C++中的Reactor原理與實現

2022-07-01 18:03:28

一、Reactor介紹

reactor設計模式是event-driven architecture的一種實現方式，處理多個使用者端並行的向伺服器端請求服務的場景。每種服務在伺服器端可能由多個方法組成。reactor會解耦並行請求的服務並分發給對應的事件處理器來處理。

中心思想是將所有要處理的I/o事件註冊到一箇中心I/o多路複用器上，同時主執行緒/程序阻塞在多路複用器上;一旦有I/o事件到來或是準備就緒(檔案描述符或socket可讀、寫)，多路複用器返回並將事先註冊的相應l/o事件分發到對應的處理器中。

處理機制為：主程式將事件以及對應事件處理的方法在Reactor上進行註冊, 如果相應的事件發生，Reactor將會主動呼叫事件註冊的介面，即回撥函數.

二、程式碼實現

前提準備：1單例模式：單例模式(Singleton Pattern，也稱為單件模式)，使用最廣泛的設計模式之一。其意圖是保證一個類（結構體）僅有一個範例，並提供一個存取它的全域性存取點，該範例被所有程式模組共用。
2.回撥函數：把一段可執行的程式碼像引數傳遞那樣傳給其他程式碼，而這段程式碼會在某個時刻被呼叫執行，這就叫做回撥。

對epoll反應堆中結構體定義

/*fd包含的屬性*/
struct nitem { // fd

	int fd;		//要監聽的檔案描述符

	int status;	//是否在監聽：1->在紅黑樹上（監聽），0->不在（不監聽）
	int events;	//對應的監聽事件，	EPOLLIN和EPOLLOUT（不同的事件，走不同的回撥函數）
	void *arg;	//指向自己結構體指標
#if 0
	NCALLBACK callback;
#else
	NCALLBACK *readcb;   // epollin
	NCALLBACK *writecb;  // epollout
	NCALLBACK *acceptcb; // epollin
#endif
	unsigned char sbuffer[BUFFER_LENGTH]; //
	int slength;

	unsigned char rbuffer[BUFFER_LENGTH];
	int rlength;
	
};

/*分塊儲存*/
struct itemblock {

	struct itemblock *next;
	struct nitem *items;

};
/*epoll反應堆中包括通訊的fd以及epoll的（epfd）*/
struct reactor {

	int epfd;
	struct itemblock *head; 

};

單例模式，建立reactor的一個範例

/*單例模式*/
struct reactor *instance = NULL;
int init_reactor(struct reactor *r) {

	if (r == NULL) return -1;

	int epfd = epoll_create(1); //int size
	r->epfd = epfd;

	// fd --> item
	r->head = (struct itemblock*)malloc(sizeof(struct itemblock));
	if (r->head == NULL) {
		close(epfd);
		return -2;
	} 
	memset(r->head, 0, sizeof(struct itemblock));

	r->head->items = (struct nitem *)malloc(MAX_EPOLL_EVENT * sizeof(struct nitem));
	if (r->head->items == NULL) {
		free(r->head);
		close(epfd);
		return -2;
	}
	memset(r->head->items, 0, (MAX_EPOLL_EVENT * sizeof(struct nitem)));
	
	r->head->next = NULL;
	
	return 0;
}
struct reactor *getInstance(void) { //singleton

	if (instance == NULL) {

		instance = (struct reactor *)malloc(sizeof(struct reactor));
		if (instance == NULL) return NULL;
		memset(instance, 0, sizeof(struct reactor));

		if (0 > init_reactor(instance)) {
			free(instance);
			return NULL;
		}

	}

	return instance;
}

事件註冊

/*nreactor_set_event(listenfd, accept_callback, ACCEPT_CB, NULL);*/
/*nreactor_set_event(fd, read_callback, READ_CB, NULL);*/
/*fd找到對應事件*/
/*驅動註冊*/
int nreactor_set_event(int fd, NCALLBACK cb, int event, void *arg) {

	struct reactor *r = getInstance();
	
	struct epoll_event ev = {0};
	//1
	if (event == READ_CB) {
		r->head->items[fd].fd = fd;
		r->head->items[fd].readcb = cb;
		r->head->items[fd].arg = arg;

		ev.events = EPOLLIN;
		
	}
	//2
	else if (event == WRITE_CB) {
		r->head->items[fd].fd = fd;
		r->head->items[fd].writecb = cb;
		r->head->items[fd].arg = arg;

		ev.events = EPOLLOUT;
	} 
	//3
	else if (event == ACCEPT_CB) {
		r->head->items[fd].fd = fd;
		r->head->items[fd].acceptcb = cb;	//回撥函數
		r->head->items[fd].arg = arg;

		ev.events = EPOLLIN;
	}

	ev.data.ptr = &r->head->items[fd];

