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一、Reactor介紹
reactor設計模式是event-driven architecture的一種實現方式，處理多個客戶端并發的向服務端請求服務的場景。每種服務在服務端可能由多個方法組成。reactor會解耦并發請求的服務并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事件注冊到一個中心I/o多路復用器上，同時主線程/進程阻塞在多路復用器上;一旦有I/o事件到來或是準備就緒(文件描述符或socket可讀、寫)，多路復用器返回并將事先注冊的相應l/o事件分發到對應的處理器中。
處理機制為：主程序將事件以及對應事件處理的方法在Reactor上進行注冊, 如果相應的事件發生，Reactor將會主動調用事件注冊的接口，即 回調函數.
二、代碼實現
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）僅有一個實例，并提供一個訪問它的全局訪問點，該實例被所有程序模塊共享。
2.回調函數：把一段可執行的代碼像參數傳遞那樣傳給其他代碼，而這段代碼會在某個時刻被調用執行，這就叫做回調。
對epoll反應堆中結構體定義
/*fd包含的屬性*/
struct nitem { // fd
int fd; //要監聽的文件描述符
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，走不同的回調函數）
void *arg; //指向自己結構體指針
#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;
};
/*分塊存儲*/
struct itemblock {
struct itemblock *next;
struct nitem *items;
};
/*epoll反應堆中包括通信的fd以及epoll的（epfd）*/
struct reactor {
int epfd;
struct itemblock *head;
};
單例模式，創建reactor的一個實例
/*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;
}
事件注冊
/*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*/
/*驅動注冊*/
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; //回調函數
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, %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;
}
回調函數書寫
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: %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);
}
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;
}
完整代碼實現
#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; //要監聽的文件描述符
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，走不同的回調函數）
void *arg; //指向自己結構體指針
#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;
};
/*分塊存儲*/
struct itemblock {
struct itemblock *next;
struct nitem *items;
};
/*epoll反應堆中包括通信的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*/
/*驅動注冊*/
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; //回調函數
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, %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;
}
/*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: %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
/*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;
}
原文鏈接：https://blog.csdn.net/weixin_52259848/article/details/125354898
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