Extend cache interface (#1318)

* Extend cache interface.

* update test.

pkg/cache/cache.go

@@ -15,6 +15,10 @@ type Cache interface {
 	Clear()
 	// Count the number of key/value pairs in the cache.
 	Count() int
+	// Keys returns all keys in the cache.
+	Keys() []string
+	// Values returns all values in the cache.
+	Values() []string
 	// Contents returns all keys in the cache encoded as a string.
 	Contents() string
 }

pkg/cache/memory/memory.go

@@ -74,6 +74,26 @@ func (c *Cache) Count() int {
 	return c.c.ItemCount()
 }
 
+// Keys returns all keys in the cache.
+func (c *Cache) Keys() []string {
+	items := c.c.Items()
+	res := make([]string, 0, len(items))
+	for k := range items {
+		res = append(res, k)
+	}
+	return res
+}
+
+// Values returns all values in the cache.
+func (c *Cache) Values() []string {
+	items := c.c.Items()
+	res := make([]string, 0, len(items))
+	for _, v := range items {
+		res = append(res, v.Object.(string))
+	}
+	return res
+}
+
 // Contents returns all key-value pairs in the cache encodes as a string.
 func (c *Cache) Contents() string {
 	items := c.c.Items()

pkg/cache/memory/memory_test.go

@@ -46,12 +46,28 @@ func TestCache(t *testing.T) {
 		t.Fatalf("Unexpected value for key10 after clear: %v, %v", v, ok)
 	}
 
-	// Test contents.
+	// Test getting only the keys.
 	keys := []string{"key1", "key2", "key3"}
-	for _, k := range keys {
-		c.Set(k, k)
+	values := []string{"value1", "value2", "value3"}
+	for i, k := range keys {
+		c.Set(k, values[i])
+	}
+	k := c.Keys()
+	sort.Strings(keys)
+	sort.Strings(k)
+	if !cmp.Equal(keys, k) {
+		t.Fatalf("Unexpected keys: %v", k)
 	}
 
+	// Test getting only the values.
+	vals := c.Values()
+	sort.Strings(vals)
+	sort.Strings(values)
+	if !cmp.Equal(values, vals) {
+		t.Fatalf("Unexpected values: %v", vals)
+	}
+
+	// Test contents.
 	items := c.Contents()
 	sort.Strings(keys)
 	res := strings.Split(items, ",")