#include <netinet/in.h>     // for socketaddr_in
#include <sys/socket.h>     // for socket functions
#include <netdb.h>          // for gethostbyname
#include <sys/errno.h>      // for errno

#include <unistd.h>
#include <string.h>
#include <stdio.h>

int main(int argc, char ** argv)
{
    const char query[] = "GET / HTTP/1.0\r\n"
                         "Host: www.baidu.com\r\n"
                         "\r\n";
    const char hostname[] = "www.baidu.com";

    struct sockaddr_in sin;
    struct hostent * h;
    const char * cp;
    int fd;
    ssize_t n_written, remaining;

    char buf[4096];

    /*
     * Look up the IP address for the hostname.
     * Watch out; this isn‘t threadsafe on most platforms.
     */
    h = gethostbyname(hostname);

    if(!h)
    {
        fprintf(stderr, "E: gethostbyname(%s) failed. ErrMsg: %s\n", hostname, hstrerror(h_errno));
        return -__LINE__;
    }

    if(h->h_addrtype != AF_INET)
    {
        fprintf(stderr, "E: gethostbyname(%s) returned an non AF_INET address.\n", hostname);
        return -__LINE__;
    }

    /*
     * Allocate a new socket
     */
    fd = socket(AF_INET, SOCK_STREAM, 0);
    if(fd < 0)
    {
        fprintf(stderr, "E: socket failed: %s\n", strerror(errno));
        return -__LINE__;
    }

    /*
     * Connect to the remote host
     */
    sin.sin_family = AF_INET;
    sin.sin_port = htons(80);
    sin.sin_addr = *((struct in_addr *)(h->h_addr));
    if(connect(fd, (struct sockaddr *)(&sin), sizeof(sin)) != 0)
    {
        fprintf(stderr, "E: connect to %s failed: %s\n", hostname, strerror(errno));
        close(fd);
        return -__LINE__;
    }

    /*
     * Write the query
     * XXX Can send succeed partially?
     */
    cp = query;
    remaining = strlen(query);
    while(remaining)
    {
        n_written = send(fd, cp, remaining, 0);
        if(n_written < 0)
        {
            fprintf(stderr, "E: send failed: %s\n", strerror(errno));
            close(fd);
            return -__LINE__;
        }

        remaining -= n_written;
        cp += n_written;
    }

    /*
     * Get an answer back
     */
    while(1)
    {
        ssize_t result = recv(fd, buf, sizeof(buf), 0);
        if(result == 0)
        {
            break;
        }
        else if(result < 0)
        {
            fprintf(stderr, "recv failed: %s\n", strerror(errno));
            close(fd);
            return -__LINE__;
        }

        fwrite(buf, 1, result, stdout);
    }

    close(fd);

    return 0;
}

char buf[4096];
int i, n;
while(i_still_want_to_read())
{
    for(i = 0; i < n_sockets; ++i)
    {
        n = recv(fd[i], buf, sizeof(buf), 0);

        if(n == 0)
        {
            handle_close(fd[i]);
        }
        else if(n < 0)
        {
            handle_error(fd[i], errno);
        }
        else
        {
            handle_input(fd[i], buf, n);
        }
    }
}

#include <netinet/in.h>     // for sockaddr_in
#include <sys/socket.h>     // for socket functions
#include <sys/errno.h>      // for errno

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

#define MAX_LINE 16384

char rot13_char(char c)
{
    if(
        (c >= ‘a‘ && c <= ‘m‘) ||
        (c >= ‘A‘ && c <= ‘M‘)
    )
    {
        return c+13;
    }
    else if(
        (c >= ‘n‘ && c <= ‘z‘) ||
        (c >= ‘N‘ && c <= ‘Z‘)
    )
    {
        return c-13;
    }
    else
    {
        return c;
    }
}

void child(int fd)
{
    char outbuf[MAX_LINE + 1];  // extra byte for ‘\0‘
    size_t outbuf_used = 0;
    ssize_t result;

    while(1)
    {
        char ch;
        result = recv(fd, &ch, 1, 0);

        if(result == 0)
        {
            break;
        }
        else if(result == -1)
        {
            perror("read");
            break;
        }

        if(outbuf_used < sizeof(outbuf))
        {
            outbuf[outbuf_used++] = rot13_char(ch);
        }

        if(ch == ‘\n‘)
        {
            send(fd, outbuf, outbuf_used, 0);
            outbuf_used = 0;
            continue;
        }
    }
}

void run(void)
{
    int listener;
    struct sockaddr_in sin;

