1/*
2Copyright (c) 2015-2016 VMware, Inc. All Rights Reserved.
3
4Licensed under the Apache License, Version 2.0 (the "License");
5you may not use this file except in compliance with the License.
6You may obtain a copy of the License at
7
8    http://www.apache.org/licenses/LICENSE-2.0
9
10Unless required by applicable law or agreed to in writing, software
11distributed under the License is distributed on an "AS IS" BASIS,
12WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13See the License for the specific language governing permissions and
14limitations under the License.
15*/
16package flags
17
18import "sync"
19
20// Key type for storing flag instances in a context.Context.
21type flagKey string
22
23// Type to help flags out with only registering/processing once.
24type common struct {
25	register sync.Once
26	process  sync.Once
27}
28
29func (c *common) RegisterOnce(fn func()) {
30	c.register.Do(fn)
31}
32
33func (c *common) ProcessOnce(fn func() error) (err error) {
34	c.process.Do(func() {
35		err = fn()
36	})
37	return err
38}
39