tagged backend

tag_backend.cpp

#include <memory>
#include <string>
#include <atomic>

class base_object {
    std::atomic<size_t> ref_count;
public:
    size_t aquire() { return ++ref_count; }
    size_t release() { return --ref_count; }
};

template<class Tag> class service;


class interface {
   service<interface>& get_service();
   const service<interface>& get_service() const;

   std::shared_ptr<service<interface>> _service;
public:

   interface( std::shared_ptr<service<interface>> service );
   bool open_file( const std::wstring& name);
};

template<>
class service<interface>
{
    public:
    virtual ~service<interface>() = default;
    virtual bool checkout(const std::wstring& name) = 0;
    virtual bool download(const std::wstring& name) = 0; 
};

interface::interface( std::shared_ptr<service<interface>> service ) 
    : _service{std::move(service)} 
{}

service<interface>& interface::get_service() 
{ return *_service; }

const service<interface>& interface::get_service() const 
{ return *_service; }

bool interface::open_file( const std::wstring& name) {
    return get_service().checkout(name) && get_service().download(name);
}