    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = 0;
    sin.sin_port = htons(40713);

    listener = socket(AF_INET, SOCK_STREAM, 0);

    int one = 1;
    setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));

    if(bind(listener, (struct sockaddr *)(&sin), sizeof(sin)) < 0)
    {
        perror("bind");
        return;
    }

    if(listen(listener, 16) < 0)
    {
        perror("listen");
        return;
    }

    while(1)
    {
        struct sockaddr_storage ss;
        socklen_t slen = sizeof(ss);
        int fd = accept(listener, (struct sockaddr *)(&ss), &slen);

        if(fd < 0)
        {
            perror("accept");
        }
        else
        {
            if(fork() == 0)
            {
                child(fd);
                exit(0);
            }
        }
    }
}

int main(int argc, char ** argv)
{
    run();
    return 0;
}

printf "abcdefghijklmnopqrstuvwxyz\n" | nc -4 -w1 localhost 40713

fcntl(fd, F_SETFL, O_NONBLOCK);

int i, n;
char buf[1024];

for(i = 0; i < n_sockets; ++i)
{
    fcntl(fd[i], F_SETFL, O_NONBLOCK);
}

while(i_still_want_to_read)
{
    for(int i = 0; i < n_sockets; ++i)
    {
        n = recv(fd[i], buf, sizeof(buf), 0);
        if(n == 0)
        {
            handle_close(fd[i]);        // peer was closed
        }
        else if(n < 0)
        {
            if(errno == EAGAIN)
            {
                // do nothing, the kernel didn‘t have any data for us to read
                // retry
            }
            else
            {
                handle_error(fd[i], errno);
            }
        }
        else
        {
            handle_input(fd[i], buf, n);    // read success
        }
    }
}

fd_set readset;
int i, n;
char buf[1024];

while(i_still_want_to_read)
{
    int maxfd = -1;
    FD_ZERO(&readset);

    // add all of the interesting fds to readset
    for(i = 0; i < n_sockets; ++i)
    {
        if(fd[i] > maxfd)
        {
            maxfd = fd[i];
        }

        FD_SET(fd[i], &readset):
    }

    select(maxfd+1, &readset, NULL, NULL, NULL);

    for(int i = 0; i < n_sockets; ++i)
    {
        if(FDD_ISSET(fd[i], &readset))
        {
            n = recv(fd[i], &readset);

            if(n == 0)
            {
                handle_close(fd[i]);
            }
            else if(n < 0)
            {
                if(errno == EAGAIN)
                {
                    // the kernel didn‘t have any data for us to read
                }
                else
                {
                    handle_error(fd[i], errno);
                }
            }
            else
            {
                handle_input(fd[i], buf, n);
            }
        }
    }
}

#include <netinet/in.h>     // for sockaddr_in
#include <sys/socket.h>     // for socket functions
#include <sys/errno.h>      // for errno
#include <fcntl.h>          // for fcntl
#include <sys/select.h>     // for select

#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

#define MAX_LINE 16384

char rot13_char(char c)
{
    if(
        (c >= ‘a‘ && c <= ‘m‘) ||
        (c >= ‘A‘ && c <= ‘M‘)
    )
    {
        return c+13;
    }
    else if(
        (c >= ‘n‘ && c <= ‘z‘) ||
        (c >= ‘N‘ && c <= ‘Z‘)
    )
    {
        return c-13;
    }
    else
    {
        return c;
    }
}

struct fd_state{
    char buffer[MAX_LINE];
    size_t buffer_used;

    int writing;
    size_t n_written;
    size_t write_upto;
};

struct fd_state * alloc_fd_state(void)
{
    struct fd_state * state = malloc(sizeof(struct fd_state));
    if(!state)
    {
        return NULL;
    }
    
