.hpp

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#pragma once

#include <functional>
#include <memory>
#include <random>
#include <type_traits>

namespace stream_client {
namespace connector {

template <typename Connector>
class pool_strategy
{
public:
    using connector_type = typename std::remove_reference<Connector>::type;
    using stream_type = typename connector_type::stream_type;
    using append_func_type = typename std::function<void(std::unique_ptr<stream_type>&& session)>;

    virtual ~pool_strategy() = default;

    virtual bool refill(connector_type& connector, std::size_t vacant_places, append_func_type append_func) = 0;
};

template <typename Connector>
class greedy_strategy: public pool_strategy<Connector>
{
public:
    using connector_type = typename pool_strategy<Connector>::connector_type;
    using stream_type = typename pool_strategy<Connector>::stream_type;
    using append_func_type = typename pool_strategy<Connector>::append_func_type;

    greedy_strategy() = default;

    virtual ~greedy_strategy() = default;

    virtual bool refill(connector_type& connector, std::size_t vacant_places, append_func_type append_func) override;
};

template <typename Connector>
class conservative_strategy: public pool_strategy<Connector>
{
public:
    using connector_type = typename pool_strategy<Connector>::connector_type;
    using stream_type = typename pool_strategy<Connector>::stream_type;
    using append_func_type = typename pool_strategy<Connector>::append_func_type;

    using clock_type = typename connector_type::clock_type;
    using time_duration_type = typename connector_type::time_duration_type;
    using time_point_type = typename connector_type::time_point_type;

    static const unsigned long kMaxBackoffMs;
    static const unsigned long kDefaultDelayMs;
    static const unsigned long kDefaultDelayMul;

    conservative_strategy(unsigned long first_delay_ms = kDefaultDelayMs, unsigned delay_multiplier = kDefaultDelayMul);

    virtual ~conservative_strategy() = default;

    virtual bool refill(connector_type& connector, std::size_t vacant_places, append_func_type append_func) override;

private:
    time_point_type wait_until_;
    unsigned long initial_delay_ms_;
    unsigned long delay_multiplier_;
    unsigned long current_delay_ms_;

    std::random_device r_device_;
    std::mt19937 r_generator_;
};

} // namespace connector
} // namespace stream_client

#include "impl/pool_strategy.ipp"