pendingReplies.hpp

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/**
 * @file
 * @ingroup daq_common_libdaq
 * @copyright 2022 ESO - European Southern Observatory
 *
 * @brief Contains declaration for classes related to pending replies
 */
#ifndef OCF_DAQ_PENDING_REPLIES_HPP_
#define OCF_DAQ_PENDING_REPLIES_HPP_
 
#include <cstdint>
#include <memory>
#include <string>
#include <vector>
#include <tuple>
 
namespace daq {
 
class PendingReplies;
 
/**
 * Token representing a not-yet-received reply.
 *
 * @ingroup daq_common_libdaq
 */
class ReplyToken {
  public:
    ReplyToken(ReplyToken&&) = default;
    ReplyToken& operator=(ReplyToken&&) = default;
    ~ReplyToken();
 
    /**
     * Release token explicitly.
     */
    void Release();
 
  protected:
    friend PendingReplies;
    explicit ReplyToken(uint64_t token, std::weak_ptr<PendingReplies> pending_replies) noexcept;
 
  private:
    uint64_t m_token;
    std::weak_ptr<PendingReplies> m_pending_replies;
};
 
/**
 * Simple class that allows you to keep track of how many replies are pending.
 *
 * Usage:
 *
 *  For each request acquire a token with `acquire`.
 *  The token is movable but not copyable to guarantee uniqueness.
 *
 *  Once reply is released release the token by deleting it.
 *
 * @ingroup daq_common_libdaq
 */
class PendingReplies : public std::enable_shared_from_this<PendingReplies> {
public:
    struct PendingReply {
        std::string source_id;
        std::string request;
    };
 
    /**
     * Create instance.
     */
    static std::shared_ptr<PendingReplies> Create();
 
    /**
     * Acquire token.
     *
     * Keep the token alive until reply is received, then delete it.
     */
    ReplyToken Acquire(std::string source_id, std::string request);
    std::shared_ptr<ReplyToken> AcquireShared(std::string source_id, std::string request);
 
    bool HasPendingReplies() const;
 
    std::vector<PendingReply> GetPendingReplies() const;
protected:
    friend ReplyToken;
    void Release(uint64_t token);
    PendingReplies() = default;
private:
    uint64_t m_next_token_id = 1;
    std::vector<std::tuple<uint64_t, PendingReply>> m_pending;
};
 
} // namespace daq
 
#endif // #ifndef OCF_DAQ_PENDING_REPLIES_HPP_