C++中的Reactor原理与实现

2022-11-13 11:11:40 reactor 原理

一、Reactor介绍

reactor设计模式是event-driven architecture的一种实现方式,处理多个客户端并发的向服务端请求服务的场景。每种服务在服务端可能由多个方法组成。reactor会解耦并发请求的服务并分发给对应的事件处理器来处理。

中心思想是将所有要处理的I/o事件注册到一个中心I/o多路复用器上,同时主线程/进程阻塞在多路复用器上;一旦有I/o事件到来或是准备就绪(文件描述符或Socket可读、写),多路复用器返回并将事先注册的相应l/o事件分发到对应的处理器中。

处理机制为:主程序将事件以及对应事件处理的方法在Reactor上进行注册, 如果相应的事件发生,Reactor将会主动调用事件注册的接口,即 回调函数.

二、代码实现

前提准备:1单例模式:单例模式(Singleton Pattern,也称为单件模式),使用最广泛的设计模式之一。其意图是保证一个类(结构体)仅有一个实例,并提供一个访问它的全局访问点,该实例被所有程序模块共享。
2.回调函数:把一段可执行的代码像参数传递那样传给其他代码,而这段代码会在某个时刻被调用执行,这就叫做回调。

对epoll反应堆中结构体定义


struct nitem { // fd

	int fd;		//要监听的文件描述符

	int status;	//是否在监听:1->在红黑树上(监听),0->不在(不监听)
	int events;	//对应的监听事件,	EPOLLIN和EPOLLOUT(不同的事件,走不同的回调函数)
	void *arg;	//指向自己结构体指针
#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;
	
};


struct itemblock {

	struct itemblock *next;
	struct nitem *items;

};

struct reactor {

	int epfd;
	struct itemblock *head; 

};

单例模式,创建reactor的一个实例


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;
}

事件注册





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;	//回调函数
		r->head->items[fd].arg = arg;

		ev.events = EPOLLIN;
	}

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

	
	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, %d\n", 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 failed\n");
			return -1;
		}
		r->head->items[fd].events = event;
	}
	
	return 0;
}

回调函数书写

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: %s\n", 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);
}

监听描述符变化

// accept --> EPOLL

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;
}

完整代码实现

#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

typedef int NCALLBACK(int fd, int event, void *arg);

struct nitem { // fd
	int fd;		//要监听的文件描述符
	int status;	//是否在监听:1->在红黑树上(监听),0->不在(不监听)
	int events;	//对应的监听事件,	EPOLLIN和EPOLLOUT(不同的事件,走不同的回调函数)
	void *arg;	//指向自己结构体指针
#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;
	
};

struct itemblock {
	struct itemblock *next;
	struct nitem *items;
};

struct reactor {
	int epfd;
	struct itemblock *head; 
};

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);

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;
}




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;	//回调函数
		r->head->items[fd].arg = arg;
		ev.events = EPOLLIN;
	}
	ev.data.ptr = &r->head->items[fd];
	
	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, %d\n", 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 failed\n");
			return -1;
		}
		r->head->items[fd].events = event;
	}
	
	return 0;
}



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: %s\n", 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

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;
}

到此这篇关于Reactor原理与实现的文章就介绍到这了,更多相关Reactor原理内容请搜索以前的文章或继续浏览下面的相关文章希望大家以后多多支持!

相关文章