Repository: maypok86/otter (go)

Issue:
Request Get Expiration With Get
# Clarification and motivation
I have a script that updating some variables and users get them from cache. But I want to get expiration for showing them last update time.

# Acceptance criteria
Get expiration time with get function or new function with expiration time


Pull request:
Add extension
## Description

Added `Extension` feature.

## Related issue(s)

- Resolves #56 

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#### Related changes (conditional)

- Tests
    - [x] If I added new functionality, I added tests covering it.
    - [x] If I fixed a bug, I added a regression test to prevent the bug from
      silently reappearing again.

- Documentation
    - [x] I checked whether I should update the docs and did so if necessary:
        - [README](../README.md)

- Public contracts
    - [x] My changes doesn't break project license.

#### Stylistic guide (mandatory)

- [x] My code complies with the [styles guide](https://github.com/uber-go/guide/blob/master/style.md).
- [x] My commit history is clean (only contains changes relating to my
  issue/pull request and no reverted-my-earlier-commit changes) and commit
  messages start with identifiers of related issues in square brackets.

  **Example:** `[#42] Short commit description`

  If necessary both of these can be achieved even after the commits have been
  made/pushed using [rebase and squash](https://git-scm.com/docs/git-rebase).

#### Before merging (mandatory)
- [x] Check __target__  branch of PR is set correctly


Patch:
diff --git a/cache.go b/cache.go
index b2704d8..bedbb0e 100644
--- a/cache.go
+++ b/cache.go
@@ -44,7 +44,7 @@ func newBaseCache[K comparable, V any](c core.Config[K, V]) baseCache[K, V] {
 	}
 }
 
-// Has checks if there is an item with the given key in the cache.
+// Has checks if there is an entry with the given key in the cache.
 func (bs baseCache[K, V]) Has(key K) bool {
 	return bs.cache.Has(key)
 }
@@ -64,7 +64,7 @@ func (bs baseCache[K, V]) DeleteByFunc(f func(key K, value V) bool) {
 	bs.cache.DeleteByFunc(f)
 }
 
-// Range iterates over all items in the cache.
+// Range iterates over all entries in the cache.
 //
 // Iteration stops early when the given function returns false.
 func (bs baseCache[K, V]) Range(f func(key K, value V) bool) {
@@ -85,7 +85,7 @@ func (bs baseCache[K, V]) Close() {
 	bs.cache.Close()
 }
 
-// Size returns the current number of items in the cache.
+// Size returns the current number of entries in the cache.
 func (bs baseCache[K, V]) Size() int {
 	return bs.cache.Size()
 }
@@ -100,6 +100,13 @@ func (bs baseCache[K, V]) Stats() Stats {
 	return newStats(bs.cache.Stats())
 }
 
+// Extension returns access to inspect and perform low-level operations on this cache based on its runtime
+// characteristics. These operations are optional and dependent on how the cache was constructed
+// and what abilities the implementation exposes.
+func (bs baseCache[K, V]) Extension() Extension[K, V] {
+	return newExtension(bs.cache)
+}
+
 // Cache is a structure performs a best-effort bounding of a hash table using eviction algorithm
 // to determine which entries to evict when the capacity is exceeded.
 type Cache[K comparable, V any] struct {
@@ -114,7 +121,7 @@ func newCache[K comparable, V any](c core.Config[K, V]) Cache[K, V] {
 
 // Set associates the value with the key in this cache.
 //
-// If it returns false, then the key-value item had too much setCostFunc and the Set was dropped.
+// If it returns false, then the key-value pair had too much cost and the Set was dropped.
 func (c Cache[K, V]) Set(key K, value V) bool {
 	return c.cache.Set(key, value)
 }
@@ -123,7 +130,7 @@ func (c Cache[K, V]) Set(key K, value V) bool {
 //
 // If the specified key is not already associated with a value, then it returns false.
 //
-// Also, it returns false if the key-value item had too much setCostFunc and the SetIfAbsent was dropped.
+// Also, it returns false if the key-value pair had too much cost and the SetIfAbsent was dropped.
 func (c Cache[K, V]) SetIfAbsent(key K, value V) bool {
 	return c.cache.SetIfAbsent(key, value)
 }
@@ -140,19 +147,19 @@ func newCacheWithVariableTTL[K comparable, V any](c core.Config[K, V]) CacheWith
 	}
 }
 