	/*NOSET_CB 0*/
	if (r->head->items[fd].events == NOSET_CB) {
		if (epoll_ctl(r->epfd, EPOLL_CTL_ADD, fd, &ev) < 0) {
			printf("epoll_ctl EPOLL_CTL_ADD failed, %dn", errno);
			return -1;
		}
		r->head->items[fd].events = event;
	} else if (r->head->items[fd].events != event) {

		if (epoll_ctl(r->epfd, EPOLL_CTL_MOD, fd, &ev) < 0) {
			printf("epoll_ctl EPOLL_CTL_MOD failedn");
			return -1;
		}
		r->head->items[fd].events = event;
	}
	
	return 0;
}

回撥函數書寫

int write_callback(int fd, int event, void *arg) {
	struct reactor *R = getInstance();
	
	unsigned char *sbuffer = R->head->items[fd].sbuffer;
	int length = R->head->items[fd].slength;
	int ret = send(fd, sbuffer, length, 0);
	if (ret < length) {
		nreactor_set_event(fd, write_callback, WRITE_CB, NULL);
	} else {
		nreactor_set_event(fd, read_callback, READ_CB, NULL);
	}
	return 0;
}
// 5k qps
int read_callback(int fd, int event, void *arg) {
	struct reactor *R = getInstance();
	unsigned char *buffer = R->head->items[fd].rbuffer;
	
#if 0 //ET
	int idx = 0, ret = 0;
	while (idx < BUFFER_LENGTH) {
		ret = recv(fd, buffer+idx, BUFFER_LENGTH-idx, 0);
		if (ret == -1) { 
			break;
		} else if (ret > 0) {
			idx += ret;
		} else {// == 0
			break;
		}
	}
	if (idx == BUFFER_LENGTH && ret != -1) {
		nreactor_set_event(fd, read_callback, READ_CB, NULL);
	} else if (ret == 0) {
		nreactor_set_event
		//close(fd);
	} else {
		nreactor_set_event(fd, write_callback, WRITE_CB, NULL);
	}
	
#else //LT
	int ret = recv(fd, buffer, BUFFER_LENGTH, 0);
	if (ret == 0) { // fin
		
		nreactor_del_event(fd, NULL, 0, NULL);
		close(fd);
		
	} else if (ret > 0) {
		unsigned char *sbuffer = R->head->items[fd].sbuffer;
		memcpy(sbuffer, buffer, ret);
		R->head->items[fd].slength = ret;
		printf("readcb: %sn", sbuffer);
		nreactor_set_event(fd, write_callback, WRITE_CB, NULL);
	}
		
#endif
	
}
// web server 
// ET / LT
int accept_callback(int fd, int event, void *arg) {
	int connfd;
	struct sockaddr_in client;
    socklen_t len = sizeof(client);
    if ((connfd = accept(fd, (struct sockaddr *)&client, &len)) == -1) {
        printf("accept socket error: %s(errno: %d)n", strerror(errno), errno);
        return 0;
    }
	nreactor_set_event(connfd, read_callback, READ_CB, NULL);
}

監聽描述符變化

// accept --> EPOLL
/*epoll_wait監聽0*/
int reactor_loop(int listenfd) {

	struct reactor *R = getInstance();	
	
	struct epoll_event events[POLL_SIZE] = {0};
	while (1) {
		int nready = epoll_wait(R->epfd, events, POLL_SIZE, -1);
		if (nready == -1) {
			continue;
		}

		int i = 0;
		for (i = 0;i < nready;i ++) {
			
			struct nitem *item = (struct nitem *)events[i].data.ptr;
			int connfd = item->fd;

			if (connfd == listenfd) { //
				item->acceptcb(listenfd, 0, NULL);
			} else {
			
				if (events[i].events & EPOLLIN) { //
					item->readcb(connfd, 0, NULL);
				
				} 
				if (events[i].events & EPOLLOUT) {
					item->writecb(connfd, 0, NULL);
		
