求索阁

char * strcpy(char* dst,const char* src)

{

    assert((dst!=NULL)&&(src!=NULL));

    char* cp=dst;

    while(*src!='\0')

    {

        *dst=*src;

        src++;

        dst++;

    }

    *dst='\0';

    return cp;

}

char* strcat ( char * dst , const char * src )

{

    char * cp = dst;

    while( *cp )

        cp++;                      /* find end of dst */

    while(*src!='\0')

    {

        *cp++=*src++;

    }

    *cp='\0';

    return dst;                  /* return dst */

} 

int strcmp(const char* str1, const char* str2)

{

    int ret = 0;

    while(!(ret=*(unsigned char*)str1-*(unsigned char*)str2) && *str1)

    {

        str1++;

        str2++

    }

    if (ret < 0)

    {

        return -1;

    }

    else if (ret > 0)

    {

        return 1;

    }

    return 0;

}

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

{

    int len2;

    if ( !(len2 = strlen(s2)) )

        return (char *)s1;

    for ( ; *s1; ++s1 )

    {

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

            return (char *)s1;

    }

    return NULL;

}