mirror of https://github.com/jetkvm/kvm.git
123 lines
3.4 KiB
Go
123 lines
3.4 KiB
Go
// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
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// SPDX-License-Identifier: MIT
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package rtcp
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import (
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"encoding/binary"
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)
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// ApplicationDefined represents an RTCP application-defined packet.
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type ApplicationDefined struct {
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SubType uint8
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SSRC uint32
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Name string
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Data []byte
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}
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// DestinationSSRC returns the SSRC value for this packet.
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func (a ApplicationDefined) DestinationSSRC() []uint32 {
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return []uint32{a.SSRC}
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}
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// Marshal serializes the application-defined struct into a byte slice with padding.
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func (a ApplicationDefined) Marshal() ([]byte, error) {
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dataLength := len(a.Data)
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if dataLength > 0xFFFF-12 {
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return nil, errAppDefinedDataTooLarge
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}
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if len(a.Name) != 4 {
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return nil, errAppDefinedInvalidName
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}
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// Calculate the padding size to be added to make the packet length a multiple of 4 bytes.
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paddingSize := 4 - (dataLength % 4)
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if paddingSize == 4 {
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paddingSize = 0
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}
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packetSize := a.MarshalSize()
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header := Header{
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Type: TypeApplicationDefined,
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Length: uint16((packetSize / 4) - 1),
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Padding: paddingSize != 0,
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Count: a.SubType,
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}
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headerBytes, err := header.Marshal()
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if err != nil {
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return nil, err
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}
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rawPacket := make([]byte, packetSize)
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copy(rawPacket, headerBytes)
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binary.BigEndian.PutUint32(rawPacket[4:8], a.SSRC)
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copy(rawPacket[8:12], a.Name)
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copy(rawPacket[12:], a.Data)
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// Add padding if necessary.
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if paddingSize > 0 {
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for i := 0; i < paddingSize; i++ {
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rawPacket[12+dataLength+i] = byte(paddingSize)
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}
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}
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return rawPacket, nil
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}
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// Unmarshal parses the given raw packet into an application-defined struct, handling padding.
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func (a *ApplicationDefined) Unmarshal(rawPacket []byte) 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| subtype | PT=APP=204 | length |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| SSRC/CSRC |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| name (ASCII) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| application-dependent data ...
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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header := Header{}
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err := header.Unmarshal(rawPacket)
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if err != nil {
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return err
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}
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if len(rawPacket) < 12 {
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return errPacketTooShort
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}
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if int(header.Length+1)*4 != len(rawPacket) {
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return errAppDefinedInvalidLength
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}
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a.SubType = header.Count
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a.SSRC = binary.BigEndian.Uint32(rawPacket[4:8])
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a.Name = string(rawPacket[8:12])
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// Check for padding.
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paddingSize := 0
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if header.Padding {
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paddingSize = int(rawPacket[len(rawPacket)-1])
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if paddingSize > len(rawPacket)-12 {
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return errWrongPadding
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}
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}
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a.Data = rawPacket[12 : len(rawPacket)-paddingSize]
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return nil
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}
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// MarshalSize returns the size of the packet once marshaled
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func (a *ApplicationDefined) MarshalSize() int {
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dataLength := len(a.Data)
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// Calculate the padding size to be added to make the packet length a multiple of 4 bytes.
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paddingSize := 4 - (dataLength % 4)
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if paddingSize == 4 {
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paddingSize = 0
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}
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return 12 + dataLength + paddingSize
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}
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