				}
			}
		}

	}
	return 0;
}

完整程式碼實現

#define MAXLNE  4096
#define POLL_SIZE	1024
#define BUFFER_LENGTH		1024
#define MAX_EPOLL_EVENT		1024
#define NOSET_CB	0
#define READ_CB		1
#define WRITE_CB	2
#define ACCEPT_CB	3
/*單例模式*/
typedef int NCALLBACK(int fd, int event, void *arg);
/*fd包含的屬性*/
struct nitem { // fd
	int fd;		//要監聽的檔案描述符
	int status;	//是否在監聽：1->在紅黑樹上（監聽），0->不在（不監聽）
	int events;	//對應的監聽事件，	EPOLLIN和EPOLLOUT（不同的事件，走不同的回撥函數）
	void *arg;	//指向自己結構體指標
#if 0
	NCALLBACK callback;
#else
	NCALLBACK *readcb;   // epollin
	NCALLBACK *writecb;  // epollout
	NCALLBACK *acceptcb; // epollin
#endif
	unsigned char sbuffer[BUFFER_LENGTH]; //
	int slength;
	unsigned char rbuffer[BUFFER_LENGTH];
	int rlength;
	
};
/*分塊儲存*/
struct itemblock {
	struct itemblock *next;
	struct nitem *items;
};
/*epoll反應堆中包括通訊的fd以及epoll的（epfd）*/
struct reactor {
	int epfd;
	struct itemblock *head; 
};
/*初始化結構體*/
int init_reactor(struct reactor *r);
int read_callback(int fd, int event, void *arg);
int write_callback(int fd, int event, void *arg);
int accept_callback(int fd, int event, void *arg);
/*單例模式*/
struct reactor *instance = NULL;
struct reactor *getInstance(void) { //singleton
	if (instance == NULL) {
		instance = (struct reactor *)malloc(sizeof(struct reactor));
		if (instance == NULL) return NULL;
		memset(instance, 0, sizeof(struct reactor));
		if (0 > init_reactor(instance)) {
			free(instance);
			return NULL;
		}
	}
	return instance;
}
/*nreactor_set_event(listenfd, accept_callback, ACCEPT_CB, NULL);*/
/*nreactor_set_event(fd, read_callback, READ_CB, NULL);*/
/*fd找到對應事件*/
/*驅動註冊*/
int nreactor_set_event(int fd, NCALLBACK cb, int event, void *arg) {
	struct reactor *r = getInstance();
	
	struct epoll_event ev = {0};
	//1
	if (event == READ_CB) {
		r->head->items[fd].fd = fd;
		r->head->items[fd].readcb = cb;
		r->head->items[fd].arg = arg;
		ev.events = EPOLLIN;
		
	}
	//2
	else if (event == WRITE_CB) {
		r->head->items[fd].fd = fd;
		r->head->items[fd].writecb = cb;
		r->head->items[fd].arg = arg;
		ev.events = EPOLLOUT;
	} 
	//3
	else if (event == ACCEPT_CB) {
		r->head->items[fd].fd = fd;
		r->head->items[fd].acceptcb = cb;	//回撥函數
		r->head->items[fd].arg = arg;
		ev.events = EPOLLIN;
	}
	ev.data.ptr = &r->head->items[fd];
	/*NOSET_CB 0*/
	if (r->head->items[fd].events == NOSET_CB) {
		if (epoll_ctl(r->epfd, EPOLL_CTL_ADD, fd, &ev) < 0) {
			printf("epoll_ctl EPOLL_CTL_ADD failed, %dn", errno);
			return -1;
		}
		r->head->items[fd].events = event;
	} else if (r->head->items[fd].events != event) {
		if (epoll_ctl(r->epfd, EPOLL_CTL_MOD, fd, &ev) < 0) {
			printf("epoll_ctl EPOLL_CTL_MOD failedn");
			return -1;
		}
		r->head->items[fd].events = event;
	}
	
	return 0;
}
/*nreactor_del_event(fd, NULL, 0, NULL);*/
/*下樹*/
/*nreactor_del_event(fd, NULL, 0, NULL);*/
int nreactor_del_event(int fd, NCALLBACK cb, int event, void *arg) {
	struct reactor *r = getInstance();
	
	struct epoll_event ev = {0};
	ev.data.ptr = arg;
	epoll_ctl(r->epfd, EPOLL_CTL_DEL, fd, &ev);
	r->head->items[fd].events = 0;
	return 0;
}
int write_callback(int fd, int event, void *arg) {
	struct reactor *R = getInstance();
	
	unsigned char *sbuffer = R->head->items[fd].sbuffer;
	int length = R->head->items[fd].slength;
	int ret = send(fd, sbuffer, length, 0);
	if (ret < length) {
		nreactor_set_event(fd, write_callback, WRITE_CB, NULL);
	} else {
		nreactor_set_event(fd, read_callback, READ_CB, NULL);
	}
	return 0;
}
// 5k qps
int read_callback(int fd, int event, void *arg) {
	struct reactor *R = getInstance();
	unsigned char *buffer = R->head->items[fd].rbuffer;
	
