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;
}