协程与Epoll的配合

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这几天是端午假期，第一天大算照着网上一大堆基于ucontext来写协程的文章自己也写一个简单的协程实现。于是第一天我就开始动手了，非常轻松愉快，毕竟是抄么。但是很多文章写到怎么用ucontext做切换就戛然而止了，很显然在我们日常协程用的比较多的网络应用中没有人会去做手工的协程切换，这些协程的切换调度其实都被封装在socket接口中，即在协程进行网络操作需要等待时调用yield使得当前协程挂起，在等待的时间到达时调用resume恢复已挂起的协程。这样我们就可以用同步的编程模式写出异步的网络程序。所以我打算把这一步也实现一下，当然这里比起用ucontext来讲还是麻烦一些，在结合epoll实现同步阻塞的read和write时调了一些时间。

在一天之内没有写完，假期么，早点回去看看电影也是应该的，顺便买点饮料饼干准备过夜。手上拿的东西比较多，进出租房的时候，一阵风把还没来得及关上的门‘喷’的一吹，过道里就传来东北房东的喊声。寄人篱下，又是深夜我知道一顿教训是没逃了，结果这逼没玩没了，我就不能忍了，搞得我故意关的，亏我平时进出都小心翼翼的都不是关而是把门‘合’上的。结果自然是我得搬走，毕竟房子是人家的。其实我倒是不太气，因为虽然这离公司不过两百米，但不到6平米的空间还包括了卫生间，这房东又住在出租的套间里，还时不时的抽烟，原来想着合同签了要反悔押金就要损失了。这回倒好，让我走，行，把押金退了就好，这货也答应。所以这个结果不知是双赢还是双输。

端午的第二天我就破天荒的走了2.5万步，奔波找房子，其实我是比较屌丝就是不想花太多钱在房租上，如果肯出个两千房子随便找，一大把。原来还不敢直接打出租房前贴的小广告电话，结果那天一口气打了二三十个，脾气好的没房子也会跟你说一句，脾气差的直接挂电话。这时候想想以前和同学一起租个套间真是好太多了，房东人也不错。

三天假期突然就到第三天了，先把租房的事情放一放，大不了睡公司，房子总是会有的，不就是个钱的问题。这天就用异步和协程切换把socket的同步阻塞读写给实现了一下，并且写了个echo server像是网络编程界的helloworld。好了talk is cheap，shou you the code！(需要使用-std=c++11编译选项)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <ucontext.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <fcntl.h>
#include <errno.h>

#include <map>
#include <list>

#define MAX_ROUTINE 		256
#define MAX_STACK_SIZE_KB 	128
#define MAX_EVENT_SIZE 		10240
enum { UNUSED = 0, IDLE = 1, RUNNING = 2 };

typedef void (*STD_ROUTINE_FUNC)(void);

typedef struct {
	ucontext_t 			ctx;
	char 				stack[ MAX_STACK_SIZE_KB * 1024 ];
	STD_ROUTINE_FUNC 	func;
	int 				status;
	int 				wait_fd;
	int 				events;
} RoutineContext;

typedef std::map<unsigned int, std::list<int> > TimeoutMap;

typedef struct {
	struct epoll_event events[MAX_ROUTINE];
	RoutineContext 	routines[MAX_ROUTINE];
	TimeoutMap		timeout_map;
	ucontext_t		main;
	int 			epoll_fd;
	int 			running_id;
	int 			routine_cnt;
} RoutineCenter; 

RoutineCenter routinecenter;

void init() {
	srand(time(NULL));
	routinecenter.running_id = -1;
}

void routine_wrap() {
	int running_id = routinecenter.running_id;
	if ( running_id < 0 ) {
		puts("current context don't attach to any routine except main.");
		return;
	}
	routinecenter.routines[running_id].func();

	routinecenter.routines[running_id].status = UNUSED;
	routinecenter.routine_cnt--;
}

int create( STD_ROUTINE_FUNC routine_proc) {
	int new_id = -1;
	for (int i = 0; i < MAX_ROUTINE; i++) {
		if ( routinecenter.routines[i].status == UNUSED ) {
			new_id = i;
			break;
		}
	}

	if ( new_id < 0 ) {
		puts("max routine number reached. no more routine.");
		return -1;
	}

	ucontext_t* pctx = &(routinecenter.routines[new_id].ctx);
	getcontext(pctx);

	pctx->uc_stack.ss_sp 	= routinecenter.routines[new_id].stack;
	pctx->uc_stack.ss_size 	= MAX_STACK_SIZE_KB * 1024;
	pctx->uc_stack.ss_flags = 0;
	pctx->uc_link 			= &(routinecenter.main);

	makecontext(pctx, routine_wrap, 0);

