Repository: edwingeng/wuid
Branch: master
Commit: 29d94c466647
Files: 39
Total size: 77.2 KB

Directory structure:
gitextract_35st_wr2/

├── .gitattributes
├── .gitignore
├── LICENSE
├── README.md
├── callback/
│   └── wuid/
│       ├── coverage.sh
│       ├── vet.sh
│       ├── wuid.go
│       └── wuid_test.go
├── check.sh
├── go.mod
├── go.sum
├── internal/
│   ├── coverage.sh
│   ├── vet.sh
│   ├── wuid.go
│   └── wuid_test.go
├── mongo/
│   ├── docker-mongo-client.sh
│   ├── docker-mongo-server.sh
│   └── wuid/
│       ├── coverage.sh
│       ├── vet.sh
│       ├── wuid.go
│       └── wuid_test.go
├── mysql/
│   ├── db.sql
│   ├── docker-mysql-client.sh
│   ├── docker-mysql-server.sh
│   └── wuid/
│       ├── coverage.sh
│       ├── vet.sh
│       ├── wuid.go
│       └── wuid_test.go
├── redis/
│   ├── docker-redis-client.sh
│   ├── docker-redis-server.sh
│   ├── v8/
│   │   └── wuid/
│   │       ├── coverage.sh
│   │       ├── vet.sh
│   │       ├── wuid.go
│   │       └── wuid_test.go
│   └── wuid/
│       ├── coverage.sh
│       ├── vet.sh
│       ├── wuid.go
│       └── wuid_test.go
└── wuid.go

================================================
FILE CONTENTS
================================================

================================================
FILE: .gitattributes
================================================
* text=auto eol=lf



================================================
FILE: .gitignore
================================================
# Binaries for programs and plugins
*.exe
*.dll
*.so
*.dylib

# Test binary, build with `go test -c`
*.test

# Output of the go coverage tool, specifically when used with LiteIDE
*.out

# Project-local glide cache, RE: https://github.com/Masterminds/glide/issues/736
.glide/

# Misc
/.idea
/vendor


================================================
FILE: LICENSE
================================================
BSD 3-Clause License

Copyright (c) 2018-2022, Edwin Geng
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice,
  this list of conditions and the following disclaimer in the documentation
  and/or other materials provided with the distribution.

* Neither the name of the copyright holder nor the names of its
  contributors may be used to endorse or promote products derived from
  this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


================================================
FILE: README.md
================================================
# Overview
- `WUID` is a universal unique identifier generator.
- `WUID` is much faster than traditional UUID. Each `WUID` instance can even generate 100M unique identifiers in a single second.
- In the nutshell, `WUID` generates 64-bit integers in sequence. The high 28 bits are loaded from a data source. By now, Redis, MySQL, MongoDB and Callback are supported.
- The uniqueness is guaranteed as long as all `WUID` instances share a same data source or each group of them has a different section ID.
- `WUID` automatically renews the high 28 bits when the low 36 bits are about to run out.
- `WUID` is thread-safe, and lock free.
- Obfuscation is supported.

# Benchmarks
```
BenchmarkWUID           159393580          7.661 ns/op        0 B/op       0 allocs/op
BenchmarkRand           100000000         14.95 ns/op         0 B/op       0 allocs/op
BenchmarkTimestamp      164224915          7.359 ns/op        0 B/op       0 allocs/op
BenchmarkUUID_V1        23629536          43.42 ns/op         0 B/op       0 allocs/op
BenchmarkUUID_V2        29351550          43.96 ns/op         0 B/op       0 allocs/op
BenchmarkUUID_V3         4703044         254.2 ns/op        144 B/op       4 allocs/op
BenchmarkUUID_V4         5796310         210.0 ns/op         16 B/op       1 allocs/op
BenchmarkUUID_V5         4051291         310.7 ns/op        168 B/op       4 allocs/op
BenchmarkRedis              2996       38725 ns/op          160 B/op       5 allocs/op
BenchmarkSnowflake       1000000        2092 ns/op            0 B/op       0 allocs/op
BenchmarkULID            5660170         207.7 ns/op         16 B/op       1 allocs/op
BenchmarkXID            49639082          26.21 ns/op         0 B/op       0 allocs/op
BenchmarkShortID         1312386         922.2 ns/op        320 B/op      11 allocs/op
BenchmarkKsuid          19717675          59.79 ns/op         0 B/op       0 allocs/op
```

# Getting Started
``` bash
go get -u github.com/edwingeng/wuid
```

# Usages
### Redis
``` go
import "github.com/edwingeng/wuid/redis/v8/wuid"

newClient := func() (redis.UniversalClient, bool, error) {
    var client redis.UniversalClient
    // ...
    return client, true, nil
}

// Setup
w := NewWUID("alpha", nil)
err := w.LoadH28FromRedis(newClient, "wuid")
if err != nil {
    panic(err)
}

// Generate
for i := 0; i < 10; i++ {
    fmt.Printf("%#016x\n", w.Next())
}
```

### MySQL
``` go
import "github.com/edwingeng/wuid/mysql/wuid"

openDB := func() (*sql.DB, bool, error) {
    var db *sql.DB
    // ...
    return db, true, nil
}

// Setup
w := NewWUID("alpha", nil)
err := w.LoadH28FromMysql(openDB, "wuid")
if err != nil {
    panic(err)
}

// Generate
for i := 0; i < 10; i++ {
    fmt.Printf("%#016x\n", w.Next())
}
```

### MongoDB
``` go
import "github.com/edwingeng/wuid/mongo/wuid"

newClient := func() (*mongo.Client, bool, error) {
    var client *mongo.Client
    // ...
    return client, true, nil
}

// Setup
w := NewWUID("alpha", nil)
err := w.LoadH28FromMongo(newClient, "test", "wuid", "default")
if err != nil {
    panic(err)
}

// Generate
for i := 0; i < 10; i++ {
    fmt.Printf("%#016x\n", w.Next())
}
```

### Callback
``` go
import "github.com/edwingeng/wuid/callback/wuid"

callback := func() (int64, func(), error) {
    var h28 int64
    // ...
    return h28, nil, nil
}

// Setup
w := NewWUID("alpha", nil)
err := w.LoadH28WithCallback(callback)
if err != nil {
    panic(err)
}

// Generate
for i := 0; i < 10; i++ {
    fmt.Printf("%#016x\n", w.Next())
}
```

# Mysql Table Creation
``` sql
CREATE TABLE IF NOT EXISTS `wuid` (
    `h` int(10) NOT NULL AUTO_INCREMENT,
    `x` tinyint(4) NOT NULL DEFAULT '0',
    PRIMARY KEY (`x`),
    UNIQUE KEY `h` (`h`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
```

# Options

- `WithSection` brands a section ID on each generated number. A section ID must be in between [0, 7].
- `WithStep` sets the step and the floor for each generated number.
- `WithObfuscation` enables number obfuscation.

