c 字符串查找，替换

char * strReplace(char *str, char *oldstr, char * newstr)
{
    char *beg = strFind(str, oldstr);
    if (!beg)
        return str;
    int lenStr = strlen(str);
    int lenOldstr = strlen(oldstr);
    int lenNewstr = strlen(newstr);
    memmove(beg + lenNewstr, beg + lenOldstr, lenStr - (beg - str) - lenOldstr + 1);
    memcpy(beg, newstr, lenNewstr);
    return str;
}

char * strFind(char * str, char * sub)
{
    char * psub = sub;
    char * pstr = str;
    while (*str){
        psub = sub;
        pstr = str;
        while (*str == *psub && *psub)
        {
            ++str;
            ++psub;
        }
        if (!*psub)
            return pstr;
        else
            str = pstr + 1;
    }
    return NULL;
}