New Streams and Quality structures

messaging/streams.go

@@ -0,0 +1,97 @@
+// Package messaging defines a structure to communication between inputs and outputs
+package messaging
+
+import (
+	"errors"
+	"log"
+	"sync"
+)
+
+// Streams hold all application streams.
+type Streams struct {
+	// Associate each stream name to the stream
+	streams map[string]*Stream
+
+	// Mutex to lock streams
+	lockStreams sync.Mutex
+
+	// Subscribers get notified when a new stream is created
+	// Use a map to be able to delete a subscriber
+	eventSubscribers map[chan string]struct{}
+
+	// Mutex to lock eventSubscribers
+	lockSubscribers sync.Mutex
+}
+
+// New creates a new stream list.
+func New() (l *Streams) {
+	l = &Streams{}
+	l.streams = make(map[string]*Stream)
+	l.eventSubscribers = make(map[chan string]struct{})
+	return l
+}
+
+// Subscribe to get notified on new stream.
+func (l *Streams) Subscribe(output chan string) {
+	l.lockSubscribers.Lock()
+	l.eventSubscribers[output] = struct{}{}
+	l.lockSubscribers.Unlock()
+}
+
+// Unsubscribe to no longer get notified on new stream.
+func (l *Streams) Unsubscribe(output chan string) {
+	// Make sure we did not already delete this subscriber
+	l.lockSubscribers.Lock()
+	if _, ok := l.eventSubscribers[output]; ok {
+		delete(l.eventSubscribers, output)
+	}
+	l.lockSubscribers.Unlock()
+}
+
+// Create a new stream.
+func (l *Streams) Create(name string) (s *Stream, err error) {
+	// If stream already exist, fail
+	if _, ok := l.streams[name]; ok {
+		return nil, errors.New("stream already exists")
+	}
+
+	// Create stream
+	s = newStream()
+	l.lockStreams.Lock()
+	l.streams[name] = s
+	l.lockStreams.Unlock()
+
+	// Notify
+	l.lockSubscribers.Lock()
+	for sub := range l.eventSubscribers {
+		select {
+		case sub <- name:
+		default:
+			log.Printf("Failed to announce stream '%s' to subscriber", name)
+		}
+	}
+	l.lockSubscribers.Unlock()
+	return s, nil
+}
+
+// Get a stream.
+func (l *Streams) Get(name string) (s *Stream, err error) {
+	// If stream does exist, return it
+	l.lockStreams.Lock()
+	s, ok := l.streams[name]
+	l.lockStreams.Unlock()
+	if !ok {
+		return nil, errors.New("stream does not exist")
+	}
+	return s, nil
+}
+
+// Delete a stream.
+func (l *Streams) Delete(name string) {
+	// Make sure we did not already delete this stream
+	l.lockStreams.Lock()
+	if _, ok := l.streams[name]; ok {
+		delete(l.streams, name)
+	}
+	l.lockStreams.Unlock()
+}