# Attentions
It is highly recommended to pass a logger to `wuid.NewWUID` and keep an eye on the warnings that include "renew failed". It indicates that the low 36 bits are about to run out in hours to hundreds of hours, and the renewal program failed for some reason. `WUID` will make many renewal attempts until succeeded. 

# Special thanks
- [dustinfog](https://github.com/dustinfog)

# Ports
- swift - https://github.com/ekscrypto/SwiftWUID


================================================
FILE: callback/wuid/coverage.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

go test -cover -coverprofile=c.out -v "$@" && go tool cover -html=c.out


================================================
FILE: callback/wuid/vet.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

printImportantMessage "====== gofmt"
gofmt -w .

printImportantMessage "====== go vet"
go vet ./...

printImportantMessage "====== gocyclo"
gocyclo -over 15 .

printImportantMessage "====== ineffassign"
ineffassign ./...

printImportantMessage "====== misspell"
misspell *


================================================
FILE: callback/wuid/wuid.go
================================================
package wuid

import (
	"errors"
	"github.com/edwingeng/slog"
	"github.com/edwingeng/wuid/internal"
)

// WUID is an extremely fast universal unique identifier generator.
type WUID struct {
	w internal.WUID
}

// NewWUID creates a new WUID instance.
func NewWUID(name string, logger slog.Logger, opts ...Option) *WUID {
	return &WUID{w: *internal.NewWUID(name, logger, opts...)}
}

// Next returns a unique identifier.
func (w *WUID) Next() int64 {
	return w.w.Next()
}

type H28Callback func() (h28 int64, cleanUp func(), err error)

// LoadH28WithCallback invokes cb to acquire a number. The number is used as the high 28 bits
// of all generated numbers. In addition, cb is saved for future renewal.
func (w *WUID) LoadH28WithCallback(cb H28Callback) error {
	if cb == nil {
		return errors.New("cb cannot be nil")
	}

	h28, cleanUp, err := cb()
	if err != nil {
		return err
	}
	if cleanUp != nil {
		defer cleanUp()
	}

	if err = w.w.VerifyH28(h28); err != nil {
		return err
	}

	w.w.Reset(h28 << 36)
	w.w.Infof("<wuid> new h28: %d. name: %s", h28, w.w.Name)

	w.w.Lock()
	defer w.w.Unlock()

	if w.w.Renew != nil {
		return nil
	}
	w.w.Renew = func() error {
		return w.LoadH28WithCallback(cb)
	}

	return nil
}

// RenewNow reacquires the high 28 bits immediately.
func (w *WUID) RenewNow() error {
	return w.w.RenewNow()
}

type Option = internal.Option

// WithH28Verifier adds an extra verifier for the high 28 bits.
func WithH28Verifier(cb func(h28 int64) error) Option {
	return internal.WithH28Verifier(cb)
}

// WithSection brands a section ID on each generated number. A section ID must be in between [0, 7].
func WithSection(section int8) Option {
	return internal.WithSection(section)
}

// WithStep sets the step and the floor for each generated number.
func WithStep(step int64, floor int64) Option {
	return internal.WithStep(step, floor)
}

// WithObfuscation enables number obfuscation.
func WithObfuscation(seed int) Option {
	return internal.WithObfuscation(seed)
}


================================================
FILE: callback/wuid/wuid_test.go
================================================
package wuid

import (
	"errors"
	"fmt"
	"github.com/edwingeng/slog"
	"github.com/edwingeng/wuid/internal"
	"math/rand"
	"strings"
	"sync/atomic"
	"testing"
	"time"
)

var (
	dumb = slog.NewDumbLogger()
)

func TestWUID_LoadH28WithCallback_Error(t *testing.T) {
	w := NewWUID("alpha", dumb)
	err1 := w.LoadH28WithCallback(nil)
	if err1 == nil {
		t.Fatal("LoadH28WithCallback should fail when cb is nil")
	}

	err2 := w.LoadH28WithCallback(func() (int64, func(), error) {
		return 0, nil, errors.New("foo")
	})
	if err2 == nil {
		t.Fatal("LoadH28WithCallback should fail when cb returns an error")
	}

	err3 := w.LoadH28WithCallback(func() (int64, func(), error) {
		return 0, nil, nil
	})
	if err3 == nil {
		t.Fatal("LoadH28WithCallback should fail when cb returns an invalid h28")
	}
}

func TestWUID_LoadH28WithCallback(t *testing.T) {
	var h28, counter int64
	done := func() {
		counter++
	}
	cb := func() (int64, func(), error) {
		return atomic.AddInt64(&h28, 1), done, nil
	}

	w := NewWUID("alpha", dumb)
	err := w.LoadH28WithCallback(cb)
	if err != nil {
		t.Fatal(err)
	}
	for i := 1; i < 1000; i++ {
		if err := w.RenewNow(); err != nil {
			t.Fatal(err)
		}
		v := (int64(i) + 1) << 36
		if atomic.LoadInt64(&w.w.N) != v {
			t.Fatalf("w.w.N is %d, while it should be %d. i: %d", atomic.LoadInt64(&w.w.N), v, i)
		}
		n := rand.Intn(10)
		for j := 0; j < n; j++ {
			w.Next()
		}
	}

	if counter != 1000 {
		t.Fatalf("the callback done do not work as expected. counter: %d", counter)
	}
}

func TestWUID_LoadH28WithCallback_Section(t *testing.T) {
	var h28 int64
	cb := func() (int64, func(), error) {
		return atomic.AddInt64(&h28, 1), nil, nil
	}

