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