protocol/rtp: commented file

protocol/rtp/client.go

@@ -3,13 +3,15 @@ NAME
   client.go
 
 DESCRIPTION
-  client.go provides an RTP client that will receive RTP on a UDP connection
+  client.go provides an RTP client, Client, that will receive RTP on a UDP
+  connection, perform an operation on the packets and then store in a ringBuffer
+  that can be read from Read, an implemntation of io.Reader.
 
 AUTHOR
   Saxon A. Nelson-Milton <saxon@ausocean.org>
 
 LICENSE
-  rtp.go is Copyright (C) 2018 the Australian Ocean Lab (AusOcean)
+  This is Copyright (C) 2019 the Australian Ocean Lab (AusOcean).
 
   It is free software: you can redistribute it and/or modify them
   under the terms of the GNU General Public License as published by the
@@ -22,7 +24,7 @@ LICENSE
   for more details.
 
   You should have received a copy of the GNU General Public License
-  along with revid in gpl.txt.  If not, see [GNU licenses](http://www.gnu.org/licenses).
+  in gpl.txt.  If not, see http://www.gnu.org/licenses.
 */
 
 package rtp
@@ -39,15 +41,24 @@ const (
 	chanSize = 10
 )
 
+// Client describes an RTP client that can receive an RTP stream and implements
+// io.Reader.
 type Client struct {
-	conn    *net.UDPConn
-	wg      sync.WaitGroup
-	done    chan struct{}
-	ring    *ring.Buffer
-	op      func([]byte) ([]byte, error)
-	ErrChan chan error
+	conn    *net.UDPConn                 // The UDP connection RTP packets will be read from.
+	wg      sync.WaitGroup               // Used to wait for recv routine to finish.
+	done    chan struct{}                //  Used to terminate the recv routine.
+	ring    *ring.Buffer                 // Processed data from RTP packets will be stored here.
+	op      func([]byte) ([]byte, error) // The operation to perform on received RTP packets before storing.
+	ErrChan chan error                   // Errors encountered during recv will be sent to this chan.
 }
 
+// NewClient returns a pointer to a new Client.
+//
+// addr is the address of form <ip>:<port> that we expect to receive
+// RTP at. op is a function, if non nil, that will be used to perform an
+// operation on each received RTP packet. For example, the op func may parse
+// out the RTP payload. The result of the operation is then what is stored
+// in the ringBuffer for reading.
 func NewClient(addr string, op func([]byte) ([]byte, error)) (*Client, error) {
 	c := &Client{
 		done: make(chan struct{}, 10),
@@ -68,11 +79,15 @@ func NewClient(addr string, op func([]byte) ([]byte, error)) (*Client, error) {
 	return c, nil
 }
 
+// Start will start the recv routine.
 func (c *Client) Start() {
 	c.wg.Add(1)
 	go c.recv()
 }
 
+// recv will read RTP packets from the UDP connection, perform the operation
+// on them given at creation of the Client and then store the result in the
+// ringBuffer for Reading.
 func (c *Client) recv() {
 	defer c.wg.Done()
 	buf := make([]byte, 4096)
@@ -107,12 +122,17 @@ func (c *Client) recv() {
 	}
 }
 
+// Stop will send a done signal to the receive routine, and also close the
+// connection.
 func (c *Client) Stop() {
 	close(c.done)
 	c.conn.Close()
 	c.wg.Wait()
 }
 
+// Read implements io.Reader.
+//
+// Read will get the next chunk from the ringBuffer and copy the bytes to p.
 func (c *Client) Read(p []byte) (int, error) {
 	chunk, err := c.ring.Next(0)
 	if err != nil {