boa初始化配置及改造利用

一，
boa通过read_config_files()调用语法分析入口函数yyparse(), 取yyparse()函数调用词法分析入口函数yylex()，读取并解析boa.conf和mime.types文件, 将其内容理解成一个个的单词，再将每一行单词的组合理解为相应的配置选项。其中yyparse()函数调用yylex()读取boa.conf和mime.types文件内容。具体的，yylex()函数读取文件内容，将文件内容按指定的"词法规则”理解成一个个的单词，并将单词返回给yyparse()函数。yyparse()将得到的单词按指定的"语法规则”理解成配置选项。

二，
yylex()是词法分析入口函数，在lex.yy.c文件中，由"flex  boa_lexer.l"命令生成。flex是词法分析生成工具，boa_lexer.l中的代码指定了"词法规则” 。
yyparse()是语法分析入口函数，在y.tab.c文件中，由"bison -y  -d boa_grammar.y"命令生成，bison是语法分析生成工具，boa_grammar.y中的代码指定了“语法规则” 。

三，
boa_lexer.l文件
boa_lexer.l是flex程序文件，包含三个部分，各部分这间用%%分割。

...定义部分...
%%
...规则部分...
%%
...用户子程序例程...

第一部分是定义部分，包含声明和选项设置。
    其中的%{和%}之间的部分会被原样复制到生成的c文件开头部分。是一些头文件包含及宏定义，变量声明等C语言代码
    %s和%x用来定义一个包含的起始状态和独占的起始状态。第二部分模式匹配时会用到。
第二部分是规则部分，包含一系列的模式和动作。
    其中的模式使用正则表达式语言。动作是模式匹配时执行的C代码。这里的C代码是用{}括住的多行语句或分号";" 
第三部分是用户子程序部分，和是则是会被复制到生成的词法分析器里面的C代码。

boa_grammar.y文件
boa_grammar.y是bison程序文件，包含三个部分，各部分这间用%%分割。

..定义部分...
%%
...规则部分...
%%
...用户子程序例程...

第一部分包含声明定义等。
    其中的%{和%}之间的部分会被原样复制到目标分析程序开头。%token,%start,%union分别用来声明记号，起始规则，名为YYSTYPE的union类型的域
第二部分规则部分是一系列的简单BNF定义的规则和动作。
第三部分则是会被复制到生成的语法分析器里面的C代码。

四，代码改造
    将代码进行适当修改，成为配置文件解析工具
修改后的代码如下：
   1，boa_lexer.l代码  

%{

/*
 * Boa, an http server
 * Copyright (C) 1995 Paul Phillips <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 1, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

/* $Id: boa_lexer.l,v 1.13.2.1 2002/07/07 23:19:55 jnelson Exp $*/

#include "y.tab.h"
#include <stdlib.h>
#include <unistd.h>
#include "parse.h"

int lineno = 1;
struct ccommand *k;
char *kptr;
%}

%%

[ \t]+        ;
#.*        ;

[^ \"\t\n]+    { /* XXX could use better checks that we are in a state to
           * accept keywords; this version matches original behavior */
          if (k = lookup_keyword(yytext)) {
              yylval.cval=k;
              return (k->type);
          } else { yylval.sval = yytext; return STRING; }
            }

\n        { lineno++; }
%%

/* In yywrap we track which file we are on.
 * 1: close boa.conf, open mime.types
 * 2: return 1;
 */

int yywrap()
{
    fclose(yyin);
    return 1;
}

int yyerror(char * msg)
{
    fprintf(stderr, "Error on line %d of %s: %s\n", lineno, "boa.conf", msg);
    return 1;
}

   2，boa_grammar.y文件代码

%{

/*
*  Boa, an http server
*  Copyright (C) 1995 Paul Phillips
*
*  This program is free software; you can redistribute it and/or modify
*  it under the terms of the GNU General Public License as published by
*  the Free Software Foundation; either version 1, or (at your option)
*  any later version.
*
*  This program is distributed in the hope that it will be useful,
*  but WITHOUT ANY WARRANTY; without even the implied warranty of
*  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*  GNU General Public License for more details.
*
*  You should have received a copy of the GNU General Public License
*  along with this program; if not, write to the Free Software
*  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*/

/* $Id: boa_grammar.y,v 1.14 1999/10/12 14:49:07 jon Exp $*/

#include
#include
#include
#include
/* #include "boa.h" */
#include "parse.h"

int yyerror(char * msg);

