C ++ - 从抽象基指针调用派生的函数 [英] C++ - calling derived function from abstract base pointer
问题描述
我一直在试图创建一个基于继承的TCP服务器模型,并取得了不同的成功。这些服务器由单独管理,它的任务是关闭这些服务器和其他简单的维护功能:
class TCPServer {
public:
TCPServer();
〜TCPServer();
void Bind(TCPDaemon * daemon){
if(!daemon-> IsRunning()){
throw TCPBindException(Daemon is inactive);
}
//如果不使用端口,则将此守护程序绑定到
if(this-> servers.count(daemon-> port())= = 0){
this-> servers [daemon-> port()] = daemon;
...
} else {
throw TCPBindException(Port is taken);
}
}
void Shutdown(){
MASON :: UINT16 i;
for(i = 0; i servers.size(); i ++){
this-> Shutdown((* this-> servers.begin())。 ;
}
}
无关闭(unsigned short port){
if(this-> servers.count(port)){
if(this-> servers [port] - > IsRunning()){
this-> servers [port] - > Stop
}
delete this-> servers [port];
this-> servers.erase(port);
}
}
private:
std :: map< unsigned short,TCPDaemon *>服务器;
};
TCPDaemon类的Stop()函数是一个纯虚函数。我的问题是,当Shutdown()函数被调用时,它试图调用这个纯虚拟而不是派生类的版本。如何强制它做正确的事?
提前感谢
不包括之前的TCPDaemon代码,它来自一个TCPSocket类(我已经检查是100%工作,是相当不言自明的)。这是:
类TCPDaemon:public TCPSocket {
public:
TCPDaemon(unsigned short port) {
this-> _enabled = false;
this-> _host.ipaddr(INADDR_ANY);
this-> _host.port(port);
this-> paused = false;
struct sockaddr_in opts = this-> _host.Compile();
#ifdef PLATFORM_WINDOWS
WSADATA wsaData;
if(WSAStartup(0x0202,& wsaData)){
throw TCPDaemonException(无法启动WSA);
}
#endif
this-> raw_socket = socket(AF_INET,SOCK_STREAM,0);
if(this-> raw_socket< = 0){
throw TCPDaemonException(无法创建套接字);
}
if(int status = bind(this-> raw_socket,(sockaddr *)& opts,sizeof(sockaddr))){
printf(error [ %i] \r\\\
,status);
throw TCPDaemonException(无法绑定到端口);
}
if(listen(this-> raw_socket,5)){
throw TCPDaemonException(Failed to listen on port);
}
this-> _enabled = true;
}
virtual〜TCPDaemon(){
this-> Shutdown();
}
virtual void Start()= 0;
virtual void Run(TCPSocket *)= 0;
virtual void Stop()= 0;
unsigned short port(){
return this-> host()。port();
}
bool IsRunning(){
return this-> _enabled;
}
TCPSocket * Accept(){
SOCKET客户端;
struct sockaddr client_addr;
int len = sizeof(client_addr);
client = accept(this-> raw_socket,& client_addr,& len);
return new TCPSocket(client,& client_addr);
}
void Shutdown(){
}
private:
bool _enabled;
bool paused;
};
这里是一个示例派生服务器及其创建方法:
class EchoServer:public TCPDaemon {
public:
EchoServer(MASON :: UINT16 port):TCPDaemon(port){
}
〜EchoServer(){}
virtual void Start(){
}
virtual void Run TCPSocket * client){
printf(RUN\r\\\
);
Accessor< TCPSocket> acc_client = client;
acc_client-> Write(Accessor< Blob>(new Blob(std :: string(hello!)))));
acc_client-> Disconnect();
}
virtual void Stop(){
}
};
myTCPServer-> Bind(new EchoServer(8008));
[edit + 1]我想问题归结为这是):
我有一个基类的std :: map,TCPDaemon,它有一个纯虚拟/抽象函数Stop()。看起来当我通过地图中的一个条目调用Stop()时,它试图调用TCPDaemon :: Stop(),而不是覆盖函数EchoServer :: Stop()。这是问题吗?
我不确定这是否是您遇到的问题,在下面的函数中肯定有一个问题。
void Shutdown(){
MASON :: UINT16 i;
for(i = 0; i servers.size(); i ++){
this-> Shutdown((* this-> servers.begin())。 ;
}
}
在每个循环迭代器之后, i
会增加一个,而 size
会减少,所以你只需要ShutDown一半的服务器。
您可以执行以下任一操作:
code> void Shutdown(){
MASON :: UINT16 i;
std :: size_t nrServers = this-> servers.size();
for(i = 0; ithis-> Shutdown((* this-> servers.begin())。
}
}
或者,我更喜欢,因为它更好地显示代码的意图:
void Shutdown(){
while(!this-> servers.empty ){
this-> Shutdown((* this-> servers.begin())。
}
}
I have been trying to create a TCP Server model based on inheritance, with varying success. These servers are managed by a singleton whose task it is to shut these servers down and other simple maintenance functions:
class TCPServer {
public:
TCPServer();
~TCPServer();
void Bind(TCPDaemon *daemon) {
if(!daemon->IsRunning()) {
throw TCPBindException("Daemon is inactive");
}
// if the port is not taken, bind this daemon to it
if(this->servers.count(daemon->port())==0) {
this->servers[daemon->port()]=daemon;
...
