add distributed cache day1 lru

gee-cache/day1-lru/geecache/go.mod

@@ -0,0 +1,3 @@
+module geecache
+
+go 1.13

gee-cache/day1-lru/geecache/lru/lru.go

@@ -0,0 +1,84 @@
+package lru
+
+import (
+	"container/list"
+	"unsafe"
+)
+
+// Cache is a LRU cache. It is not safe for concurrent access.
+type Cache struct {
+	maxBytes int
+	nbytes   int
+	ll       *list.List
+	cache    map[string]*list.Element
+	// optional and executed when an entry is purged.
+	OnEvicted func(key string, value interface{})
+}
+
+type entry struct {
+	key   string
+	value interface{}
+}
+
+// New is the Constructor of Cache
+func New(maxBytes int, onEvicted func(string, interface{})) *Cache {
+	return &Cache{
+		maxBytes: maxBytes,
+		ll:       list.New(),
+		cache:    make(map[string]*list.Element),
+	}
+}
+
+// Add adds a value to the cache.
+func (c *Cache) Add(key string, value interface{}) {
+	if ele, ok := c.cache[key]; ok {
+		c.ll.MoveToFront(ele)
+		kv := ele.Value.(*entry)
+		kv.value = value
+		return
+	}
+	ele := c.ll.PushFront(&entry{key, value})
+	c.cache[key] = ele
+	c.nbytes += len(key) + sizeof(value)
+
+	for c.maxBytes != 0 && c.maxBytes < c.nbytes {
+		c.RemoveOldest()
+	}
+}
+
+// Get look ups a key's value
+func (c *Cache) Get(key string) (value interface{}, ok bool) {
+	if ele, ok := c.cache[key]; ok {
+		c.ll.MoveToFront(ele)
+		kv := ele.Value.(*entry)
+		return kv.value, true
+	}
+	return
+}
+
+// RemoveOldest removes the oldest item
+func (c *Cache) RemoveOldest() {
+	ele := c.ll.Back()
+	if ele != nil {
+		c.ll.Remove(ele)
+		kv := ele.Value.(*entry)
+		delete(c.cache, kv.key)
+		c.nbytes -= len(kv.key) + sizeof(kv.value)
+		if c.OnEvicted != nil {
+			c.OnEvicted(kv.key, kv.value)
+		}
+	}
+}
+
+// Value is optional interface for the value
+// if it's not implemented, use unsafe.Sizeof to count
+type Value interface {
+	Len() int // count how many bytes it takes
+}
+
+func sizeof(value interface{}) int {
+	if m, ok := value.(Value); ok {
+		return m.Len()
+	}
+	return int(unsafe.Sizeof(value))
+}

gee-cache/day1-lru/geecache/lru/lru_test.go

@@ -0,0 +1,16 @@
+package lru
+
+import (
+	"testing"
+)
+
+func TestGet(t *testing.T) {
+	lru := New(0, nil)
+	lru.Add("key1", 1234)
+	if v, ok := lru.Get("key1"); !ok || v != 1234 {
+		t.Fatalf("cache hit key1=1234 failed")
+	}
+	if _, ok := lru.Get("key2"); ok {
+		t.Fatalf("cache miss key2 failed")
+	}
+}