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|
package datachannel
import (
"encoding/binary"
"github.com/pkg/errors"
)
/*
channelOpen represents a DATA_CHANNEL_OPEN Message
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type | Channel Type | Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reliability Parameter |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Length | Protocol Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Label |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Protocol |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
type channelOpen struct {
ChannelType ChannelType
Priority uint16
ReliabilityParameter uint32
Label []byte
Protocol []byte
}
const (
channelOpenHeaderLength = 12
)
// ChannelType determines the reliability of the WebRTC DataChannel
type ChannelType byte
// ChannelType enums
const (
// ChannelTypeReliable determines the Data Channel provides a
// reliable in-order bi-directional communication.
ChannelTypeReliable ChannelType = 0x00
// ChannelTypeReliableUnordered determines the Data Channel
// provides a reliable unordered bi-directional communication.
ChannelTypeReliableUnordered ChannelType = 0x80
// ChannelTypePartialReliableRexmit determines the Data Channel
// provides a partially-reliable in-order bi-directional communication.
// User messages will not be retransmitted more times than specified in the Reliability Parameter.
ChannelTypePartialReliableRexmit ChannelType = 0x01
// ChannelTypePartialReliableRexmitUnordered determines
// the Data Channel provides a partial reliable unordered bi-directional communication.
// User messages will not be retransmitted more times than specified in the Reliability Parameter.
ChannelTypePartialReliableRexmitUnordered ChannelType = 0x81
// ChannelTypePartialReliableTimed determines the Data Channel
// provides a partial reliable in-order bi-directional communication.
// User messages might not be transmitted or retransmitted after
// a specified life-time given in milli- seconds in the Reliability Parameter.
// This life-time starts when providing the user message to the protocol stack.
ChannelTypePartialReliableTimed ChannelType = 0x02
// The Data Channel provides a partial reliable unordered bi-directional
// communication. User messages might not be transmitted or retransmitted
// after a specified life-time given in milli- seconds in the Reliability Parameter.
// This life-time starts when providing the user message to the protocol stack.
ChannelTypePartialReliableTimedUnordered ChannelType = 0x82
)
// ChannelPriority enums
const (
ChannelPriorityBelowNormal uint16 = 128
ChannelPriorityNormal uint16 = 256
ChannelPriorityHigh uint16 = 512
ChannelPriorityExtraHigh uint16 = 1024
)
// Marshal returns raw bytes for the given message
func (c *channelOpen) Marshal() ([]byte, error) {
labelLength := len(c.Label)
protocolLength := len(c.Protocol)
totalLen := channelOpenHeaderLength + labelLength + protocolLength
raw := make([]byte, totalLen)
raw[0] = uint8(dataChannelOpen)
raw[1] = byte(c.ChannelType)
binary.BigEndian.PutUint16(raw[2:], c.Priority)
binary.BigEndian.PutUint32(raw[4:], c.ReliabilityParameter)
binary.BigEndian.PutUint16(raw[8:], uint16(labelLength))
binary.BigEndian.PutUint16(raw[10:], uint16(protocolLength))
endLabel := channelOpenHeaderLength + labelLength
copy(raw[channelOpenHeaderLength:endLabel], c.Label)
copy(raw[endLabel:endLabel+protocolLength], c.Protocol)
return raw, nil
}
// Unmarshal populates the struct with the given raw data
func (c *channelOpen) Unmarshal(raw []byte) error {
if len(raw) < channelOpenHeaderLength {
return errors.Errorf("Length of input is not long enough to satisfy header %d", len(raw))
}
c.ChannelType = ChannelType(raw[1])
c.Priority = binary.BigEndian.Uint16(raw[2:])
c.ReliabilityParameter = binary.BigEndian.Uint32(raw[4:])
labelLength := binary.BigEndian.Uint16(raw[8:])
protocolLength := binary.BigEndian.Uint16(raw[10:])
if len(raw) != int(channelOpenHeaderLength+labelLength+protocolLength) {
return errors.Errorf("Label + Protocol length don't match full packet length")
}
c.Label = raw[channelOpenHeaderLength : channelOpenHeaderLength+labelLength]
c.Protocol = raw[channelOpenHeaderLength+labelLength : channelOpenHeaderLength+labelLength+protocolLength]
return nil
}
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