	w := NewWUID("alpha", dumb, WithSection(1))
	for i := 0; i < 1000; i++ {
		err := w.LoadH28WithCallback(cb)
		if err != nil {
			t.Fatal(err)
		}
		v := (int64(i) + 1 + 0x1000000) << 36
		if atomic.LoadInt64(&w.w.N) != v {
			t.Fatalf("w.w.N is %d, while it should be %d. i: %d", atomic.LoadInt64(&w.w.N), v, i)
		}
		n := rand.Intn(10)
		for j := 0; j < n; j++ {
			w.Next()
		}
	}
}

func TestWUID_LoadH28WithCallback_Same(t *testing.T) {
	cb := func() (int64, func(), error) {
		return 100, nil, nil
	}

	w1 := NewWUID("alpha", dumb)
	_ = w1.LoadH28WithCallback(cb)
	if err := w1.LoadH28WithCallback(cb); err == nil {
		t.Fatal("LoadH28WithCallback should return an error")
	}

	w2 := NewWUID("alpha", dumb, WithSection(1))
	_ = w2.LoadH28WithCallback(cb)
	if err := w2.LoadH28WithCallback(cb); err == nil {
		t.Fatal("LoadH28WithCallback should return an error")
	}
}

func waitUntilNumRenewedReaches(t *testing.T, w *WUID, expected int64) {
	t.Helper()
	startTime := time.Now()
	for time.Since(startTime) < time.Second {
		if atomic.LoadInt64(&w.w.Stats.NumRenewed) == expected {
			return
		}
		time.Sleep(time.Millisecond * 10)
	}
	t.Fatal("timeout")
}

func TestWUID_Renew(t *testing.T) {
	w := NewWUID("alpha", slog.NewScavenger())
	err := w.LoadH28WithCallback(func() (h28 int64, clean func(), err error) {
		return (atomic.LoadInt64(&w.w.N) >> 36) + 1, nil, nil
	})
	if err != nil {
		t.Fatal(err)
	}

	h28 := atomic.LoadInt64(&w.w.N) >> 36
	atomic.StoreInt64(&w.w.N, (h28<<36)|internal.Bye)
	n1a := w.Next()
	if n1a>>36 != h28 {
		t.Fatal(`n1a>>36 != h28`)
	}

	waitUntilNumRenewedReaches(t, w, 1)
	n1b := w.Next()
	if n1b != (h28+1)<<36+1 {
		t.Fatal(`n1b != (h28+1)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+1)<<36)|internal.Bye)
	n2a := w.Next()
	if n2a>>36 != h28+1 {
		t.Fatal(`n2a>>36 != h28+1`)
	}

	waitUntilNumRenewedReaches(t, w, 2)
	n2b := w.Next()
	if n2b != (h28+2)<<36+1 {
		t.Fatal(`n2b != (h28+2)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+2)<<36)|internal.Bye)
	n3a := w.Next()
	if n3a>>36 != h28+2 {
		t.Fatal(`n3a>>36 != h28+2`)
	}

	waitUntilNumRenewedReaches(t, w, 3)
	n3b := w.Next()
	if n3b != (h28+3)<<36+1 {
		t.Fatal(`n3b != (h28+3)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+2)<<36)+internal.Bye+1)
	for i := 0; i < 100; i++ {
		w.Next()
	}
	if atomic.LoadInt64(&w.w.Stats.NumRenewAttempts) != 3 {
		t.Fatal(`atomic.LoadInt64(&w.w.Stats.NumRenewAttempts) != 3`)
	}

	var num int
	sc := w.w.Logger.(*slog.Scavenger)
	sc.Filter(func(level, msg string) bool {
		if level == slog.LevelInfo && strings.Contains(msg, "renew succeeded") {
			num++
		}
		return true
	})
	if num != 3 {
		t.Fatal(`num != 3`)
	}
}

func Example() {
	callback := func() (int64, func(), error) {
		var h28 int64
		// ...
		return h28, nil, nil
	}

	// Setup
	w := NewWUID("alpha", nil)
	err := w.LoadH28WithCallback(callback)
	if err != nil {
		panic(err)
	}

	// Generate
	for i := 0; i < 10; i++ {
		fmt.Printf("%#016x\n", w.Next())
	}
}


================================================
FILE: check.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

find . -name coverage.sh | xargs -n 1 bash -c \
    'cmp --silent internal/coverage.sh "$0" || echo "files are different. file: $0"'
find . -name vet.sh | xargs -n 1 bash -c \
    'cmp --silent internal/vet.sh "$0" || echo "files are different. file: $0"'


================================================
FILE: go.mod
================================================
module github.com/edwingeng/wuid

go 1.18

require (
	github.com/edwingeng/slog v0.0.0-20221027170832-482f0dfb6247
	github.com/go-redis/redis v6.15.9+incompatible
	github.com/go-redis/redis/v8 v8.11.5
	github.com/go-sql-driver/mysql v1.6.0
	go.mongodb.org/mongo-driver v1.10.2
)

require (
	github.com/cespare/xxhash/v2 v2.1.2 // indirect
	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
	github.com/golang/snappy v0.0.1 // indirect
	github.com/klauspost/compress v1.13.6 // indirect
	github.com/montanaflynn/stats v0.0.0-20171201202039-1bf9dbcd8cbe // indirect
	github.com/pkg/errors v0.9.1 // indirect
	github.com/xdg-go/pbkdf2 v1.0.0 // indirect
	github.com/xdg-go/scram v1.1.1 // indirect
	github.com/xdg-go/stringprep v1.0.3 // indirect
	github.com/youmark/pkcs8 v0.0.0-20181117223130-1be2e3e5546d // indirect
	go.uber.org/atomic v1.10.0 // indirect
	go.uber.org/multierr v1.8.0 // indirect
	go.uber.org/zap v1.23.0 // indirect
	golang.org/x/crypto v0.0.0-20220622213112-05595931fe9d // indirect
	golang.org/x/net v0.7.0 // indirect
	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c // indirect
	golang.org/x/sys v0.5.0 // indirect
	golang.org/x/text v0.7.0 // indirect
)


