strstr实现

// strstr.c查找完全匹配的子字符串

#include<stdio.h>

#include<string.h>



char *my_strstr(const char *s1,const char *s2)

{

    const char *p=s1;

    const int len=strlen(s2);

    for(;(p=strchr(p,*s2))!=0;p++)

    {

        if(strncmp(p,s2,len)==0)

        return(char *)p;

    }

    return (0);

}



char *my_strstr1(const char *s1, const char *s2)

{

    int n;

    if (*s2)

    {

        while (*s1)

        {

            for (n=0; *(s1 + n) == *(s2 + n); n++)

            {

                if (!*(s2 + n + 1))

                return (char *)s1;

            }

            s1++;

        }

        return NULL;

    }

    else

    return (char *)s1;

}



char *my_strstr2( const char *s1, const char *s2 )

{

    int len2;

    if ( !(len2 = strlen(s2)) )//此种情况下s2不能指向空，否则strlen无法测出长度，这条语句错误

        return (char *)s1;

    for ( ; *s1; ++s1 )

    {

        if ( *s1 == *s2 && strncmp( s1, s2, len2 )==0 )

        return (char *)s1;

    }

    return NULL;

}



int main()

{

    char *s="Golden Global View";

    char *l="lob";

    char *p;

    //p=strstr(s,l);

    //p=my_strstr(s,l);

    p=my_strstr(s,l);

    if(p)

        printf("s=%s,p=%s\n",s,p);

    else

        printf("Not Found!\n");

    

    {

        char * rmlst = "ppp3.3/222.222.222.222";

        char * cp1=NULL,* ipintf=NULL,*pubAddr=NULL;

        cp1 = strstr(rmlst, "/");

        if ( cp1 == NULL ) 

           return;

/*

        *cp1 = '\0';

        strncpy(ipintf, rmlst, cp1-rmlst);

        strcpy(pubAddr, cp1+1);

*/

        printf("~~~~~~~~~~~,rmlst=%s,ipintf=%s,pubAddr=%s,cp1+1=%s\n\n\n\n", rmlst,ipintf,pubAddr,cp1+1);

    }



    getchar();        

    return 0;

}