    state->buffer_used = state->n_written = state->writing = state->write_upto = 0;
    return state;
}

void free_fd_state(struct fd_state * state)
{
    free(state);
}

void make_nonblocking(int fd)
{
    fcntl(fd, F_SETFL, O_NONBLOCK);
}

int do_read(int fd, struct fd_state * state)
{
    char buf[1024];
    int i;
    ssize_t result;

    while(1)
    {
        result = recv(fd, buf, sizeof(buf), 0);

        if(result <= 0)
        {
            break;
        }

        for(int i = 0; i < result; ++i)
        {
            if(state->buffer_used < sizeof(state->buffer))
            {
                state->buffer[state->buffer_used++] = rot13_char(buf[i]);
            }

            if(buf[i] == ‘\n‘)
            {
                state->writing = 1;
                state->write_upto = state->buffer_used;
            }
        }
    }

    if(result == 0)
    {
        return 1;
    }
    else if(result < 0)
    {
        if(errno == EAGAIN)
        {
            return 0;
        }

        return -1;
    }

    return 0;
}

int do_write(int fd, struct fd_state * state)
{
    while(state->n_written < state->write_upto)
    {
        ssize_t result = send(fd, state->buffer + state->n_written, state->write_upto - state->n_written, 0);

        if(result < 0)
        {
            if(errno == EAGAIN)
            {
                return 0;
            }

            return -1;
        }

        assert(result != 0);

        state->n_written += result;
    }

    if(state->n_written == state->buffer_used)
    {
        state->n_written = state->write_upto = state->buffer_used = 0;
    }

    state->writing = 0;

    return 0;
}

void run(void)
{
    int listener;
    struct fd_state * state[FD_SETSIZE];
    struct sockaddr_in sin;
    int i, maxfd;
    fd_set readset, writeset, exset;

    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = 0;
    sin.sin_port = htons(40713);
    
    for(i = 0; i < FD_SETSIZE; ++i)
    {
        state[i] = NULL;
    }

    listener = socket(AF_INET, SOCK_STREAM, 0);
    make_nonblocking(listener);

    int one = 1;
    setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));

    if(bind(listener, (struct sockaddr *)(&sin), sizeof(sin)) < 0)
    {
        perror("bind");
        return;
    }

    if(listen(listener, 16) < 0)
    {
        perror("listen");
        return;
    }

    FD_ZERO(&readset);
    FD_ZERO(&writeset);
    FD_ZERO(&exset);

    while(1)
    {
        maxfd = listener;

        FD_ZERO(&readset);
        FD_ZERO(&writeset);
        FD_ZERO(&exset);

        FD_SET(listener, &readset);

        for(i = 0; i < FD_SETSIZE; ++i)
        {
            if(state[i])
            {
                if(i > maxfd)
                {
                    maxfd = i;
                }

                FD_SET(i, &readset);

                if(state[i]->writing)
                {
                    FD_SET(i, &writeset);
                }
            }
        }

        if(select(maxfd + 1, &readset, &writeset, &exset, NULL) < 0)
        {
            perror("select");
            return;
        }

        if(FD_ISSET(listener, &readset))
        {
            struct sockaddr_storage ss;
            socklen_t slen = sizeof(ss);

            int fd = accept(listener, (struct sockaddr *)(&ss), &slen);

            if(fd < 0)
            {
                perror("accept");
            }
            else if(fd > FD_SETSIZE)
            {
                close(fd);
            }
            else
            {
                make_nonblocking(fd);
                state[fd] = alloc_fd_state();
                assert(state[fd]);
            }
        }

        for(i = 0; i < maxfd + 1; ++i)
        {
            int r = 0;

            if(i == listener)
            {
                continue;
            }

            if(FD_ISSET(i, &readset))
            {
                r = do_read(i, state[i]);
            }

            if(r == 0 && FD_ISSET(i, &writeset))
            {
                r = do_write(i, state[i]);
            }

            if(r)
            {
                free_fd_state(state[i]);
                state[i] = NULL;
                close(i);
            }
        }
    }
}

int main(int argc, char ** argv)
{
    setvbuf(stdout, NULL, _IONBF, 0);

    run();

    return 0;
}

/* For sockaddr_in */
#include <netinet/in.h>
/* For socket functions */
#include <sys/socket.h>
/* For fcntl */
#include <fcntl.h>