================================================
FILE: go.sum
================================================
github.com/benbjohnson/clock v1.1.0 h1:Q92kusRqC1XV2MjkWETPvjJVqKetz1OzxZB7mHJLju8=
github.com/cespare/xxhash/v2 v2.1.2 h1:YRXhKfTDauu4ajMg1TPgFO5jnlC2HCbmLXMcTG5cbYE=
github.com/cespare/xxhash/v2 v2.1.2/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f h1:lO4WD4F/rVNCu3HqELle0jiPLLBs70cWOduZpkS1E78=
github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cuUVRXasLTGF7a8hSLbxyZXjz+1KgoB3wDUb6vlszIc=
github.com/edwingeng/slog v0.0.0-20221027170832-482f0dfb6247 h1:1Vb/cbeFfMh9q+CxEMLSJlHciX9x3JHdaNyHlvhGxhk=
github.com/edwingeng/slog v0.0.0-20221027170832-482f0dfb6247/go.mod h1:mfngKiTrPWlUpIkQjkVzlumITH8chNhxsAiMklqH4Bo=
github.com/fsnotify/fsnotify v1.4.9 h1:hsms1Qyu0jgnwNXIxa+/V/PDsU6CfLf6CNO8H7IWoS4=
github.com/go-redis/redis v6.15.9+incompatible h1:K0pv1D7EQUjfyoMql+r/jZqCLizCGKFlFgcHWWmHQjg=
github.com/go-redis/redis v6.15.9+incompatible/go.mod h1:NAIEuMOZ/fxfXJIrKDQDz8wamY7mA7PouImQ2Jvg6kA=
github.com/go-redis/redis/v8 v8.11.5 h1:AcZZR7igkdvfVmQTPnu9WE37LRrO/YrBH5zWyjDC0oI=
github.com/go-redis/redis/v8 v8.11.5/go.mod h1:gREzHqY1hg6oD9ngVRbLStwAWKhA0FEgq8Jd4h5lpwo=
github.com/go-sql-driver/mysql v1.6.0 h1:BCTh4TKNUYmOmMUcQ3IipzF5prigylS7XXjEkfCHuOE=
github.com/go-sql-driver/mysql v1.6.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LBy8hT2VhHyBg=
github.com/golang/snappy v0.0.1 h1:Qgr9rKW7uDUkrbSmQeiDsGa8SjGyCOGtuasMWwvp2P4=
github.com/golang/snappy v0.0.1/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
github.com/google/go-cmp v0.5.2 h1:X2ev0eStA3AbceY54o37/0PQ/UWqKEiiO2dKL5OPaFM=
github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
github.com/klauspost/compress v1.13.6 h1:P76CopJELS0TiO2mebmnzgWaajssP/EszplttgQxcgc=
github.com/klauspost/compress v1.13.6/go.mod h1:/3/Vjq9QcHkK5uEr5lBEmyoZ1iFhe47etQ6QUkpK6sk=
github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
github.com/montanaflynn/stats v0.0.0-20171201202039-1bf9dbcd8cbe h1:iruDEfMl2E6fbMZ9s0scYfZQ84/6SPL6zC8ACM2oIL0=
github.com/montanaflynn/stats v0.0.0-20171201202039-1bf9dbcd8cbe/go.mod h1:wL8QJuTMNUDYhXwkmfOly8iTdp5TEcJFWZD2D7SIkUc=
github.com/nxadm/tail v1.4.8 h1:nPr65rt6Y5JFSKQO7qToXr7pePgD6Gwiw05lkbyAQTE=
github.com/onsi/ginkgo v1.16.5 h1:8xi0RTUf59SOSfEtZMvwTvXYMzG4gV23XVHOZiXNtnE=
github.com/onsi/gomega v1.18.1 h1:M1GfJqGRrBrrGGsbxzV5dqM2U2ApXefZCQpkukxYRLE=
github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=
github.com/tidwall/pretty v1.0.0 h1:HsD+QiTn7sK6flMKIvNmpqz1qrpP3Ps6jOKIKMooyg4=
github.com/tidwall/pretty v1.0.0/go.mod h1:XNkn88O1ChpSDQmQeStsy+sBenx6DDtFZJxhVysOjyk=
github.com/xdg-go/pbkdf2 v1.0.0 h1:Su7DPu48wXMwC3bs7MCNG+z4FhcyEuz5dlvchbq0B0c=
github.com/xdg-go/pbkdf2 v1.0.0/go.mod h1:jrpuAogTd400dnrH08LKmI/xc1MbPOebTwRqcT5RDeI=
github.com/xdg-go/scram v1.1.1 h1:VOMT+81stJgXW3CpHyqHN3AXDYIMsx56mEFrB37Mb/E=
github.com/xdg-go/scram v1.1.1/go.mod h1:RaEWvsqvNKKvBPvcKeFjrG2cJqOkHTiyTpzz23ni57g=
github.com/xdg-go/stringprep v1.0.3 h1:kdwGpVNwPFtjs98xCGkHjQtGKh86rDcRZN17QEMCOIs=
github.com/xdg-go/stringprep v1.0.3/go.mod h1:W3f5j4i+9rC0kuIEJL0ky1VpHXQU3ocBgklLGvcBnW8=
github.com/youmark/pkcs8 v0.0.0-20181117223130-1be2e3e5546d h1:splanxYIlg+5LfHAM6xpdFEAYOk8iySO56hMFq6uLyA=
github.com/youmark/pkcs8 v0.0.0-20181117223130-1be2e3e5546d/go.mod h1:rHwXgn7JulP+udvsHwJoVG1YGAP6VLg4y9I5dyZdqmA=
go.mongodb.org/mongo-driver v1.10.2 h1:4Wk3cnqOrQCn0P92L3/mmurMxzdvWWs5J9jinAVKD+k=
go.mongodb.org/mongo-driver v1.10.2/go.mod h1:z4XpeoU6w+9Vht+jAFyLgVrD+jGSQQe0+CBWFHNiHt8=
go.uber.org/atomic v1.7.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
go.uber.org/atomic v1.10.0 h1:9qC72Qh0+3MqyJbAn8YU5xVq1frD8bn3JtD2oXtafVQ=
go.uber.org/atomic v1.10.0/go.mod h1:LUxbIzbOniOlMKjJjyPfpl4v+PKK2cNJn91OQbhoJI0=
go.uber.org/goleak v1.1.11 h1:wy28qYRKZgnJTxGxvye5/wgWr1EKjmUDGYox5mGlRlI=
go.uber.org/multierr v1.8.0 h1:dg6GjLku4EH+249NNmoIciG9N/jURbDG+pFlTkhzIC8=
go.uber.org/multierr v1.8.0/go.mod h1:7EAYxJLBy9rStEaz58O2t4Uvip6FSURkq8/ppBp95ak=
go.uber.org/zap v1.23.0 h1:OjGQ5KQDEUawVHxNwQgPpiypGHOxo2mNZsOqTak4fFY=
go.uber.org/zap v1.23.0/go.mod h1:D+nX8jyLsMHMYrln8A0rJjFt/T/9/bGgIhAqxv5URuY=
golang.org/x/crypto v0.0.0-20220622213112-05595931fe9d h1:sK3txAijHtOK88l68nt020reeT1ZdKLIYetKl95FzVY=
golang.org/x/crypto v0.0.0-20220622213112-05595931fe9d/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
golang.org/x/net v0.0.0-20211112202133-69e39bad7dc2/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
golang.org/x/net v0.7.0 h1:rJrUqqhjsgNp7KqAIc25s9pZnjU7TUcSY7HcVZjdn1g=
golang.org/x/net v0.7.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/sys v0.5.0 h1:MUK/U/4lj1t1oPg0HfuXDN/Z1wv31ZJ/YcPiGccS4DU=
golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
golang.org/x/text v0.7.0 h1:4BRB4x83lYWy72KwLD/qYDuTu7q9PjSagHvijDw7cLo=
golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 h1:uRGJdciOHaEIrze2W8Q3AKkepLTh2hOroT7a+7czfdQ=
gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=


