forked from pion/webrtc
/
chunk_payload_data.go
153 lines (130 loc) · 4.93 KB
/
chunk_payload_data.go
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package sctp
import (
"encoding/binary"
"fmt"
)
/*
chunkPayloadData represents an SCTP Chunk of type DATA
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0 | Reserved|U|B|E| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TSN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Identifier S | Stream Sequence Number n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Protocol Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| User Data (seq n of Stream S) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
An unfragmented user message shall have both the B and E bits set to
'1'. Setting both B and E bits to '0' indicates a middle fragment of
a multi-fragment user message, as summarized in the following table:
B E Description
============================================================
| 1 0 | First piece of a fragmented user message |
+----------------------------------------------------------+
| 0 0 | Middle piece of a fragmented user message |
+----------------------------------------------------------+
| 0 1 | Last piece of a fragmented user message |
+----------------------------------------------------------+
| 1 1 | Unfragmented message |
============================================================
| Table 1: Fragment Description Flags |
============================================================
*/
type chunkPayloadData struct {
chunkHeader
unordered bool
beginingFragment bool
endingFragment bool
immediateSack bool
tsn uint32
streamIdentifier uint16
streamSequenceNumber uint16
payloadType PayloadProtocolIdentifier
userData []byte
}
const (
payloadDataEndingFragmentBitmask = 1
payloadDataBeginingFragmentBitmask = 2
payloadDataUnorderedBitmask = 4
payloadDataImmediateSACK = 8
payloadDataHeaderSize = 12
)
// PayloadProtocolIdentifier is an enum for DataChannel payload types
type PayloadProtocolIdentifier uint32
// PayloadProtocolIdentifier enums
const (
PayloadTypeWebRTCDCEP PayloadProtocolIdentifier = 50
PayloadTypeWebRTCString PayloadProtocolIdentifier = 51
PayloadTypeWebRTCBinary PayloadProtocolIdentifier = 53
PayloadTypeWebRTCStringEmpty PayloadProtocolIdentifier = 56
PayloadTypeWebRTCBinaryEmpty PayloadProtocolIdentifier = 57
)
func (p PayloadProtocolIdentifier) String() string {
switch p {
case PayloadTypeWebRTCDCEP:
return "WebRTC DCEP"
case PayloadTypeWebRTCString:
return "WebRTC String"
case PayloadTypeWebRTCBinary:
return "WebRTC Binary"
case PayloadTypeWebRTCStringEmpty:
return "WebRTC String (Empty)"
case PayloadTypeWebRTCBinaryEmpty:
return "WebRTC Binary (Empty)"
default:
return fmt.Sprintf("Unknown Payload Protocol Identifier: %d", p)
}
}
func (p *chunkPayloadData) unmarshal(raw []byte) error {
if err := p.chunkHeader.unmarshal(raw); err != nil {
return err
}
p.immediateSack = p.flags&payloadDataImmediateSACK != 0
p.unordered = p.flags&payloadDataUnorderedBitmask != 0
p.beginingFragment = p.flags&payloadDataBeginingFragmentBitmask != 0
p.endingFragment = p.flags&payloadDataEndingFragmentBitmask != 0
p.tsn = binary.BigEndian.Uint32(p.raw[0:])
p.streamIdentifier = binary.BigEndian.Uint16(p.raw[4:])
p.streamSequenceNumber = binary.BigEndian.Uint16(p.raw[6:])
p.payloadType = PayloadProtocolIdentifier(binary.BigEndian.Uint32(p.raw[8:]))
p.userData = p.raw[payloadDataHeaderSize:]
return nil
}
func (p *chunkPayloadData) marshal() ([]byte, error) {
payRaw := make([]byte, payloadDataHeaderSize+len(p.userData))
binary.BigEndian.PutUint32(payRaw[0:], p.tsn)
binary.BigEndian.PutUint16(payRaw[4:], p.streamIdentifier)
binary.BigEndian.PutUint16(payRaw[6:], p.streamSequenceNumber)
binary.BigEndian.PutUint32(payRaw[8:], uint32(p.payloadType))
copy(payRaw[payloadDataHeaderSize:], p.userData)
flags := uint8(0)
if p.endingFragment {
flags = 1
}
if p.beginingFragment {
flags |= 1 << 1
}
if p.unordered {
flags |= 1 << 2
}
if p.immediateSack {
flags |= 1 << 3
}
p.chunkHeader.flags = flags
p.chunkHeader.typ = PAYLOADDATA
p.chunkHeader.raw = payRaw
return p.chunkHeader.marshal()
}
func (p *chunkPayloadData) check() (abort bool, err error) {
return false, nil
}
// String makes chunkPayloadData printable
func (p *chunkPayloadData) String() string {
return fmt.Sprintf("%s\n%d", p.chunkHeader, p.tsn)
}