跨子類的C++互斥鎖和STL列表

Question

我目前正在編寫一個使用Poco的多線程C++服務器，現在我需要保留哪些用戶連接的信息，每個連接有多少個連接，以及因爲它是一個代理服務器，其中每個連接都通過代理進行連接。

爲此，我創建了一個ServerStats類，它包含一個ServerUser對象的STL列表。 ServerStats類包括可以從列表中添加和刪除對象以及在列表中找到用戶的函數，並返回指向它們的指針，以便我可以訪問列表中任何給定的ServerUser對象內的成員函數。

ServerUser類包含一個ServerConnection對象的STL列表，非常類似於ServerStats類，它包含添加，刪除和查找此列表中的元素的函數。

現在所有上述工作，但我現在試圖使它線程安全。

我已經在ServerStats類中定義了一個Poco :: FastMutex，並且可以在適當的位置鎖定/解鎖它，以便STL容器在搜索時不會同時被修改。但是我有一個問題ServerUser類中建立互斥體，並正在以下編譯器錯誤：

/root/poco/Foundation/include/Poco/Mutex.h: In copy constructor âServerUser::ServerUser(const ServerUser&)â: src/SocksServer.cpp:185:
instantiated from âvoid __gnu_cxx::new_allocator<_Tp>::construct(_Tp*, const _Tp&) [with _Tp = ServerUser]â /usr/include/c++/4.4/bits/stl_list.h:464: instantiated from âstd::_List_node<_Tp>* std::list<_Tp, _Alloc>::_M_create_node(const _Tp&) [with _Tp = ServerUser, _Alloc = std::allocator]â /usr/include/c++/4.4/bits/stl_list.h:1407: instantiated from âvoid std::list<_Tp, _Alloc>::_M_insert(std::_List_iterator<_Tp>, const _Tp&) [with _Tp = ServerUser, _Alloc = std::allocator]â /usr/include/c++/4.4/bits/stl_list.h:920: instantiated from âvoid std::list<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = ServerUser, _Alloc = std::allocator]â src/SocksServer.cpp:301:
instantiated from here /root/poco/Foundation/include/Poco/Mutex.h:164: error: âPoco::FastMutex::FastMutex(const Poco::FastMutex&)â is private src/SocksServer.cpp:185: error: within this context In file included from /usr/include/c++/4.4/x86_64-linux-gnu/bits/c++allocator.h:34, from /usr/include/c++/4.4/bits/allocator.h:48, from /usr/include/c++/4.4/string:43, from /root/poco/Foundation/include/Poco/Bugcheck.h:44, from /root/poco/Foundation/include/Poco/Foundation.h:147, from /root/poco/Net/include/Poco/Net/Net.h:45, from /root/poco/Net/include/Poco/Net/TCPServerParams.h:43, from src/SocksServer.cpp:1: /usr/include/c++/4.4/ext/new_allocator.h: In member function âvoid __gnu_cxx::new_allocator<_Tp>::construct(_Tp*, const _Tp&) [with _Tp = ServerUser]â: /usr/include/c++/4.4/ext/new_allocator.h:105: note: synthesized method âServerUser::ServerUser(const ServerUser&)â first required here src/SocksServer.cpp: At global scope: src/SocksServer.cpp:118: warning: âstd::string getWord(std::string)â defined but not used make: *** [/root/poco/SocksServer/obj/Linux/x86_64/debug_shared/SocksServer.o] Error 1

爲ServerStats，ServerUser和一個ServerConnection類的代碼如下：

class ServerConnection 
{ 
public: 
    bool continue_connection; 
    int bytes_in; 
    int bytes_out; 
    string source_address; 
    string destination_address; 

    ServerConnection() 
    { 
     continue_connection = true; 
    } 

    ~ServerConnection() 
    { 
    } 
}; 

class ServerUser 
{ 
public: 
    string username; 
    int connection_count; 
    string client_ip; 

    ServerUser() 
    { 
    } 

    ~ServerUser() 
    { 
    } 

    ServerConnection* addConnection(string source_address, string destination_address) 
    { 
     //FastMutex::ScopedLock lock(_connection_mutex); 

     ServerConnection connection; 
     connection.source_address = source_address; 
     connection.destination_address = destination_address; 
     client_ip = getWord(source_address, ":"); 

     _connections.push_back(connection); 
     connection_count++; 

     return &_connections.back(); 
    } 

    void removeConnection(string source_address) 
    { 
     //FastMutex::ScopedLock lock(_connection_mutex); 

     for(list<ServerConnection>::iterator it = _connections.begin(); it != _connections.end(); it++) 
     { 
      if(it->source_address == source_address) 
      { 
       it = _connections.erase(it); 
       connection_count--; 
      } 
     } 
    } 

    void disconnect() 
    {  
     //FastMutex::ScopedLock lock(_connection_mutex); 

     for(list<ServerConnection>::iterator it = _connections.begin(); it != _connections.end(); it++) 
     { 
      it->continue_connection = false; 
     } 
    } 

    list<ServerConnection>* getConnections() 
    { 
     return &_connections; 
    } 

private: 
    list<ServerConnection> _connections; 

    //UNCOMMENTING THIS LINE BREAKS IT: 
    //mutable FastMutex _connection_mutex; 
}; 

class ServerStats 
{ 
public: 
    int current_users; 

ServerStats() 
{ 
    current_users = 0; 
} 

~ServerStats() 
{ 
} 

ServerUser* addUser(string username) 
{ 
    FastMutex::ScopedLock lock(_user_mutex); 

    for(list<ServerUser>::iterator it = _users.begin(); it != _users.end(); it++) 
    { 
     if(it->username == username) 
     { 
      return &(*it); 
     } 
    } 

    ServerUser newUser; 
    newUser.username = username; 
    _users.push_back(newUser); 
    current_users++; 

    return &_users.back(); 
} 

void removeUser(string username) 
{ 
    FastMutex::ScopedLock lock(_user_mutex); 

    for(list<ServerUser>::iterator it = _users.begin(); it != _users.end(); it++) 
    { 
     if(it->username == username) 
     { 
      _users.erase(it); 
      current_users--; 
      break; 
     } 
    } 
} 

ServerUser* getUser(string username) 
{ 
    FastMutex::ScopedLock lock(_user_mutex); 

    for(list<ServerUser>::iterator it = _users.begin(); it != _users.end(); it++) 
    { 
     if(it->username == username) 
     { 
      return &(*it); 
     } 
    } 
    return NULL; 
} 

private: 
    list<ServerUser> _users; 
    mutable FastMutex _user_mutex; 
}; 

現在我從來沒有使用過C++來處理這個大小的項目或者互斥體，所以請簡單點:)

首先，誰能告訴我爲什麼上面的代碼會導致編譯器錯誤？

其次，任何人都可以提出一個更好的方式來存儲我需要的信息嗎？請記住，無論連接何時出現，我都需要更新此信息，並且它需要對整個服務器是全局的。

Answer 1

問題是FastMutex不可複製，因此ServerUser不可複製。將對象插入STL容器時，必須將其複製。我認爲你將不得不改變你的課程設計。另外，你必須非常小心地返回指向存儲在STL容器中的對象的指針，因爲當你從容器中插入和移除東西時，它們可能因爲對象被重新組合而變得無效。