/* yydebug = 1; */

#ifdef DEBUG
#define DBG(x) x
#else
#define DBG(x)
#endif

char *arg1hold;
char mime_type[256];            /* global to inherit */

%}

%union {
char *	sval;
int		ival;
struct ccommand * cval;
};

/* boa.conf tokens */
%token  STMT_NO_ARGS STMT_ONE_ARG STMT_TWO_ARGS

/* mime.type tokens */
%token  STRING
%token  INTEGER
%token  KEY
%token  VALUE

%start BoaConfigStmts

%%

BoaConfigStmts:		BoaConfigStmts BoaConfigStmt
|		/* empty */
;

BoaConfigStmt:
StmtNoArgs
|		StmtOneArg
|		StmtTwoArgs
;

StmtNoArgs:		STMT_NO_ARGS
{ if ($1->action) {
DBG(printf("StmtNoArgs: %s\n",$1->name);)
$1->action(NULL,NULL,$1->object);
}
}
;

StmtOneArg:		STMT_ONE_ARG STRING
{ if ($1->action) {
DBG(printf("StmtOneArg: %s %s\n",$1->name,$2);)
$1->action($2,NULL,$1->object);
}
}
;

StmtTwoArgs:		STMT_TWO_ARGS STRING
{ arg1hold = strdup($2); }
STRING
{ if ($1->action) {
DBG(printf("StmtTwoArgs: '%s' '%s' '%s'\n",
$1->name,arg1hold,$4);)
$1->action($4,arg1hold,$1->object);
}
free(arg1hold);
}
;

%%

3，config.c代码
  

/*
 * Boa, an http server
 * Copyright (C) 1999 Larry Doolittle <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 1, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

/* $Id: config.c,v 1.31.2.3 2002/07/26 03:04:29 jnelson Exp $*/

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>

#include "y.tab.h"
#include "parse.h"

int yyparse(void); /* Better match the output of lex */
char *mime_types;

#ifdef DEBUG
#define DBG(x) x
#else
#define DBG(x)
#endif


int server_port;
uid_t server_uid;
gid_t server_gid;
char *server_root;
char *server_name;
char *server_admin;
char *server_ip;
char *myString;
int virtualhost;
long int max_connections;

char *document_root;
char *user_dir;
char *directory_index;
char *default_type;
char *dirmaker;
char *cachedir;

char *tempdir;

char *cgi_path = NULL;
int single_post_limit = (1024 * 1024);
int verbose_cgi_logs = 0;

int ka_timeout;
int ka_max;
int myint;

int backlog = 250;

/* These came from log.c */
char *error_log_name;
char *access_log_name;
char *cgi_log_name;

int use_localtime;

/* These are new */
static void c_set_user(char *v1, char *v2, void *t);
static void c_set_group(char *v1, char *v2, void *t);
static void c_set_string(char *v1, char *v2, void *t);
static void c_set_int(char *v1, char *v2, void *t);
static void c_set_unity(char *v1, char *v2, void *t);
static void c_add_type(char *v1, char *v2, void *t);
static void c_add_alias(char *v1, char *v2, void *t);

/* Fakery to keep the value passed to action() a void *,
   see usage in table and c_add_alias() below */
static int script_number = 1;
static int redirect_number = 2;
static int alias_number = 0;
static uid_t current_uid=0;

/* Help keep the table below compact */
#define S0A STMT_NO_ARGS
#define S1A STMT_ONE_ARG
#define S2A STMT_TWO_ARGS

struct ccommand clist[] = {
    {"Port", S1A, c_set_int, &server_port},
    {"Listen", S1A, c_set_string, &server_ip},
    {"MyString", S1A, c_set_string, &myString},
    {"BackLog", S1A, c_set_int, &backlog},
    {"User", S1A, c_set_user, NULL},
    {"Group", S1A, c_set_group, NULL},
    {"ServerAdmin", S1A, c_set_string, &server_admin},
    {"ServerRoot", S1A, c_set_string, &server_root},
    {"ErrorLog", S1A, c_set_string, &error_log_name},
    {"AccessLog", S1A, c_set_string, &access_log_name},
    {"UseLocaltime", S0A, c_set_unity, &use_localtime},
    {"CgiLog", S1A, c_set_string, &cgi_log_name},
    {"VerboseCGILogs", S0A, c_set_unity, &verbose_cgi_logs},
    {"ServerName", S1A, c_set_string, &server_name},
    {"VirtualHost", S0A, c_set_unity, &virtualhost},
    {"DocumentRoot", S1A, c_set_string, &document_root},
    {"UserDir", S1A, c_set_string, &user_dir},
    {"DirectoryIndex", S1A, c_set_string, &directory_index},
    {"DirectoryMaker", S1A, c_set_string, &dirmaker},
    {"DirectoryCache", S1A, c_set_string, &cachedir},
    {"KeepAliveMax", S1A, c_set_int, &ka_max},
    {"Myint", S1A, c_set_int, &myint},
    {"KeepAliveTimeout", S1A, c_set_int, &ka_timeout},
    {"MimeTypes", S1A, c_set_string, &mime_types},
    {"DefaultType", S1A, c_set_string, &default_type},
    {"AddType", S2A, c_add_type, NULL},
    {"ScriptAlias", S2A, c_add_alias, &script_number},
    {"Redirect", S2A, c_add_alias, &redirect_number},
    {"Alias", S2A, c_add_alias, &alias_number},
    {"SinglePostLimit", S1A, c_set_int, &single_post_limit},
    {"CGIPath", S1A, c_set_string, &cgi_path},
    {"MaxConnections", S1A, c_set_int, &max_connections},
};

