Move retransmittable frame logic to the ackhandler package

ackhandler/retransmittable.go

@@ -0,0 +1,38 @@
+package ackhandler
+
+import (
+	"github.com/lucas-clemente/quic-go/frames"
+)
+
+// Returns a new slice with all non-retransmittable frames deleted.
+func stripNonRetransmittableFrames(fs []frames.Frame) []frames.Frame {
+	res := make([]frames.Frame, 0, len(fs))
+	for _, f := range fs {
+		if IsFrameRetransmittable(f) {
+			res = append(res, f)
+		}
+	}
+	return res
+}
+
+// IsFrameRetransmittable returns true if the frame should be retransmitted.
+func IsFrameRetransmittable(f frames.Frame) bool {
+	switch f.(type) {
+	case *frames.StopWaitingFrame:
+		return false
+	case *frames.AckFrame:
+		return false
+	default:
+		return true
+	}
+}
+
+// HasRetransmittableFrames returns true if at least one frame is retransmittable.
+func HasRetransmittableFrames(fs []frames.Frame) bool {
+	for _, f := range fs {
+		if IsFrameRetransmittable(f) {
+			return true
+		}
+	}
+	return false
+}