#include <event2/event.h>

#include <assert.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

#define MAX_LINE 16384

void do_read(evutil_socket_t fd, short events, void *arg);
void do_write(evutil_socket_t fd, short events, void *arg);

char
rot13_char(char c)
{
    /* We don‘t want to use isalpha here; setting the locale would change
     * which characters are considered alphabetical. */
    if ((c >= ‘a‘ && c <= ‘m‘) || (c >= ‘A‘ && c <= ‘M‘))
        return c + 13;
    else if ((c >= ‘n‘ && c <= ‘z‘) || (c >= ‘N‘ && c <= ‘Z‘))
        return c - 13;
    else
        return c;
}

struct fd_state {
    char buffer[MAX_LINE];
    size_t buffer_used;

    size_t n_written;
    size_t write_upto;

    struct event *read_event;
    struct event *write_event;
};

struct fd_state *
alloc_fd_state(struct event_base *base, evutil_socket_t fd)
{
    struct fd_state *state = malloc(sizeof(struct fd_state));
    if (!state)
        return NULL;
    state->read_event = event_new(base, fd, EV_READ|EV_PERSIST, do_read, state);
    if (!state->read_event) {
        free(state);
        return NULL;
    }
    state->write_event =
        event_new(base, fd, EV_WRITE|EV_PERSIST, do_write, state);

    if (!state->write_event) {
        event_free(state->read_event);
        free(state);
        return NULL;
    }

    state->buffer_used = state->n_written = state->write_upto = 0;

    assert(state->write_event);
    return state;
}

void
free_fd_state(struct fd_state *state)
{
    event_free(state->read_event);
    event_free(state->write_event);
    free(state);
}

void
do_read(evutil_socket_t fd, short events, void *arg)
{
    struct fd_state *state = arg;
    char buf[1024];
    int i;
    ssize_t result;
    while (1) {
        assert(state->write_event);
        result = recv(fd, buf, sizeof(buf), 0);
        if (result <= 0)
            break;

        for (i=0; i < result; ++i)  {
            if (state->buffer_used < sizeof(state->buffer))
                state->buffer[state->buffer_used++] = rot13_char(buf[i]);
            if (buf[i] == ‘\n‘) {
                assert(state->write_event);
                event_add(state->write_event, NULL);
                state->write_upto = state->buffer_used;
            }
        }
    }

    if (result == 0) {
        free_fd_state(state);
    } else if (result < 0) {
        if (errno == EAGAIN) // XXXX use evutil macro
            return;
        perror("recv");
        free_fd_state(state);
    }
}

void
do_write(evutil_socket_t fd, short events, void *arg)
{
    struct fd_state *state = arg;

    while (state->n_written < state->write_upto) {
        ssize_t result = send(fd, state->buffer + state->n_written,
                              state->write_upto - state->n_written, 0);
        if (result < 0) {
            if (errno == EAGAIN) // XXX use evutil macro
                return;
            free_fd_state(state);
            return;
        }
        assert(result != 0);

        state->n_written += result;
    }

    if (state->n_written == state->buffer_used)
        state->n_written = state->write_upto = state->buffer_used = 1;

    event_del(state->write_event);
}

void
do_accept(evutil_socket_t listener, short event, void *arg)
{
    struct event_base *base = arg;
    struct sockaddr_storage ss;
    socklen_t slen = sizeof(ss);
    int fd = accept(listener, (struct sockaddr*)&ss, &slen);
    if (fd < 0) { // XXXX eagain??
        perror("accept");
    } else if (fd > FD_SETSIZE) {
        close(fd); // XXX replace all closes with EVUTIL_CLOSESOCKET */
    } else {
        struct fd_state *state;
        evutil_make_socket_nonblocking(fd);
        state = alloc_fd_state(base, fd);
        assert(state); /*XXX err*/
        assert(state->write_event);
        event_add(state->read_event, NULL);
    }
}

void
run(void)
{
    evutil_socket_t listener;
    struct sockaddr_in sin;
    struct event_base *base;
    struct event *listener_event;

    base = event_base_new();
    if (!base)
        return; /*XXXerr*/

    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = 0;
    sin.sin_port = htons(40713);

    listener = socket(AF_INET, SOCK_STREAM, 0);
    evutil_make_socket_nonblocking(listener);