-// Set associates the value with the key in this cache and sets the custom ttl for this key-value item.
+// Set associates the value with the key in this cache and sets the custom ttl for this key-value pair.
 //
-// If it returns false, then the key-value item had too much setCostFunc and the Set was dropped.
+// If it returns false, then the key-value pair had too much cost and the Set was dropped.
 func (c CacheWithVariableTTL[K, V]) Set(key K, value V, ttl time.Duration) bool {
 	return c.cache.SetWithTTL(key, value, ttl)
 }
 
 // SetIfAbsent if the specified key is not already associated with a value associates it with the given value
-// and sets the custom ttl for this key-value item.
+// and sets the custom ttl for this key-value pair.
 //
 // If the specified key is not already associated with a value, then it returns false.
 //
-// Also, it returns false if the key-value item had too much setCostFunc and the SetIfAbsent was dropped.
+// Also, it returns false if the key-value pair had too much cost and the SetIfAbsent was dropped.
 func (c CacheWithVariableTTL[K, V]) SetIfAbsent(key K, value V, ttl time.Duration) bool {
 	return c.cache.SetIfAbsentWithTTL(key, value, ttl)
 }
diff --git a/cmd/generator/main.go b/cmd/generator/main.go
index dd7bb2a..757e18f 100644
--- a/cmd/generator/main.go
+++ b/cmd/generator/main.go
@@ -336,10 +336,10 @@ func (g *generator) printFunctions() {
 	g.p("}")
 	g.p("")
 
