// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- 
	// vim: ts=8 sw=2 smarttab
	/*
	 * Ceph - scalable distributed file system
	 *
	 * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
	 *
	 * This is free software; you can redistribute it and/or
	 * modify it under the terms of the GNU Lesser General Public
	 * License version 2.1, as published by the Free Software 
	 * Foundation.  See file COPYING.
	 * 
	 */
	
	#ifndef CEPH_REFCOUNTEDOBJ_H
	#define CEPH_REFCOUNTEDOBJ_H
	 
	#include "common/ceph_mutex.h"
	#include "common/ref.h"
	
	#include <atomic>
	
	/* This class provides mechanisms to make a sub-class work with
	 * boost::intrusive_ptr (aka ceph::ref_t).
	 *
	 * Generally, you'll want to inherit from RefCountedObjectSafe and not from
	 * RefCountedObject directly. This is because the ::get and ::put methods are
	 * public and can be used to create/delete references outside of the
	 * ceph::ref_t pointers with the potential to leak memory.
	 *
	 * It is also suggested that you make constructors and destructors private in
	 * your final class. This prevents instantiation of the object with assignment
	 * to a raw pointer. Consequently, you'll want to use ceph::make_ref<> to
	 * create a ceph::ref_t<> holding your object:
	 *
	 *    auto ptr = ceph::make_ref<Foo>(...);
	 *
	 * Use FRIEND_MAKE_REF(ClassName) to allow ceph::make_ref to call the private
	 * constructors.
	 *
	 */
	
	class RefCountedObject {
	public:
	  void set_cct(class CephContext *c) {
	    cct = c;
	  }
	
	  uint64_t get_nref() const {
	    return nref;
	  }
	
	  const RefCountedObject *get() const {
	    _get();
	    return this;
	  }
	  RefCountedObject *get() {
	    _get();
	    return this;
	  }
	  void put() const;
	
	protected:
	  RefCountedObject() = default;
	  RefCountedObject(const RefCountedObject& o) : cct(o.cct) {}
	  RefCountedObject& operator=(const RefCountedObject& o) = delete;
	  RefCountedObject(RefCountedObject&&) = delete;
	  RefCountedObject& operator=(RefCountedObject&&) = delete;
	  RefCountedObject(class CephContext* c) : cct(c) {}
	
	  virtual ~RefCountedObject();
	
	private:
	  void _get() const;
	
	#ifndef WITH_SEASTAR
	  mutable std::atomic<uint64_t> nref{1};
	#else
	  // crimson is single threaded at the moment
	  mutable uint64_t nref{1};
	#endif
	  class CephContext *cct{nullptr};
	};
	
	class RefCountedObjectSafe : public RefCountedObject {
	public:
	  RefCountedObject *get() = delete;
	  const RefCountedObject *get() const = delete;
	  void put() const = delete;
	protected:
	template<typename... Args>
	  RefCountedObjectSafe(Args&&... args) : RefCountedObject(std::forward<Args>(args)...) {}
	  virtual ~RefCountedObjectSafe() override {}
	};
	
	#ifndef WITH_SEASTAR
	
	/**
	 * RefCountedCond
	 *
	 *  a refcounted condition, will be removed when all references are dropped
	 */
	struct RefCountedCond : public RefCountedObject {
	  RefCountedCond() = default;
	  ~RefCountedCond() = default;
	
	  int wait() {
	    std::unique_lock l(lock);
	    while (!complete) {
	      cond.wait(l);
	    }
	    return rval;
	  }
	
	  void done(int r) {
	    std::lock_guard l(lock);
	    rval = r;
	    complete = true;
	    cond.notify_all();
	  }
	
	  void done() {
	    done(0);
	  }
	
	private:
	  bool complete = false;
	  ceph::mutex lock = ceph::make_mutex("RefCountedCond::lock");
	  ceph::condition_variable cond;
	  int rval = 0;
	};
	
	/**
	 * RefCountedWaitObject
	 *
	 * refcounted object that allows waiting for the object's last reference.
	 * Any referrer can either put or put_wait(). A simple put() will return
	 * immediately, a put_wait() will return only when the object is destroyed.
	 * e.g., useful when we want to wait for a specific event completion. We
	 * use RefCountedCond, as the condition can be referenced after the object
	 * destruction. 
	 *    
	 */
	struct RefCountedWaitObject {
	  std::atomic<uint64_t> nref = { 1 };
	  RefCountedCond *c;
	
	  RefCountedWaitObject() {
	    c = new RefCountedCond;
	  }

	  virtual ~RefCountedWaitObject() {

	    c->put();
	  }
	
	  RefCountedWaitObject *get() {
	    nref++;
	    return this;
	  }
	
	  bool put() {
	    bool ret = false;
	    RefCountedCond *cond = c;
	    cond->get();
	    if (--nref == 0) {
	      cond->done();
	      delete this;
	      ret = true;
	    }
	    cond->put();
	    return ret;
	  }
	
	  void put_wait() {
	    RefCountedCond *cond = c;
	
	    cond->get();
	    if (--nref == 0) {
	      cond->done();
	      delete this;
	    } else {
	      cond->wait();
	    }
	    cond->put();
	  }
	};
	
	#endif // WITH_SEASTAR
	
	static inline void intrusive_ptr_add_ref(const RefCountedObject *p) {
	  p->get();
	}
	static inline void intrusive_ptr_release(const RefCountedObject *p) {
	  p->put();
	}
	
	using RefCountedPtr = ceph::ref_t<RefCountedObject>;
	
	#endif