#ifndef WIN32
    {
        int one = 1;
        setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
    }
#endif

    if (bind(listener, (struct sockaddr*)&sin, sizeof(sin)) < 0) {
        perror("bind");
        return;
    }

    if (listen(listener, 16)<0) {
        perror("listen");
        return;
    }

    listener_event = event_new(base, listener, EV_READ|EV_PERSIST, do_accept, (void*)base);
    /*XXX check it */
    event_add(listener_event, NULL);

    event_base_dispatch(base);
}

int
main(int c, char **v)
{
    setvbuf(stdout, NULL, _IONBF, 0);

    run();
    return 0;
}

/* For sockaddr_in */
#include <netinet/in.h>
/* For socket functions */
#include <sys/socket.h>
/* For fcntl */
#include <fcntl.h>

#include <event2/event.h>
#include <event2/buffer.h>
#include <event2/bufferevent.h>

#include <assert.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

#define MAX_LINE 16384

void do_read(evutil_socket_t fd, short events, void *arg);
void do_write(evutil_socket_t fd, short events, void *arg);

char
rot13_char(char c)
{
    /* We don‘t want to use isalpha here; setting the locale would change
     * which characters are considered alphabetical. */
    if ((c >= ‘a‘ && c <= ‘m‘) || (c >= ‘A‘ && c <= ‘M‘))
        return c + 13;
    else if ((c >= ‘n‘ && c <= ‘z‘) || (c >= ‘N‘ && c <= ‘Z‘))
        return c - 13;
    else
        return c;
}

void
readcb(struct bufferevent *bev, void *ctx)
{
    struct evbuffer *input, *output;
    char *line;
    size_t n;
    int i;
    input = bufferevent_get_input(bev);
    output = bufferevent_get_output(bev);

    while ((line = evbuffer_readln(input, &n, EVBUFFER_EOL_LF))) {
        for (i = 0; i < n; ++i)
            line[i] = rot13_char(line[i]);
        evbuffer_add(output, line, n);
        evbuffer_add(output, "\n", 1);
        free(line);
    }

    if (evbuffer_get_length(input) >= MAX_LINE) {
        /* Too long; just process what there is and go on so that the buffer
         * doesn‘t grow infinitely long. */
        char buf[1024];
        while (evbuffer_get_length(input)) {
            int n = evbuffer_remove(input, buf, sizeof(buf));
            for (i = 0; i < n; ++i)
                buf[i] = rot13_char(buf[i]);
            evbuffer_add(output, buf, n);
        }
        evbuffer_add(output, "\n", 1);
    }
}

void
errorcb(struct bufferevent *bev, short error, void *ctx)
{
    if (error & BEV_EVENT_EOF) {
        /* connection has been closed, do any clean up here */
        /* ... */
    } else if (error & BEV_EVENT_ERROR) {
        /* check errno to see what error occurred */
        /* ... */
    } else if (error & BEV_EVENT_TIMEOUT) {
        /* must be a timeout event handle, handle it */
        /* ... */
    }
    bufferevent_free(bev);
}

void
do_accept(evutil_socket_t listener, short event, void *arg)
{
    struct event_base *base = arg;
    struct sockaddr_storage ss;
    socklen_t slen = sizeof(ss);
    int fd = accept(listener, (struct sockaddr*)&ss, &slen);
    if (fd < 0) {
        perror("accept");
    } else if (fd > FD_SETSIZE) {
        close(fd);
    } else {
        struct bufferevent *bev;
        evutil_make_socket_nonblocking(fd);
        bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
        bufferevent_setcb(bev, readcb, NULL, errorcb, NULL);
        bufferevent_setwatermark(bev, EV_READ, 0, MAX_LINE);
        bufferevent_enable(bev, EV_READ|EV_WRITE);
    }
}

void
run(void)
{
    evutil_socket_t listener;
    struct sockaddr_in sin;
    struct event_base *base;
    struct event *listener_event;

    base = event_base_new();
    if (!base)
        return; /*XXXerr*/

    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = 0;
    sin.sin_port = htons(40713);

    listener = socket(AF_INET, SOCK_STREAM, 0);
    evutil_make_socket_nonblocking(listener);

