blob: db286283d13303430845786ad73a4f0b0bd64061 (
plain) (
blame)
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
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
|
// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package sync
// OnceFunc returns a function that invokes f only once. The returned function
// may be called concurrently.
//
// If f panics, the returned function will panic with the same value on every call.
func OnceFunc(f func()) func() {
var (
once Once
valid bool
p any
)
// Construct the inner closure just once to reduce costs on the fast path.
g := func() {
defer func() {
p = recover()
if !valid {
// Re-panic immediately so on the first call the user gets a
// complete stack trace into f.
panic(p)
}
}()
f()
f = nil // Do not keep f alive after invoking it.
valid = true // Set only if f does not panic.
}
return func() {
once.Do(g)
if !valid {
panic(p)
}
}
}
// OnceValue returns a function that invokes f only once and returns the value
// returned by f. The returned function may be called concurrently.
//
// If f panics, the returned function will panic with the same value on every call.
func OnceValue[T any](f func() T) func() T {
var (
once Once
valid bool
p any
result T
)
g := func() {
defer func() {
p = recover()
if !valid {
panic(p)
}
}()
result = f()
f = nil
valid = true
}
return func() T {
once.Do(g)
if !valid {
panic(p)
}
return result
}
}
// OnceValues returns a function that invokes f only once and returns the values
// returned by f. The returned function may be called concurrently.
//
// If f panics, the returned function will panic with the same value on every call.
func OnceValues[T1, T2 any](f func() (T1, T2)) func() (T1, T2) {
var (
once Once
valid bool
p any
r1 T1
r2 T2
)
g := func() {
defer func() {
p = recover()
if !valid {
panic(p)
}
}()
r1, r2 = f()
f = nil
valid = true
}
return func() (T1, T2) {
once.Do(g)
if !valid {
panic(p)
}
return r1, r2
}
}
|