-	g.p("func (n *%s[K, V]) IsExpired() bool {", g.structName)
+	g.p("func (n *%s[K, V]) HasExpired() bool {", g.structName)
 	g.in()
 	if g.features[expiration] {
-		g.p("return n.expiration > 0 && n.expiration < unixtime.Now()")
+		g.p("return n.expiration <= unixtime.Now()")
 	} else {
 		g.p("return false")
 	}
@@ -501,8 +501,8 @@ type Node[K comparable, V any] interface {
 	NextExp() Node[K, V]
 	// SetNextExp sets the next node in the expiration policy.
 	SetNextExp(v Node[K, V])
-	// IsExpired returns true if node is expired.
-	IsExpired() bool
+	// HasExpired returns true if node has expired.
+	HasExpired() bool
 	// Expiration returns the expiration time.
 	Expiration() uint32
 	// Cost returns the cost of the node.
diff --git a/entry.go b/entry.go
new file mode 100644
index 0000000..5dcfaf0
--- /dev/null
+++ b/entry.go
@@ -0,0 +1,82 @@
+// Copyright (c) 2024 Alexey Mayshev. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package otter
+
+import "time"
+
+// Entry is a key-value pair that may include policy metadata for the cached entry.
+//
+// It is an immutable snapshot of the cached data at the time of this entry's creation, and it will not
+// reflect changes afterward.
+type Entry[K comparable, V any] struct {
+	key        K
+	value      V
+	expiration int64
+	cost       uint32
+}
+
+// Key returns the entry's key.
+func (e Entry[K, V]) Key() K {
+	return e.key
+}
+
+// Value returns the entry's value.
+func (e Entry[K, V]) Value() V {
+	return e.value
+}
+
+// Expiration returns the entry's expiration time as a unix time,
+// the number of seconds elapsed since January 1, 1970 UTC.
+//
+// If the cache was not configured with an expiration policy then this value is always 0.
+func (e Entry[K, V]) Expiration() int64 {
+	return e.expiration
+}
+
+// TTL returns the entry's ttl.
+//
+// If the cache was not configured with an expiration policy then this value is always -1.
+//
+// If the entry is expired then this value is always 0.
+func (e Entry[K, V]) TTL() time.Duration {
+	expiration := e.Expiration()
+	if expiration == 0 {
+		return -1
+	}
+
+	now := time.Now().Unix()
+	if expiration <= now {
+		return 0
+	}
+
+	return time.Duration(expiration-now) * time.Second
+}
+
+// HasExpired returns true if the entry has expired.
+func (e Entry[K, V]) HasExpired() bool {
+	expiration := e.Expiration()
+	if expiration == 0 {
+		return false
+	}
+
+	return expiration <= time.Now().Unix()
+}
+
+// Cost returns the entry's cost.
+//
+// If the cache was not configured with a cost then this value is always 1.
+func (e Entry[K, V]) Cost() uint32 {
+	return e.cost
+}
diff --git a/extension.go b/extension.go
new file mode 100644
index 0000000..83a511b
--- /dev/null
+++ b/extension.go
@@ -0,0 +1,89 @@
+// Copyright (c) 2024 Alexey Mayshev. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package otter
+
+import (
+	"github.com/maypok86/otter/internal/core"
+	"github.com/maypok86/otter/internal/generated/node"
+	"github.com/maypok86/otter/internal/unixtime"
+)
+
+func zeroValue[V any]() V {
+	var zero V
+	return zero
+}
+
+// Extension is an access point for inspecting and performing low-level operations based on the cache's runtime
+// characteristics. These operations are optional and dependent on how the cache was constructed
+// and what abilities the implementation exposes.
+type Extension[K comparable, V any] struct {
+	cache *core.Cache[K, V]
+}
+
+func newExtension[K comparable, V any](cache *core.Cache[K, V]) Extension[K, V] {
+	return Extension[K, V]{
+		cache: cache,
+	}
+}
+
+func (e Extension[K, V]) createEntry(n node.Node[K, V]) Entry[K, V] {
+	var expiration int64
+	if e.cache.WithExpiration() {
+		expiration = unixtime.StartTime() + int64(n.Expiration())
+	}
+
+	return Entry[K, V]{
+		key:        n.Key(),
+		value:      n.Value(),
+		expiration: expiration,
+		cost:       n.Cost(),
+	}
+}
+
+// GetQuietly returns the value associated with the key in this cache.
+//
+// Unlike Get in the cache, this function does not produce any side effects
+// such as updating statistics or the eviction policy.
+func (e Extension[K, V]) GetQuietly(key K) (V, bool) {
+	n, ok := e.cache.GetNodeQuietly(key)
+	if !ok {
+		return zeroValue[V](), false
+	}
+
+	return n.Value(), true
+}
+
+// GetEntry returns the cache entry associated with the key in this cache.
+func (e Extension[K, V]) GetEntry(key K) (Entry[K, V], bool) {
+	n, ok := e.cache.GetNode(key)
+	if !ok {
+		return Entry[K, V]{}, false
+	}
+
+	return e.createEntry(n), true
+}
+
+// GetEntryQuietly returns the cache entry associated with the key in this cache.
+//
+// Unlike GetEntry, this function does not produce any side effects
+// such as updating statistics or the eviction policy.
+func (e Extension[K, V]) GetEntryQuietly(key K) (Entry[K, V], bool) {
+	n, ok := e.cache.GetNodeQuietly(key)
+	if !ok {
+		return Entry[K, V]{}, false
+	}
+
+	return e.createEntry(n), true
+}
diff --git a/internal/core/cache.go b/internal/core/cache.go
index d05b0b6..3bcee0d 100644
--- a/internal/core/cache.go
+++ b/internal/core/cache.go
@@ -18,7 +18,7 @@ import (
 	"sync"
 	"time"
 
-	"github.com/maypok86/otter/internal/expire"
+	"github.com/maypok86/otter/internal/expiry"
 	"github.com/maypok86/otter/internal/generated/node"
 	"github.com/maypok86/otter/internal/hashtable"
 	"github.com/maypok86/otter/internal/lossy"
@@ -53,9 +53,12 @@ func zeroValue[V any]() V {
 	return zero
 }
 
+func getTTL(ttl time.Duration) uint32 {
+	return uint32((ttl + time.Second - 1) / time.Second)
+}
+
 func getExpiration(ttl time.Duration) uint32 {
-	ttlSecond := (ttl + time.Second - 1) / time.Second
-	return unixtime.Now() + uint32(ttlSecond)
+	return unixtime.Now() + getTTL(ttl)
 }
 
