small HTTP server : 200行

webserver.c

    /* micro_httpd - really small HTTP server
     **
     ** Copyright (c) 1999,2005 by Jef Poskanzer <jef@mail.acme.com>.
     ** All rights reserved.
     **
     ** Redistribution and use in source and binary forms, with or without
     ** modification, are permitted provided that the following conditions
     ** are met:
     ** 1. Redistributions of source code must retain the above copyright
     **    notice, this list of conditions and the following disclaimer.
     ** 2. Redistributions in binary form must reproduce the above copyright
     **    notice, this list of conditions and the following disclaimer in the
     **    documentation and/or other materials provided with the distribution.
     **
     ** THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     ** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     ** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     ** ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     ** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     ** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     ** OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     ** HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     ** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     ** SUCH DAMAGE.
     */ 
 
    /*
    #######################################
    1.此程序对输入输出使用的是stdin和stdout
    借助xinetd，microhttpd在处理请求时，可从标准输入读取客户端的请求，向标准输出写入对客户端的响应。所以micro_httpd的核心在于分析http请求参数，并发送响应数据。
    2.此程序没有创建socket服务
    需要其它程序为其创建socket服务
特点：
* 支持安全的 .. 上级目录过滤
* 支持通用的MIME类型
* 支持简单的目录
* 支持目录列表
* 支持使用 index.html 作为首页
* Trailing-slash redirection
    ######################################
     */
    #include <sys/types.h>
    #include <unistd.h>
    #include <stdlib.h>
    #include <stdio.h>
    #include <string.h>
    #include <dirent.h>
    #include <ctype.h>
    #include <time.h>
    #include <sys/stat.h>  
 
    #define SERVER_NAME "micro_httpd"
    #define SERVER_URL "http://208.115.207.24:8090/"
    #define PROTOCOL "HTTP/1.0"
    #define RFC1123FMT "%a, %d %b %Y %H:%M:%S GMT"  
 
    /* Forwards. */
    //输出文件相关属性的详细信息
    static void file_details( char* dir, char* name );
    //返回出错页面
    static void send_error( int status, char* title, char* extra_header, char* text );
    //设置reponse
    static void send_headers( int status, char* title, char* extra_header, char* mime_type, off_t length, time_t mod );
    //通过文件名推断文件mime_type
    static char* get_mime_type( char* name );
    //URL 解码
    static void strdecode( char* to, char* from );
    //十六进制转换为十进制数
    static int hexit( char c );
    //用于文件名编码
    static void strencode( char* to, size_t tosize, const char* from );  
 
      int   main( int argc, char** argv )
    {
        char line[10000], method[10000], path[10000], protocol[10000], idx[20000], location[20000], command[20000];
        char* file;
        size_t len;
        int ich;
        struct stat sb;
        FILE* fp;
        struct dirent **dl;
        int i, n;  
 
