/*
 * =====================================================================================
 *
 *       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 "log.h"
#include <atomic>
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/sync/interprocess_mutex.hpp>
#include <boost/noncopyable.hpp>
#include <thread>

namespace bhome_shm
{

using namespace boost::interprocess;

typedef managed_shared_memory mshm_t;

class MutexWithPidCheck
{
	typedef boost::interprocess::interprocess_mutex MutexT;
	static pid_t pid()
	{
		static pid_t val = getpid();
		return val;
	}
	static bool Killed(pid_t pid)
	{
		char buf[64] = {0};
		snprintf(buf, sizeof(buf) - 1, "/proc/%d/stat", pid);
		return access(buf, F_OK) != 0;
	}
	bool PidCas(pid_t exp, pid_t val) { return pid_.compare_exchange_strong(exp, val); }
	MutexT mutex_;
	std::atomic<pid_t> pid_;

public:
	typedef MutexT::internal_mutex_type internal_mutex_type;
	const internal_mutex_type &internal_mutex() const { return mutex_.internal_mutex(); }
	internal_mutex_type &internal_mutex() { return mutex_.internal_mutex(); }
	MutexWithPidCheck() :
	    pid_(0) {}
	bool try_lock()
	{
		bool r = false;
		if (mutex_.try_lock()) {
			auto old = pid_.load();
			r = PidCas(old, pid());
		} else {
			auto old = pid_.load();
			if (Killed(old)) {
				r = PidCas(old, pid());
				if (r) {
					LOG_DEBUG() << "PidCheck captured pid " << old << " -> " << pid();
				}
			}
		}
		return r;
	}

	void lock()
	{
		while (!try_lock()) {
			std::this_thread::yield();
		}
	}
	void unlock()
	{
		auto old = pid_.load();
		if (old == pid()) {
			mutex_.unlock();
		}
	}
};

typedef interprocess_mutex Mutex;
typedef scoped_lock<Mutex> Guard;
// typedef robust::Guard<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)...);
	}
	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>
	void Dealloc(offset_ptr<T> ptr) { return Dealloc(ptr.get()); }

	template <class T, class... Params>
	T *New(Params &&...params)
	{
		Guard lock(*pmutex_);
		return construct<T>(anonymous_instance, std::nothrow)(std::forward<decltype(params)>(params)...);
	}
	template <class T>
	void Delete(T *p)
	{
		Guard lock(*pmutex_);
		if (p) { destroy_ptr<T>(p); };
	}
	template <class T>
	void Delete(offset_ptr<T> p) { Delete(p.get()); }
	template <class T>
	T *Find(const std::string &name) { return find<T>(name.c_str()).first; }
};

template <class D>
using Allocator = allocator<D, SharedMemory::segment_manager>;
template <class D>
using Deleter = deleter<D, SharedMemory::segment_manager>;
template <class D>
using SharedPtr = shared_ptr<D, Allocator<void>, Deleter<D>>;

// ShmObject manages an object in shared memory, but ShmObject itself is not in shared memory.
template <class T>
class ShmObject : 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>
	ShmObject(ShmType &segment, const std::string &name, Params &&...t) :
	    shm_(segment), name_(name)
	{
		pdata_ = shm_.FindOrCreate<Data>(ObjName(name_), std::forward<decltype(t)>(t)...);
		if (!IsOk()) {
			throw("Error: Not enough memory, can not allocate \"" + name_ + "\"");
		}
	}
	template <class... Params>
	ShmObject(ShmType &segment, const bool create_or_else_find, const std::string &name, Params &&...t) :
	    shm_(segment), name_(name)
	{
		if (create_or_else_find) {
			pdata_ = shm_.Create<Data>(ObjName(name_), std::forward<decltype(t)>(t)...);
		} else {
			pdata_ = shm_.Find<Data>(ObjName(name_));
		}
	}
	ShmObject(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).c_str()); }
	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 ~ShmObject() {}
	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