 // Config is a set of cache settings.
@@ -70,7 +73,7 @@ type Config[K comparable, V any] struct {
 	DeletionListener func(key K, value V, cause DeletionCause)
 }
 
-type expirePolicy[K comparable, V any] interface {
+type expiryPolicy[K comparable, V any] interface {
 	Add(n node.Node[K, V])
 	Delete(n node.Node[K, V])
 	RemoveExpired(expired []node.Node[K, V]) []node.Node[K, V]
@@ -83,7 +86,7 @@ type Cache[K comparable, V any] struct {
 	nodeManager      *node.Manager[K, V]
 	hashmap          *hashtable.Map[K, V]
 	policy           *s3fifo.Policy[K, V]
-	expirePolicy     expirePolicy[K, V]
+	expiryPolicy     expiryPolicy[K, V]
 	stats            *stats.Stats
 	readBuffers      []*lossy.Buffer[K, V]
 	writeBuffer      *queue.Growable[task[K, V]]
@@ -123,21 +126,21 @@ func NewCache[K comparable, V any](c Config[K, V]) *Cache[K, V] {
 		hashmap = hashtable.NewWithSize[K, V](nodeManager, *c.InitialCapacity)
 	}
 
-	var expPolicy expirePolicy[K, V]
+	var expPolicy expiryPolicy[K, V]
 	switch {
 	case c.TTL != nil:
-		expPolicy = expire.NewFixed[K, V]()
+		expPolicy = expiry.NewFixed[K, V]()
 	case c.WithVariableTTL:
-		expPolicy = expire.NewVariable[K, V](nodeManager)
+		expPolicy = expiry.NewVariable[K, V](nodeManager)
 	default:
-		expPolicy = expire.NewDisabled[K, V]()
+		expPolicy = expiry.NewDisabled[K, V]()
 	}
 
 	cache := &Cache[K, V]{
 		nodeManager:      nodeManager,
 		hashmap:          hashmap,
 		policy:           s3fifo.NewPolicy[K, V](uint32(c.Capacity)),
-		expirePolicy:     expPolicy,
+		expiryPolicy:     expPolicy,
 		readBuffers:      readBuffers,
 		writeBuffer:      queue.NewGrowable[task[K, V]](minWriteBufferCapacity, maxWriteBufferCapacity),
 		doneClear:        make(chan struct{}),
@@ -151,7 +154,7 @@ func NewCache[K comparable, V any](c Config[K, V]) *Cache[K, V] {
 		cache.stats = stats.New()
 	}
 	if c.TTL != nil {
-		cache.ttl = uint32((*c.TTL + time.Second - 1) / time.Second)
+		cache.ttl = getTTL(*c.TTL)
 	}
 
 	cache.withExpiration = c.TTL != nil || c.WithVariableTTL
@@ -178,22 +181,45 @@ func (c *Cache[K, V]) Has(key K) bool {
 
 // Get returns the value associated with the key in this cache.
 func (c *Cache[K, V]) Get(key K) (V, bool) {
-	got, ok := c.hashmap.Get(key)
-	if !ok || !got.IsAlive() {
-		c.stats.IncMisses()
+	n, ok := c.GetNode(key)
+	if !ok {
 		return zeroValue[V](), false
 	}
 
-	if got.IsExpired() {
-		c.writeBuffer.Push(newDeleteTask(got))
+	return n.Value(), true
+}
+
+// GetNode returns the node associated with the key in this cache.
+func (c *Cache[K, V]) GetNode(key K) (node.Node[K, V], bool) {
+	n, ok := c.hashmap.Get(key)
+	if !ok || !n.IsAlive() {
 		c.stats.IncMisses()
-		return zeroValue[V](), false
+		return nil, false
+	}
+
+	if n.HasExpired() {
+		c.writeBuffer.Push(newDeleteTask(n))
+		c.stats.IncMisses()
+		return nil, false
 	}
 
-	c.afterGet(got)
+	c.afterGet(n)
 	c.stats.IncHits()
 
