src
├── ae.c  
├── ae.h
├── ae_epoll.c
├── ae_evport.c
├── ae_kqueue.c
└── ae_select.c

/* A simple event-driven programming library. Originally I wrote this code
 * for the Jim's event-loop (Jim is a Tcl interpreter) but later translated
 * it in form of a library for easy reuse.
 */

#ifdef HAVE_EVPORT
#include "ae_evport.c"
#else
    #ifdef HAVE_EPOLL
    #include "ae_epoll.c"
    #else
        #ifdef HAVE_KQUEUE
        #include "ae_kqueue.c"
        #else
        #include "ae_select.c"
        #endif
    #endif
#endif

#ifdef __sun
#include <sys/feature_tests.h>
#ifdef _DTRACE_VERSION
#define HAVE_EVPORT 1
#define HAVE_PSINFO 1
#endif
#endif

#ifdef __linux__
#define HAVE_EPOLL 1
#endif

#if (defined(__APPLE__) && defined(MAC_OS_X_VERSION_10_6)) || defined(__FreeBSD__) || defined(__OpenBSD__) || defined (__NetBSD__)
#define HAVE_KQUEUE 1
#endif

root@ivansli ~# gcc -dM -E - < /dev/null | grep __linux
#define __linux 1
#define __linux__ 1

/* State of an event based program 事件驅動程序的狀態 */
typedefstruct aeEventLoop {
    int maxfd;   /* highest file descriptor currently registered. 當前已注冊的最高文件描述符 */
    int setsize; /* max number of file descriptors tracked. [events/fired數組的大小] */
    longlong timeEventNextId; /* 時間事件的下一個ID */

    /* events/fired 都是數組 */
    /* events 數組，下標含義：為某個fd。fd=>aeFileEvent，即 文件描述符=>文件事件 */
    /* fired 為 io多路復用返回的數組，每一個值為就緒的fd */
    /* 通過 fired 中的 fd 去 events 查找對應的事件信息(事件信息包含conn) */
    aeFileEvent *events; /* Registered events 已注冊事件，數組 */
    aeFiredEvent *fired; /* Fired events 觸發的事件，數組 */

    aeTimeEvent *timeEventHead; /* 時間事件，鏈表 */
    int stop; /* 停止事件循環 */
    void *apidata; /* This is used for polling API specific data. 這用于獲取特定的API數據，aeApiState *state 包含io多路復用fd等字段 */

    aeBeforeSleepProc *beforesleep;
    aeBeforeSleepProc *aftersleep;

    int flags;
} aeEventLoop;

// ae_epoll.c
typedefstruct aeApiState {/* 在 aeApiCreate 中初始化，linux則在 ae_linux.c 文件 */
    int epfd; /* io多路復用fd */
    struct epoll_event *events;/* 就緒的事件數組  */
} aeApiState;

// ae_kqueue.c
typedefstruct aeApiState {
    int kqfd;
    struct kevent *events;

    /* Events mask for merge read and write event.
     * To reduce memory consumption, we use 2 bits to store the mask
     * of an event, so that 1 byte will store the mask of 4 events. */
    char *eventsMask; 
} aeApiState;

// ae_evport.c
typedefstruct aeApiState {
    int     portfd;                             /* event port */
    uint_t  npending;                           /* # of pending fds */
    int     pending_fds[MAX_EVENT_BATCHSZ];     /* pending fds */
    int     pending_masks[MAX_EVENT_BATCHSZ];   /* pending fds' masks */
} aeApiState;

// ae_select.c
typedefstruct aeApiState {
    fd_set rfds, wfds;
    /* We need to have a copy of the fd sets as it's not safe to reuse
     * FD sets after select(). */
    fd_set _rfds, _wfds;
} aeApiState;

aeEventLoop *aeCreateEventLoop(int setsize);
void aeDeleteEventLoop(aeEventLoop *eventLoop);
void aeStop(aeEventLoop *eventLoop);

int aeCreateFileEvent(aeEventLoop *eventLoop, int fd, int mask, aeFileProc *proc, void *clientData);
void aeDeleteFileEvent(aeEventLoop *eventLoop, int fd, int mask);
int aeGetFileEvents(aeEventLoop *eventLoop, int fd);
void *aeGetFileClientData(aeEventLoop *eventLoop, int fd);

long long aeCreateTimeEvent(aeEventLoop *eventLoop, long long milliseconds,
        aeTimeProc *proc, void *clientData, aeEventFinalizerProc *finalizerProc);
int aeDeleteTimeEvent(aeEventLoop *eventLoop, long long id);

int aeProcessEvents(aeEventLoop *eventLoop, int flags);
int aeWait(int fd, int mask, long long milliseconds);

void aeMain(aeEventLoop *eventLoop);

char *aeGetApiName(void);

void aeSetBeforeSleepProc(aeEventLoop *eventLoop, aeBeforeSleepProc *beforesleep);
void aeSetAfterSleepProc(aeEventLoop *eventLoop, aeBeforeSleepProc *aftersleep);

int aeGetSetSize(aeEventLoop *eventLoop);
int aeResizeSetSize(aeEventLoop *eventLoop, int setsize);
void aeSetDontWait(aeEventLoop *eventLoop, int noWait);

int main(){
    lfd = socket(AF_INET,SOCK_STREAM,0); // 創建socket
    bind(lfd, ...); // 綁定IP地址與端口
    listen(lfd, ...); // 監聽
 
    // 創建epoll對象
    efd = epoll_create(...);
    // 把 listen socket 的事件管理起來
    epoll_ctl(efd, EPOLL_CTL_ADD, lfd, ...);
 
    //事件循環
    for (;;) {
        size_t nready = epoll_wait(efd, ep, ...);
  
        for (int i = 0; i < nready; ++i){
            if(ep[i].data.fd == lfd){
                fd = accept(listenfd, ...); //lfd上發生事件表示都連接到達，accept接收它
                epoll_ctl(efd, EPOLL_CTL_ADD, fd, ...);
            }else{
                //其它socket發生的事件都是讀寫請求、或者關閉連接
                ...
            }
        }
    }
}