strtok函数实现与应用

转自：http://blog.csdn.net/ast_224/article/details/3977311

strtok:
#include <string.h>
char *strtok(char *str, const char *delim);
char *strtok_r(char *str, const char *delim, char **saveptr);
功能：分解字符串为一组标记串。str为要分解的字符串，delim为分隔符字符串。
说明：首次调用时，str必须指向要分解的字符串，随后调用要把s设成NULL。
      strtok在str中查找包含在delim中的字符并用NULL('/0')来替换，直到找遍整个字符串。
      返回指向下一个标记串。当没有标记串时则返回空字符NULL。
实例：用strtok来判断ip地址是否合法：ip_strtok.c：

 //ip_strtok.c
 #include <stdio.h>
 #include <string.h>
 int main(int argc, char **argv)
 {
    char temp_buf[100] = {};
    char p_temp[100];
    char *p=NULL;
    char *t = ".";
    int m,n,i;
    int j=0,s=0;

    if(argc!=2)
    {
      printf("param must 2/n");
      return -1;
    }
    strcpy(temp_buf, argv[1]);
    for(i=0; i<strlen(temp_buf);i++)
    {
      if(temp_buf[i] == *t)j++;
      if(temp_buf[i] == *t && (temp_buf[i+1]>='0'&&temp_buf[i+1]<='9'))
      {
        s++;
      }
    }
    if(j!=3 || j!=s)
    {
      printf("ip param format error/n");
      return -1;
    }
    p = strtok(temp_buf, t);

    while(p!=NULL)
    {
       strcpy(p_temp, p);
       printf("%s /n", p_temp);
       for(n=0; n<strlen(p_temp);n++)
       {
         if(!(p_temp[n]>='0'&&p_temp[n]<='9'))
         {
           printf("ip param error/n");
           return -1;
         }
       }

       m = atoi(p_temp);
       if(m>255)
       {
         printf("ip invalid /n");
         return -1;
       }

       p=strtok(NULL, ".");
       printf("p = %s/n",p);
    }
    printf("ok! ip correct! ip=%s/n", argv[1]);
    return 0;
 }

编译运行：

[root@localhost liuxltest]# uname -r
2.6.26  
[root@localhost liuxltest]# gcc -Wall ip_strtok.c -o ip_strtok
[root@localhost liuxltest]# ./ip_strtok 172.18.4.255
172 
p = 18
18 
p = 4
4 
p = 255
255 
p = (null)
ok! ip correct! ip=172.18.4.255
[root@localhost liuxltest]# ./ip_strtok 172.18.
ip param format error

 

strtok实现函数：

xl_strtok.c

 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
 char *xl_strtok(char *str, const char *delim);
 int main(int argc, char **argv)
 {
     if(argc != 3)
     {
         printf("param must be 3 /n");
         return -1;
     }

         char *temp;
         char *p_temp;
     char *p;
     temp=(char *)malloc(100);
     p_temp=(char *)malloc(100);
     strcpy(temp, argv[1]);
     strcpy(p_temp, argv[2]);
     printf("temp = %s /n",temp);
     printf("p_temp = %s /n", p_temp);
         p = xl_strtok(temp, p_temp);
         printf("%s/n", p);
         return 0;
 }
 char *xl_strtok(char *s, const char *dm)
 {
         static char *last;
         char *tok;
         if(s == NULL)
                 s = last;
         if(s == NULL)
                 return NULL;
         tok = s;
         while (*s != '/0')
     {
                 while (*dm)
         {
                         if (*s == *dm)
             {
                                 *s = '/0';
                                 last = s + 1;
                                 break;
                         }
                         s++;
                 }
         }
         return tok;
 }

 

strtok源码：

/*********************************************************************/
/***
*strtok.c - tokenize a string with given delimiters
*
*       Copyright (c) Microsoft Corporation. All rights reserved.
*
*Purpose:
*       defines strtok() - breaks string into series of token
*       via repeated calls.
*
*******************************************************************************/

#include <cruntime.h>
#include <string.h>
#ifdef _SECURE_VERSION
#include <internal.h>
#else  /* _SECURE_VERSION */
#include <mtdll.h>
#endif  /* _SECURE_VERSION */

/***
*char *strtok(string, control) - tokenize string with delimiter in control
*
*Purpose:
*       strtok considers the string to consist of a sequence of zero or more
*       text tokens separated by spans of one or more control chars. the first
*       call, with string specified, returns a pointer to the first char of the
*       first token, and will write a null char into string immediately
*       following the returned token. subsequent calls with zero for the first
*       argument (string) will work thru the string until no tokens remain. the
*       control string may be different from call to call. when no tokens remain
*       in string a NULL pointer is returned. remember the control chars with a
*       bit map, one bit per ascii char. the null char is always a control char.
*
*Entry:
*       char *string - string to tokenize, or NULL to get next token
*       char *control - string of characters to use as delimiters
*
*Exit:
*       returns pointer to first token in string, or if string
*       was NULL, to next token
*       returns NULL when no more tokens remain.
*
*Uses:
*
*Exceptions:
*
*******************************************************************************/

#ifdef _SECURE_VERSION
#define _TOKEN *context
#else  /* _SECURE_VERSION */
#define _TOKEN ptd->_token
#endif  /* _SECURE_VERSION */

#ifdef _SECURE_VERSION
char * __cdecl strtok_s (
        char * string,
        const char * control,
        char ** context
        )
#else  /* _SECURE_VERSION */
char * __cdecl strtok (
        char * string,
        const char * control
        )
#endif  /* _SECURE_VERSION */
{
        unsigned char *str;
        const unsigned char *ctrl = control;

        unsigned char map[32];
        int count;

#ifdef _SECURE_VERSION

        /* validation section */
        _VALIDATE_RETURN(context != NULL, EINVAL, NULL);
        _VALIDATE_RETURN(string != NULL || *context != NULL, EINVAL, NULL);
        _VALIDATE_RETURN(control != NULL, EINVAL, NULL);

        /* no static storage is needed for the secure version */

#else  /* _SECURE_VERSION */

        _ptiddata ptd = _getptd();

#endif  /* _SECURE_VERSION */

        /* Clear control map */
        for (count = 0; count < 32; count++)
                map[count] = 0;

        /* Set bits in delimiter table */
        do {
                map[*ctrl >> 3] |= (1 << (*ctrl & 7));
        } while (*ctrl++);

        /* Initialize str */

        /* If string is NULL, set str to the saved
         * pointer (i.e., continue breaking tokens out of the string
         * from the last strtok call) */
        if (string)
                str = string;
        else
                str = _TOKEN;

        /* Find beginning of token (skip over leading delimiters). Note that
         * there is no token iff this loop sets str to point to the terminal
         * null (*str == '/0') */
        while ( (map[*str >> 3] & (1 << (*str & 7))) && *str )
                str++;

        string = str;

        /* Find the end of the token. If it is not the end of the string,
         * put a null there. */
        for ( ; *str ; str++ )
                if ( map[*str >> 3] & (1 << (*str & 7)) ) {
                        *str++ = '/0';
                        break;
                }

        /* Update nextoken (or the corresponding field in the per-thread data
         * structure */
        _TOKEN = str;

        /* Determine if a token has been found. */
        if ( string == str )
                return NULL;
        else
                return string;
}