-	return got.Value(), ok
+	return n, true
+}
+
+// GetNodeQuietly returns the node associated with the key in this cache.
+//
+// Unlike GetNode, this function does not produce any side effects
+// such as updating statistics or the eviction policy.
+func (c *Cache[K, V]) GetNodeQuietly(key K) (node.Node[K, V], bool) {
+	n, ok := c.hashmap.Get(key)
+	if !ok || !n.IsAlive() || n.HasExpired() {
+		return nil, false
+	}
+
+	return n, true
 }
 
 func (c *Cache[K, V]) afterGet(got node.Node[K, V]) {
@@ -300,7 +326,7 @@ func (c *Cache[K, V]) afterDelete(deleted node.Node[K, V]) {
 // DeleteByFunc deletes the association for this key from the cache when the given function returns true.
 func (c *Cache[K, V]) DeleteByFunc(f func(key K, value V) bool) {
 	c.hashmap.Range(func(n node.Node[K, V]) bool {
-		if !n.IsAlive() || n.IsExpired() {
+		if !n.IsAlive() || n.HasExpired() {
 			return true
 		}
 
@@ -331,7 +357,7 @@ func (c *Cache[K, V]) cleanup() {
 			return
 		}
 
-		expired = c.expirePolicy.RemoveExpired(expired)
+		expired = c.expiryPolicy.RemoveExpired(expired)
 		for _, n := range expired {
 			c.policy.Delete(n)
 		}
@@ -365,7 +391,7 @@ func (c *Cache[K, V]) process() {
 
 			c.evictionMutex.Lock()
 			c.policy.Clear()
-			c.expirePolicy.Clear()
+			c.expiryPolicy.Clear()
 			if t.isClose() {
 				c.isClosed = true
 			}
@@ -389,26 +415,26 @@ func (c *Cache[K, V]) process() {
 				n := t.node()
 				switch {
 				case t.isDelete():
-					c.expirePolicy.Delete(n)
+					c.expiryPolicy.Delete(n)
 					c.policy.Delete(n)
 				case t.isAdd():
 					if n.IsAlive() {
-						c.expirePolicy.Add(n)
+						c.expiryPolicy.Add(n)
 						deleted = c.policy.Add(deleted, n)
 					}
 				case t.isUpdate():
 					oldNode := t.oldNode()
-					c.expirePolicy.Delete(oldNode)
+					c.expiryPolicy.Delete(oldNode)
 					c.policy.Delete(oldNode)
 					if n.IsAlive() {
-						c.expirePolicy.Add(n)
+						c.expiryPolicy.Add(n)
 						deleted = c.policy.Add(deleted, n)
 					}
 				}
 			}
 
 			for _, n := range deleted {
-				c.expirePolicy.Delete(n)
+				c.expiryPolicy.Delete(n)
 			}
 
 			c.evictionMutex.Unlock()
@@ -446,7 +472,7 @@ func (c *Cache[K, V]) process() {
 // Iteration stops early when the given function returns false.
 func (c *Cache[K, V]) Range(f func(key K, value V) bool) {
 	c.hashmap.Range(func(n node.Node[K, V]) bool {
-		if !n.IsAlive() || n.IsExpired() {
+		if !n.IsAlive() || n.HasExpired() {
 			return true
 		}
 
@@ -500,6 +526,11 @@ func (c *Cache[K, V]) Stats() *stats.Stats {
 	return c.stats
 }
 
+// WithExpiration returns true if the cache was configured with the expiration policy enabled.
+func (c *Cache[K, V]) WithExpiration() bool {
+	return c.withExpiration
+}
+
 func clearBuffer[T any](buffer []T) []T {
 	var zero T
 	for i := 0; i < len(buffer); i++ {
diff --git a/internal/expire/disabled.go b/internal/expiry/disabled.go
similarity index 98%
rename from internal/expire/disabled.go
rename to internal/expiry/disabled.go
index fb46cd5..61271f8 100644
--- a/internal/expire/disabled.go
+++ b/internal/expiry/disabled.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package expire
+package expiry
 
 import "github.com/maypok86/otter/internal/generated/node"
 
diff --git a/internal/expire/fixed.go b/internal/expiry/fixed.go
similarity index 94%
rename from internal/expire/fixed.go
rename to internal/expiry/fixed.go
index ceb0cfa..6ca7f9b 100644
--- a/internal/expire/fixed.go
+++ b/internal/expiry/fixed.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package expire
+package expiry
 
 import "github.com/maypok86/otter/internal/generated/node"
 
