1// Copyright 2019, OpenCensus Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package trace
16
17import (
18	"github.com/golang/groupcache/lru"
19)
20
21// A simple lru.Cache wrapper that tracks the keys of the current contents and
22// the cumulative number of evicted items.
23type lruMap struct {
24	cacheKeys    map[lru.Key]bool
25	cache        *lru.Cache
26	droppedCount int
27}
28
29func newLruMap(size int) *lruMap {
30	lm := &lruMap{
31		cacheKeys:    make(map[lru.Key]bool),
32		cache:        lru.New(size),
33		droppedCount: 0,
34	}
35	lm.cache.OnEvicted = func(key lru.Key, value interface{}) {
36		delete(lm.cacheKeys, key)
37		lm.droppedCount++
38	}
39	return lm
40}
41
42func (lm lruMap) len() int {
43	return lm.cache.Len()
44}
45
46func (lm lruMap) keys() []interface{} {
47	keys := make([]interface{}, len(lm.cacheKeys))
48	for k := range lm.cacheKeys {
49		keys = append(keys, k)
50	}
51	return keys
52}
53
54func (lm *lruMap) add(key, value interface{}) {
55	lm.cacheKeys[lru.Key(key)] = true
56	lm.cache.Add(lru.Key(key), value)
57}
58
59func (lm *lruMap) get(key interface{}) (interface{}, bool) {
60	return lm.cache.Get(key)
61}
62