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vendor.github.com.pion.rtp.packet.go Maven / Gradle / Ivy
package rtp
import (
"encoding/binary"
"fmt"
"io"
)
// Extension RTP Header extension
type Extension struct {
id uint8
payload []byte
}
// Header represents an RTP packet header
type Header struct {
Version uint8
Padding bool
Extension bool
Marker bool
PayloadType uint8
SequenceNumber uint16
Timestamp uint32
SSRC uint32
CSRC []uint32
ExtensionProfile uint16
Extensions []Extension
}
// Packet represents an RTP Packet
type Packet struct {
Header
Payload []byte
PaddingSize byte
}
const (
headerLength = 4
versionShift = 6
versionMask = 0x3
paddingShift = 5
paddingMask = 0x1
extensionShift = 4
extensionMask = 0x1
extensionProfileOneByte = 0xBEDE
extensionProfileTwoByte = 0x1000
extensionIDReserved = 0xF
ccMask = 0xF
markerShift = 7
markerMask = 0x1
ptMask = 0x7F
seqNumOffset = 2
seqNumLength = 2
timestampOffset = 4
timestampLength = 4
ssrcOffset = 8
ssrcLength = 4
csrcOffset = 12
csrcLength = 4
)
// String helps with debugging by printing packet information in a readable way
func (p Packet) String() string {
out := "RTP PACKET:\n"
out += fmt.Sprintf("\tVersion: %v\n", p.Version)
out += fmt.Sprintf("\tMarker: %v\n", p.Marker)
out += fmt.Sprintf("\tPayload Type: %d\n", p.PayloadType)
out += fmt.Sprintf("\tSequence Number: %d\n", p.SequenceNumber)
out += fmt.Sprintf("\tTimestamp: %d\n", p.Timestamp)
out += fmt.Sprintf("\tSSRC: %d (%x)\n", p.SSRC, p.SSRC)
out += fmt.Sprintf("\tPayload Length: %d\n", len(p.Payload))
return out
}
// Unmarshal parses the passed byte slice and stores the result in the Header.
// It returns the number of bytes read n and any error.
func (h *Header) Unmarshal(buf []byte) (n int, err error) { //nolint:gocognit
if len(buf) < headerLength {
return 0, fmt.Errorf("%w: %d < %d", errHeaderSizeInsufficient, len(buf), headerLength)
}
/*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |V=2|P|X| CC |M| PT | sequence number |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | timestamp |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | synchronization source (SSRC) identifier |
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* | contributing source (CSRC) identifiers |
* | .... |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
h.Version = buf[0] >> versionShift & versionMask
h.Padding = (buf[0] >> paddingShift & paddingMask) > 0
h.Extension = (buf[0] >> extensionShift & extensionMask) > 0
nCSRC := int(buf[0] & ccMask)
if cap(h.CSRC) < nCSRC || h.CSRC == nil {
h.CSRC = make([]uint32, nCSRC)
} else {
h.CSRC = h.CSRC[:nCSRC]
}
n = csrcOffset + (nCSRC * csrcLength)
if len(buf) < n {
return n, fmt.Errorf("size %d < %d: %w", len(buf), n,
errHeaderSizeInsufficient)
}
h.Marker = (buf[1] >> markerShift & markerMask) > 0
h.PayloadType = buf[1] & ptMask
h.SequenceNumber = binary.BigEndian.Uint16(buf[seqNumOffset : seqNumOffset+seqNumLength])
h.Timestamp = binary.BigEndian.Uint32(buf[timestampOffset : timestampOffset+timestampLength])
h.SSRC = binary.BigEndian.Uint32(buf[ssrcOffset : ssrcOffset+ssrcLength])
for i := range h.CSRC {
offset := csrcOffset + (i * csrcLength)
h.CSRC[i] = binary.BigEndian.Uint32(buf[offset:])
}
if h.Extensions != nil {
h.Extensions = h.Extensions[:0]
}
if h.Extension {
if expected := n + 4; len(buf) < expected {
return n, fmt.Errorf("size %d < %d: %w",
len(buf), expected,
errHeaderSizeInsufficientForExtension,
)
}
h.ExtensionProfile = binary.BigEndian.Uint16(buf[n:])
n += 2
extensionLength := int(binary.BigEndian.Uint16(buf[n:])) * 4
n += 2
if expected := n + extensionLength; len(buf) < expected {
return n, fmt.Errorf("size %d < %d: %w",
len(buf), expected,
errHeaderSizeInsufficientForExtension,
)
}
switch h.ExtensionProfile {
// RFC 8285 RTP One Byte Header Extension
case extensionProfileOneByte:
end := n + extensionLength
for n < end {
if buf[n] == 0x00 { // padding
n++
continue
}
extid := buf[n] >> 4
len := int(buf[n]&^0xF0 + 1)
n++
if extid == extensionIDReserved {
break
}
extension := Extension{id: extid, payload: buf[n : n+len]}
h.Extensions = append(h.Extensions, extension)
n += len
}
// RFC 8285 RTP Two Byte Header Extension
case extensionProfileTwoByte:
end := n + extensionLength
for n < end {
if buf[n] == 0x00 { // padding
n++
continue
}
extid := buf[n]
n++
len := int(buf[n])
n++
extension := Extension{id: extid, payload: buf[n : n+len]}
h.Extensions = append(h.Extensions, extension)
n += len
}
default: // RFC3550 Extension
if len(buf) < n+extensionLength {
return n, fmt.Errorf("%w: %d < %d",
errHeaderSizeInsufficientForExtension, len(buf), n+extensionLength)
}
extension := Extension{id: 0, payload: buf[n : n+extensionLength]}
h.Extensions = append(h.Extensions, extension)
n += len(h.Extensions[0].payload)
}
}
return n, nil
}
// Unmarshal parses the passed byte slice and stores the result in the Packet.
