lnd.xprv/htlcswitch/queue.go

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package htlcswitch
import (
"container/list"
"sync"
"github.com/lightningnetwork/lnd/lnwire"
)
// packetQueue represent the wrapper around the original queue plus the
// functionality for releasing the queue objects in object channel. Such
// structures allows storing of all pending object in queue before the moment
// of actual releasing.
//
// TODO(andrew.shvv) structure not preserve the order if object failed second
// time.
type packetQueue struct {
*list.List
sync.Mutex
// pending channel is needed in order to send the object which should
// be re-proceed.
pending chan *htlcPacket
// grab channel represents the channel-lock which is needed in order to
// make "release" goroutines block during other release goroutine
// processing.
grab chan struct{}
}
func newWaitingQueue() *packetQueue {
// Initialize grab channel and release one slot, otherwise release
// function will block.
done := make(chan struct{}, 1)
done <- struct{}{}
return &packetQueue{
pending: make(chan *htlcPacket),
grab: done,
List: list.New(),
}
}
// consume function take the given packet and store it in queue till release
// function will be executed.
func (q *packetQueue) consume(packet *htlcPacket) {
q.Lock()
defer q.Unlock()
q.PushBack(packet)
}
// release function spawn the goroutine which grab the object from pending
// queue and pass it in processing channel.
func (q *packetQueue) release() {
q.Lock()
defer q.Unlock()
if q.Len() == 0 {
return
}
go func() {
// Grab the pending mutex so that other goroutines waits before
// grabbing the object, otherwise the objects will be send in
// the pending channel in random sequence.
<-q.grab
defer func() {
// Release the channel-lock and give other goroutines
// the ability to
q.grab <- struct{}{}
}()
// Fetch object after releasing the pending mutex in order to
// preserver the order of the stored objects.
q.Lock()
e := q.Front()
q.Unlock()
if e != nil {
// Send the object in object queue and wait it to be
// processed by other side.
q.pending <- e.Value.(*htlcPacket)
// After object have been preprocessed remove it from
// the queue.
q.Lock()
q.Remove(e)
q.Unlock()
return
}
}()
}
// length returns the number of pending htlc packets which is stored in queue.
func (q *packetQueue) length() int {
q.Lock()
defer q.Unlock()
return q.Len()
}
// pendingAmount returns the amount of money which is stored in pending queue.
func (q *packetQueue) pendingAmount() lnwire.MilliSatoshi {
q.Lock()
defer q.Unlock()
var amount lnwire.MilliSatoshi
for e := q.Front(); e != nil; e = e.Next() {
packet := e.Value.(*htlcPacket)
htlc := packet.htlc.(*lnwire.UpdateAddHTLC)
amount += htlc.Amount
}
return amount
}