C语言实现http服务器（一）-创新互联

  在实现http服务器之前，我们先需要一个可以接收数据和发送数据的tcp服务器。网络连接上消息处理可以分为两个阶段：1. 等待消息准备好  2. 消息处理。

  对于高并发tcp服务器来说，将上述两个阶段分开是最好的选择。等待消息如何做到？就引出了I/O多路复用，使用一个I/O复用来监督多个网络连接，当网络连接上出现可用事件时，则I/O多路复用可返回相应的连接。

  对于一个I/O复用来说，需要关注的是三种事件：1. I/O事件 2. 定时器事件 3. 信号。

  对于Linux来说，底层提供了三种I/O复用，分别是:1. select 2. poll 3. epoll。其中epoll是一个高效的选择，但是epoll太底层，它只是一个Linux的系统调用，需要通过某种事件处理机制进行进一步的封装。

  reactor作为一种高效的事件处理模型，对epoll系统调用进行了进一步的封装。在普通的事件处理机制中，首先程序调用某个函数，然后函数执行，程序等待，当函数执行完毕后函数将结果和控制权返回给程序，最后程序继续处理。与普通函数不同的是，reactor模式中，并不是主动取调用某个API完成处理，而是相反。对于事件处理流程进行了逆置，应用程序需要提供相应的接口并且注册到reactor上，如果相应的事件发生，reactor将主动调用应用程序注册的接口，这些接口又被称为“回调函数”。reactor模型分为以下几个部分：

事件源（handle）：由操作系统提供，用于识别每一个事件，如Socket描述符、文件描述符等。在服务端系统中用一个整数表示。该事件可能来自外部，如来自客户端的连接请求、数据等。也可能来自内部，如定时器事件。

事件反应器（reactor）：定义和应用程序控制事件调度，以及应用程序注册、删除事件处理器和相关描述符相关的接口。它是事件处理器的调度核心，使用事件分离器来等待事件的发生。一旦事件发生，反应器先是分离每个事件，然后调度具体事件的事件处理器中的回调函数处理事件。

事件分离器（demultiplexer）：是一个有操作系统提供的I/O复用函数，在此我们选用epoll。用来等待一个或多个事件的发生。调用者将会被阻塞，直到分离器分离的描述符集上有事件发生。

事件处理器（even handler）：事件处理程序提供了一组接口，每个接口对应了一种类型的事件，供reactor在相应的事件发生时调用，执行相应的事件处理。一般每个具体的事件处理器总是绑定一个有效的描述符句柄，用来识别事件和服务。

#include#include#include#include#include#include#include 
#include#define BUFFER_LENGTH 2048
#define MAX_EPOLLSIZE 1024

typedef int (*HTTPCALLBACK)(int, int, void *);

struct _http_base;
struct _http_event;
struct _http_eventblock;

typedef struct _http_base
{
    int _epoll_fd;                   // epoll句柄
    struct _http_eventblock *_block; // 存储事件块链
    int _block_cnt;                  // 块链块数
} http_base;

typedef struct _http_event
{
    int _fd;                             // 事件句柄
    int _event;                          // 事件
    HTTPCALLBACK _callback;              // 对应回调函数
    void *_arg;                          // 回调函数参数
    struct _http_base *_base;            // 所属base
    char _send_buffer[BUFFER_LENGTH];    // 发送缓冲区
    int _send_length;                    // 待发送字节数
    char _receive_buffer[BUFFER_LENGTH]; // 接收缓冲区
    int _receive_length;                 // 接收数据长度
    int _status;                         // 当前事件存在状态(0-epoll不管理状态 1-epoll管理状态)
    int _is_listenfd;                    // 是否为监听套接字
} http_event;

typedef struct _http_eventblock
{
    struct _http_event *events;
    struct _http_eventblock *next;
} http_eventblock;

// 分配一个http_eventblock
http_eventblock *http_eventblock_new();

// 初始化http_base
http_base *http_base_new();

// 销毁http_base
void http_base_free(http_base *base);

// 事件循环
void dispatch(http_base *base);

// 增加http_eventblock块
int http_eventblock_alloc(http_base *base);

// 返回fd对应的http_event地址
struct _http_event *http_eventblock_index(http_base *base, int fd);

// 设置http_event
int http_event_set(http_base *base, http_event *h_event, int fd, int event, int is_listenfd, HTTPCALLBACK callback, void *arg);

