// exportPtr returns *permPtrMsg if importer is nil, and *ptrMsg otherwise.
func (r *Runtime) exportPtr(v interface{}, importer n.Addr) interface{} {
// Add exported value to export table
exph := r.exp.Add(v, importer)
// log.Printf("exporting %T with handle %s for importer %v", v, exph.ID.String(), importer)
if importer == nil {
return &permPtrMsg{ID: exph.ID, TypeID: exph.Type.ID}
}
// Monitor the importer for liveness.
// DropPtr the handles upon importer death.
r.lk.Lock()
defer r.lk.Unlock()
_, ok := r.live[importer.WorkerID()]
if !ok {
r.live[importer.WorkerID()] = struct{}{}
// The anonymous function creates a "lifeline" connection to the worker importing v.
// When this conncetion is broken, v is released.
go func() {
// Defer removal of v's handle from the export table to the end of this function
defer func() {
r.lk.Lock()
delete(r.live, importer.WorkerID())
r.lk.Unlock()
// DropPtr/forget all exported handles
r.exp.RemoveImporter(importer)
}()
conn, err := r.t.Dial(importer)
if err != nil {
// log.Println("problem dialing lifeline to", importer.String(), err.Error())
return
}
defer conn.Close()
if conn.Write(&dontReplyMsg{}) != nil {
log.Println("problem writing on lifeline to", importer.String(), err.Error())
return
}
// Read returns when the remote dies and
// runs the conn into an error
conn.Read()
}()
}
return &ptrMsg{ID: exph.ID, TypeID: exph.Type.ID}
}
