-
Notifications
You must be signed in to change notification settings - Fork 0
/
etag.go
52 lines (47 loc) · 1.36 KB
/
etag.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
/****************************************************************************
*
* Copyright (c) 2024 plgd.dev s.r.o.
*
* 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 resources
import (
"crypto/rand"
"encoding/binary"
"sync/atomic"
"time"
)
var globalETag atomic.Uint64
func generateNextETag(currentETag uint64) uint64 {
buf := make([]byte, 4)
_, err := rand.Read(buf)
if err != nil {
return currentETag + uint64(time.Now().UnixNano()%1000)
}
return currentETag + uint64(binary.BigEndian.Uint32(buf)%1000)
}
func GetETag() uint64 {
for {
now := uint64(time.Now().UnixNano())
oldEtag := globalETag.Load()
etag := oldEtag
if now > etag {
etag = now
}
newEtag := generateNextETag(etag)
if globalETag.CompareAndSwap(oldEtag, newEtag) {
return newEtag
}
}
}