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package tanja
type Session struct {
node *Node
disp chan<- interface{} // either a *Message (queued) or a chan<-*Message (closed)
calls int // number of active callback registrations
callch chan *Message
rets map[*ReturnPath]bool
}
type sesQueue struct {
next, prev *sesQueue
msg *Message
}
func (s *Session) dispatcher(ch <-chan interface{}) {
var head *sesQueue
var tail *sesQueue
rem := func() {
if tail.prev != nil {
tail.prev.next = nil
} else {
head = nil
}
tail = tail.prev
}
L:
for {
// Remove any inactive messages from the tail
for tail != nil && !tail.msg.reg.active {
tail.msg.Close()
rem()
}
// Get latest message
var snd chan<- *Message
var msg *Message
if tail != nil {
msg = tail.msg
if c, ok := msg.reg.data.(chan<- *Message); ok {
snd = c
} else {
snd = msg.reg.recv.(*Session).callch
}
}
// Send/receive
select {
case m, ok := <-ch:
if !ok {
break L
} else if msg, ok := m.(*Message); ok {
q := &sesQueue{head, nil, msg}
if head != nil {
head.prev = q
} else {
tail = q
}
head = q
} else if ch, ok := m.(chan<- *Message); ok {
close(ch)
}
case snd <- msg:
rem()
}
}
// If the queue isn't empty, make sure to close the messages before exiting.
for n := tail; n != nil; n = n.prev {
n.msg.Close()
}
}
func (n *Node) Session() *Session {
s := &Session{}
s.rets = make(map[*ReturnPath]bool)
s.node = n
ch := make(chan interface{})
s.disp = ch
go s.dispatcher(ch)
return s
}
func (s *Session) register(willReply bool, p Tuple) *Registration {
r := &Registration{}
r.recv = s
r.pat = p
r.willReply = willReply
return r
}
func (s *Session) Register(willReply bool, p ...interface{}) *Registration {
return s.register(willReply, Tup(p...))
}
func (s *Session) Close() {
s.node.lock.Lock()
s.node.unregMatch(func(r *Registration) bool {
return r.recv == s
})
s.node.lock.Unlock()
close(s.disp)
for ret := range s.rets {
ret.Close()
}
}
// Must be called when the node lock is held
func (s *Session) refCalls() {
if s.calls == 0 {
s.callch = make(chan *Message)
}
s.calls++
}
// Must be called when the node lock is held
func (s *Session) unrefCalls() {
s.calls--
if s.calls == 0 {
// It shouldn't be possible for the dispatcher to write to it at this
// point. No callback patterns are currently registered, and the
// dispatcher is synchronously notified when something is unregistered.
close(s.callch)
s.callch = nil
}
}
func (s *Session) Chan() <-chan *Message {
// Ensure that we won't return nil when s.callch is modified in some other
// goroutine.
s.node.lock.Lock()
c := s.callch
s.node.lock.Unlock()
if c == nil {
c = make(chan *Message)
close(c)
}
return c
}
func (s *Session) Run() {
for msg := range s.Chan() {
msg.Dispatch()
}
}
func (s *Session) Send(wantReply bool, t ...interface{}) *ReturnPath {
s.node.lock.Lock()
var r *ReturnPath
if wantReply {
r = newReturnPathSession(s)
s.rets[r] = true
}
s.node.send(Tup(t...), r, nil)
s.node.lock.Unlock()
return r
}
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