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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,130 @@ | ||
| /* | ||
| Copyright 2013 Google Inc. | ||
| 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 lru implements an LRU cache. | ||
| package lru | ||
|
|
||
| import "container/list" | ||
|
|
||
| // Cache is an LRU cache. It is not safe for concurrent access. | ||
| type Cache[K comparable, V any] struct { | ||
| // MaxEntries is the maximum number of cache entries before | ||
| // an item is evicted. Zero means no limit. | ||
| MaxEntries int | ||
|
|
||
| // OnEvicted optionally specifies a callback function to be | ||
| // executed when an entry is purged from the cache. | ||
| OnEvicted func(key K, value V) | ||
|
|
||
| ll *list.List | ||
| cache map[K]*list.Element | ||
| } | ||
|
|
||
| type entry[K comparable, V any] struct { | ||
| key K | ||
| value V | ||
| } | ||
|
|
||
| // New creates a new Cache. | ||
| // If maxEntries is zero, the cache has no limit and it's assumed | ||
| // that eviction is done by the caller. | ||
| func New[K comparable, V any](maxEntries int) *Cache[K, V] { | ||
| return &Cache[K, V]{ | ||
| MaxEntries: maxEntries, | ||
| ll: list.New(), | ||
| cache: make(map[K]*list.Element), | ||
| } | ||
| } | ||
|
|
||
| // Add adds a value to the cache. | ||
| func (c *Cache[K, V]) Add(key K, value V) { | ||
| if c.cache == nil { | ||
| c.cache = make(map[K]*list.Element) | ||
| c.ll = list.New() | ||
| } | ||
| if ee, ok := c.cache[key]; ok { | ||
| c.ll.MoveToFront(ee) | ||
| ee.Value.(*entry[K, V]).value = value | ||
| return | ||
| } | ||
| ele := c.ll.PushFront(&entry[K, V]{key, value}) | ||
| c.cache[key] = ele | ||
| if c.MaxEntries != 0 && c.ll.Len() > c.MaxEntries { | ||
| c.RemoveOldest() | ||
| } | ||
| } | ||
|
|
||
| // Get looks up a key's value from the cache. | ||
| func (c *Cache[K, V]) Get(key K) (value V, ok bool) { | ||
| if c.cache == nil { | ||
| return | ||
| } | ||
| if ele, hit := c.cache[key]; hit { | ||
| c.ll.MoveToFront(ele) | ||
| return ele.Value.(*entry[K, V]).value, true | ||
| } | ||
| return | ||
| } | ||
|
|
||
| // Remove removes the provided key from the cache. | ||
| func (c *Cache[K, V]) Remove(key K) { | ||
| if c.cache == nil { | ||
| return | ||
| } | ||
| if ele, hit := c.cache[key]; hit { | ||
| c.removeElement(ele) | ||
| } | ||
| } | ||
|
|
||
| // RemoveOldest removes the oldest item from the cache. | ||
| func (c *Cache[K, V]) RemoveOldest() { | ||
| if c.cache == nil { | ||
| return | ||
| } | ||
| ele := c.ll.Back() | ||
| if ele != nil { | ||
| c.removeElement(ele) | ||
| } | ||
| } | ||
|
|
||
| func (c *Cache[K, V]) removeElement(e *list.Element) { | ||
| c.ll.Remove(e) | ||
| kv := e.Value.(*entry[K, V]) | ||
| delete(c.cache, kv.key) | ||
| if c.OnEvicted != nil { | ||
| c.OnEvicted(kv.key, kv.value) | ||
| } | ||
| } | ||
|
|
||
| // Len returns the number of items in the cache. | ||
| func (c *Cache[K, V]) Len() int { | ||
| if c.cache == nil { | ||
| return 0 | ||
| } | ||
| return c.ll.Len() | ||
| } | ||
|
|
||
| // Clear purges all stored items from the cache. | ||
| func (c *Cache[K, V]) Clear() { | ||
| if c.OnEvicted != nil { | ||
| for _, e := range c.cache { | ||
| kv := e.Value.(*entry[K, V]) | ||
| c.OnEvicted(kv.key, kv.value) | ||
| } | ||
| } | ||
| c.ll = nil | ||
| c.cache = nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,97 @@ | ||
| /* | ||
| Copyright 2013 Google Inc. | ||
| 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 lru | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "testing" | ||
| ) | ||
|
|
||
| type simpleStruct struct { | ||
| int | ||
| string | ||
| } | ||
|
|
||
| type complexStruct struct { | ||
| int | ||
| simpleStruct | ||
| } | ||
|
|
||
| var getTests = []struct { | ||
| name string | ||
| keyToAdd interface{} | ||
| keyToGet interface{} | ||
| expectedOk bool | ||
| }{ | ||
| {"string_hit", "myKey", "myKey", true}, | ||
| {"string_miss", "myKey", "nonsense", false}, | ||
| {"simple_struct_hit", simpleStruct{1, "two"}, simpleStruct{1, "two"}, true}, | ||
| {"simple_struct_miss", simpleStruct{1, "two"}, simpleStruct{0, "noway"}, false}, | ||
| {"complex_struct_hit", complexStruct{1, simpleStruct{2, "three"}}, | ||
| complexStruct{1, simpleStruct{2, "three"}}, true}, | ||
| } | ||
|
|
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| func TestGet(t *testing.T) { | ||
| for _, tt := range getTests { | ||
| lru := New(0) | ||
| lru.Add(tt.keyToAdd, 1234) | ||
| val, ok := lru.Get(tt.keyToGet) | ||
| if ok != tt.expectedOk { | ||
| t.Fatalf("%s: cache hit = %v; want %v", tt.name, ok, !ok) | ||
| } else if ok && val != 1234 { | ||
| t.Fatalf("%s expected get to return 1234 but got %v", tt.name, val) | ||
| } | ||
| } | ||
| } | ||
|
|
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| func TestRemove(t *testing.T) { | ||
| lru := New(0) | ||
| lru.Add("myKey", 1234) | ||
| if val, ok := lru.Get("myKey"); !ok { | ||
| t.Fatal("TestRemove returned no match") | ||
| } else if val != 1234 { | ||
| t.Fatalf("TestRemove failed. Expected %d, got %v", 1234, val) | ||
| } | ||
|
|
||
| lru.Remove("myKey") | ||
| if _, ok := lru.Get("myKey"); ok { | ||
| t.Fatal("TestRemove returned a removed entry") | ||
| } | ||
| } | ||
|
|
||
| func TestEvict(t *testing.T) { | ||
| evictedKeys := make([]Key, 0) | ||
| onEvictedFun := func(key Key, value interface{}) { | ||
| evictedKeys = append(evictedKeys, key) | ||
| } | ||
|
|
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| lru := New(20) | ||
| lru.OnEvicted = onEvictedFun | ||
| for i := 0; i < 22; i++ { | ||
| lru.Add(fmt.Sprintf("myKey%d", i), 1234) | ||
| } | ||
|
|
||
| if len(evictedKeys) != 2 { | ||
| t.Fatalf("got %d evicted keys; want 2", len(evictedKeys)) | ||
| } | ||
| if evictedKeys[0] != Key("myKey0") { | ||
| t.Fatalf("got %v in first evicted key; want %s", evictedKeys[0], "myKey0") | ||
| } | ||
| if evictedKeys[1] != Key("myKey1") { | ||
| t.Fatalf("got %v in second evicted key; want %s", evictedKeys[1], "myKey1") | ||
| } | ||
| } |