	routinecenter.routines[new_id].status 	= IDLE;
	routinecenter.routines[new_id].func 	= routine_proc;
	routinecenter.routine_cnt++;
	return new_id;
}

int yield() {
	if ( routinecenter.running_id < 0 ) {
		puts("no routine running except main.");
		return 0;
	}
	int running_id 			= routinecenter.running_id;
	RoutineContext* info 	= &(routinecenter.routines[running_id]);
	info->status 			= IDLE;
	info->events			= 0;
	swapcontext( &(info->ctx), &(routinecenter.main) );
	return 0;	
}

int resume(int id, int events = 0) {
	if ( id < 0 || id >= MAX_ROUTINE ) {
		puts("routine id out of bound.");
		return -1;
	}
	int running_id          = routinecenter.running_id;
	if (id == running_id) {
		puts("current routine is running already.");
		return 0;
	}
	if (routinecenter.routines[id].status != IDLE) {
		puts("target routine is not in idel status. can't resume");
		return -1;
	}

	routinecenter.running_id 			= id;
	routinecenter.routines[id].status 	= RUNNING;
	routinecenter.routines[id].events 	= events;
	if (running_id < 0) {
		// in main
		swapcontext( &(routinecenter.main), &(routinecenter.routines[id].ctx));
		routinecenter.running_id = -1;
	} else {
		// in other routine
		routinecenter.routines[running_id].status = IDLE;
		swapcontext( &(routinecenter.routines[running_id].ctx), &(routinecenter.routines[id].ctx) );
		routinecenter.running_id = running_id;
	}
	return 0;
}

int routine_id() { return routinecenter.running_id; }

void set_nonblocking(int fd) {
	int flags = fcntl(fd, F_GETFL, 0);
	int ret = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
	if (ret < 0) {
		perror("set nonblocking fail.");
		exit(-1);
	}
}

void mod_event(int fd, int events, int op, int routine_id) {
	struct epoll_event ev = {0};
	if ( EPOLL_CTL_DEL != op ) {
		ev.data.fd= routine_id;
		routinecenter.routines[routine_id].wait_fd = fd;
	}
	ev.events = events;

	int ret = epoll_ctl(routinecenter.epoll_fd, op, fd, &ev);
	if (ret < 0) {
		if ( errno == EEXIST && op != EPOLL_CTL_DEL) {
			epoll_ctl(routinecenter.epoll_fd, EPOLL_CTL_MOD, fd, &ev);
		}
	}
}

int routine_read(int fd, char* buff, int size) {
	mod_event(fd, EPOLLIN, EPOLL_CTL_ADD, routine_id());
	while (!(routinecenter.routines[routine_id()].events & EPOLLIN)) {
		yield();	
	}
	while (routinecenter.routines[routine_id()].events & EPOLLIN) {
		int need 	= size;
		int readin 	= 0;
		while (need > 0) {
			int ret = read(fd, buff + readin, need);
			if (ret <= 0) {
				break;
			} else {
				readin += ret;
				need -= ret;
			}
		}
		if (readin == 0 && size != 0) {
			yield();
			continue;
		} else {
			mod_event(fd, EPOLLIN, EPOLL_CTL_DEL, routine_id());
		}
		return readin;
	} 
	printf("routine[%d][%s]routine system ran out of order.
", routine_id(), __func__);
	return 0;
}

int routine_write(int fd, char* buff, int size) {
	mod_event(fd, EPOLLOUT, EPOLL_CTL_ADD, routine_id());
	while (!(routinecenter.routines[routine_id()].events & EPOLLOUT)) {
		yield();	
	}
	while (routinecenter.routines[routine_id()].events & EPOLLOUT) {
		int need 	= size;
		int wrout 	= 0;
		while (need > 0) {
			int ret = write(fd, buff + wrout, need);
			if (ret <= 0) {
				break;
			} else {
				wrout += ret;
				need -= ret;
			}
		}
		if ( wrout == 0 && size != 0 ) {
			yield();	
			continue;
		} else {
			mod_event(fd, EPOLLOUT, EPOLL_CTL_DEL, routine_id());
		}
		return wrout;
	}
	printf("routine[%d][%s]routine system ran out of order.
", routine_id(), __func__);
	return 0;
}

void routine_delay_resume(int rid, int delay_sec) {
	if (delay_sec <= 0) {
		resume(rid);
		return;
	}
	routinecenter.timeout_map[time(NULL) + delay_sec].push_back(rid);
}

void routine_sleep(int time_sec) {
	routine_delay_resume(routine_id(), time_sec);
	yield();
}

int routine_nearest_timeout() {
	if (routinecenter.timeout_map.empty()) {
		return 60 * 1000; // default epoll timeout
	}
	unsigned int now 	= time(NULL);
	int diff			= routinecenter.timeout_map.begin()->first - now;
	return diff < 0 ? 0 : diff * 1000;
}

