feat: LRU缓存实现

.gitignore

@@ -0,0 +1,23 @@
+### Go template
+# If you prefer the allow list template instead of the deny list, see community template:
+# https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore
+#
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Dependency directories (remove the comment below to include it)
+# vendor/
+
+# Go workspace file
+go.work
+

lfu/lfu.go

@@ -9,6 +9,7 @@ import (
 // @Description:LFU，即最少使用，也就是淘汰缓存中访问频率最低的记录。
 // LFU 认为，如果数据过去被访问多次，那么将来被访问的频率也更高。
 // LFU 的实现需要维护一个按照访问次数排序的队列，每次访问，访问次数加 1，队列重新排序，淘汰时选择访问次数最少的即可
+// 利用最小堆属性对访问次数排序实现
 type lfu struct {
 	// 缓存最大容量
 	maxBytes int
@@ -41,7 +42,7 @@ func (l *lfu) Set(key string, value any) {
 		l.cache[key] = en
 		l.usedBytes += en.Len()
 		if l.maxBytes > 0 && l.usedBytes > l.maxBytes {
-
+			l.removeElement(heap.Pop(l.queue))
 		}
 	}
 }
@@ -61,11 +62,14 @@ func (l *lfu) Del(Key string) {
 }
 
 func (l *lfu) DelOldest() {
-
+	if l.queue.Len() == 0 {
+		return
+	}
+	l.removeElement(heap.Pop(l.queue))
 }
 
 func (l *lfu) Len() int {
-	return 0
+	return l.queue.Len()
 }
 
 func (l *lfu) removeElement(x any) {
@@ -75,4 +79,7 @@ func (l *lfu) removeElement(x any) {
 	en := x.(*entry)
 	delete(l.cache, en.key)
 	l.usedBytes -= en.Len()
+	if l.onEvicted != nil {
+		l.onEvicted(en.key, en.value)
+	}
 }

lfu/lfu_test.go

@@ -0,0 +1,34 @@
+package lfu_test
+
+import (
+	"cache/lfu"
+	"github.com/matryer/is"
+	"testing"
+)
+
+func TestSet(t *testing.T) {
+	is := is.New(t)
+	cache := lfu.New(24, nil)
+	cache.DelOldest()
+	cache.Set("k1", 1)
+	v := cache.Get("k1")
+	is.Equal(v, 1)
+	cache.Del("k1")
+	is.Equal(0, cache.Len())
+}
+
+func TestOnEvicted(t *testing.T) {
+	is := is.New(t)
+	keys := make([]string, 0, 8)
+	onEvicted := func(key string, value interface{}) {
+		keys = append(keys, key)
+	}
+	cache := lfu.New(32, onEvicted)
+	cache.Set("k1", 1)
+	cache.Set("k2", 2)
+	cache.Set("k3", 3)
+	cache.Set("k4", 4)
+	expected := []string{"k1", "k3"}
+	is.Equal(expected, keys)
+	is.Equal(2, cache.Len())
+}