#ifndef WIN32
    {
        int one = 1;
        setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
    }
#endif

    if (bind(listener, (struct sockaddr*)&sin, sizeof(sin)) < 0) {
        perror("bind");
        return;
    }

    if (listen(listener, 16)<0) {
        perror("listen");
        return;
    }

    listener_event = event_new(base, listener, EV_READ|EV_PERSIST, do_accept, (void*)base);
    /*XXX check it */
    event_add(listener_event, NULL);

    event_base_dispatch(base);
}

int
main(int c, char ** argv)
{
    setvbuf(stdout, NULL, _IONBF, 0);

    run();
    return 0;
}

#include <event2/xxxx>
#include <event2/xxxx>
#include <event2/xxxx>
#include <event2/xxxx>

// 以下是日志级别
#define EVENT_LOG_DEBUG 0
#define EVENT_LOG_MSG   1
#define EVENT_LOG_WARN  2
#define EVENT_LOG_ERR   3

// 以下是已经被废弃的日志级别定义
/* Deprecated; see note at the end of this section */
#define _EVENT_LOG_DEBUG EVENT_LOG_DEBUG
#define _EVENT_LOG_MSG   EVENT_LOG_MSG
#define _EVENT_LOG_WARN  EVENT_LOG_WARN
#define _EVENT_LOG_ERR   EVENT_LOG_ERR

// 这个是一个函数指针类型别名, 指向日志输出函数
// 日志输出函数应当是一个双参, 无返回值的函数, 第一个参数severity为日志级别, 第二个参数为日志字符串
typedef void (*event_log_cb)(int severity, const char *msg);

// 这是用户自定义设置日志处理函数的接口. 如果调用该函数时入参设置为NULL
// 则将采用默认行为
void event_set_log_callback(event_log_cb cb);

#include <event2/event.h>
#include <stdio.h>

// 丢弃日志
static void discard_cb(int severity, const char * msg)
{
    // 这个日志函数内部什么也不做
}

// 将日志记录至文件
static FILE * logfile = NULL;
static void write_to_file_cb(int severity, const char * msg)
{
    const char * s;
    if(!logfile)
    {
        return;
    }

    switch(severity)
    {
        case EVENT_LOG_DEBUG:   s = "[DBG]";    break;
        case EVENT_LOG_MSG:     s = "[MSG]";    break;
        case EVENT_LOG_WARN:    s = "[WRN]";    break;
        case EVENT_LOG_ERR:     s = "[ERR]";    break;
        default:                s = "[???]";    break;
    }

    fprintf(logfile, "[%s][%s][%s] %s\n", __FILE__, __func__, s, msg);
}

void suppress_logging(void)
{
    event_set_log_callback(discard_cb);
}

void set_logfile(FILE * f)
{
    logfile = f;
    event_set_log_callback(write_to_file_cb);
}

#define EVENT_DBG_NONE 0
#define EVENT_DBG_ALL 0xffffffffu

// 如果传入 EVENT_DBG_NONE, 将保持默认状态: 不输出调试日志
// 如果传入 EVENT_DEG_ALL, 将开启调试日志的输出
void event_enable_debug_logging(ev_uint32_t which);

typedef void (*event_fatal_cb)(int err);
void event_set_fatal_callback(event_fatal_cb cb);

void event_set_mem_functions(void *(*malloc_fn)(size_t sz),
                             void *(*realloc_fn)(void *ptr, size_t sz),
                             void (*free_fn)(void *ptr));