@@ -35,7 +35,7 @@ func (f *Fixed[K, V]) Delete(n node.Node[K, V]) {
 }
 
 func (f *Fixed[K, V]) RemoveExpired(expired []node.Node[K, V]) []node.Node[K, V] {
-	for !f.q.isEmpty() && f.q.head.IsExpired() {
+	for !f.q.isEmpty() && f.q.head.HasExpired() {
 		expired = append(expired, f.q.pop())
 	}
 	return expired
diff --git a/internal/expire/queue.go b/internal/expiry/queue.go
similarity index 99%
rename from internal/expire/queue.go
rename to internal/expiry/queue.go
index dc906b9..18c5a85 100644
--- a/internal/expire/queue.go
+++ b/internal/expiry/queue.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package expire
+package expiry
 
 import "github.com/maypok86/otter/internal/generated/node"
 
diff --git a/internal/expire/variable.go b/internal/expiry/variable.go
similarity index 99%
rename from internal/expire/variable.go
rename to internal/expiry/variable.go
index 522a318..b5791a1 100644
--- a/internal/expire/variable.go
+++ b/internal/expiry/variable.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package expire
+package expiry
 
 import (
 	"math"
diff --git a/internal/generated/node/b.go b/internal/generated/node/b.go
index 28190aa..a10e484 100644
--- a/internal/generated/node/b.go
+++ b/internal/generated/node/b.go
@@ -87,7 +87,7 @@ func (n *B[K, V]) SetNextExp(v Node[K, V]) {
 	panic("not implemented")
 }
 
-func (n *B[K, V]) IsExpired() bool {
+func (n *B[K, V]) HasExpired() bool {
 	return false
 }
 
diff --git a/internal/generated/node/bc.go b/internal/generated/node/bc.go
index 7342597..962ecde 100644
--- a/internal/generated/node/bc.go
+++ b/internal/generated/node/bc.go
@@ -91,7 +91,7 @@ func (n *BC[K, V]) SetNextExp(v Node[K, V]) {
 	panic("not implemented")
 }
 
-func (n *BC[K, V]) IsExpired() bool {
+func (n *BC[K, V]) HasExpired() bool {
 	return false
 }
 
diff --git a/internal/generated/node/be.go b/internal/generated/node/be.go
index 15377d9..ef66eef 100644
--- a/internal/generated/node/be.go
+++ b/internal/generated/node/be.go
@@ -103,8 +103,8 @@ func (n *BE[K, V]) SetNextExp(v Node[K, V]) {
 	n.nextExp = (*BE[K, V])(v.AsPointer())
 }
 
-func (n *BE[K, V]) IsExpired() bool {
-	return n.expiration > 0 && n.expiration < unixtime.Now()
+func (n *BE[K, V]) HasExpired() bool {
+	return n.expiration <= unixtime.Now()
 }
 
 func (n *BE[K, V]) Expiration() uint32 {
diff --git a/internal/generated/node/bec.go b/internal/generated/node/bec.go
index e438d13..f4813ca 100644
--- a/internal/generated/node/bec.go
+++ b/internal/generated/node/bec.go
@@ -107,8 +107,8 @@ func (n *BEC[K, V]) SetNextExp(v Node[K, V]) {
 	n.nextExp = (*BEC[K, V])(v.AsPointer())
 }
 
-func (n *BEC[K, V]) IsExpired() bool {
-	return n.expiration > 0 && n.expiration < unixtime.Now()
+func (n *BEC[K, V]) HasExpired() bool {
+	return n.expiration <= unixtime.Now()
 }
 