func (p *Packet) Unmarshal(buf []byte) error {
n, err := p.Header.Unmarshal(buf)
if err != nil {
return err
}
end := len(buf)
if p.Header.Padding {
p.PaddingSize = buf[end-1]
end -= int(p.PaddingSize)
}
if end < n {
return errTooSmall
}
p.Payload = buf[n:end]
return nil
}
// Marshal serializes the header into bytes.
func (h Header) Marshal() (buf []byte, err error) {
buf = make([]byte, h.MarshalSize())
n, err := h.MarshalTo(buf)
if err != nil {
return nil, err
}
return buf[:n], nil
}
// MarshalTo serializes the header and writes to the buffer.
func (h Header) MarshalTo(buf []byte) (n int, err error) {
/*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |V=2|P|X| CC |M| PT | sequence number |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | timestamp |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | synchronization source (SSRC) identifier |
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* | contributing source (CSRC) identifiers |
* | .... |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
size := h.MarshalSize()
if size > len(buf) {
return 0, io.ErrShortBuffer
}
// The first byte contains the version, padding bit, extension bit,
// and csrc size.
buf[0] = (h.Version << versionShift) | uint8(len(h.CSRC))
if h.Padding {
buf[0] |= 1 << paddingShift
}
if h.Extension {
buf[0] |= 1 << extensionShift
}
// The second byte contains the marker bit and payload type.
buf[1] = h.PayloadType
if h.Marker {
buf[1] |= 1 << markerShift
}
binary.BigEndian.PutUint16(buf[2:4], h.SequenceNumber)
binary.BigEndian.PutUint32(buf[4:8], h.Timestamp)
binary.BigEndian.PutUint32(buf[8:12], h.SSRC)
n = 12
for _, csrc := range h.CSRC {
binary.BigEndian.PutUint32(buf[n:n+4], csrc)
n += 4
}
if h.Extension {
extHeaderPos := n
binary.BigEndian.PutUint16(buf[n+0:n+2], h.ExtensionProfile)
n += 4
startExtensionsPos := n
switch h.ExtensionProfile {
// RFC 8285 RTP One Byte Header Extension
case extensionProfileOneByte:
for _, extension := range h.Extensions {
buf[n] = extension.id<<4 | (uint8(len(extension.payload)) - 1)
n++
n += copy(buf[n:], extension.payload)
}
// RFC 8285 RTP Two Byte Header Extension
case extensionProfileTwoByte:
for _, extension := range h.Extensions {
buf[n] = extension.id
n++
buf[n] = uint8(len(extension.payload))
n++
n += copy(buf[n:], extension.payload)
}
default: // RFC3550 Extension
extlen := len(h.Extensions[0].payload)
if extlen%4 != 0 {
// the payload must be in 32-bit words.
return 0, io.ErrShortBuffer
}
n += copy(buf[n:], h.Extensions[0].payload)
}
// calculate extensions size and round to 4 bytes boundaries
extSize := n - startExtensionsPos
roundedExtSize := ((extSize + 3) / 4) * 4
binary.BigEndian.PutUint16(buf[extHeaderPos+2:extHeaderPos+4], uint16(roundedExtSize/4))
// add padding to reach 4 bytes boundaries
for i := 0; i < roundedExtSize-extSize; i++ {
buf[n] = 0
n++
}
}
return n, nil
}
// MarshalSize returns the size of the header once marshaled.
func (h Header) MarshalSize() int {
// NOTE: Be careful to match the MarshalTo() method.