        if ( argc != 2 )   //如果没有指明根目录，xinetd中的server_args
            send_error( 500, "Internal Error", (char*) 0, "Config error - no dir specified." );
        //更改工作目录
        if ( chdir( argv[1] ) < 0 )  //切换目录失败
            send_error( 500, "Internal Error", (char*) 0, "Config error - couldn't chdir()." );
        if ( fgets( line, sizeof(line), stdin ) == (char*) 0 )  //提取请求行，包含请求方法、路径、协议
            send_error( 400, "Bad Request", (char*) 0, "No request found." );
        //解析请求 形如 GET /abc/index.html   HTTP/1.0
        if ( sscanf( line, "%[^ ] %[^ ] %[^ ]", method, path, protocol ) != 3 )  //提取方法、路径、协议
            send_error( 400, "Bad Request", (char*) 0, "Can't parse request." );
        while ( fgets( line, sizeof(line), stdin ) != (char*) 0 ) // 读到请求头结束
        {
            if ( strcmp( line, "\n" ) == 0 || strcmp( line, "\r\n" ) == 0 )
                break;
        }
        if ( strcasecmp( method, "get" ) != 0 )   // micro_httpd只支持get请求
            send_error( 501, "Not Implemented", (char*) 0, "That method is not implemented." );
        if ( path[0] != '/' )  // 路径名不以斜杠开头
            send_error( 400, "Bad Request", (char*) 0, "Bad filename." );
        file = &(path[1]);
        strdecode( file, file );  // 解码路径名，相对于micro_httpd的根目录argv[1]
        if ( file[0] == '\0' )
            file = "./";
        len = strlen( file );  // 检查路径名是否会越界访问到根目录上级目录，..snoop
        if ( file[0] == '/' || strcmp( file, ".." ) == 0 || strncmp( file, "../", 3 ) == 0 || strstr( file, "/../" ) != (char*) 0 || strcmp( &(file[len-3]), "/.." ) == 0 )
            send_error( 400, "Bad Request", (char*) 0, "Illegal filename." );
        if ( stat( file, &sb ) < 0 )   // 访问的文件（或目录）不存在
            send_error( 404, "Not Found", (char*) 0, "File not found." );
        //请求路径是文件夹吗
        if ( S_ISDIR( sb.st_mode ) )   // 路径名对应目录
        {   // 如果文件名最后不是以 '/'为结尾的。如这样的  GET /index/default HTTP/1.1 。而他也是一个目录。
            if ( file[len-1] != '/' )  // 目录名要以斜杠结尾
            {
                (void) snprintf( location, sizeof(location), "Location: %s/", path );
                send_error( 302, "Found", location, "Directories must end with a slash." );
            }   // 如果有则访问本目录下index.html文件 。并给变量 idx 给值，并给了完正的文件全名
            (void) snprintf( idx, sizeof(idx), "%sindex.html", file );
            if ( stat( idx, &sb ) >= 0 )   // 目录之下存在index.html文件，则返回index.html的内容
            {    // 在判断一次如果文件有效则输出，如果不成功，正明本目录没有index.html文件 。
                file = idx;
                goto do_file;
            }
            //显示请求文件夹下的文件列表
            send_headers( 200, "Ok", (char*) 0, "text/html", -1, sb.st_mtime );
            (void) printf( "<html><head><title>Index of %s</title></head>\n<body bgcolor=\"#99cc99\"><h4>Index of %s</h4>\n<pre>\n", file, file );
            n = scandir( file, &dl, NULL, alphasort );  // 读取目录下的各个目录项，并返回每个文件的信息
            if ( n < 0 )   // 扫喵本目录，成功返回目录下 文件数目，如果小于0系统报错。
                perror( "scandir" );
            else
                for ( i = 0; i < n; ++i )
                    file_details( file, dl[i]->d_name );
            (void) printf( "</pre>\n<hr>\n<address><a href=\"%s\">%s</a></address>\n</body></html>\n", SERVER_URL, SERVER_NAME );
        }
        else
        {  //返回请求的文件
    do_file:  // 获取文件的内容并返回给客户端
            fp = fopen( file, "r" );
            if ( fp == (FILE*) 0 )
                send_error( 403, "Forbidden", (char*) 0, "File is protected." );
            send_headers( 200, "Ok", (char*) 0, get_mime_type( file ), sb.st_size, sb.st_mtime );
            while ( ( ich = getc( fp ) ) != EOF )  // 向标准输出中输出index.html内容
                putchar( ich );
        }  
 
        (void) fflush( stdout );
        exit( 0 );
    }
      /*  获取文件的信息，并响应文件的超链接信息  */
    //输出文件相关属性的详细信息
        static void
    file_details( char* dir, char* name )
    {
        static char encoded_name[1000];
        static char path[2000];
        struct stat sb;
        char timestr[16];  
 
        strencode( encoded_name, sizeof(encoded_name), name );
        (void) snprintf( path, sizeof(path), "%s/%s", dir, name );
        if ( lstat( path, &sb ) < 0 )
            (void) printf( "<a href=\"%s\">%-32.32s</a>    ???\n", encoded_name, name );
        else
        {
            (void) strftime( timestr, sizeof(timestr), "%d%b%Y %H:%M", localtime( &sb.st_mtime ) );
            (void) printf( "<a href=\"%s\">%-32.32s</a>    %15s %14lld\n", encoded_name, name, timestr, (int64_t) sb.st_size );
        }
    }  
 
    //返回出错页面  /* 出错时，发送错误响应信息 */
        static void
    send_error( int status, char* title, char* extra_header, char* text )
    {
        send_headers( status, title, extra_header, "text/html", -1, -1 );
        (void) printf( "<html><head><title>%d %s</title></head>\n<body bgcolor=\"#cc9999\"><h4>%d %s</h4>\n", status, title, status, title );
        (void) printf( "%s\n", text );
        (void) printf( "<hr>\n<address><a href=\"%s\">%s</a></address>\n</body></html>\n", SERVER_URL, SERVER_NAME );
        (void) fflush( stdout );
        exit( 1 );
    }  
 