void routine_resume_timeout() {
	// printf("[epoll] process timeout
");
	if ( routinecenter.timeout_map.empty() ) {
		return;
	}
	unsigned int timestamp 		= routinecenter.timeout_map.begin()->first;

	if (timestamp > time(NULL)) {
		return;
	}

	std::list<int>& routine_ids = routinecenter.timeout_map.begin()->second;

	for (int i : routine_ids) {
		resume(i);
	}
	routinecenter.timeout_map.erase(timestamp);
}

void routine_resume_event(int n) {
	// printf("[epoll] process event
");
	for (int i = 0; i < n; i++) {
		int rid = routinecenter.events[i].data.fd;
		resume(rid, routinecenter.events[i].events);
	 }
}

void create_routine_poll() {
	routinecenter.epoll_fd = epoll_create1 (0);	

	if (routinecenter.epoll_fd == -1) {
		perror ("epoll_create");
		exit(-1);
	}
}

void routine_poll() {

	for (;;) {
		int n = epoll_wait (routinecenter.epoll_fd, routinecenter.events, MAX_EVENT_SIZE, routine_nearest_timeout());
		// printf("[epoll] event_num:%d
", n);
		routine_resume_timeout();
		routine_resume_event(n);
	}
}

void echo_server_routine() {
	int conn_fd = routinecenter.routines[routine_id()].wait_fd;
	
	printf("routine[%d][%s] server start. conn_fd: %d
", routine_id(), __func__, conn_fd);

	for (;;) {
		printf("routine[%d][%s] loop start. conn_fd: %d
", routine_id(), __func__, conn_fd);
		char buf[512] = {0};
		int n 		= 0;
		
		n = routine_read( conn_fd, buf, sizeof (buf) );
		if (n < 0) {
			perror("server read error.");
			break;
		}
		buf[n] = '';
		printf("routine[%d][%s] server read: %s", routine_id(), __func__, buf);

		unsigned int in_ts = time(NULL);
		routine_sleep(1);
		unsigned int out_ts= time(NULL);

		char obuf[512] = {0};
		snprintf(obuf, sizeof(obuf), "%s rev_ts:%u sent_ts:%u
", buf, in_ts, out_ts);
		printf("routine[%d][%s] server write: %s", routine_id(), __func__, obuf);

		n = routine_write(conn_fd, obuf, strlen(obuf) + 1);
		if (n < 0) {
			perror("server write error.");
			break;
		}
	}
	printf("routine[%d][%s] server start. conn_fd: %d
", routine_id(), __func__, conn_fd);
}

void request_accept() {
	for (;;) {
		struct sockaddr_in addr 	= {0};
		socklen_t			slen 	= sizeof(addr);
		int fd = accept(routinecenter.routines[routine_id()].wait_fd, (struct sockaddr*)&addr, &slen);
		struct sockaddr_in peer = {0};
		int ret = getpeername(fd, (struct sockaddr*)&peer, &slen);
		if (ret < 0) {
			perror("getpeername error.");
			exit(-1);
		}
		printf("routine[%d][%s] accept from %s conn_fd:%d
", routine_id(), __func__, inet_ntoa(peer.sin_addr), fd);
		set_nonblocking(fd);
		int rid = create( echo_server_routine );
		routinecenter.routines[rid].wait_fd = fd;

		mod_event(fd, EPOLLIN, EPOLL_CTL_ADD, rid);

		resume(rid);

		yield();
	}
}

void bind_listen(unsigned short port) {
	int listen_fd 			= socket(AF_INET, SOCK_STREAM, 0);
	struct sockaddr_in addr = {0};
	addr.sin_family 		= AF_INET;
	addr.sin_port			= htons(port);
	addr.sin_addr.s_addr	= INADDR_ANY;
	int ret = bind( listen_fd, (struct sockaddr*)&addr, sizeof(struct sockaddr) );
	if (ret < 0) {
		perror("bind fail.");
		exit(-1);
	}
	ret = listen( listen_fd, 20 );
	if (ret < 0) {
		perror("listen fail.");
		exit(-1);
	}
	printf("routine[%d] listen bind at port: %u
", routine_id(), port);
	set_nonblocking( listen_fd );
	int rid = create( request_accept );
	mod_event( listen_fd, EPOLLIN, EPOLL_CTL_ADD, rid );
}

int main() {
	init();

	create_routine_poll();

	bind_listen(55667);
	bind_listen(55668);
	bind_listen(55669);

	routine_delay_resume(create( [](){ printf("routine[%d] alarm fired
", routine_id()); } ), 3);

	routine_poll();

	puts("all routine exit");

	return 0;
}