void printConfig(void)
{
    printf("\n\nserver_port = %d\n", server_port);
    printf("server_ip = %s\n", server_ip);
    printf("MyString = %s\n", myString);
    printf("backlog = %d\n", backlog);
    printf("server_admin = %s\n", server_admin);
    printf("server_root = %s\n", server_root);
    printf("error_log_name = %s\n", error_log_name);
    printf("access_log_name = %s\n", access_log_name);
    printf("use_localtime = %d\n", use_localtime);
    printf("cgi_log_name = %s\n", cgi_log_name);
    printf("verbose_cgi_logs = %d\n", verbose_cgi_logs);
    printf("server_name = %s\n", server_name);
    printf("virtualhost = %d\n", virtualhost);
    printf("document_root = %s\n", document_root);
    printf("user_dir = %s\n", user_dir);
    printf("directory_index = %s\n", directory_index);
    printf("dirmaker = %s\n", dirmaker);
    printf("cachedir = %s\n", cachedir);
    printf("ka_max = %d\n", ka_max);
    printf("myint = %d\n", myint);
    printf("ka_timeout = %d\n", ka_timeout);
    printf("mime_types = %s\n", mime_types);
    printf("default_type = %s\n", default_type);
    printf("script_number = %d\n", script_number);
    printf("redirect_number = %d\n", redirect_number);
    printf("alias_number = %d\n", alias_number);
    printf("single_post_limit = %d\n", single_post_limit);
    printf("cgi_path = %s\n", cgi_path);
    printf("max_connections = %ld\n", max_connections);
}

void add_mime_type(char *extension, char *type)
{
}

void add_alias(char *fakename, char *realname, int type)
{
}

static void c_set_user(char *v1, char *v2, void *t)
{
    struct passwd *passwdbuf;
    char *endptr;
    int i;

    DBG(printf("User %s = ", v1);
        )
        i = strtol(v1, &endptr, 0);
    if (*v1 != '\0' && *endptr == '\0') {
        server_uid = i;
    } else {
        passwdbuf = getpwnam(v1);
        if (!passwdbuf) {
            if (current_uid)
                return;
            fprintf(stderr, "No such user: %s\n", v1);
            exit(1);
        }
        server_uid = passwdbuf->pw_uid;
    }
    DBG(printf("%d\n", server_uid);
        )
}

static void c_set_group(char *v1, char *v2, void *t)
{
    struct group *groupbuf;
    char *endptr;
    int i;
    DBG(printf("Group %s = ", v1);
        )
        i = strtol(v1, &endptr, 0);
    if (*v1 != '\0' && *endptr == '\0') {
        server_gid = i;
    } else {
        groupbuf = getgrnam(v1);
        if (!groupbuf) {
            if (current_uid)
                return;
            fprintf(stderr, "No such group: %s\n", v1);
            exit(1);
        }
        server_gid = groupbuf->gr_gid;
    }
    DBG(printf("%d\n", server_gid);
        )
}

static void c_set_string(char *v1, char *v2, void *t)
{
    char *s;
    DBG(printf("Setting pointer %p to string %s ..", t, v1);
        )
        if (t) {
        s = *(char **) t;
        if (s)
            free(s);
        *(char **) t = strdup(v1);
        if (!*(char **) t) {
            printf("[%s-%d]Unable to strdup in c_set_string", __FILE__, __LINE__);
            exit(1);
        }
        DBG(printf("done.\n");
            )
    } else {
        DBG(printf("skipped.\n");
            )
    }
}

