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mnp_connection_layer.go
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mnp_connection_layer.go
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package protocol
import (
"fmt"
"gdcl/fsm"
"os"
"time"
)
const (
IDLE = iota
LINK_REQUEST
DATA_PHASE
DISCONNECTING
)
const (
LR byte = 1
LD byte = 2
LT byte = 4
LA byte = 5
)
type PacketType struct {
packetType byte
}
type OutstandingPacket struct {
data []byte
sendSequenceNumber byte
}
type AckInfo struct {
credit byte
receiveSequenceNumber byte
lastAckSequenceNumber byte
}
type MNPConnectionLayer struct {
state int
stateTable map[int][]fsm.State
maxInfoLength uint16
lastAckSequenceNumber byte
FromDockLink chan []byte
ToDockLink chan []byte
FromPacketLayer chan Packet
ToPacketLayer chan []byte
writeQueue chan []byte
ackChannel chan AckInfo
outstandingPackets []OutstandingPacket
sendCreditStateVariable byte
receiveCreditStateVariable byte
sendStateVariable byte
receiveStateVariable byte
}
var connectionLayer MNPConnectionLayer
func (packetType PacketType) Matches(input interface{}) bool {
return input.(*Packet).packetType == packetType.packetType
}
func sendLinkRequestResponse(state int, input interface{}, output interface{}, data interface{}) {
layer := data.(*MNPConnectionLayer)
packet := input.(*Packet)
framingMode := packet.data[11]
maxOutstanding := packet.data[14]
dataPhaseOpt := packet.data[21]
if dataPhaseOpt&0x1 == 0x1 {
layer.maxInfoLength = 256
} else {
layer.maxInfoLength = 64
}
buf := []byte{23, LR, 2,
1, 6, 1, 0, 0, 0, 0, 255,
2, 1, framingMode,
3, 1, maxOutstanding,
4, 2, 64, 0,
8, 1, dataPhaseOpt}
layer.outstandingPackets = make([]OutstandingPacket, 0, maxOutstanding)
layer.ToPacketLayer <- buf
}
func handleLinkAcknowledgement(state int, input interface{}, output interface{}, data interface{}) {
layer := data.(*MNPConnectionLayer)
packet := input.(*Packet)
receiveStateVariable := packet.data[0]
adjustedCredit := int(packet.data[1]) - len(layer.outstandingPackets)
if adjustedCredit > 0 && adjustedCredit <= 8 {
layer.receiveCreditStateVariable = byte(adjustedCredit)
} else {
layer.receiveCreditStateVariable = 0
}
layer.ackChannel <- AckInfo{layer.receiveCreditStateVariable, receiveStateVariable, layer.lastAckSequenceNumber}
layer.lastAckSequenceNumber = receiveStateVariable
}
func handleLinkTransfer(state int, input interface{}, output interface{}, data interface{}) {
layer := data.(*MNPConnectionLayer)
packet := input.(*Packet)
layer.receiveStateVariable = packet.data[0]
packet.data = packet.data[1:]
layer.sendLinkAcknowledgement(layer.receiveStateVariable, 8)
layer.ToDockLink <- packet.data
}
func closeConnection(state int, input interface{}, output interface{}, data interface{}) {
fmt.Println("Disconnected")
os.Exit(0)
}
func (layer *MNPConnectionLayer) sendLinkAcknowledgement(receiveSequenceNumber byte, credit byte) {
buf := []byte{3, LA, receiveSequenceNumber, credit}
layer.ToPacketLayer <- buf
}
func (layer *MNPConnectionLayer) sendLinkTransfer(data []byte) {
layer.sendStateVariable++
buf := make([]byte, len(data)+3)
buf[0] = 2
buf[1] = LT
buf[2] = layer.sendStateVariable
copy(buf[3:], data)
layer.writeQueue <- buf
}
func (layer *MNPConnectionLayer) clearAcknowledgedPackets(ack AckInfo) {
n := len(layer.outstandingPackets) - 1
for n >= 0 && layer.outstandingPackets[n].sendSequenceNumber != ack.receiveSequenceNumber {
n--
}
layer.outstandingPackets = layer.outstandingPackets[n+1:]
if ack.receiveSequenceNumber == ack.lastAckSequenceNumber {
for i := 0; i < int(layer.receiveCreditStateVariable) && i < len(layer.outstandingPackets); i++ {
layer.ToPacketLayer <- layer.outstandingPackets[i].data
}
}
}
func (layer *MNPConnectionLayer) transition(packet *Packet) {
layer.state = fsm.Transition(layer.stateTable, layer.state, packet, nil, layer)
}
func (layer *MNPConnectionLayer) reader() {
go func() {
for {
packet := <-layer.FromPacketLayer
layer.transition(&packet)
}
}()
}
func (layer *MNPConnectionLayer) writer() {
go func() {
for {
buf := <-layer.FromDockLink
for len(buf) > 0 {
n := len(buf)
if n > int(layer.maxInfoLength) {
n = int(layer.maxInfoLength)
}
layer.sendLinkTransfer(buf[:n])
buf = buf[n:]
}
}
}()
}
func (layer *MNPConnectionLayer) writeQueueHandler() {
go func() {
for {
if layer.receiveCreditStateVariable > 0 {
select {
case buf := <-layer.writeQueue:
layer.outstandingPackets = append(layer.outstandingPackets, OutstandingPacket{buf, buf[2]})
layer.ToPacketLayer <- buf
layer.receiveCreditStateVariable--
case ack := <-layer.ackChannel:
layer.clearAcknowledgedPackets(ack)
}
} else {
ack := <-layer.ackChannel
layer.clearAcknowledgedPackets(ack)
}
}
}()
}
func (layer *MNPConnectionLayer) keepAlive() {
go func() {
for {
time.Sleep(3 * time.Second)
if layer.state == DATA_PHASE {
layer.sendLinkAcknowledgement(layer.receiveStateVariable, 8)
}
}
}()
}
func MNPConnectionLayerNew(fromPacketLayer chan Packet, toPacketLayer chan []byte) *MNPConnectionLayer {
connectionLayer.receiveCreditStateVariable = 8
connectionLayer.FromPacketLayer = fromPacketLayer
connectionLayer.ToPacketLayer = toPacketLayer
connectionLayer.FromDockLink = make(chan []byte)
connectionLayer.ToDockLink = make(chan []byte)
connectionLayer.writeQueue = make(chan []byte)
connectionLayer.ackChannel = make(chan AckInfo)
connectionLayer.stateTable = map[int][]fsm.State{
IDLE: {{Input: PacketType{LR}, NewState: LINK_REQUEST, Action: sendLinkRequestResponse}},
LINK_REQUEST: {
{Input: PacketType{LR}, NewState: LINK_REQUEST},
{Input: PacketType{LA}, NewState: DATA_PHASE},
{Input: PacketType{LD}, NewState: IDLE},
{Input: PacketType{LT}, NewState: IDLE},
},
DATA_PHASE: {
{Input: PacketType{LR}, NewState: IDLE},
{Input: PacketType{LA}, NewState: DATA_PHASE, Action: handleLinkAcknowledgement},
{Input: PacketType{LD}, NewState: IDLE, Action: closeConnection},
{Input: PacketType{LT}, NewState: DATA_PHASE, Action: handleLinkTransfer},
},
}
connectionLayer.writeQueueHandler()
connectionLayer.reader()
connectionLayer.writer()
connectionLayer.keepAlive()
return &connectionLayer
}