// 重新设置http_event
int http_event_reset(http_base *base, http_event *h_event, int fd, int event, int is_listenfd, HTTPCALLBACK callback, void *arg);

// http_event加入epoll管理
int http_event_add(http_event *hpev);

// http_event修改epoll管理
int http_event_mod(http_event *hpev);

// http_event删除epoll管理
int http_event_del(http_event *hpev);

// 分配一个http_eventblock块(内部函数)
http_eventblock *http_eventblock_new()
{
    // 分配events
    http_event *new_events = malloc(sizeof(http_event) * MAX_EPOLLSIZE);
    if (!new_events)
    {
        printf("create events in %s err %s\n", __func__, strerror(errno));
        return NULL;
    }
    memset(new_events, 0, sizeof(http_event) * MAX_EPOLLSIZE);

    // 分配block块
    http_eventblock *new_block = malloc(sizeof(http_eventblock));
    if (!new_block)
    {
        printf("create block in %s err %s\n", __func__, strerror(errno));
        free(new_events);
        return NULL;
    }
    memset(new_block, 0, sizeof(http_eventblock));

    // 整合
    new_block->events = new_events;
    new_block->next = NULL;

    return new_block;
}

http_base *http_base_new()
{
    // 初始化base
    http_base *base = malloc(sizeof(http_base));
    if (!base)
    {
        printf("create base in %s err %s\n", __func__, strerror(errno));
        return NULL;
    }
    memset(base, 0, sizeof(http_base));

    // 初始化epoll_fd
    base->_epoll_fd = epoll_create(1);
    if (base->_epoll_fd<= 0)
    {
        printf("create epoll in %s err %s\n", __func__, strerror(errno));
        free(base);
        return NULL;
    }

    // 初始化块
    base->_block = http_eventblock_new();
    if (!base->_block)
    {
        printf("create block in %s err %s\n", __func__, strerror(errno));
        close(base->_epoll_fd);
        free(base);
        return NULL;
    }

    // 初始化块数
    base->_block_cnt = 1;

    return base;
}

void http_base_free(http_base *base)
{
    // 销毁epoll_fd;
    close(base->_epoll_fd);

    // 销毁httpevent_block
    http_eventblock *block = base->_block;
    while (block)
    {
        http_eventblock *next_block = block->next;
        free(block->events);
        free(block);
        base->_block_cnt--;
        block = next_block;
    }

    // 销毁base
    free(base);
}

void dispatch(http_base *base)
{
    if (!base)
    {
        return;
    }
    if (!base->_block)
    {
        return;
    }
    if (base->_epoll_fd<= 0)
    {
        return;
    }
    struct epoll_event events[MAX_EPOLLSIZE];

    while (1)
    {
        int n_ready = epoll_wait(base->_epoll_fd, events, MAX_EPOLLSIZE, -1);
        for (int i = 0; i< n_ready; ++i)
        {
            http_event *hpev = events[i].data.ptr;
            if (hpev->_is_listenfd)
            {
                hpev->_callback(hpev->_fd, events[i].events, hpev->_arg);
            }
            else if (hpev->_event & EPOLLIN)
            {
                if (!hpev->_callback(hpev->_fd, events[i].events, hpev->_arg))
                {
                    http_event_del(hpev);
                    close(hpev->_fd);
                }
            }
            else if (hpev->_event & EPOLLOUT)
            {
                if (!hpev->_callback(hpev->_fd, events[i].events, hpev->_arg))
                {
                    http_event_del(hpev);
                    close(hpev->_fd);
                }
            }
            else if (hpev->_event & (EPOLLERR | EPOLLRDHUP | EPOLLHUP))
            {
                http_event_del(hpev);
                close(hpev->_fd);
            }
            else
            {
            }
        }
    }
}

int http_eventblock_alloc(http_base *base)
{
    if (!base)
    {
        printf("!base in %s err %s\n", __func__, strerror(errno));
        return 0;
    }
    if (!base->_block)
    {
        printf("!block in %s err %s\n", __func__, strerror(errno));
        return 0;
    }

    http_eventblock *block = base->_block;

    while (block->next)
    {
        block = block->next;
    }

    http_eventblock *new_block = http_eventblock_new();
    if (!new_block)
    {
        return 0;
    }

    block->next = new_block;
    base->_block_cnt++;

    return 1;
}

struct _http_event *http_eventblock_index(http_base *base, int fd)
{
    int block_index = fd / MAX_EPOLLSIZE;

