idea

• When receive and parse the response from server.

  • for header, we read line by line, with Rio_readlineb().
  • for body, we parse the body size from the header info, and read the body at once, with Rio_readnb().

• [TRY]: if we can parse the header info and send that information to the client at the same time.

• use Rio instead of normal IO for read and write.

• whenver init with char var[xx], note that such var refers to random memory, should mark the ending position as \0, such that we know where to stop, and not printing out random trash.

LFU policy:

• when frequency = 1, >= min entry in LFU table will not evict any existing entry. when frequency > 1, >= will take effect.