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- // Copyright 2017 Google LLC
- //
- // 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 uid supports generating unique IDs. Its chief purpose is to prevent
- // multiple test executions from interfering with each other, and to facilitate
- // cleanup of old entities that may remain if tests exit early.
- package uid
-
- import (
- "fmt"
- "regexp"
- "strconv"
- "sync/atomic"
- "time"
- )
-
- // A Space manages a set of unique IDs distinguished by a prefix.
- type Space struct {
- Prefix string // Prefix of UIDs. Read-only.
- Sep rune // Separates UID parts. Read-only.
- Time time.Time // Timestamp for UIDs. Read-only.
- re *regexp.Regexp
- count int32 // atomic
- short bool
- }
-
- // Options are optional values for a Space.
- type Options struct {
- Sep rune // Separates parts of the UID. Defaults to '-'.
- Time time.Time // Timestamp for all UIDs made with this space. Defaults to current time.
-
- // Short, if true, makes the result of space.New shorter by 6 characters.
- // This can be useful for character restricted IDs. It will use a shorter
- // but less readable time representation, and will only use two characters
- // for the count suffix instead of four.
- //
- // e.x. normal: gotest-20181030-59751273685000-0001
- // e.x. short: gotest-1540917351273685000-01
- Short bool
- }
-
- // NewSpace creates a new UID space. A UID Space is used to generate unique IDs.
- func NewSpace(prefix string, opts *Options) *Space {
- var short bool
- sep := '-'
- tm := time.Now().UTC()
- if opts != nil {
- short = opts.Short
- if opts.Sep != 0 {
- sep = opts.Sep
- }
- if !opts.Time.IsZero() {
- tm = opts.Time
- }
- }
- var re string
-
- if short {
- re = fmt.Sprintf(`^%s%[2]c(\d+)%[2]c\d+$`, regexp.QuoteMeta(prefix), sep)
- } else {
- re = fmt.Sprintf(`^%s%[2]c(\d{4})(\d{2})(\d{2})%[2]c(\d+)%[2]c\d+$`,
- regexp.QuoteMeta(prefix), sep)
- }
-
- return &Space{
- Prefix: prefix,
- Sep: sep,
- Time: tm,
- re: regexp.MustCompile(re),
- short: short,
- }
- }
-
- // New generates a new unique ID. The ID consists of the Space'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 sep.
- func (s *Space) New() string {
- c := atomic.AddInt32(&s.count, 1)
-
- if s.short && c > 99 {
- // Short spaces only have space for 99 IDs. (two characters)
- panic("Short space called New more than 99 times. Ran out of IDs.")
- } else if c > 9999 {
- // Spaces only have space for 9999 IDs. (four characters)
- panic("New called more than 9999 times. Ran out of IDs.")
- }
-
- if s.short {
- return fmt.Sprintf("%s%c%d%c%02d", s.Prefix, s.Sep, s.Time.UnixNano(), s.Sep, c)
- }
-
- // 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 := s.Time.Date()
- ns := s.Time.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%c%04d%02d%02d%c%d%c%04d",
- s.Prefix, s.Sep, y, m, d, s.Sep, ns, s.Sep, 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 *Space) Timestamp(uid string) (time.Time, bool) {
- subs := s.re.FindStringSubmatch(uid)
- if subs == nil {
- return time.Time{}, false
- }
-
- if s.short {
- ns, err := strconv.ParseInt(subs[1], 10, 64)
- if err != nil {
- return time.Time{}, false
- }
- return time.Unix(ns/1e9, ns%1e9), true
- }
-
- 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 *Space) Older(uid string, d time.Duration) bool {
- ts, ok := s.Timestamp(uid)
- if !ok {
- return false
- }
- return time.Since(ts) > d
- }
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