flannel/vendor/k8s.io/kubernetes/pkg/util/uuid/uuid.go

/*
Copyright 2014 The Kubernetes Authors.

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 uuid

import (
	"sync"

	"github.com/pborman/uuid"
	"k8s.io/kubernetes/pkg/types"
)

var uuidLock sync.Mutex
var lastUUID uuid.UUID

func NewUUID() types.UID {
	uuidLock.Lock()
	defer uuidLock.Unlock()
	result := uuid.NewUUID()
	// The UUID package is naive and can generate identical UUIDs if the
	// time interval is quick enough.
	// The UUID uses 100 ns increments so it's short enough to actively
	// wait for a new value.
	for uuid.Equal(lastUUID, result) == true {
		result = uuid.NewUUID()
	}
	lastUUID = result
	return types.UID(result.String())
}