rtp: created rtp packet structure, wrote byte function (interprets packet structure and creates equivalent byte slice and started writing test utilities

stream/rtp/encoder.go

@@ -0,0 +1,28 @@
+/*
+NAME
+  encoder.go
+
+DESCRIPTION
+  See Readme.md
+
+AUTHOR
+  Saxon Nelson-Milton (saxon@ausocean.org)
+
+LICENSE
+  encoder.go is Copyright (C) 2018 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
+  Free Software Foundation, either version 3 of the License, or (at your
+  option) any later version.
+
+  It is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public 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 http://www.gnu.org/licenses.
+*/
+
+package rtp

stream/rtp/rtp.go

@@ -0,0 +1,87 @@
+/*
+NAME
+  rtp.go - provides a data structure intended to encapsulate the properties
+  of an rtp packet and also functions to allow manipulation of these packets.
+
+DESCRIPTION
+  See Readme.md
+
+AUTHOR
+  Saxon A. Nelson-Milton <saxon@ausocean.org>
+
+LICENSE
+  rtp.go is Copyright (C) 2018 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
+  Free Software Foundation, either version 3 of the License, or (at your
+  option) any later version.
+
+  It is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public 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).
+*/
+
+// See https://tools.ietf.org/html/rfc6184 for rtp packet format
+
+package rtp
+
+const (
+	rtpVer          = 2
+	defaultHeadSize = 3 * 4 // bytes
+)
+
+type Pkt struct {
+	V       byte
+	P       byte
+	X       byte
+	CC      byte
+	M       byte
+	PT      byte
+	SN      int16
+	TS      int32
+	SSRC    int32
+	Payload []byte
+	Padding int
+}
+
+func (p *Pkt) Bytes() []byte {
+	if p.V == 0 {
+		p.V = rtpVer
+	}
+
+	if p.P != 0 && p.Padding == 0 {
+		panic("Padding bit set to something other than 1, but there is no padding size defined!")
+	} else if p.P == 0 && p.Padding != 0 {
+		panic("Padding bit is set to zero, but it's indicated that there is padding!")
+	}
+
+	if p.CC != 0 {
+		panic("CC has been set to something other than 0 - this is not supported yet!")
+	}
+
+	buf := make([]byte, defaultHeadSize, defaultHeadSize+len(p.Payload)+p.Padding)
+	// First 4 bytes
+	buf[0] |= p.V<<6 | p.P<<5 | p.CC
+	buf[1] |= p.M<<7 | p.PT
+	buf[2] |= byte(p.SN >> 8)
+	buf[3] |= byte(p.SN)
+	// Second lot of 4 bytes
+	buf[4] |= byte(p.TS >> 24)
+	buf[5] |= byte(p.TS >> 16)
+	buf[6] |= byte(p.TS >> 8)
+	buf[7] |= byte(p.TS)
+	// Third lot of 4 bytes
+	buf[8] |= byte(p.SSRC >> 24)
+	buf[9] |= byte(p.SSRC >> 16)
+	buf[10] |= byte(p.SSRC >> 8)
+	buf[11] |= byte(p.SSRC)
+	// Add payload and padding
+	buf = append(buf, p.Payload...)
+	buf = append(buf, append(make([]byte, p.Padding-1, p.Padding), byte(p.Padding))...)
+	return buf
+}

stream/rtp/rtp_test.go

@@ -0,0 +1,43 @@
+/*
+NAME
+  rtp_test.go
+
+DESCRIPTION
+  See Readme.md
+
+AUTHOR
+  Saxon Nelson-Milton (saxon@ausocean.org)
+
+LICENSE
+  rtp_test.go is Copyright (C) 2017 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
+  Free Software Foundation, either version 3 of the License, or (at your
+  option) any later version.
+
+  It is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public 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 http://www.gnu.org/licenses.
+*/
+
+package rtp
+
+var rtpTests = []struct {
+	pkt        Pkt
+	byteOutput []byte
+}{
+	{
+		pkt: Pkt{},
+	},
+	{
+		name:  "null short",
+		input: []byte{0x00, 0x00, 0x01, 0x0},
+		delay: 0,
+		want:  [][]byte{{0x0, 0x0, 0x1, 0x9, 0xf0, 0x00, 0x00, 0x01, 0x0}},
+	},
+}