    //设置reponse  header  /* 发送http响应头部信息 */
    //状态 标题  mime_type 文件最后被修改的时间
        static void
    send_headers( int status, char* title, char* extra_header, char* mime_type, off_t length, time_t mod )
    {
        time_t now;
        char timebuf[100];
        //\015\012 回车换行
        (void) printf( "%s %d %s\015\012", PROTOCOL, status, title );
        (void) printf( "Server: %s\015\012", SERVER_NAME );
        now = time( (time_t*) 0 );
        //将时间格式化后存在timebuf中
        (void) strftime( timebuf, sizeof(timebuf), RFC1123FMT, gmtime( &now ) );
        (void) printf( "Date: %s\015\012", timebuf );
        if ( extra_header != (char*) 0 )
            (void) printf( "%s\015\012", extra_header );
        if ( mime_type != (char*) 0 )
            (void) printf( "Content-Type: %s\015\012", mime_type );
        if ( length >= 0 )
            (void) printf( "Content-Length: %lld\015\012", (int64_t) length );
        if ( mod != (time_t) -1 )
        {
            (void) strftime( timebuf, sizeof(timebuf), RFC1123FMT, gmtime( &mod ) );
            (void) printf( "Last-Modified: %s\015\012", timebuf );
        }
        (void) printf( "Connection: close\015\012" );
        (void) printf( "\015\012" );
    }  
 
    //通过文件名推断文件mime_type  /* 根据文件名获取mime类型，通过分析文件后缀名 */
        static char*
    get_mime_type( char* name )
    {
        char* dot;  
 
        dot = strrchr( name, '.' );
        if ( dot == (char*) 0 )
            return "text/plain; charset=iso-8859-1";
        if ( strcmp( dot, ".html" ) == 0 || strcmp( dot, ".htm" ) == 0 )
            return "text/html; charset=iso-8859-1";
        if ( strcmp( dot, ".jpg" ) == 0 || strcmp( dot, ".jpeg" ) == 0 )
            return "image/jpeg";
        if ( strcmp( dot, ".gif" ) == 0 )
            return "image/gif";
        if ( strcmp( dot, ".png" ) == 0 )
            return "image/png";
        if ( strcmp( dot, ".css" ) == 0 )
            return "text/css";
        if ( strcmp( dot, ".au" ) == 0 )
            return "audio/basic";
        if ( strcmp( dot, ".wav" ) == 0 )
            return "audio/wav";
        if ( strcmp( dot, ".avi" ) == 0 )
            return "video/x-msvideo";
        if ( strcmp( dot, ".mov" ) == 0 || strcmp( dot, ".qt" ) == 0 )
            return "video/quicktime";
        if ( strcmp( dot, ".mpeg" ) == 0 || strcmp( dot, ".mpe" ) == 0 )
            return "video/mpeg";
        if ( strcmp( dot, ".vrml" ) == 0 || strcmp( dot, ".wrl" ) == 0 )
            return "model/vrml";
        if ( strcmp( dot, ".midi" ) == 0 || strcmp( dot, ".mid" ) == 0 )
            return "audio/midi";
        if ( strcmp( dot, ".mp3" ) == 0 )
            return "audio/mpeg";
        if ( strcmp( dot, ".ogg" ) == 0 )
            return "application/ogg";
        if ( strcmp( dot, ".pac" ) == 0 )
            return "application/x-ns-proxy-autoconfig";
        return "text/plain; charset=iso-8859-1";
    }  
 
    //用于URL 解码  /* 对路径名解码 */
        static void
    strdecode( char* to, char* from )
    {
        for ( ; *from != '\0'; ++to, ++from )
        {
            if ( from[0] == '%' && isxdigit( from[1] ) && isxdigit( from[2] ) )
            {
                *to = hexit( from[1] ) * 16 + hexit( from[2] );
                from += 2;
            }
            else
                *to = *from;
        }
        *to = '\0';
    }  
 
    //十六进制转换为十进制数
        static int
    hexit( char c )
    {
        if ( c >= '0' && c <= '9' )
            return c - '0';
        if ( c >= 'a' && c <= 'f' )
            return c - 'a' + 10;
        if ( c >= 'A' && c <= 'F' )
            return c - 'A' + 10;
        return 0;       /* shouldn't happen, we're guarded by isxdigit() */
    }  
 
    //用于文件名编码  /* 对路径名编码，URL encoding*/
        static void
    strencode( char* to, size_t tosize, const char* from )
    {
        int tolen;  
 
        for ( tolen = 0; *from != '\0' && tolen + 4 < tosize; ++from )
        {
            //ASCII 字符、数字 或者 "/_.-~" 中的一个
            if ( isalnum(*from) || strchr( "/_.-~", *from ) != (char*) 0 )
            {
                *to = *from;
                ++to;
                ++tolen;
            }
            else  //对特殊字符进行编码  问题：什么样的特殊字符需要这样编码？
            {
                (void) sprintf( to, "%%%02x", (int) *from & 0xff );
                to += 3;
                tolen += 3;
            }
        }
        *to = '\0';
    }