boa初始化配置及改造利用

文章轉自：http://blog.chinaunix.net/uid-20718037-id-4560951.html

前言

用到boa搭建的web服務器，不懂yacc，所以也不明白參數解析原理！

索性就不理解了，退而求其次會用就好了。 看到這一篇有如神助！。

正文

一，
boa通過read_config_files()調用語法分析入口函數yyparse(), 取yyparse()函數調用詞法分析入口函數yylex()，讀取並解析boa.conf和mime.types文件, 將其內容理解成一個個的單詞，再將每一行單詞的組合理解爲相應的配置選項。其中yyparse()函數調用yylex()讀取boa.conf和mime.types文件內容。具體的，yylex()函數讀取文件內容，將文件內容按指定的"詞法規則”理解成一個個的單詞，並將單詞返回給yyparse()函數。yyparse()將得到的單詞按指定的"語法規則”理解成配置選項。

二，
yylex()是詞法分析入口函數，在lex.yy.c文件中，由"flex  boa_lexer.l"命令生成。flex是詞法分析生成工具，boa_lexer.l中的代碼指定了"詞法規則” 。
yyparse()是語法分析入口函數，在y.tab.c文件中，由"bison -y  -d boa_grammar.y"命令生成，bison是語法分析生成工具，boa_grammar.y中的代碼指定了“語法規則” 。

三，
boa_lexer.l文件
boa_lexer.l是flex程序文件，包含三個部分，各部分這間用%%分割。

...定義部分...
%%
...規則部分...
%%
...用戶子程序例程...

第一部分是定義部分，包含聲明和選項設置。
    其中的%{和%}之間的部分會被原樣複製到生成的c文件開頭部分。是一些頭文件包含及宏定義，變量聲明等C語言代碼
    %s和%x用來定義一個包含的起始狀態和獨佔的起始狀態。第二部分模式匹配時會用到。
第二部分是規則部分，包含一系列的模式和動作。
    其中的模式使用正則表達式語言。動作是模式匹配時執行的C代碼。這裏的C代碼是用{}括住的多行語句或分號";" 
第三部分是用戶子程序部分，和是則是會被複制到生成的詞法分析器裏面的C代碼。

boa_grammar.y文件
boa_grammar.y是bison程序文件，包含三個部分，各部分這間用%%分割。

..定義部分...
%%
...規則部分...
%%
...用戶子程序例程...

第一部分包含聲明定義等。
    其中的%{和%}之間的部分會被原樣複製到目標分析程序開頭。%token,%start,%union分別用來聲明記號，起始規則，名爲YYSTYPE的union類型的域
第二部分規則部分是一系列的簡單BNF定義的規則和動作。
第三部分則是會被複制到生成的語法分析器裏面的C代碼。

四，代碼改造
    將代碼進行適當修改，成爲配置文件解析工具
修改後的代碼如下：
   1，boa_lexer.l代碼  

點擊(此處)摺疊或打開

%{

/*
 * 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文件代碼

點擊(此處)摺疊或打開

%{

/*
* Boa, an http server
* Copyright (C) 1995 Paul Phillips <[email protected]>
*
* 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 <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
/* #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 <cval> STMT_NO_ARGS STMT_ONE_ARG STMT_TWO_ARGS

/* mime.type tokens */
%token <sval> STRING
%token <ival> INTEGER
%token <sval> KEY
%token <sval> 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代碼
  

點擊(此處)摺疊或打開

/*
 * 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

點擊(此處)摺疊或打開

/*
 * 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，測試用的文件boa.conf
    

點擊(此處)摺疊或打開

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
   

點擊(此處)摺疊或打開

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

以上是修改及測試涉及到的全部文件。

五，測試輸出及說明
將以上文件置於同一目錄下，運行make生成parse可執行文件，輸出如下：
  
然後執行./parse，輸出如下：

上面的輸出結果中有“MyString = ValueOfMyString”, "myint = 123456"是自己另外加上的。
要添加自己的配置項，只要修改4個地方即可。以添加myint項爲例：
        1,添加一個全局變量int myint;  
        2,在struct ccommand clist[]數組中添加一項“ {"Myint", S1A, c_set_int, &myint},”
        3,如果要看修改後的結果，在“printConfig()函數”中添加“ printf("myint = %d\n", myint);”
         4,在boa.conf文件中添加相應的賦值項。
添加"MyString"項的步驟與添加“myint”的相同，只是myint 是int型數據，在struct ccommand clist[]數組中的賦值函數用c_set_int；而MyString是char *類型，在struct ccommand clist[]數組中的賦值函數用c_set_string。

   修改config.c文件main()函數指定要解析的文件，或將文件名以函數參數的形式傳入，就可以解析指定的文件名中的配置參數。