紧密循环泄漏阅读器

Question

I have the following code that I think is leaking heavily. And analysing it I suspect that the defer r.Close() is never called.

Would there be a better way of using the Reader and gzip here at all?

// Read client data from channel
func (c *Client) listen() {
    timeoutDuration := 30 * time.Second

    reader := bufio.NewReader(c.conn)

    clientBuffer := new(bytes.Buffer)

    for {
        c.conn.SetReadDeadline(time.Now().Add(timeoutDuration))

        byte, err := reader.ReadByte()

        if err != nil {
            c.conn.Close()
            c.server.onClientConnectionClosed(c, err)
            return
        }

        clientBuffer.WriteByte(byte)
        packet := popPacketFromBuffer(clientBuffer)

        if packet != nil {
            packetBuffer := bytes.NewBuffer(packet)

            r, _ := gzip.NewReader(packetBuffer)
            defer r.Close()

            b, err := ioutil.ReadAll(r)
            if err != nil {
                log.Fatal(err)
            }

            c.server.onNewMessage(c, b)
        }

    }
}

Answer 1

Your problem is that defer functions are only called at the end of the function. Not the loop. So, yes, it is probable that they stay open.

One method would be to encapsulate your tight-loop into a function.

func uncompress(packet []byte) ([]byte, error) {
    r, _ := gzip.NewReader(bytes.NewBuffer(packet))
    defer r.Close()
    return ioutil.ReadAll(r)
}

// Read client data from channel
func (c *Client) listen() {
    /* … */

    for {
        /* … */

        if packet != nil {
            b, err := uncompress(packet)
            if err != nil {
                log.Fatal(err)
            }
            c.server.onNewMessage(c, b)
        }

    }
}

Another would be to unroll the defer call and do it manually.

// Read client data from channel
func (c *Client) listen() {
    /* … */

    for {
        /* … */

        if packet != nil {
            r, _ := gzip.NewReader(bytes.NewBuffer(packet))
            b, err := ioutil.ReadAll(r)
            if err != nil {
                log.Fatal(err)
            }
            r.Close()
            c.server.onNewMessage(c, b)
        }

    }
}