From 0086967dc945ea732dcca604b3fc87dab4b2984b Mon Sep 17 00:00:00 2001
From: Raphael Cohen <raphael.cohen@sekoia.fr>
Date: Sat, 28 Oct 2023 11:24:54 +0200
Subject: [PATCH 1/2] feat: Add function to check if cache contains a key

---
 bigcache.go      |  7 +++++++
 bigcache_test.go | 28 ++++++++++++++++++++++++++++
 shard.go         | 10 ++++++++++
 3 files changed, 45 insertions(+)

diff --git a/bigcache.go b/bigcache.go
index 5620c0ef..afb7b2ba 100644
--- a/bigcache.go
+++ b/bigcache.go
@@ -229,6 +229,13 @@ func (c *BigCache) Iterator() *EntryInfoIterator {
 	return newIterator(c)
 }
 
+// Contains returns whether the given key exists in cache
+func (c *BigCache) Contains(key string) bool {
+	hashedKey := c.hash.Sum64(key)
+	shard := c.getShard(hashedKey)
+	return shard.contains(key, hashedKey)
+}
+
 func (c *BigCache) onEvict(oldestEntry []byte, currentTimestamp uint64, evict func(reason RemoveReason) error) bool {
 	oldestTimestamp := readTimestampFromEntry(oldestEntry)
 	if currentTimestamp < oldestTimestamp {
diff --git a/bigcache_test.go b/bigcache_test.go
index 43ec3f57..278af117 100644
--- a/bigcache_test.go
+++ b/bigcache_test.go
@@ -1388,3 +1388,31 @@ func TestRemoveNonExpiredData(t *testing.T) {
 		noError(t, err)
 	}
 }
+
+func TestContainsExists(t *testing.T) {
+	t.Parallel()
+
+	// given
+	cache, _ := New(context.Background(), DefaultConfig(5*time.Second))
+	value := []byte("value")
+
+	// when
+	cache.Set("key", value)
+	exists := cache.Contains("key")
+
+	// then
+	assertEqual(t, true, exists)
+}
+
+func TestContainsNotExists(t *testing.T) {
+	t.Parallel()
+
+	// given
+	cache, _ := New(context.Background(), DefaultConfig(5*time.Second))
+
+	// when
+	exists := cache.Contains("key")
+
+	// then
+	assertEqual(t, false, exists)
+}
diff --git a/shard.go b/shard.go
index 4f03b53e..0b7c2442 100644
--- a/shard.go
+++ b/shard.go
@@ -117,6 +117,16 @@ func (s *cacheShard) getValidWrapEntry(key string, hashedKey uint64) ([]byte, er
 	return wrappedEntry, nil
 }
 
+func (s *cacheShard) contains(key string, hashedKey uint64) bool {
+	s.lock.RLock()
+	defer s.lock.RUnlock()
+	wrappedEntry, err := s.getWrappedEntry(hashedKey)
+	if err != nil {
+		return false
+	}
+	return key == readKeyFromEntry(wrappedEntry)
+}
+
 func (s *cacheShard) set(key string, hashedKey uint64, entry []byte) error {
 	currentTimestamp := uint64(s.clock.Epoch())
 

From 76e25b351da68832a12d6da119bab05e47a33c56 Mon Sep 17 00:00:00 2001
From: Raphael Cohen <raphael.cohen@sekoia.fr>
Date: Thu, 2 Nov 2023 19:39:40 +0100
Subject: [PATCH 2/2] feat: Applies PR review suggestions

---
 shard.go | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/shard.go b/shard.go
index 0b7c2442..fc922e4c 100644
--- a/shard.go
+++ b/shard.go
@@ -119,12 +119,14 @@ func (s *cacheShard) getValidWrapEntry(key string, hashedKey uint64) ([]byte, er
 
 func (s *cacheShard) contains(key string, hashedKey uint64) bool {
 	s.lock.RLock()
-	defer s.lock.RUnlock()
 	wrappedEntry, err := s.getWrappedEntry(hashedKey)
 	if err != nil {
+		s.lock.RUnlock()
 		return false
 	}
-	return key == readKeyFromEntry(wrappedEntry)
+	entryKey := readKeyFromEntry(wrappedEntry)
+	s.lock.RUnlock()
+	return key == entryKey
 }
 
 func (s *cacheShard) set(key string, hashedKey uint64, entry []byte) error {