================================================
FILE: internal/coverage.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

go test -cover -coverprofile=c.out -v "$@" && go tool cover -html=c.out


================================================
FILE: internal/vet.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

printImportantMessage "====== gofmt"
gofmt -w .

printImportantMessage "====== go vet"
go vet ./...

printImportantMessage "====== gocyclo"
gocyclo -over 15 .

printImportantMessage "====== ineffassign"
ineffassign ./...

printImportantMessage "====== misspell"
misspell *


================================================
FILE: internal/wuid.go
================================================
package internal

import (
	"errors"
	"fmt"
	"github.com/edwingeng/slog"
	"sync"
	"sync/atomic"
)

const (
	// PanicValue indicates when Next starts to panic.
	PanicValue int64 = ((1 << 36) * 96 / 100) & ^1023
	// CriticalValue indicates when to renew the high 28 bits.
	CriticalValue int64 = ((1 << 36) * 80 / 100) & ^1023
	// RenewIntervalMask indicates the 'time' between two renewal attempts.
	RenewIntervalMask int64 = 0x20000000 - 1
)

const (
	Bye = ((CriticalValue + RenewIntervalMask) & ^RenewIntervalMask) - 1
)

const (
	H28Mask = 0x07FFFFFF << 36
	L36Mask = 0x0FFFFFFFFF
)

type WUID struct {
	N     int64
	Step  int64
	Floor int64

	Flags           int8
	Obfuscation     bool
	Monolithic      bool
	ObfuscationMask int64
	Section         int64

	slog.Logger
	Name        string
	H28Verifier func(h28 int64) error

	sync.Mutex
	Renew func() error

	Stats struct {
		NumRenewAttempts int64
		NumRenewed       int64
	}
}

func NewWUID(name string, logger slog.Logger, opts ...Option) (w *WUID) {
	w = &WUID{Step: 1, Name: name, Monolithic: true}
	if logger != nil {
		w.Logger = logger
	} else {
		w.Logger = slog.NewDevelopmentConfig().MustBuild()
	}
	for _, opt := range opts {
		opt(w)
	}
	if !w.Obfuscation || w.Floor == 0 {
		return
	}

	ones := w.Step - 1
	w.ObfuscationMask |= ones
	return
}

func (w *WUID) Next() int64 {
	v1 := atomic.AddInt64(&w.N, w.Step)
	v2 := v1 & L36Mask
	if v2 >= PanicValue {
		panicValue := v1&H28Mask | PanicValue
		atomic.CompareAndSwapInt64(&w.N, v1, panicValue)
		panic(fmt.Errorf("the low 36 bits are about to run out"))
	}
	if v2 >= CriticalValue && v2&RenewIntervalMask == 0 {
		go renewImpl(w)
	}

	switch w.Flags {
	case 0:
		return v1
	case 1:
		x := v1 ^ w.ObfuscationMask
		r := v1&H28Mask | x&L36Mask
		return r
	case 2:
		r := v1 / w.Floor * w.Floor
		return r
	case 3:
		x := v1 ^ w.ObfuscationMask
		q := v1&H28Mask | x&L36Mask
		r := q / w.Floor * w.Floor
		return r
	default:
		panic("impossible")
	}
}

func renewImpl(w *WUID) {
	defer func() {
		atomic.AddInt64(&w.Stats.NumRenewAttempts, 1)
	}()
	defer func() {
		if r := recover(); r != nil {
			w.Warnf("<wuid> panic, renew failed. name: %s, reason: %+v", w.Name, r)
		}
	}()

	err := w.RenewNow()
	if err != nil {
		w.Warnf("<wuid> renew failed. name: %s, reason: %+v", w.Name, err)
	} else {
		w.Infof("<wuid> renew succeeded. name: %s", w.Name)
		atomic.AddInt64(&w.Stats.NumRenewed, 1)
	}
}

func (w *WUID) RenewNow() error {
	w.Lock()
	f := w.Renew
	w.Unlock()
	return f()
}

func (w *WUID) Reset(n int64) {
	if n < 0 {
		panic("n cannot be negative")
	}
	if n&L36Mask >= PanicValue {
		panic("n is too old")
	}

	if w.Monolithic {
		// Empty
	} else {
		const L60Mask = 0x0FFFFFFFFFFFFFFF
		n = n&L60Mask | w.Section
	}
	if w.Floor > 1 {
		if n&(w.Step-1) == 0 {
			atomic.StoreInt64(&w.N, n)
		} else {
			atomic.StoreInt64(&w.N, n&^(w.Step-1)+w.Step)
		}
	} else {
		atomic.StoreInt64(&w.N, n)
	}
}

