From 02c3c5afe052333cda7a2f0dfa448038a3f79b07 Mon Sep 17 00:00:00 2001
From: clitetailor <ducnhatphung@gmail.com>
Date: Sat, 26 Oct 2019 09:46:57 +0700
Subject: [PATCH] Add Memoize

---
 cache.go      | 16 ++++++++++++++++
 cache_test.go | 23 +++++++++++++++++++++++
 2 files changed, 39 insertions(+)

diff --git a/cache.go b/cache.go
index db88d2f..b5d7f24 100644
--- a/cache.go
+++ b/cache.go
@@ -81,6 +81,22 @@ func (c *cache) set(k string, x interface{}, d time.Duration) {
 	}
 }
 
+// Lazily compute the given function and store its result item
+// to cache. Returns the computed item and a bool indicating
+// whether the item was updated.
+func (c *cache) Memoize(k string, f func() interface{}, d time.Duration) (interface{}, bool) {
+	c.mu.Lock()
+	v, found := c.get(k)
+	if found {
+		c.mu.Unlock()
+		return v, !found
+	}
+	v = f()
+	c.set(k, v, d)
+	c.mu.Unlock()
+	return v, !found
+}
+
 // Add an item to the cache, replacing any existing item, using the default
 // expiration.
 func (c *cache) SetDefault(k string, x interface{}) {
diff --git a/cache_test.go b/cache_test.go
index de3e9d6..8b088d8 100644
--- a/cache_test.go
+++ b/cache_test.go
@@ -154,6 +154,29 @@ func TestStorePointerToStruct(t *testing.T) {
 	}
 }
 
+func TestMemoizeFunction(t *testing.T) {
+	f := func() interface{} {
+		return 5
+	}
+
+	tc := New(DefaultExpiration, 0)
+	x, updated := tc.Memoize("tmemoize", f, DefaultExpiration)
+	if !updated {
+		t.Fatal("tmemoize was not updated")
+	}
+	if x.(int) != 5 {
+		t.Fatal("tmemoize is not 5:", x)
+	}
+
+	y, updated := tc.Memoize("tmemoize", f, DefaultExpiration)
+	if updated {
+		t.Fatal("tmemoize was updated")
+	}
+	if y.(int) != 5 {
+		t.Fatal("tmemoize is not 5:", y)
+	}
+}
+
 func TestIncrementWithInt(t *testing.T) {
 	tc := New(DefaultExpiration, 0)
 	tc.Set("tint", 1, DefaultExpiration)