Initial commit

internal/smtpsender/fifo.go

@@ -0,0 +1,58 @@
+package smtpsender
+
+import (
+	"sync"
+)
+
+type fifoQueue struct {
+	frames []interface{}
+	count  int
+	mutex  sync.Mutex
+	notifs chan struct{}
+}
+
+func newFIFOQueue() *fifoQueue {
+	q := &fifoQueue{
+		notifs: make(chan struct{}),
+	}
+	return q
+}
+
+func (q *fifoQueue) push(frame interface{}) bool {
+	q.mutex.Lock()
+	defer q.mutex.Unlock()
+	q.frames = append(q.frames, frame)
+	q.count++
+	select {
+	case q.notifs <- struct{}{}:
+	default:
+	}
+	return true
+}
+
+func (q *fifoQueue) pop() (interface{}, bool) {
+	q.mutex.Lock()
+	defer q.mutex.Unlock()
+	if q.count == 0 {
+		return nil, false
+	}
+	frame := q.frames[0]
+	q.frames[0] = nil
+	q.frames = q.frames[1:]
+	q.count--
+	if q.count == 0 {
+		q.frames = nil
+	}
+	return frame, true
+}
+
+func (q *fifoQueue) wait() <-chan struct{} {
+	q.mutex.Lock()
+	defer q.mutex.Unlock()
+	if q.count > 0 {
+		ch := make(chan struct{})
+		close(ch)
+		return ch
+	}
+	return q.notifs
+}