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notifications.go
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/
notifications.go
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package notifications
import (
pubsub "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/briantigerchow/pubsub"
context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
blocks "github.com/ipfs/go-ipfs/blocks"
key "github.com/ipfs/go-ipfs/blocks/key"
)
const bufferSize = 16
type PubSub interface {
Publish(block *blocks.Block)
Subscribe(ctx context.Context, keys ...key.Key) <-chan *blocks.Block
Shutdown()
}
func New() PubSub {
return &impl{*pubsub.New(bufferSize)}
}
type impl struct {
wrapped pubsub.PubSub
}
func (ps *impl) Publish(block *blocks.Block) {
topic := string(block.Key())
ps.wrapped.Pub(block, topic)
}
func (ps *impl) Shutdown() {
ps.wrapped.Shutdown()
}
// Subscribe returns a channel of blocks for the given |keys|. |blockChannel|
// is closed if the |ctx| times out or is cancelled, or after sending len(keys)
// blocks.
func (ps *impl) Subscribe(ctx context.Context, keys ...key.Key) <-chan *blocks.Block {
blocksCh := make(chan *blocks.Block, len(keys))
valuesCh := make(chan interface{}, len(keys)) // provide our own channel to control buffer, prevent blocking
if len(keys) == 0 {
close(blocksCh)
return blocksCh
}
ps.wrapped.AddSubOnceEach(valuesCh, toStrings(keys)...)
go func() {
defer close(blocksCh)
defer ps.wrapped.Unsub(valuesCh) // with a len(keys) buffer, this is an optimization
for {
select {
case <-ctx.Done():
return
case val, ok := <-valuesCh:
if !ok {
return
}
block, ok := val.(*blocks.Block)
if !ok {
return
}
select {
case <-ctx.Done():
return
case blocksCh <- block: // continue
}
}
}
}()
return blocksCh
}
func toStrings(keys []key.Key) []string {
strs := make([]string, 0)
for _, key := range keys {
strs = append(strs, string(key))
}
return strs
}