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
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
|
package protocol
import (
"crypto/rand"
"fmt"
"reflect"
)
// RandReader is the random reader the protocol package will use to read
// random bytes from. This is exported for testing, and should not be used.
var RandReader = rand.Reader
const idempotencyTokenFillTag = `idempotencyToken`
// CanSetIdempotencyToken returns true if the struct field should be
// automatically populated with a Idempotency token.
//
// Only *string and string type fields that are tagged with idempotencyToken
// which are not already set can be auto filled.
func CanSetIdempotencyToken(v reflect.Value, f reflect.StructField) bool {
switch u := v.Interface().(type) {
// To auto fill an Idempotency token the field must be a string,
// tagged for auto fill, and have a zero value.
case *string:
return u == nil && len(f.Tag.Get(idempotencyTokenFillTag)) != 0
case string:
return len(u) == 0 && len(f.Tag.Get(idempotencyTokenFillTag)) != 0
}
return false
}
// GetIdempotencyToken returns a randomly generated idempotency token.
func GetIdempotencyToken() string {
b := make([]byte, 16)
RandReader.Read(b)
return UUIDVersion4(b)
}
// SetIdempotencyToken will set the value provided with a Idempotency Token.
// Given that the value can be set. Will panic if value is not setable.
func SetIdempotencyToken(v reflect.Value) {
if v.Kind() == reflect.Ptr {
if v.IsNil() && v.CanSet() {
v.Set(reflect.New(v.Type().Elem()))
}
v = v.Elem()
}
v = reflect.Indirect(v)
if !v.CanSet() {
panic(fmt.Sprintf("unable to set idempotnecy token %v", v))
}
b := make([]byte, 16)
_, err := rand.Read(b)
if err != nil {
// TODO handle error
return
}
v.Set(reflect.ValueOf(UUIDVersion4(b)))
}
// UUIDVersion4 returns a Version 4 random UUID from the byte slice provided
func UUIDVersion4(u []byte) string {
// https://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_.28random.29
// 13th character is "4"
u[6] = (u[6] | 0x40) & 0x4F
// 17th character is "8", "9", "a", or "b"
u[8] = (u[8] | 0x80) & 0xBF
return fmt.Sprintf(`%X-%X-%X-%X-%X`, u[0:4], u[4:6], u[6:8], u[8:10], u[10:])
}
|