} else {
throw TCPBindException("Port is taken");
}
}
void Shutdown() {
MASON::UINT16 i;
for(i=0;i<this->servers.size();i++) {
this->Shutdown((*this->servers.begin()).first);
}
}
void Shutdown(unsigned short port) {
if(this->servers.count(port)) {
if(this->servers[port]->IsRunning()) {
this->servers[port]->Stop();
}
delete this->servers[port];
this->servers.erase(port);
}
}
private:
std::map<unsigned short, TCPDaemon*> servers;
};
The TCPDaemon class's Stop() function is a pure virtual. My problem is that when the Shutdown() function is called, it is attempting to call this pure virtual instead of the derived class' version. How can I force it to do the right thing?
Thanks in advance
[edit] sorry I did not include the TCPDaemon code before, it derives from a TCPSocket class (which I have checked to be 100% working and is fairly self-explanatory). Here it is:
class TCPDaemon: public TCPSocket {
public:
TCPDaemon(unsigned short port) {
this->_enabled=false;
this->_host.ipaddr(INADDR_ANY);
this->_host.port(port);
this->paused=false;
struct sockaddr_in opts=this->_host.Compile();
#ifdef PLATFORM_WINDOWS
WSADATA wsaData;
if(WSAStartup(0x0202, &wsaData)) {
throw TCPDaemonException("Failed to start WSA");
}
#endif
this->raw_socket=socket(AF_INET, SOCK_STREAM, 0);
if(this->raw_socket<=0) {
throw TCPDaemonException("Failed to create socket");
}
if(int status=bind(this->raw_socket, (sockaddr*)&opts, sizeof(sockaddr))) {
printf("error [%i]\r\n", status);
throw TCPDaemonException("Failed to bind to port");
}
if(listen(this->raw_socket, 5)) {
throw TCPDaemonException("Failed to listen on port");
}
this->_enabled=true;
}
virtual ~TCPDaemon() {
this->Shutdown();
}
virtual void Start()=0;
virtual void Run(TCPSocket*)=0;
virtual void Stop()=0;
unsigned short port() {
return this->host().port();
}
bool IsRunning() {
return this->_enabled;
}
TCPSocket *Accept() {
SOCKET client;
struct sockaddr client_addr;
int len=sizeof(client_addr);
client=accept(this->raw_socket, &client_addr, &len);
return new TCPSocket(client, &client_addr);
}
void Shutdown() {
}
private:
bool _enabled;
bool paused;
};
and here is a sample derived server and its method of creation:
class EchoServer: public TCPDaemon {
public:
EchoServer(MASON::UINT16 port): TCPDaemon(port) {
}
~EchoServer() {}
virtual void Start() {
}
virtual void Run(TCPSocket *client) {
printf("RUN\r\n");
Accessor<TCPSocket> acc_client=client;
acc_client->Write(Accessor<Blob> (new Blob(std::string("hello!"))));
acc_client->Disconnect();
}
virtual void Stop() {
}
};
myTCPServer->Bind(new EchoServer(8008));
[edit+1] I think what the problem boils down to is this (i could easily be wrong): I have a std::map of the base class, TCPDaemon, which has a pure virtual/abstract function Stop(). It appears that when I call Stop() through one of the entries in the map, it is attempting to call TCPDaemon::Stop(), as opposed to the overriding function EchoServer::Stop(). Could this be the issue? If so, how do I resolve it?
I'm not sure if this is the problem you're seeing, but there's certainly a problem in the following function.
void Shutdown() {
MASON::UINT16 i;
for(i=0;i<this->servers.size();i++) {
this->Shutdown((*this->servers.begin()).first);
}
}
After each loop iterator, i
will increase by one AND size
will decrease, so you'll only ShutDown half your servers. Maybe keeping some open is the cause of further errors.
You could do either:
void Shutdown() {
MASON::UINT16 i;
std::size_t nrServers = this->servers.size();
for(i=0;i<nrServers;i++) {
this->Shutdown((*this->servers.begin()).first);
}
}
or, which I would prefer as it better shows the intention of the code:
void Shutdown() {
while (!this->servers.empty()) {
this->Shutdown((*this->servers.begin()).first);
}
}
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