1 // Copyright 2022-2025 The sacloud/packages-go 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 15 package mutexkv
16 17 import (
18 "sync"
19 )
20 21 // MutexKV is a simple key/value store for arbitrary mutexes. It can be used to
22 // serialize changes across arbitrary collaborators that share knowledge of the
23 // keys they must serialize on.
24 type MutexKV struct {
25 lock sync.Mutex
26 store map[string]*sync.Mutex
27 }
28 29 // Lock the mutex for the given key. Caller is responsible for calling Unlock
30 // for the same key
31 func (m *MutexKV) Lock(key string) {
32 m.get(key).Lock()
33 }
34 35 // Unlock the mutex for the given key. Caller must have called Lock for the same key first
36 func (m *MutexKV) Unlock(key string) {
37 m.get(key).Unlock()
38 }
39 40 // Returns a mutex for the given key, no guarantee of its lock status
41 func (m *MutexKV) get(key string) *sync.Mutex {
42 m.lock.Lock()
43 defer m.lock.Unlock()
44 mutex, ok := m.store[key]
45 if !ok {
46 mutex = &sync.Mutex{}
47 m.store[key] = mutex
48 }
49 return mutex
50 }
51 52 // NewMutexKV Returns a properly initialized MutexKV
53 func NewMutexKV() *MutexKV {
54 return &MutexKV{
55 store: make(map[string]*sync.Mutex),
56 }
57 }
58