/*
 * =====================================================================================
 *
 *       Filename:  shm.h
 *
 *    Description:  
 *
 *        Version:  1.0
 *        Created:  2021年03月22日 16时19分21秒
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Li Chao (), 
 *   Organization:  
 *
 * =====================================================================================
 */

#ifndef SHM_6CHO6D6C
#define SHM_6CHO6D6C

#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/sync/interprocess_mutex.hpp>
#include <boost/noncopyable.hpp>
#include <string>

namespace bhome_shm
{

using namespace boost::interprocess;

typedef managed_shared_memory mshm_t;
typedef interprocess_mutex Mutex;
typedef scoped_lock<Mutex> Guard;

class SharedMemory : public mshm_t
{
	std::string name_;
	Mutex *pmutex_ = 0;

	static permissions AllowAll()
	{
		permissions perm;
		perm.set_unrestricted();
		return perm;
	}
	void Swap(SharedMemory &a);

public:
	static bool Remove(const std::string &name) { return shared_memory_object::remove(name.c_str()); }

	SharedMemory(const std::string &name, const uint64_t size);
	~SharedMemory();
	std::string name() const { return name_; }
	bool Remove() { return Remove(name()); }
	template <class T, class... Params>
	T *FindOrCreate(const std::string &name, Params &&...params)
	{
		return find_or_construct<T>(name.c_str(), std::nothrow)(std::forward<decltype(params)>(params)...);
	}
	template <class T, class... Params>
	T *Create(const std::string &name, Params &&...params)
	{
		return construct<T>(name.c_str(), std::nothrow)(std::forward<decltype(params)>(params)...);
	}
	template <class T>
	bool Destroy(const std::string &name) { return destroy<T>(name.c_str()); }

	void *Alloc(const size_t size)
	{
		Guard lock(*pmutex_);
		return allocate(size, std::nothrow);
	}
	void Dealloc(void *p)
	{
		Guard lock(*pmutex_);
		if (p) { deallocate(p); }
	}

	template <class T>
	T *Find(const std::string &name) { return find<T>(name.c_str()).first; }
};

enum Mode {
	eOpen = 0,
	eCreate = 1,
	eOpenOrCreate = 2
};

// NamedShmObject manages an object in shared memory, but NamedShmObject itself is not in shared memory.
template <class T>
class NamedShmObject : private boost::noncopyable
{
	static std::string ObjName(const std::string &name) { return "obj" + name; }

public:
	typedef T Data;
	typedef SharedMemory ShmType;
	ShmType &shm() const { return shm_; }

	template <class... Params>
	NamedShmObject(ShmType &segment, const std::string &name, Mode mode, Params &&...t) :
	    shm_(segment), name_(name)
	{
		switch (mode) {
		case eOpen:
			pdata_ = shm_.Find<Data>(ObjName(name_));
			break;
		case eCreate:
			pdata_ = shm_.Create<Data>(ObjName(name_), std::forward<decltype(t)>(t)...);
			break;
		case eOpenOrCreate:
			pdata_ = shm_.FindOrCreate<Data>(ObjName(name_), std::forward<decltype(t)>(t)...);
			break;
		default: break;
		}
		if (!IsOk()) {
			throw std::runtime_error("Error: shm can not create/open \"" + name_ + "\"");
		}
	}

	NamedShmObject(const int64_t offset, ShmType &segment, const std::string &name) :
	    shm_(segment), name_(name)
	{
		pdata_ = reinterpret_cast<Data *>(Addr(shm_.get_address()) + offset);
	}

	bool IsOk() const { return pdata_; }

	static bool Remove(SharedMemory &shm, const std::string &name) { return shm.Destroy<Data>(ObjName(name)); }
	static Data *Find(SharedMemory &shm, const std::string &name) { return shm.Find<Data>(ObjName(name)); }
	Data *Find(const std::string &name) { return Find(shm_, ObjName(name)); }
	virtual ~NamedShmObject() {}
	std::string name() const { return name_; }
	Data *data() { return pdata_; }
	const Data *data() const { return pdata_; }
	int64_t offset() const { return Addr(pdata_) - Addr(shm_.get_address()); }
	Data *operator->() { return data(); }
	const Data *operator->() const { return data(); }
	bool Remove() { return Remove(shm_, name_); }

private:
	static int64_t Addr(const void *p) { return reinterpret_cast<int64_t>(p); }
	ShmType &shm_;
	std::string name_;
	Data *pdata_ = nullptr;
};

} // namespace bhome_shm

#endif // end of include guard: SHM_6CHO6D6C