#include <event2/event.h>
#include <sys/types.h>
#include <stdlib.h>

union alignment
{
    size_t sz;
    void * ptr;
    double dbl;
};

#define ALIGNMENT sizeof(union alignment)

#define OUTPTR(ptr)     (((char *)ptr) + ALIGNMENT)
#define INPTR(ptr)      (((char *)ptr) - ALIGNMENT)

static size_t total_allocated = 0;

static void * my_malloc(size_t sz)
{
    void * chunk = malloc(sz + ALIGNMENT);
    if(!chunk)  return chunk;

    total_allocated += sz;

    *(size_t *)chunk = sz;

    return OUTPTR(chunk);
}

static void * my_realloc(void * ptr, size_t sz)
{
    size_t old_size = 0;

    if(ptr)
    {
        ptr = INPTR(ptr);
        old_size = *(size_t*)ptr;
    }

    ptr = realloc(ptr, sz + ALIGNMENT);

    if(!ptr)
    {
        return NULL;
    }

    *(size_t *)ptr = sz;

    total_allocated = total_allocated - old_size + sz;

    return OUTPTR(ptr);
}

static void my_free(void * ptr)
{
    ptr = INPTR(ptr);
    total_allocated -= *(size_t *)ptr;
    free(ptr);
}

void start_counting_bytes(void)
{
    event_set_mem_functions(
        my_malloc, my_realloc, my_free
    );
}

#ifdef WIN32
int evthread_use_windows_threads(void);
#define EVTHREAD_USE_WINDOWS_THREADS_IMPLEMENTED
#endif

#ifdef _EVENT_HAVE_PTHREADS
int evthread_use_pthreads();
#define EVTHREAD_USE_PTHREADS_IMPLEMENTED
#endif

// 锁模式是 lock 与 unlock 函数的参数, 它指定了加锁解锁时的一些额外信息
// 如果调用 lock 或 unlock 时的锁都不满足下面的三种模式, 参数传0即可
#define EVTHREAD_WRITE  0x04        // 锁模式: 仅对读写锁使用: 获取或释放写锁
#define EVTHREAD_READ   0x08        // 锁模式: 仅对读写锁使用: 获取或释放读锁
#define EVTHREAD_TRY    0x10        // 锁模式: 仅在加锁时使用: 仅在可以立即加锁的时候才去加锁. 
                                    //         若当前不可加锁, 则lock函数立即返回失败, 而不是阻塞

// 锁类型是 alloc 与 free 函数的参数, 它指定了创建与销毁的锁的类型
// 锁类型可以是 EVTHREAD_LOCKTYPE_XXX 之一或者为0
// 所有支持的锁类型均需要被登记在 supported_locktypes 中, 如果支持多种锁, 则多个宏之间用 | 连结构成该字段的值
                                            // 当锁类型为0时, 指的是普通的, 非递归锁
#define EVTHREAD_LOCKTYPE_RECURSIVE 1       // 锁类型: 递归锁, 你必须提供一种递归锁给libevent使用
#define EVTHREAD_LOCKTYPE_READWRITE 2       // 锁类型: 读写锁, 在2.0.4版本之前, libevent内部没有使用到读写锁

#define EVTHREAD_LOCK_API_VERSION 1

// 将你要用的有关锁的所有信息放在这个结构里
struct evthread_lock_callbacks {
       int lock_api_version;                // 必须与宏 EVTHREAD_LOCK_API_VERSION的值一致
       unsigned supported_locktypes;        // 必须是宏 EVTHREAD_LOCKTYPE_XXX 的或组合, 或为0
       void *(*alloc)(unsigned locktype);               // 锁分配, 需要指定锁类型
       void (*free)(void *lock, unsigned locktype);     // 锁销毁, 需要指定锁类型
       int (*lock)(unsigned mode, void *lock);          // 加锁, 需要指定锁模式
       int (*unlock)(unsigned mode, void *lock);        // 解锁, 需要指定锁模式
};

// 调用该函数以设置相关锁函数
int evthread_set_lock_callbacks(const struct evthread_lock_callbacks *);

// 调该函数以设置线程ID检测函数
void evthread_set_id_callback(unsigned long (*id_fn)(void));

