restic/vendor/cloud.google.com/go/internal/testutil/unique.go

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2017-08-05 18:17:15 +00:00
// Copyright 2017 Google Inc. All Rights Reserved.
//
// 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.
// This file supports generating unique IDs so that multiple test executions
// don't interfere with each other, and cleaning up old entities that may
// remain if tests exit early.
package testutil
import (
"fmt"
"regexp"
"strconv"
"sync"
"time"
)
var startTime = time.Now().UTC()
// A UIDSpace manages a set of unique IDs distinguished by a prefix.
type UIDSpace struct {
Prefix string
re *regexp.Regexp
mu sync.Mutex
count int
}
func NewUIDSpace(prefix string) *UIDSpace {
return &UIDSpace{
Prefix: prefix,
re: regexp.MustCompile("^" + regexp.QuoteMeta(prefix) + `-(\d{4})(\d{2})(\d{2})-(\d+)-\d+$`),
}
}
// New generates a new unique ID . The ID consists of the UIDSpace's prefix, a
// timestamp, and a counter value. All unique IDs generated in the same test
// execution will have the same timestamp.
//
// Aside from the characters in the prefix, IDs contain only letters, numbers
// and hyphens.
func (s *UIDSpace) New() string { return s.newID(startTime) }
func (s *UIDSpace) newID(t time.Time) string {
s.mu.Lock()
c := s.count
s.count++
s.mu.Unlock()
// Write the time as a date followed by nanoseconds from midnight of that date.
// That makes it easier to see the approximate time of the ID when it is displayed.
y, m, d := t.Date()
ns := t.Sub(time.Date(y, m, d, 0, 0, 0, 0, time.UTC))
// Zero-pad the counter for lexical sort order for IDs with the same timestamp.
return fmt.Sprintf("%s-%04d%02d%02d-%d-%04d", s.Prefix, y, m, d, ns, c)
}
// Timestamp extracts the timestamp of uid, which must have been generated by
// s. The second return value is true on success, false if there was a problem.
func (s *UIDSpace) Timestamp(uid string) (time.Time, bool) {
subs := s.re.FindStringSubmatch(uid)
if subs == nil {
return time.Time{}, false
}
y, err1 := strconv.Atoi(subs[1])
m, err2 := strconv.Atoi(subs[2])
d, err3 := strconv.Atoi(subs[3])
ns, err4 := strconv.Atoi(subs[4])
if err1 != nil || err2 != nil || err3 != nil || err4 != nil {
return time.Time{}, false
}
return time.Date(y, time.Month(m), d, 0, 0, 0, ns, time.UTC), true
}
// Older reports whether uid was created by m and has a timestamp older than
// the current time by at least d.
func (s *UIDSpace) Older(uid string, d time.Duration) bool {
ts, ok := s.Timestamp(uid)
if !ok {
return false
}
return time.Since(ts) > d
}