static void c_set_int(char *v1, char *v2, void *t)
{
    char *endptr;
    int i;
    DBG(printf("Setting pointer %p to integer string %s ..", t, v1);
        )
        if (t) {
        i = strtol(v1, &endptr, 0); /* Automatic base 10/16/8 switching */
        if (*v1 != '\0' && *endptr == '\0') {
            *(int *) t = i;
            DBG(printf(" Integer converted as %d, done\n", i);
                )
        } else {
            /* XXX should tell line number to user */
            fprintf(stderr, "Error: %s found where integer expected\n",
                    v1);
        }
    } else {
        DBG(printf("skipped.\n");
            )
    }
}

static void c_set_unity(char *v1, char *v2, void *t)
{
    DBG(printf("Setting pointer %p to unity\n", t);
        )
        if (t)
        *(int *) t = 1;
}

static void c_add_type(char *v1, char *v2, void *t)
{
    add_mime_type(v1, v2);
}

static void c_add_alias(char *v1, char *v2, void *t)
{
    add_alias(v2, v1, *(int *) t);
}

struct ccommand *lookup_keyword(char *c)
{
    struct ccommand *p;
    DBG(printf("Checking string '%s' against keyword list\n", c);
        )
        for (p = clist;
             p < clist + (sizeof (clist) / sizeof (struct ccommand)); p++) {
        if (strcmp(c, p->name) == 0)
            return p;
    }
    return NULL;
}

extern FILE *yyin;
int main(int argc, char * argv[])
{
    yyin = fopen("./boa.conf", "r");
    if (!yyin) {
        fputs("Could not open boa.conf for reading.\n", stderr);
        exit(1);
    }

    yyparse();

    printConfig();
    return 0;
}

4，parse.h

/*
 * Boa, an http server
 * Copyright (C) 1999 Larry Doolittle <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 1, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * parse.h
 * minimum interaction point between Boa's parser (boa_lexer.l and
 * boa_grammar.y) and the rest of Boa.
 */

/* $Id: parse.h,v 1.5 2000/02/12 21:52:45 jon Exp $*/

struct ccommand {
    char *name;
    int type;
    void (*action) (char *, char *, void *);
    void *object;
};

struct ckey {
    char *name;
    int type;
};
struct ckey *lookup_key(char *c);
struct ccommand *lookup_keyword(char *c);
void add_mime_type(char *extension, char *type);

5，测试用的文件boa.conf
    

Port 80
User root
Group root
ErrorLog /dev/console
AccessLog /dev/null
ServerName zhanglong
DocumentRoot /web
DirectoryIndex index.html
KeepAliveMax 1000
Myint   123456
KeepAliveTimeout 10
MimeTypes /etc/mime.types
DefaultType text/plain
CGIPath /bin
AddType application/x-httpd-cgi cgi
MyString    valueOfMyString

6，Makefile
   

all:
bison -y  -d boa_grammar.y
#gcc  -g -O2 -pipe -Wall -I.   -c -o y.tab.o y.tab.c -DDEBUG
gcc  -g -O2 -pipe -Wall -I.   -c -o y.tab.o y.tab.c
flex  boa_lexer.l
gcc  -g -O2 -pipe -Wall -I.   -c -o lex.yy.o lex.yy.c
gcc  -g -O2 -pipe -Wall -I.   -c -o config.o config.c
gcc -o parse y.tab.o lex.yy.o config.o

clean:
rm -f y.tab.c y.tab.h lex.yy.c *.o parse

以上是修改及测试涉及到的全部文件。

五，测试输出及说明
将以上文件置于同一目录下，运行make生成parse可执行文件，输出如下：
  
然后执行./parse，输出如下：

上面的输出结果中有“MyString = ValueOfMyString”, "myint = 123456"是自己另外加上的。
要添加自己的配置项，只要修改4个地方即可。以添加myint项为例：
        1,添加一个全局变量int myint;  
        2,在struct ccommand clist[]数组中添加一项“ {"Myint", S1A, c_set_int, &myint},”
        3,如果要看修改后的结果，在“printConfig()函数”中添加“ printf("myint = %d\n", myint);”
         4,在boa.conf文件中添加相应的赋值项。
添加"MyString"项的步骤与添加“myint”的相同，只是myint 是int型数据，在struct ccommand clist[]数组中的赋值函数用c_set_int；而MyString是char *类型，在struct ccommand clist[]数组中的赋值函数用c_set_string。

   修改config.c文件main()函数指定要解析的文件，或将文件名以函数参数的形式传入，就可以解析指定的文件名中的配置参数。