func (w *WUID) VerifyH28(h28 int64) error {
	if h28 <= 0 {
		return errors.New("h28 must be positive")
	}

	if w.Monolithic {
		if h28 > 0x07FFFFFF {
			return errors.New("h28 should not exceed 0x07FFFFFF")
		}
	} else {
		if h28 > 0x00FFFFFF {
			return errors.New("h28 should not exceed 0x00FFFFFF")
		}
	}

	current := atomic.LoadInt64(&w.N) >> 36
	if w.Monolithic {
		if h28 == current {
			return fmt.Errorf("h28 should be a different value other than %d", h28)
		}
	} else {
		if h28 == current&0x00FFFFFF {
			return fmt.Errorf("h28 should be a different value other than %d", h28)
		}
	}

	if w.H28Verifier != nil {
		if err := w.H28Verifier(h28); err != nil {
			return err
		}
	}

	return nil
}

type Option func(w *WUID)

func WithH28Verifier(cb func(h28 int64) error) Option {
	return func(w *WUID) {
		w.H28Verifier = cb
	}
}

func WithSection(section int8) Option {
	if section < 0 || section > 7 {
		panic("section must be in between [0, 7]")
	}
	return func(w *WUID) {
		w.Monolithic = false
		w.Section = int64(section) << 60
	}
}

func WithStep(step int64, floor int64) Option {
	switch step {
	case 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024:
	default:
		panic("the step must be one of these values: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024")
	}
	if floor != 0 && (floor < 0 || floor >= step) {
		panic(fmt.Errorf("floor must be in between [0, %d)", step))
	}
	return func(w *WUID) {
		if w.Step != 1 {
			panic("a second WithStep detected")
		}
		w.Step = step
		if floor >= 2 {
			w.Floor = floor
			w.Flags |= 2
		}
	}
}

func WithObfuscation(seed int) Option {
	if seed == 0 {
		panic("seed cannot be zero")
	}
	return func(w *WUID) {
		w.Obfuscation = true
		x := uint64(seed)
		x = (x ^ (x >> 30)) * uint64(0xbf58476d1ce4e5b9)
		x = (x ^ (x >> 27)) * uint64(0x94d049bb133111eb)
		x = (x ^ (x >> 31)) & 0x7FFFFFFFFFFFFFFF
		w.ObfuscationMask = int64(x)
		w.Flags |= 1
	}
}


================================================
FILE: internal/wuid_test.go
================================================
package internal

import (
	"errors"
	"github.com/edwingeng/slog"
	"math/rand"
	"sort"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"
)

func (w *WUID) Scavenger() *slog.Scavenger {
	return w.Logger.(*slog.Scavenger)
}

func TestWUID_Next(t *testing.T) {
	for i := 0; i < 100; i++ {
		w := NewWUID("alpha", nil)
		w.Reset(int64(i+1) << 36)
		v := atomic.LoadInt64(&w.N)
		for j := 0; j < 100; j++ {
			v++
			if id := w.Next(); id != v {
				t.Fatalf("the id is %d, while it should be %d", id, v)
			}
		}
	}
}

func TestWUID_Next_Concurrent(t *testing.T) {
	w := NewWUID("alpha", nil)
	var mu sync.Mutex
	const N1 = 100
	const N2 = 100
	a := make([]int64, 0, N1*N2)

	var wg sync.WaitGroup
	for i := 0; i < N1; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for j := 0; j < N2; j++ {
				id := w.Next()
				mu.Lock()
				a = append(a, id)
				mu.Unlock()
			}
		}()
	}

	wg.Wait()
	sort.Slice(a, func(i, j int) bool {
		return a[i] < a[j]
	})

	for i := 0; i < N1*N2-1; i++ {
		if a[i] == a[i+1] {
			t.Fatalf("duplication detected")
		}
	}
}

func TestWUID_Next_Panic(t *testing.T) {
	const total = 100
	w := NewWUID("alpha", nil)
	atomic.StoreInt64(&w.N, PanicValue)

	ch := make(chan int64, total)
	for i := 0; i < total; i++ {
		go func() {
			defer func() {
				if r := recover(); r != nil {
					ch <- 0
				}
			}()

			ch <- w.Next()
		}()
	}

	for i := 0; i < total; i++ {
		v := <-ch
		if v != 0 {
			t.Fatal("something is wrong with Next()")
		}
	}
}

func waitUntilNumRenewAttemptsReaches(t *testing.T, w *WUID, expected int64) {
	t.Helper()
	startTime := time.Now()
	for time.Since(startTime) < time.Second {
		if atomic.LoadInt64(&w.Stats.NumRenewAttempts) == expected {
			return
		}
		time.Sleep(time.Millisecond * 10)
	}
	t.Fatal("timeout")
}

func waitUntilNumRenewedReaches(t *testing.T, w *WUID, expected int64) {
	t.Helper()
	startTime := time.Now()
	for time.Since(startTime) < time.Second {
		if atomic.LoadInt64(&w.Stats.NumRenewed) == expected {
			return
		}
		time.Sleep(time.Millisecond * 10)
	}
	t.Fatal("timeout")
}

func TestWUID_Renew(t *testing.T) {
	w := NewWUID("alpha", slog.NewScavenger())
	w.Renew = func() error {
		w.Reset(((atomic.LoadInt64(&w.N) >> 36) + 1) << 36)
		return nil
	}

	w.Reset(Bye)
	n1a := w.Next()
	if n1a>>36 != 0 {
		t.Fatal(`n1a>>36 != 0`)
	}

	waitUntilNumRenewedReaches(t, w, 1)
	n1b := w.Next()
	if n1b != 1<<36+1 {
		t.Fatal(`n1b != 1<<36+1`)
	}

	w.Reset(1<<36 | Bye)
	n2a := w.Next()
	if n2a>>36 != 1 {
		t.Fatal(`n2a>>36 != 1`)
	}

	waitUntilNumRenewedReaches(t, w, 2)
	n2b := w.Next()
	if n2b != 2<<36+1 {
		t.Fatal(`n2b != 2<<36+1`)
	}

	w.Reset(2<<36 | Bye + RenewIntervalMask + 1)
	n3a := w.Next()
	if n3a>>36 != 2 {
		t.Fatal(`n3a>>36 != 2`)
	}

