Implement packetcache.Last.

packetcache/packetcache.go

@@ -388,6 +388,20 @@ func (cache *Cache) Get(seqno uint16, result []byte) uint16 {
 	return 0
 }
 
+func (cache *Cache) Last() (bool, uint16, uint32) {
+	cache.mu.Lock()
+	defer cache.mu.Unlock()
+	if !cache.lastValid {
+		return false, 0, 0
+	}
+	buf := make([]byte, BufSize)
+	len, ts, _ := get(cache.last, cache.entries, buf)
+	if len == 0 {
+		return false, 0, 0
+	}
+	return true, cache.last, ts
+}
+
 // GetAt retrieves a packet from the cache assuming it is at the given index.
 func (cache *Cache) GetAt(seqno uint16, index uint16, result []byte) uint16 {
 	cache.mu.Lock()

packetcache/packetcache_test.go

@@ -20,8 +20,23 @@ func TestCache(t *testing.T) {
 	buf1 := randomBuf()
 	buf2 := randomBuf()
 	cache := New(16)
-	_, i1 := cache.Store(13, 0, false, false, buf1)
+
-	_, i2 := cache.Store(17, 0, false, false, buf2)
+	found, _, _ := cache.Last()
+	if found {
+		t.Errorf("Found in empty cache")
+	}
+
+	_, i1 := cache.Store(13, 42, false, false, buf1)
+	_, i2 := cache.Store(17, 42, false, false, buf2)
+
+	found, seqno, ts := cache.Last()
+	if !found {
+		t.Errorf("Not found")
+	}
+	if seqno != 17 || ts != 42 {
+		t.Errorf("Expected %v, %v, got %v, %v",
+			17, 42, seqno, ts)
+	}
 
 	buf := make([]byte, BufSize)