Added function GetNotExpiredItems to get all not expired items in a threadsafe manner

cache.go

@@ -1009,6 +1009,22 @@ func (c *cache) Items() map[string]Item {
 	return c.items
 }
 
+// Returns all not expired items in the cache. This method is save to use with
+// an active janitor since it copies the underlying map. Therefore method is
+// costly in terms of time and memory. You can read while using this method but
+// not write. Use with caution.
+func (c *cache) GetNotExpiredItems() map[string]Item {
+	retMap := make(map[string]Item, c.ItemCount())
+	c.mu.RLock()
+	for key, item := range c.items{
+		if !item.Expired() {
+			retMap[key] = item
+		}
+	}
+	c.mu.RUnlock()
+	return retMap
+}
+
 // Returns the number of items in the cache. This may include items that have
 // expired, but have not yet been cleaned up. Equivalent to len(c.Items()).
 func (c *cache) ItemCount() int {

cache_test.go

@@ -8,6 +8,7 @@ import (
 	"sync"
 	"testing"
 	"time"
+	"fmt"
 )
 
 type TestStruct struct {
@@ -1247,6 +1248,29 @@ func TestOnEvicted(t *testing.T) {
 	}
 }
 
+func TestCacheGetAllNotExpiredItems(t *testing.T) {
+	tc := New(time.Minute*1, 0)
+	tc.Set("a", "a", DefaultExpiration)
+	tc.Set("b", "b", DefaultExpiration)
+	tc.Set("c", "c", time.Millisecond*1)
+	time.Sleep(time.Millisecond*2)
+	allNotExpiredItems := tc.GetNotExpiredItems()
+	if len(allNotExpiredItems) != 2 {
+		t.Error("There are more or less items in the result than the two unexpired.")
+	}
+	for _, key := range []string{"a", "b"} {
+		if _, ok := tc.Get(key); !ok{
+			t.Error("Could not find unexpired item %s", key)
+		}
+	}
+	if _, ok := tc.Get("c"); ok {
+		t.Error("Found expired item c.")
+	}
+	if &allNotExpiredItems == &tc.cache.items {
+		t.Error("Returned map is equal to internal map.")
+	}
+}
+
 func TestCacheSerialization(t *testing.T) {
 	tc := New(DefaultExpiration, 0)
 	testFillAndSerialize(t, tc)
@@ -1676,3 +1700,18 @@ func BenchmarkDeleteExpiredLoop(b *testing.B) {
 		tc.DeleteExpired()
 	}
 }
+
+func BenchmarkGetAllNotExpiredItems(b *testing.B) {
+	for i:= 0; i < 20; i++ {
+		b.Run(fmt.Sprintf("BenchmarkGetAllNotExpiredItemsWith %d000 Items", i), func(b *testing.B){
+			tc := New(20*time.Minute, 0)
+			for j:= 0; j < i*1000; j++{
+				tc.Set(strconv.Itoa(i), "bar", DefaultExpiration)
+			}
+			b.ResetTimer()
+			for j:= 0; j < b.N; j++{
+				tc.GetNotExpiredItems()
+			}
+		})
+	}
+}