	waitUntilNumRenewedReaches(t, w, 3)
	n3b := w.Next()
	if n3b != 3<<36+1 {
		t.Fatal(`n3b != 3<<36+1`)
	}

	w.Reset(Bye + 1)
	for i := 0; i < 100; i++ {
		w.Next()
	}
	if atomic.LoadInt64(&w.Stats.NumRenewAttempts) != 3 {
		t.Fatal(`atomic.LoadInt64(&w.Stats.NumRenewAttempts) != 3`)
	}

	var num int
	w.Scavenger().Filter(func(level, msg string) bool {
		if level == slog.LevelInfo && strings.Contains(msg, "renew succeeded") {
			num++
		}
		return true
	})
	if num != 3 {
		t.Fatal(`num != 3`)
	}
}

func TestWUID_Renew_Error(t *testing.T) {
	w := NewWUID("alpha", slog.NewScavenger())
	w.Renew = func() error {
		return errors.New("foo")
	}

	w.Reset((1 >> 36 << 36) | Bye)
	w.Next()
	waitUntilNumRenewAttemptsReaches(t, w, 1)
	w.Next()

	w.Reset((2 >> 36 << 36) | Bye)
	w.Next()
	waitUntilNumRenewAttemptsReaches(t, w, 2)

	for i := 0; i < 100; i++ {
		w.Next()
	}
	if atomic.LoadInt64(&w.Stats.NumRenewAttempts) != 2 {
		t.Fatal(`atomic.LoadInt64(&w.Stats.NumRenewAttempts) != 2`)
	}
	if atomic.LoadInt64(&w.Stats.NumRenewed) != 0 {
		t.Fatal(`atomic.LoadInt64(&w.Stats.NumRenewed) != 0`)
	}

	var num int
	w.Scavenger().Filter(func(level, msg string) bool {
		if level == slog.LevelWarn && strings.Contains(msg, "renew failed") && strings.Contains(msg, "foo") {
			num++
		}
		return true
	})
	if num != 2 {
		t.Fatal(`num != 2`)
	}
}

func TestWUID_Renew_Panic(t *testing.T) {
	w := NewWUID("alpha", slog.NewScavenger())
	w.Renew = func() error {
		panic("foo")
	}

	w.Reset((1 >> 36 << 36) | Bye)
	w.Next()
	waitUntilNumRenewAttemptsReaches(t, w, 1)
	w.Next()

	w.Reset((2 >> 36 << 36) | Bye)
	w.Next()
	waitUntilNumRenewAttemptsReaches(t, w, 2)

	for i := 0; i < 100; i++ {
		w.Next()
	}
	if atomic.LoadInt64(&w.Stats.NumRenewAttempts) != 2 {
		t.Fatal(`atomic.LoadInt64(&w.Stats.NumRenewAttempts) != 2`)
	}
	if atomic.LoadInt64(&w.Stats.NumRenewed) != 0 {
		t.Fatal(`atomic.LoadInt64(&w.Stats.NumRenewed) != 0`)
	}

	var num int
	w.Scavenger().Filter(func(level, msg string) bool {
		if level == slog.LevelWarn && strings.Contains(msg, "renew failed") && strings.Contains(msg, "foo") {
			num++
		}
		return true
	})
	if num != 2 {
		t.Fatal(`num != 2`)
	}
}

func TestWUID_Step(t *testing.T) {
	const step = 16
	w := NewWUID("alpha", slog.NewScavenger(), WithStep(step, 0))
	w.Reset(17 << 36)

	w.Renew = func() error {
		w.Reset(((atomic.LoadInt64(&w.N) >> 36) + 1) << 36)
		return nil
	}

	for i := int64(1); i < 100; i++ {
		if w.Next()&L36Mask != step*i {
			t.Fatal("w.Next()&L36Mask != step*i")
		}
	}

	n1 := w.Next()
	w.Reset(((n1 >> 36 << 36) | Bye) & ^(step - 1))
	w.Next()
	waitUntilNumRenewedReaches(t, w, 1)
	n2 := w.Next()

	w.Reset(((n2 >> 36 << 36) | Bye) & ^(step - 1))
	w.Next()
	waitUntilNumRenewedReaches(t, w, 2)
	n3 := w.Next()

	if n2>>36-n1>>36 != 1 || n3>>36-n2>>36 != 1 {
		t.Fatalf("the renew mechanism does not work as expected: %x, %x, %x", n1>>36, n2>>36, n3>>36)
	}

	var num int
	w.Scavenger().Filter(func(level, msg string) bool {
		if level == slog.LevelInfo && strings.Contains(msg, "renew succeeded") {
			num++
		}
		return true
	})
	if num != 2 {
		t.Fatal(`num != 2`)
	}

	func() {
		defer func() {
			_ = recover()
		}()
		NewWUID("alpha", nil, WithStep(5, 0))
		t.Fatal("WithStep should have panicked")
	}()
}

func TestWUID_Floor(t *testing.T) {
	r := rand.New(rand.NewSource(time.Now().Unix()))
	allSteps := []int64{1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024}
	for loop := 0; loop < 10000; loop++ {
		step := allSteps[r.Intn(len(allSteps))]
		var floor = r.Int63n(step)
		w := NewWUID("alpha", slog.NewScavenger(), WithStep(step, floor))
		if floor < 2 {
			if w.Flags != 0 {
				t.Fatal(`w.Flags != 0`)
			}
		} else {
			if w.Flags != 2 {
				t.Fatal(`w.Flags != 2`)
			}
		}

		w.Reset(r.Int63n(100) << 36)
		baseValue := atomic.LoadInt64(&w.N)

		for i := int64(1); i < 100; i++ {
			x := w.Next()
			if floor != 0 {
				if reminder := x % floor; reminder != 0 {
					t.Fatal("reminder != 0")
				}
			}
			if x <= baseValue+i*step-step || x > baseValue+i*step {
				t.Fatal("x <= baseValue+i*step-step || x > baseValue+i*step")
			}
		}
	}

	func() {
		defer func() {
			_ = recover()
		}()
		NewWUID("alpha", nil, WithStep(1024, 2000))
		t.Fatal("WithStep should have panicked")
	}()

	func() {
		defer func() {
			_ = recover()
		}()
		NewWUID("alpha", nil, WithStep(1024, 0), WithStep(128, 0))
		t.Fatal("WithStep should have panicked")
	}()
}