size := 12 + (len(h.CSRC) * csrcLength)
if h.Extension {
extSize := 4
switch h.ExtensionProfile {
// RFC 8285 RTP One Byte Header Extension
case extensionProfileOneByte:
for _, extension := range h.Extensions {
extSize += 1 + len(extension.payload)
}
// RFC 8285 RTP Two Byte Header Extension
case extensionProfileTwoByte:
for _, extension := range h.Extensions {
extSize += 2 + len(extension.payload)
}
default:
extSize += len(h.Extensions[0].payload)
}
// extensions size must have 4 bytes boundaries
size += ((extSize + 3) / 4) * 4
}
return size
}
// SetExtension sets an RTP header extension
func (h *Header) SetExtension(id uint8, payload []byte) error { //nolint:gocognit
if h.Extension {
switch h.ExtensionProfile {
// RFC 8285 RTP One Byte Header Extension
case extensionProfileOneByte:
if id < 1 || id > 14 {
return fmt.Errorf("%w actual(%d)", errRFC8285OneByteHeaderIDRange, id)
}
if len(payload) > 16 {
return fmt.Errorf("%w actual(%d)", errRFC8285OneByteHeaderSize, len(payload))
}
// RFC 8285 RTP Two Byte Header Extension
case extensionProfileTwoByte:
if id < 1 || id > 255 {
return fmt.Errorf("%w actual(%d)", errRFC8285TwoByteHeaderIDRange, id)
}
if len(payload) > 255 {
return fmt.Errorf("%w actual(%d)", errRFC8285TwoByteHeaderSize, len(payload))
}
default: // RFC3550 Extension
if id != 0 {
return fmt.Errorf("%w actual(%d)", errRFC3550HeaderIDRange, id)
}
}
// Update existing if it exists else add new extension
for i, extension := range h.Extensions {
if extension.id == id {
h.Extensions[i].payload = payload
return nil
}
}
h.Extensions = append(h.Extensions, Extension{id: id, payload: payload})
return nil
}
// No existing header extensions
h.Extension = true
switch len := len(payload); {
case len <= 16:
h.ExtensionProfile = extensionProfileOneByte
case len > 16 && len < 256:
h.ExtensionProfile = extensionProfileTwoByte
}
h.Extensions = append(h.Extensions, Extension{id: id, payload: payload})
return nil
}
// GetExtensionIDs returns an extension id array
func (h *Header) GetExtensionIDs() []uint8 {
if !h.Extension {
return nil
}
if len(h.Extensions) == 0 {
return nil
}
ids := make([]uint8, 0, len(h.Extensions))
for _, extension := range h.Extensions {
ids = append(ids, extension.id)
}
return ids
}
// GetExtension returns an RTP header extension
func (h *Header) GetExtension(id uint8) []byte {
if !h.Extension {
return nil
}
for _, extension := range h.Extensions {
if extension.id == id {
return extension.payload
}
}
return nil
}
// DelExtension Removes an RTP Header extension
func (h *Header) DelExtension(id uint8) error {
if !h.Extension {
return errHeaderExtensionsNotEnabled
}
for i, extension := range h.Extensions {
if extension.id == id {
h.Extensions = append(h.Extensions[:i], h.Extensions[i+1:]...)
return nil
}
}
return errHeaderExtensionNotFound
}
// Marshal serializes the packet into bytes.
func (p Packet) Marshal() (buf []byte, err error) {
buf = make([]byte, p.MarshalSize())
n, err := p.MarshalTo(buf)
if err != nil {
return nil, err
}
return buf[:n], nil
}
// MarshalTo serializes the packet and writes to the buffer.
func (p Packet) MarshalTo(buf []byte) (n int, err error) {
p.Header.Padding = p.PaddingSize != 0
n, err = p.Header.MarshalTo(buf)
if err != nil {
return 0, err
}
// Make sure the buffer is large enough to hold the packet.
if n+len(p.Payload)+int(p.PaddingSize) > len(buf) {
return 0, io.ErrShortBuffer
}
m := copy(buf[n:], p.Payload)
if p.Header.Padding {
buf[n+m+int(p.PaddingSize-1)] = p.PaddingSize
}
return n + m + int(p.PaddingSize), nil
}
// MarshalSize returns the size of the packet once marshaled.
func (p Packet) MarshalSize() int {
return p.Header.MarshalSize() + len(p.Payload) + int(p.PaddingSize)
}
// Clone returns a deep copy of p.
func (p Packet) Clone() *Packet {
clone := &Packet{}
clone.Header = p.Header.Clone()
if p.Payload != nil {
clone.Payload = make([]byte, len(p.Payload))
copy(clone.Payload, p.Payload)
}
clone.PaddingSize = p.PaddingSize
return clone
}
// Clone returns a deep copy h.
func (h Header) Clone() Header {
clone := h
if h.CSRC != nil {
clone.CSRC = make([]uint32, len(h.CSRC))
copy(clone.CSRC, h.CSRC)
}
if h.Extensions != nil {
ext := make([]Extension, len(h.Extensions))
for i, e := range h.Extensions {
ext[i] = e
if e.payload != nil {
ext[i].payload = make([]byte, len(e.payload))
copy(ext[i].payload, e.payload)
}
}
clone.Extensions = ext
}
return clone
}
