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