shttpd源码分析(3)几个重要数据结构

shttpd中为了简化处理将服务器与客户端之间的交互抽象成流（stream），流中包含建立的连接的信息、IO类型、IO操作方法(封装在io_class中)、最后读的字节的位置、头部长度、内容长度、流的当前状态标志等。

 

/*
 * Data exchange stream. It is backed by some communication channel:
 * opened file, socket, etc. The 'read' and 'write' methods are
 * determined by a communication channel.
 */
 struct stream {
    struct conn        *conn;
    union channel        chan;        /* Descriptor        */
    struct io        io;        /* IO buffer        */
    const struct io_class    *io_class;    /* IO class        */
    int            nread_last;    /* Bytes last read    */
    int            headers_len;
    big_int_t        content_len;
    unsigned int        flags;
 #define    FLAG_HEADERS_PARSED    1
 #define    FLAG_SSL_ACCEPTED    2
 #define    FLAG_R            4        /* Can read in general    */
 #define    FLAG_W            8        /* Can write in general    */
 #define    FLAG_CLOSED        16
 #define    FLAG_DONT_CLOSE        32
 #define    FLAG_ALWAYS_READY    64        /* File, dir, user_func    */
};
 

 

再来看看流结构中的几个结构struct conn、union channel、struct io、const struct io_class

 

先看看conn 结构的定义，其中保存了conn 结构(struct llhead)的链表、shttpd上下文(struct shttpd_ctx)、封装了远程socket的结构(struct usa)、创建时间(time_t)、过期时间(time_t)、本地端口、回复状态、请求方法、解码后的uri、HTTP主版本号、HTTP此版本号、请求行、请求头部、uri中的QUERY_STRING部分、PATH_INFO、Mime类型、解析过后的头部结构(struct headers)、本地流和远程流。

 

struct conn {
    struct llhead    link;        /* Connections chain        */
    struct shttpd_ctx *ctx;        /* Context this conn belongs to */
    struct usa    sa;        /* Remote socket address    */
    time_t        birth_time;    /* Creation time        */
    time_t        expire_time;    /* Expiration time        */

    int        loc_port;    /* Local port            */
    int        status;        /* Reply status code        */
    int        method;        /* Request method        */
    char        *uri;        /* Decoded URI            */
    unsigned long    major_version;    /* Major HTTP version number    */
    unsigned long    minor_version;    /* Minor HTTP version number    */
    char        *request;    /* Request line            */
    char        *headers;    /* Request headers        */
    char        *query;        /* QUERY_STRING part of the URI    */
    char        *path_info;    /* PATH_INFO thing        */
    const char    *mime_type;    /* Mime type            */

    struct headers    ch;        /* Parsed client headers    */

    struct stream    loc;        /* Local stream            */
    struct stream    rem;        /* Remote stream        */

#if !defined(NO_SSI)
    void            *ssi;    /* SSI descriptor        */
#endif /* NO_SSI */
};

 

 

接下来看看union channel，保存交流的类型的信息。比如，如果是文件，则使用channel.fd；如果是socket，则使用channel.sock

 

/*
 * The communication channel
 */
union channel {
    int        fd;        /* Regular static file        */
    int        sock;        /* Connected socket        */
    struct {
        int        sock;    /* XXX important. must be first    */
        SSL        *ssl;    /* shttpd_poll() assumes that    */
    } ssl;                /* SSL-ed socket        */
    struct {
        DIR    *dirp;
        char    *path;
    } dir;                /* Opened directory        */
    struct {
        void        *state;    /* For keeping state        */
        union variant    func;    /* User callback function    */
        void        *data;    /* User defined parameters    */
    } emb;                /* Embedded, user callback    */
};

接着看看io结构，这个主要是保存io操作的一些状态信息

 

/*
 * I/O buffer descriptor
 */
struct io {
    char        *buf;        /* IO Buffer            */
    size_t        size;        /* IO buffer size        */
    size_t        head;        /* Bytes read            */
    size_t        tail;        /* Bytes written        */
    size_t        total;        /* Total bytes read        */
};

 

再来看看io_class的结构，包括IO类别的名称、此类IO的读写和关闭操作的函数指针。

这里使用函数指针的好处是提供统一的接口调用，而可以在实际调用的时候使用不同的实现。这就类似于c++中的多态吧，只是这里用c的方式来实现。

 

/*
 * IO class descriptor (file, directory, socket, SSL, CGI, etc)
 * These classes are defined in io_*.c files.
 */
struct io_class {
    const char *name;
    int (*read)(struct stream *, void *buf, size_t len);
    int (*write)(struct stream *, const void *buf, size_t len);
    void (*close)(struct stream *);
};

 

例如在io_socket.c中定义的io_scoket

 

const struct io_class    io_socket =  {
    "socket",
    read_socket,
    write_socket,
    close_socket
};

然后在io_socket.c中是实现了read_socket、write_socket、close_socket来完成读写和关闭socket的操作