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sync.go
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sync.go
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package queue
import (
context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
peer "github.com/ipfs/go-ipfs/p2p/peer"
eventlog "github.com/ipfs/go-ipfs/thirdparty/eventlog"
)
var log = eventlog.Logger("peerqueue")
// ChanQueue makes any PeerQueue synchronizable through channels.
type ChanQueue struct {
Queue PeerQueue
EnqChan chan<- peer.ID
DeqChan <-chan peer.ID
}
// NewChanQueue creates a ChanQueue by wrapping pq.
func NewChanQueue(ctx context.Context, pq PeerQueue) *ChanQueue {
cq := &ChanQueue{Queue: pq}
cq.process(ctx)
return cq
}
func (cq *ChanQueue) process(ctx context.Context) {
// construct the channels here to be able to use them bidirectionally
enqChan := make(chan peer.ID)
deqChan := make(chan peer.ID)
cq.EnqChan = enqChan
cq.DeqChan = deqChan
go func() {
log.Debug("processing")
defer log.Debug("closed")
defer close(deqChan)
var next peer.ID
var item peer.ID
var more bool
for {
if cq.Queue.Len() == 0 {
// log.Debug("wait for enqueue")
select {
case next, more = <-enqChan:
if !more {
return
}
// log.Debug("got", next)
case <-ctx.Done():
return
}
} else {
next = cq.Queue.Dequeue()
// log.Debug("peek", next)
}
select {
case item, more = <-enqChan:
if !more {
if cq.Queue.Len() > 0 {
return // we're done done.
}
enqChan = nil // closed, so no use.
}
// log.Debug("got", item)
cq.Queue.Enqueue(item)
cq.Queue.Enqueue(next) // order may have changed.
next = ""
case deqChan <- next:
// log.Debug("dequeued", next)
next = ""
case <-ctx.Done():
return
}
}
}()
}