 func (n *BEC[K, V]) Expiration() uint32 {
diff --git a/internal/generated/node/manager.go b/internal/generated/node/manager.go
index 8ea396e..e48b900 100644
--- a/internal/generated/node/manager.go
+++ b/internal/generated/node/manager.go
@@ -45,8 +45,8 @@ type Node[K comparable, V any] interface {
 	NextExp() Node[K, V]
 	// SetNextExp sets the next node in the expiration policy.
 	SetNextExp(v Node[K, V])
-	// IsExpired returns true if node is expired.
-	IsExpired() bool
+	// HasExpired returns true if node has expired.
+	HasExpired() bool
 	// Expiration returns the expiration time.
 	Expiration() uint32
 	// Cost returns the cost of the node.
diff --git a/internal/s3fifo/main.go b/internal/s3fifo/main.go
index d03bf80..684e262 100644
--- a/internal/s3fifo/main.go
+++ b/internal/s3fifo/main.go
@@ -44,7 +44,7 @@ func (m *main[K, V]) evict(deleted []node.Node[K, V]) []node.Node[K, V] {
 	for m.cost > 0 {
 		n := m.q.pop()
 
-		if !n.IsAlive() || n.IsExpired() || n.Frequency() == 0 {
+		if !n.IsAlive() || n.HasExpired() || n.Frequency() == 0 {
 			n.Unmark()
 			m.cost -= n.Cost()
 			return append(deleted, n)
diff --git a/internal/s3fifo/small.go b/internal/s3fifo/small.go
index cb84528..acab906 100644
--- a/internal/s3fifo/small.go
+++ b/internal/s3fifo/small.go
@@ -53,7 +53,7 @@ func (s *small[K, V]) evict(deleted []node.Node[K, V]) []node.Node[K, V] {
 	n := s.q.pop()
 	s.cost -= n.Cost()
 	n.Unmark()
-	if !n.IsAlive() || n.IsExpired() {
+	if !n.IsAlive() || n.HasExpired() {
 		return append(deleted, n)
 	}
 
diff --git a/internal/unixtime/unixtime.go b/internal/unixtime/unixtime.go
index 0737adf..a446921 100644
--- a/internal/unixtime/unixtime.go
+++ b/internal/unixtime/unixtime.go
@@ -23,7 +23,8 @@ import (
 var (
 	// We need this package because time.Now() is slower, allocates memory,
 	// and we don't need a more precise time for the expiry time (and most other operations).
-	now uint32
+	now       uint32
+	startTime int64
 
 	mutex         sync.Mutex
 	countInstance int
@@ -32,7 +33,7 @@ var (
 
 func startTimer() {
 	done = make(chan struct{})
-	startTime := time.Now().Unix()
+	atomic.StoreInt64(&startTime, time.Now().Unix())
 	atomic.StoreUint32(&now, uint32(0))
 
 	go func() {
@@ -41,7 +42,7 @@ func startTimer() {
 		for {
 			select {
 			case t := <-ticker.C:
-				atomic.StoreUint32(&now, uint32(t.Unix()-startTime))
+				atomic.StoreUint32(&now, uint32(t.Unix()-StartTime()))
 			case <-done:
 				return
 			}
@@ -84,3 +85,8 @@ func Now() uint32 {
 func SetNow(t uint32) {
 	atomic.StoreUint32(&now, t)
 }
+
+// StartTime returns the start time of the program.
+func StartTime() int64 {
+	return atomic.LoadInt64(&startTime)
+}


Test patch:
diff --git a/cache_test.go b/cache_test.go
index 39969dc..d573f45 100644
--- a/cache_test.go
+++ b/cache_test.go
@@ -317,6 +317,60 @@ func TestCache_DeleteByFunc(t *testing.T) {
 	}
 }
 