// 将你要用的有关条件变量的所有信息都放在这个结构里
struct evthread_condition_callbacks {
        int condition_api_version;
        void *(*alloc_condition)(unsigned condtype);
        void (*free_condition)(void *cond);
        int (*signal_condition)(void *cond, int broadcast);
        int (*wait_condition)(void *cond, void *lock,
            const struct timeval *timeout);
};

// 通过该函数以设置相关的条件变量函数
int evthread_set_condition_callbacks(
        const struct evthread_condition_callbacks *);

void evthread_enable_lock_debugging(void);
#define evthread_enable_lock_debuging() evthread_enable_lock_debugging()

void event_enable_debug_mode(void);

void event_debug_unassign(struct event * ev);

#include <event2/event.h>
#include <event2/event_struct.h>

#include <stdlib.h>

void cb(evutil_socket_t fd, short what, void *ptr)
{
    struct event *ev = ptr;

    if (ev)     // 通过判断入参是否为NULL, 来确认入参携带的事件实例是event_new来的还是event_assign来的
        event_debug_unassign(ev); // 如果是event_assign来的, 那么就放弃对它的追踪
}

/*
 * 下面是一个简单的循环, 等待fd1与fd2同时可读
 */
void mainloop(evutil_socket_t fd1, evutil_socket_t fd2, int debug_mode)
{
    struct event_base *base;
    struct event event_on_stack, *event_on_heap;        // 一个是栈上的事件实例, 一个是堆上的事件实例

    if (debug_mode)
       event_enable_debug_mode();       // 开启调试模式

    base = event_base_new();

    event_on_heap = event_new(base, fd1, EV_READ, cb, NULL);    // 通过event_new来创建堆上的实例, 并把事件回调的入参设置为NULL
    event_assign(&event_on_stack, base, fd2, EV_READ, cb, &event_on_stack); // 通过event_assign来初始化栈上的实例, 并把事件回调的入参设置为事件实例自身的指针

    event_add(event_on_heap, NULL);
    event_add(&event_on_stack, NULL);

    event_base_dispatch(base);

    event_free(event_on_heap);
    event_base_free(base);
}

#define LIBEVENT_VERSION_NUMBER 0x02000300
#define LIBEVENT_VERSION "2.0.3-alpha"
const char *event_get_version(void);        // 获取字符串形式的版本信息
ev_uint32_t event_get_version_number(void); // 获取值形式的版本信息

#include <event2/event.h>

#if !defined(LIBEVENT_VERSION_NUMBER) || LIBEVENT_VERSION_NUMBER < 0x02000100
#error "This version of Libevent is not supported; Get 2.0.1-alpha or later."
#endif

int
make_sandwich(void)
{
        /* Let‘s suppose that Libevent 6.0.5 introduces a make-me-a
           sandwich function. */
#if LIBEVENT_VERSION_NUMBER >= 0x06000500
        evutil_make_me_a_sandwich();
        return 0;
#else
        return -1;
#endif
}

#include <event2/event.h>
#include <string.h>

int
check_for_old_version(void)
{
    const char *v = event_get_version();
    /* This is a dumb way to do it, but it is the only thing that works
       before Libevent 2.0. */
    if (!strncmp(v, "0.", 2) ||
        !strncmp(v, "1.1", 3) ||
        !strncmp(v, "1.2", 3) ||
        !strncmp(v, "1.3", 3)) {

        printf("Your version of Libevent is very old.  If you run into bugs,"
               " consider upgrading.\n");
        return -1;
    } else {
        printf("Running with Libevent version %s\n", v);
        return 0;
    }
}

int
check_version_match(void)
{
    ev_uint32_t v_compile, v_run;
    v_compile = LIBEVENT_VERSION_NUMBER;
    v_run = event_get_version_number();
    if ((v_compile & 0xffff0000) != (v_run & 0xffff0000)) {
        printf("Running with a Libevent version (%s) very different from the "
               "one we were built with (%s).\n", event_get_version(),
               LIBEVENT_VERSION);
        return -1;
    }
    return 0;
}

void libevent_global_shutdown(void);