#if 0 //ET
	int idx = 0, ret = 0;
	while (idx < BUFFER_LENGTH) {
		ret = recv(fd, buffer+idx, BUFFER_LENGTH-idx, 0);
		if (ret == -1) { 
			break;
		} else if (ret > 0) {
			idx += ret;
		} else {// == 0
			break;
		}
	}
	if (idx == BUFFER_LENGTH && ret != -1) {
		nreactor_set_event(fd, read_callback, READ_CB, NULL);
	} else if (ret == 0) {
		nreactor_set_event
		//close(fd);
	} else {
		nreactor_set_event(fd, write_callback, WRITE_CB, NULL);
	}
	
#else //LT
	int ret = recv(fd, buffer, BUFFER_LENGTH, 0);
	if (ret == 0) { // fin
		
		nreactor_del_event(fd, NULL, 0, NULL);
		close(fd);
		
	} else if (ret > 0) {
		unsigned char *sbuffer = R->head->items[fd].sbuffer;
		memcpy(sbuffer, buffer, ret);
		R->head->items[fd].slength = ret;
		printf("readcb: %sn", sbuffer);
		nreactor_set_event(fd, write_callback, WRITE_CB, NULL);
	}
		
#endif
	
}
// web server 
// ET / LT
int accept_callback(int fd, int event, void *arg) {
	int connfd;
	struct sockaddr_in client;
    socklen_t len = sizeof(client);
    if ((connfd = accept(fd, (struct sockaddr *)&client, &len)) == -1) {
        printf("accept socket error: %s(errno: %d)n", strerror(errno), errno);
        return 0;
    }
	nreactor_set_event(connfd, read_callback, READ_CB, NULL);
}
int init_server(int port) {
	int listenfd;
    struct sockaddr_in servaddr;
    char buff[MAXLNE];
 
    if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        printf("create socket error: %s(errno: %d)n", strerror(errno), errno);
        return 0;
    }
 
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(port);
 
    if (bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1) {
        printf("bind socket error: %s(errno: %d)n", strerror(errno), errno);
        return 0;
    }
 
    if (listen(listenfd, 10) == -1) {
        printf("listen socket error: %s(errno: %d)n", strerror(errno), errno);
        return 0;
    }
	return listenfd;
}
int init_reactor(struct reactor *r) {
	if (r == NULL) return -1;
	int epfd = epoll_create(1); //int size
	r->epfd = epfd;
	// fd --> item
	r->head = (struct itemblock*)malloc(sizeof(struct itemblock));
	if (r->head == NULL) {
		close(epfd);
		return -2;
	} 
	memset(r->head, 0, sizeof(struct itemblock));
	r->head->items = (struct nitem *)malloc(MAX_EPOLL_EVENT * sizeof(struct nitem));
	if (r->head->items == NULL) {
		free(r->head);
		close(epfd);
		return -2;
	}
	memset(r->head->items, 0, (MAX_EPOLL_EVENT * sizeof(struct nitem)));
	
	r->head->next = NULL;
	
	return 0;
}
// accept --> EPOLL
/*epoll_wait監聽0*/
int reactor_loop(int listenfd) {
	struct reactor *R = getInstance();	
	
	struct epoll_event events[POLL_SIZE] = {0};
	while (1) {
		int nready = epoll_wait(R->epfd, events, POLL_SIZE, -1);
		if (nready == -1) {
			continue;
		}
		int i = 0;
		for (i = 0;i < nready;i ++) {
			
			struct nitem *item = (struct nitem *)events[i].data.ptr;
			int connfd = item->fd;
			if (connfd == listenfd) { //
				item->acceptcb(listenfd, 0, NULL);
			} else {
			
				if (events[i].events & EPOLLIN) { //
					item->readcb(connfd, 0, NULL);
				
				} 
				if (events[i].events & EPOLLOUT) {
					item->writecb(connfd, 0, NULL);
		
				}
			}
		}
	}
	return 0;
}
int main(int argc, char **argv) 
{
    
 	int  connfd, n;
	int listenfd = init_server(9999);
	nreactor_set_event(listenfd, accept_callback, ACCEPT_CB, NULL);
	//nreactor_set_event(listenfd, accept_callback, read_callback, write_callback);
	
	reactor_loop(listenfd);
	 
    return 0;
}

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C++中的Reactor原理與實現

目錄

一、Reactor介紹

二、程式碼實現

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