+func TestCache_Advanced(t *testing.T) {
+	size := 256
+	defaultTTL := time.Hour
+	c, err := MustBuilder[int, int](size).
+		WithTTL(defaultTTL).
+		Build()
+	if err != nil {
+		t.Fatalf("can not create builder: %v", err)
+	}
+
+	for i := 0; i < size; i++ {
+		c.Set(i, i)
+	}
+
+	k1 := 4
+	v1, ok := c.Extension().GetQuietly(k1)
+	if !ok {
+		t.Fatalf("not found key %d", k1)
+	}
+
+	e1, ok := c.Extension().GetEntryQuietly(k1)
+	if !ok {
+		t.Fatalf("not found key %d", k1)
+	}
+
+	e2, ok := c.Extension().GetEntry(k1)
+	if !ok {
+		t.Fatalf("not found key %d", k1)
+	}
+
+	time.Sleep(time.Second)
+
+	isValidEntries := e1.Key() == k1 &&
+		e1.Value() == v1 &&
+		e1.Cost() == 1 &&
+		e1 == e2 &&
+		e1.TTL() < defaultTTL &&
+		!e1.HasExpired()
+
+	if !isValidEntries {
+		t.Fatalf("found not valid entries. e1: %+v, e2: %+v, v1:%d", e1, e2, v1)
+	}
+
+	if _, ok := c.Extension().GetQuietly(size); ok {
+		t.Fatalf("found not valid key: %d", size)
+	}
+	if _, ok := c.Extension().GetEntryQuietly(size); ok {
+		t.Fatalf("found not valid key: %d", size)
+	}
+	if _, ok := c.Extension().GetEntry(size); ok {
+		t.Fatalf("found not valid key: %d", size)
+	}
+}
+
 func TestCache_Ratio(t *testing.T) {
 	var mutex sync.Mutex
 	m := make(map[DeletionCause]int)
diff --git a/entry_test.go b/entry_test.go
new file mode 100644
index 0000000..e2a8f11
--- /dev/null
+++ b/entry_test.go
@@ -0,0 +1,69 @@
+// Copyright (c) 2024 Alexey Mayshev. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package otter
+
+import (
+	"testing"
+	"time"
+)
+
+func TestEntry(t *testing.T) {
+	k := 2
+	v := 3
+	exp := int64(0)
+	c := uint32(5)
+	e := Entry[int, int]{
+		key:        k,
+		value:      v,
+		expiration: exp,
+		cost:       c,
+	}
+
+	if e.Key() != k {
+		t.Fatalf("not valid key. want %d, got %d", k, e.Key())
+	}
+	if e.Value() != v {
+		t.Fatalf("not valid value. want %d, got %d", v, e.Value())
+	}
+	if e.Cost() != c {
+		t.Fatalf("not valid cost. want %d, got %d", c, e.Cost())
+	}
+	if e.Expiration() != exp {
+		t.Fatalf("not valid expiration. want %d, got %d", exp, e.Expiration())
+	}
+	if ttl := e.TTL(); ttl != -1 {
+		t.Fatalf("not valid ttl. want -1, got %d", ttl)
+	}
+	if e.HasExpired() {
+		t.Fatal("entry should not be expire")
+	}
+
+	newTTL := int64(10)
+	e.expiration = time.Now().Unix() + newTTL
+	if ttl := e.TTL(); ttl <= 0 || ttl > time.Duration(newTTL)*time.Second {
+		t.Fatalf("ttl should be in the range (0, %d] seconds, but got %d seconds", newTTL, ttl/time.Second)
+	}
+	if e.HasExpired() {
+		t.Fatal("entry should not be expire")
+	}
+
+	e.expiration -= 2 * newTTL
+	if ttl := e.TTL(); ttl != 0 {
+		t.Fatalf("ttl should be 0 seconds, but got %d seconds", ttl/time.Second)
+	}
+	if !e.HasExpired() {
+		t.Fatalf("entry should have expired")
+	}
+}
diff --git a/internal/expire/queue_test.go b/internal/expiry/queue_test.go
similarity index 99%
rename from internal/expire/queue_test.go
rename to internal/expiry/queue_test.go
index 2b6034f..9a31856 100644
--- a/internal/expire/queue_test.go
+++ b/internal/expiry/queue_test.go
@@ -9,7 +9,7 @@
 // license that can be found in the LICENSE file.
 // That can be found at https://cs.opensource.google/go/go/+/refs/tags/go1.21.5:LICENSE
 
-package expire
+package expiry
 
 import (
 	"strconv"
diff --git a/internal/expire/variable_test.go b/internal/expiry/variable_test.go
similarity index 99%
rename from internal/expire/variable_test.go
rename to internal/expiry/variable_test.go
index ef10431..f041e7e 100644
--- a/internal/expire/variable_test.go
+++ b/internal/expiry/variable_test.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package expire
+package expiry
 
 import (
 	"testing"