New Streams and Quality structures

messaging/quality.go

@@ -0,0 +1,79 @@
+// Package messaging defines a structure to communication between inputs and outputs
+package messaging
+
+import (
+	"sync"
+)
+
+// Quality holds a specific stream quality.
+// It makes packages able to subscribe to an incoming stream.
+type Quality struct {
+	// Incoming data come from this channel
+	Broadcast chan<- []byte
+
+	// Incoming data will be outputed to all those outputs.
+	// Use a map to be able to delete an item.
+	outputs map[chan []byte]struct{}
+
+	// Mutex to lock outputs map
+	lockOutputs sync.Mutex
+}
+
+func newQuality() (q *Quality) {
+	q = &Quality{}
+	broadcast := make(chan []byte, 1024)
+	q.Broadcast = broadcast
+	q.outputs = make(map[chan []byte]struct{})
+	go q.run(broadcast)
+	return q
+}
+
+func (q *Quality) run(broadcast <-chan []byte) {
+	for msg := range broadcast {
+		q.lockOutputs.Lock()
+		for output := range q.outputs {
+			select {
+			case output <- msg:
+			default:
+				// If full, do a ring buffer
+				// Check that output is not of size zero
+				if len(output) > 1 {
+					<-output
+				}
+			}
+		}
+		q.lockOutputs.Unlock()
+	}
+
+	// Incoming chan has been closed, close all outputs
+	q.lockOutputs.Lock()
+	for ch := range q.outputs {
+		delete(q.outputs, ch)
+		close(ch)
+	}
+	q.lockOutputs.Unlock()
+}
+
+// Close the incoming chan, this will also delete all outputs.
+func (q *Quality) Close() {
+	close(q.Broadcast)
+}
+
+// Register a new output on a stream.
+func (q *Quality) Register(output chan []byte) {
+	q.lockOutputs.Lock()
+	q.outputs[output] = struct{}{}
+	q.lockOutputs.Unlock()
+}
+
+// Unregister removes an output.
+func (q *Quality) Unregister(output chan []byte) {
+	// Make sure we did not already close this output
+	q.lockOutputs.Lock()
+	_, ok := q.outputs[output]
+	if ok {
+		delete(q.outputs, output)
+		close(output)
+	}
+	defer q.lockOutputs.Unlock()
+}