/*
 * =====================================================================================
 *
 *       Filename:  msg.h
 *
 *    Description:  
 *
 *        Version:  1.0
 *        Created:  2021年03月24日 16时49分20秒
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Li Chao (), 
 *   Organization:  
 *
 * =====================================================================================
 */
#ifndef MSG_5BILLZET
#define MSG_5BILLZET

#include <stdint.h>
#include "shm.h"
#include <boost/interprocess/offset_ptr.hpp>
#include <boost/uuid/uuid_generators.hpp>

namespace bhome_shm {

// msg is safe to be stored in shared memory, so POD data or offset_ptr is required.
// message format: header(meta) + body(data).
enum MsgType {
    kMsgTypeNull = 0,
    kMsgTypeNormal = 1,
    kMsgTypeMaxValue
};

typedef boost::uuids::uuid MQId;

const uint32_t kMsgMetaTag = 0xf1e2d3c4;

struct MsgMetaV1 {
    uint16_t self_size_ = sizeof(MsgMetaV1); // sizeof(*this)
    uint16_t type_ = kMsgTypeNormal; // msg type.
    uint32_t tag_ = kMsgMetaTag;
    uint32_t data_size_ = 0;
    MQId src_id_;
    // more fields add at end, must not change

    MsgMetaV1():src_id_(boost::uuids::nil_uuid()){}
    bool Parse(const void *p);
    void Pack(void *p);
};

// store ref count, msgs shareing the same data should also hold a pointer of the same RefCount object.
class RefCount : private boost::noncopyable
{
public:
    int Inc() { Guard lk(mutex_); return ++num_; }
    int Dec() { Guard lk(mutex_); return --num_; }
    int Get() { Guard lk(mutex_); return num_; }
private:
    Mutex mutex_;
    int num_ = 1;
};

class Msg {
private:
    offset_ptr<void> ptr_;
    offset_ptr<RefCount> count_;
public:
    Msg(void *p=0, RefCount *c=0):ptr_(p), count_(c) {}
    void swap(Msg &a) { std::swap(ptr_, a.ptr_); std::swap(count_, a.count_); }

    // ~Msg() { RemoveRef(); }
    // Msg(const Msg &a):ptr_(a.ptr_), count_(a.count_) { AddRef(); }
    // Msg(Msg &&a):ptr_(a.ptr_), count_(a.count_) { a.ptr_ = 0; a.count_ = 0; }
    // Msg & operator = (const Msg &a) { Msg(a).swap(*this); }
    // Msg & operator = (Msg &&a) { Msg(std::move(a)).swap(*this); }

    template <class T = void> T *get() { return static_cast<T*>(ptr_.get()); }
    int AddRef() const { return IsCounted() ? count_->Inc() : 1; }
    int RemoveRef()  const{ return IsCounted() ? count_->Dec() : 0; }
    int Count()  const{ return IsCounted() ? count_->Get() : 1; }
    bool IsCounted() const { return static_cast<bool>(count_); }
    bool Build(SharedMemory &shm, const MQId &src_id, const void *p, const size_t size, const bool refcount);
    void FreeFrom(SharedMemory &shm);
};

inline void swap(Msg &m1, Msg &m2) { m1.swap(m2); }


} // namespace bhome_shm



#endif // end of include guard: MSG_5BILLZET