On delete, always set promotions == -2 and node == nil

Also, item.promotions doesn't need to be loaded/stored using atomic. Once upon a
time it did. Cache was updated long ago to not use atomic operations on it, but
LayeredCache wasn't. They are both consistent now (they don't use atomic
operations).

Fixes: https://github.com/karlseguin/ccache/issues/76

cache.go

@@ -394,6 +394,8 @@ func (c *Cache[T]) doDelete(item *Item[T]) {
 			c.onDelete(item)
 		}
 		c.list.Remove(item.node)
+		item.node = nil
+		item.promotions = -2
 	}
 }
 
@@ -438,6 +440,7 @@ func (c *Cache[T]) gc() int {
 				c.onDelete(item)
 			}
 			dropped += 1
+			item.node = nil
 			item.promotions = -2
 		}
 		node = prev

cache_test.go

@@ -1,6 +1,7 @@
 package ccache
 
 import (
+	"math/rand"
 	"sort"
 	"strconv"
 	"sync/atomic"
@@ -313,6 +314,29 @@ func Test_CacheForEachFunc(t *testing.T) {
 	assert.DoesNotContain(t, forEachKeys(cache), "stop")
 }
 
+func Test_CachePrune(t *testing.T) {
+	maxSize := int64(500)
+	cache := New(Configure[string]().MaxSize(maxSize).ItemsToPrune(50))
+	epoch := 0
+	for i := 0; i < 10000; i++ {
+		epoch += 1
+		expired := make([]string, 0)
+		for i := 0; i < 50; i += 1 {
+			key := strconv.FormatInt(rand.Int63n(maxSize*20), 10)
+			item := cache.Get(key)
+			if item == nil || item.TTL() > 1*time.Minute {
+				expired = append(expired, key)
+			}
+		}
+		for _, key := range expired {
+			cache.Set(key, key, 5*time.Minute)
+		}
+		if epoch%500 == 0 {
+			assert.True(t, cache.GetSize() <= 500)
+		}
+	}
+}
+
 type SizedItem struct {
 	id int
 	s  int64

layeredcache.go

@@ -266,13 +266,15 @@ func (c *LayeredCache[T]) worker() {
 	}
 	deleteItem := func(item *Item[T]) {
 		if item.node == nil {
-			atomic.StoreInt32(&item.promotions, -2)
+			item.promotions = -2
 		} else {
 			c.size -= item.size
 			if c.onDelete != nil {
 				c.onDelete(item)
 			}
 			c.list.Remove(item.node)
+			item.node = nil
+			item.promotions = -2
 		}
 	}
 	for {
@@ -318,13 +320,13 @@ func (c *LayeredCache[T]) worker() {
 
 func (c *LayeredCache[T]) doPromote(item *Item[T]) bool {
 	// deleted before it ever got promoted
-	if atomic.LoadInt32(&item.promotions) == -2 {
+	if item.promotions == -2 {
 		return false
 	}
 	if item.node != nil { //not a new item
 		if item.shouldPromote(c.getsPerPromote) {
 			c.list.MoveToFront(item.node)
-			atomic.StoreInt32(&item.promotions, 0)
+			item.promotions = 0
 		}
 		return false
 	}
@@ -355,6 +357,7 @@ func (c *LayeredCache[T]) gc() int {
 			if c.onDelete != nil {
 				c.onDelete(item)
 			}
+			item.node = nil
 			item.promotions = -2
 			dropped += 1
 		}

layeredcache_test.go

@@ -1,6 +1,7 @@
 package ccache
 
 import (
+	"math/rand"
 	"sort"
 	"strconv"
 	"sync/atomic"
@@ -372,6 +373,29 @@ func Test_LayeredCache_EachFunc(t *testing.T) {
 	assert.DoesNotContain(t, forEachKeysLayered[int](cache, "1"), "stop")
 }
 
+func Test_LayeredCachePrune(t *testing.T) {
+	maxSize := int64(500)
+	cache := Layered(Configure[string]().MaxSize(maxSize).ItemsToPrune(50))
+	epoch := 0
+	for i := 0; i < 10000; i++ {
+		epoch += 1
+		expired := make([]string, 0)
+		for i := 0; i < 50; i += 1 {
+			key := strconv.FormatInt(rand.Int63n(maxSize*20), 10)
+			item := cache.Get(key, key)
+			if item == nil || item.TTL() > 1*time.Minute {
+				expired = append(expired, key)
+			}
+		}
+		for _, key := range expired {
+			cache.Set(key, key, key, 5*time.Minute)
+		}
+		if epoch%500 == 0 {
+			assert.True(t, cache.GetSize() <= 500)
+		}
+	}
+}
+
 func newLayered[T any]() *LayeredCache[T] {
 	c := Layered[T](Configure[T]())
 	c.Clear()