    // 块不够分配
    while (base->_block_cnt<= block_index)
    {
        http_eventblock_alloc(base);
    }

    // 寻找块
    http_eventblock *block = base->_block;
    while (block_index)
    {
        block = block->next;
        block_index--;
    }

    return &(block->events[fd % MAX_EPOLLSIZE]);
}

int http_event_set(http_base *base, http_event *hpev, int fd, int event, int is_listenfd, HTTPCALLBACK callback, void *arg)
{
    if (!base)
    {
        return 0;
    }
    if (!hpev)
    {
        return 0;
    }

    hpev->_base = base;
    hpev->_fd = fd;
    hpev->_event = event;
    hpev->_is_listenfd = is_listenfd;
    hpev->_callback = callback;
    hpev->_arg = arg;
    hpev->_status = 0;
    memset(hpev->_receive_buffer, 0, BUFFER_LENGTH);
    memset(hpev->_send_buffer, 0, BUFFER_LENGTH);
    hpev->_receive_length = 0;
    hpev->_send_length = 0;

    return 1;
}

int http_event_reset(http_base *base, http_event *hpev, int fd, int event, int is_listenfd, HTTPCALLBACK callback, void *arg)
{
    if (!base)
    {
        return 0;
    }
    if (!hpev)
    {
        return 0;
    }

    hpev->_base = base;
    hpev->_fd = fd;
    hpev->_event = event;
    hpev->_is_listenfd = is_listenfd;
    hpev->_callback = callback;
    hpev->_arg = arg;

    return 1;
}

int http_event_add(http_event *hpev)
{
    if (!hpev)
    {
        printf("event in %s err %s\n", __func__, strerror(errno));
        return 0;
    }
    if (hpev->_status == 1)
    {
        printf("event in %s exist %s\n", __func__, strerror(errno));
        return 0;
    }

    hpev->_status = 1;

    struct epoll_event ev = {0, {0}};
    ev.data.ptr = hpev;
    ev.events = hpev->_event;

    http_base *base = hpev->_base;

    if (epoll_ctl(base->_epoll_fd, EPOLL_CTL_ADD, hpev->_fd, &ev)< 0)
    {
        printf("event add failed [fd=%d], events[%d]\n", hpev->_fd, hpev->_event);
        return 0;
    }

    return 1;
}

int http_event_mod(http_event *hpev)
{
    if (!hpev)
    {
        printf("event in %s err %s\n", __func__, strerror(errno));
        return 0;
    }
    if (hpev->_status == 0)
    {
        printf("event in %s is not exist %s\n", __func__, strerror(errno));
        return 0;
    }

    struct epoll_event ev = {0, {0}};
    ev.data.ptr = hpev;
    ev.events = hpev->_event;

    http_base *base = hpev->_base;

    if (epoll_ctl(base->_epoll_fd, EPOLL_CTL_MOD, hpev->_fd, &ev)< 0)
    {
        printf("event mod failed [fd=%d], events[%d]\n", hpev->_fd, hpev->_event);
        return 0;
    }

    return 1;
}

int http_event_del(http_event *hpev)
{
    if (!hpev)
    {
        printf("event in %s err %s\n", __func__, strerror(errno));
        return 0;
    }
    if (hpev->_status == 0)
    {
        printf("event in %s is not exist %s\n", __func__, strerror(errno));
        return 0;
    }

    hpev->_status = 0;

    http_base *base = hpev->_base;

    struct epoll_event ev = {0, {0}};
    ev.data.ptr = hpev;
    ev.events = hpev->_event;

    epoll_ctl(base->_epoll_fd, EPOLL_CTL_DEL, hpev->_fd, &ev);

    printf("disconnect, pos[%d]\n", hpev->_fd);

    return 1;
}

int accept_callback(int fd, int event, void *arg);
int read_callback(int fd, int event, void *arg);
int send_callback(int fd, int event, void *arg);

int accept_callback(int fd, int event, void *arg)
{
    http_base *base = (http_base *)arg;
    if (!base)
    {
        return 0;
    }

    struct sockaddr_in client_address;
    socklen_t client_address_len = sizeof(client_address);

