这篇文章主要介绍“C++中Reactor怎么实现”，在日常操作中，相信很多人在C++中Reactor怎么实现问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”C++中Reactor怎么实现”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
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 { // fdint 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 0NCALLBACK callback;#elseNCALLBACK *readcb; // epollinNCALLBACK *writecb; // epolloutNCALLBACK *acceptcb; // epollin#endifunsigned 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 sizer->epfd = epfd;// fd --> itemr->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) { //singletonif (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};//1if (event == READ_CB) {r->head->items[fd].fd = fd;r->head->items[fd].readcb = cb;r->head->items[fd].arg = arg;ev.events = EPOLLIN;}//2else 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;} //3else 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 qpsint read_callback(int fd, int event, void *arg) {struct reactor *R = getInstance();unsigned char *buffer = R->head->items[fd].rbuffer;#if 0 //ETint 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 {// == 0break;}}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 //LTint ret = recv(fd, buffer, BUFFER_LENGTH, 0);if (ret == 0) { // finnreactor_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 / LTint 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 --> EPOLLint 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_SIZE1024#define BUFFER_LENGTH1024#define MAX_EPOLL_EVENT1024#define NOSET_CB0#define READ_CB1#define WRITE_CB2#define ACCEPT_CB3typedef int NCALLBACK(int fd, int event, void *arg);struct nitem { // fdint 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 0NCALLBACK callback;#elseNCALLBACK *readcb; // epollinNCALLBACK *writecb; // epolloutNCALLBACK *acceptcb; // epollin#endifunsigned 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) { //singletonif (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};//1if (event == READ_CB) {r->head->items[fd].fd = fd;r->head->items[fd].readcb = cb;r->head->items[fd].arg = arg;ev.events = EPOLLIN;}//2else 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;} //3else 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 qpsint read_callback(int fd, int event, void *arg) {struct reactor *R = getInstance();unsigned char *buffer = R->head->items[fd].rbuffer;#if 0 //ETint 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 {// == 0break;}}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 //LTint ret = recv(fd, buffer, BUFFER_LENGTH, 0);if (ret == 0) { // finnreactor_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 / LTint 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 sizer->epfd = epfd;// fd --> itemr->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 --> EPOLLint 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，关于“C++中Reactor怎么实现”的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注编程网网站，小编会继续努力为大家带来更多实用的文章！
