char* str_replace(char* dst, int num, const char* str,
                  const char* orig, const char* rep){
    const char* ptr;
    size_t len1 = strlen(orig);
    size_t len2 = strlen(rep);
    char*  tmp  = dst;

    num -= 1;
    while((ptr = strstr(str, orig)) != NULL){
        num -= (ptr - str) + len2;
        if(num < 1)
            break;

        strncpy(dst, str, (size_t)(ptr - str));
        dst += ptr - str;
        strncpy(dst, rep, len2);
        dst += len2;
        str  = ptr + len1;
    }

    for(; (*dst = *str) && (num > 0); --num){
        ++dst;
        ++str;
    }
    return tmp;
}