    int client_fd;
    if ((client_fd = accept(fd, (struct sockaddr *)&client_address, &client_address_len)) == -1)
    {
        printf("accept: %s\n", strerror(errno));
        return 0;
    }

    int flag = 0;
    if ((flag = fcntl(client_fd, F_SETFL, O_NONBLOCK))< 0)
    {
        printf("%s: fcntl nonblocking failed, %d\n", __func__, MAX_EPOLLSIZE);
    }

    http_event *hpev = http_eventblock_index(base, client_fd);
    http_event_set(base, hpev, client_fd, EPOLLIN | EPOLLET | EPOLLRDHUP, 0, read_callback, base);
    http_event_add(hpev);

    printf("new connect [%s:%d], pos[%d]\n",
           inet_ntoa(client_address.sin_addr), ntohs(client_address.sin_port), client_fd);

    return 1;
}

int read_callback(int fd, int event, void *arg)
{
    http_base *base = (http_base *)arg;
    http_event *hpev = http_eventblock_index(base, fd);
    if (hpev->_receive_length >= BUFFER_LENGTH)
    {
        return 0;
    }

    int byte_read = 0;
    while (1)
    {
        byte_read = recv(fd,
                         hpev->_receive_buffer + hpev->_receive_length,
                         BUFFER_LENGTH - hpev->_receive_length, 0);
        if (byte_read == -1)
        {
            if (errno == EINTR) {
                continue;
            }
            else if (errno == EAGAIN || errno == EWOULDBLOCK)
            {
                http_event_reset(base, hpev, fd, EPOLLOUT | EPOLLET | EPOLLRDHUP, 0, send_callback, base);
                http_event_mod(hpev);
                break;
            }
            return 0;
        }
        else if (byte_read == 0)
        {
            return 0;
        }
        hpev->_receive_length += byte_read;
    }

    printf("receive %s\n", hpev->_receive_buffer);
    memcpy(hpev->_send_buffer, hpev->_receive_buffer, hpev->_receive_length);
    hpev->_send_length = hpev->_receive_length;

    memset(hpev->_receive_buffer, 0, BUFFER_LENGTH);
    hpev->_receive_length = 0;

    return 1;
}

int send_callback(int fd, int event, void *arg)
{
    http_base *base = (http_base *)arg;
    http_event *hpev = http_eventblock_index(base, fd);
    int temp = 0;
    int byte_have_send = 0;
    int byte_to_send = hpev->_send_length;

    while (1)
    {
        if (byte_to_send == 0)
        {
            http_event_reset(base, hpev, fd, EPOLLIN | EPOLLET | EPOLLRDHUP, 0, read_callback, base);
            http_event_mod(hpev);
            break;
        }

        temp = send(hpev->_fd, hpev->_send_buffer, byte_to_send, 0);
        if (temp == -1)
        {
            // 中断
            if (errno == EINTR)
            {
                continue;
            }
            // 写缓冲区无数据
            else if (errno == EAGAIN || errno == EWOULDBLOCK)
            {
                http_event_reset(base, hpev, fd, EPOLLIN | EPOLLET | EPOLLRDHUP, 0, read_callback, base);
                http_event_mod(hpev);
                break;
            }
            // 错误
            else {
                return 0;
            }
            
        }

        byte_to_send -= temp;
        byte_have_send += temp;
    }

    memset(hpev->_send_buffer, 0, BUFFER_LENGTH);
    hpev->_send_length = 0;

    return 1;
}

int init_sock(short port)
{

    int fd = socket(AF_INET, SOCK_STREAM, 0);
    fcntl(fd, F_SETFL, O_NONBLOCK);

    int reuse = 1;
    setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse));

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(port);

    bind(fd, (struct sockaddr *)&server_addr, sizeof(server_addr));

    if (listen(fd, 20)< 0)
    {
        printf("listen failed : %s\n", strerror(errno));
    }

    return fd;
}

int main()
{
    // 创建base
    http_base *base = http_base_new();

    // 创建监听事件
    int listen_fd = init_sock(8080);

    // 加入epoll管理
    http_event *listen_event = http_eventblock_index(base, listen_fd);
    http_event_set(base, listen_event, listen_fd, EPOLLIN, 1, accept_callback, base);
    http_event_add(listen_event);

    // 事件循环
    dispatch(base);

    // 消除事件管理
    http_event_del(listen_event);

    // 销毁base
    http_base_free(base);
    return 0;
}

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