From 0f96f9441719fc70e055cc3ee8c4be998c7ffbf9 Mon Sep 17 00:00:00 2001
From: Juliusz Chroboczek <jch@irif.fr>
Date: Mon, 8 Jun 2020 21:55:38 +0200
Subject: [PATCH] Implement packetcache.GetLast.

---
 packetcache/packetcache.go      | 15 +++++++++++++++
 packetcache/packetcache_test.go |  4 ++++
 2 files changed, 19 insertions(+)

diff --git a/packetcache/packetcache.go b/packetcache/packetcache.go
index aa1e040..a9902e1 100644
--- a/packetcache/packetcache.go
+++ b/packetcache/packetcache.go
@@ -135,6 +135,21 @@ func (cache *Cache) Get(seqno uint16, result []byte) uint16 {
 	return 0
 }
 
+func (cache *Cache) GetLast(result []byte) uint16 {
+	cache.mu.Lock()
+	defer cache.mu.Unlock()
+
+	i := cache.tail - 1
+	if i >= uint16(len(cache.entries)) {
+		i = 0
+	}
+
+	return uint16(copy(
+		result[:cache.entries[i].length],
+		cache.entries[i].buf[:]),
+	)
+}
+
 func (cache *Cache) GetAt(seqno uint16, index uint16, result []byte) uint16 {
 	cache.mu.Lock()
 	defer cache.mu.Unlock()
diff --git a/packetcache/packetcache_test.go b/packetcache/packetcache_test.go
index 6680842..51968ab 100644
--- a/packetcache/packetcache_test.go
+++ b/packetcache/packetcache_test.go
@@ -33,6 +33,10 @@ func TestCache(t *testing.T) {
 	if !bytes.Equal(buf[:l], buf1) {
 		t.Errorf("Couldn't get 13 at %v", i1)
 	}
+	l = cache.GetLast(buf)
+	if !bytes.Equal(buf[:l], buf2) {
+		t.Errorf("Couldn't get last")
+	}
 
 	l = cache.Get(17, buf)
 	if !bytes.Equal(buf[:l], buf2) {