func TestWUID_VerifyH28(t *testing.T) {
	w1 := NewWUID("alpha", nil)
	w1.Reset(H28Mask)
	if err := w1.VerifyH28(100); err != nil {
		t.Fatalf("VerifyH28 does not work as expected. n: 100, error: %s", err)
	}
	if err := w1.VerifyH28(0); err == nil {
		t.Fatalf("VerifyH28 does not work as expected. n: 0")
	}
	if err := w1.VerifyH28(0x08000000); err == nil {
		t.Fatalf("VerifyH28 does not work as expected. n: 0x08000000")
	}
	if err := w1.VerifyH28(0x07FFFFFF); err == nil {
		t.Fatalf("VerifyH28 does not work as expected. n: 0x07FFFFFF")
	}

	w2 := NewWUID("alpha", nil, WithSection(1))
	w2.Reset(H28Mask)
	if err := w2.VerifyH28(100); err != nil {
		t.Fatalf("VerifyH28 does not work as expected. section: 1, n: 100, error: %s", err)
	}
	if err := w2.VerifyH28(0); err == nil {
		t.Fatalf("VerifyH28 does not work as expected. section: 1, n: 0")
	}
	if err := w2.VerifyH28(0x01000000); err == nil {
		t.Fatalf("VerifyH28 does not work as expected. section: 1, n: 0x01000000")
	}
	if err := w2.VerifyH28(0x00FFFFFF); err == nil {
		t.Fatalf("VerifyH28 does not work as expected. section: 1, n: 0x00FFFFFF")
	}
}

func TestWithSection_Panic(t *testing.T) {
	for i := -100; i <= 100; i++ {
		func(j int8) {
			defer func() {
				_ = recover()
			}()
			WithSection(j)
			if j >= 8 {
				t.Fatalf("WithSection should only accept the values in [0, 7]. j: %d", j)
			}
		}(int8(i))
	}
}

func TestWithSection_Reset(t *testing.T) {
	for i := 0; i < 28; i++ {
		n := int64(1) << (uint(i) + 36)
		func() {
			defer func() {
				if r := recover(); r != nil {
					if i != 27 {
						t.Fatal(r)
					}
				}
			}()
			for j := int8(1); j < 8; j++ {
				w := NewWUID("alpha", nil, WithSection(j))
				w.Reset(n)
				v := atomic.LoadInt64(&w.N)
				if v>>60 != int64(j) {
					t.Fatalf("w.Section does not work as expected. w.N: %x, n: %x, i: %d, j: %d", v, n, i, j)
				}
			}
		}()
	}

	func() {
		defer func() {
			_ = recover()
		}()
		w := NewWUID("alpha", nil)
		w.Reset((1 << 36) | PanicValue)
		t.Fatal("Reset should have panicked")
	}()
}

func TestWithH28Verifier(t *testing.T) {
	w := NewWUID("alpha", nil, WithH28Verifier(func(h28 int64) error {
		if h28 >= 20 {
			return errors.New("bomb")
		}
		return nil
	}))
	if err := w.VerifyH28(10); err != nil {
		t.Fatal("the H28Verifier should not return error")
	}
	if err := w.VerifyH28(20); err == nil || err.Error() != "bomb" {
		t.Fatal("the H28Verifier was not called")
	}
}

//gocyclo:ignore
func TestWithObfuscation(t *testing.T) {
	w1 := NewWUID("alpha", nil, WithObfuscation(1))
	if w1.Flags != 1 {
		t.Fatal(`w1.Flags != 1`)
	}
	if w1.ObfuscationMask == 0 {
		t.Fatal(`w1.ObfuscationMask == 0`)
	}

	w1.Reset(1 << 36)
	for i := 1; i < 100; i++ {
		v := w1.Next()
		if v&H28Mask != 1<<36 {
			t.Fatal(`v&H28Mask != 1<<36`)
		}
		tmp := v ^ w1.ObfuscationMask
		if tmp&L36Mask != int64(i) {
			t.Fatal(`tmp&L36Mask != int64(i)`)
		}
	}

	w2 := NewWUID("alpha", nil, WithObfuscation(1), WithStep(128, 100))
	if w2.Flags != 3 {
		t.Fatal(`w2.Flags != 3`)
	}
	if w2.ObfuscationMask == 0 {
		t.Fatal(`w2.ObfuscationMask == 0`)
	}

	w2.Reset(1 << 36)
	for i := 1; i < 100; i++ {
		v := w2.Next()
		if v%w2.Floor != 0 {
			t.Fatal(`v%w2.Floor != 0`)
		}
		if v&H28Mask != 1<<36 {
			t.Fatal(`v&H28Mask != 1<<36`)
		}
		tmp := v ^ w2.ObfuscationMask
		if tmp&L36Mask&^(w2.Step-1) != w2.Step*int64(i) {
			t.Fatal(`tmp&L36Mask&^(w2.Step-1) != w2.Step*int64(i)`)
		}
	}

	w3 := NewWUID("alpha", nil, WithObfuscation(1), WithStep(1024, 659))
	if w3.Flags != 3 {
		t.Fatal(`w3.Flags != 3`)
	}
	if w3.ObfuscationMask == 0 {
		t.Fatal(`w3.ObfuscationMask == 0`)
	}

	w3.Reset(1<<36 + 1)
	for i := 1; i < 100; i++ {
		v := w3.Next()
		if v%w3.Floor != 0 {
			t.Fatal(`v%w3.Floor != 0`)
		}
		if v&H28Mask != 1<<36 {
			t.Fatal(`v&H28Mask != 1<<36`)
		}
		tmp := v ^ w3.ObfuscationMask
		if tmp&L36Mask&^(w3.Step-1) != w3.Step*int64(i+1) {
			t.Fatal(`tmp&L36Mask&^(w3.Step-1) != w3.Step*int64(i+1)`)
		}
	}

	func() {
		defer func() {
			_ = recover()
		}()
		NewWUID("alpha", nil, WithObfuscation(0))
		t.Fatal("WithObfuscation should have panicked")
	}()
}


================================================
FILE: mongo/docker-mongo-client.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

docker run -it --rm mongo mongosh host.docker.internal


================================================
FILE: mongo/docker-mongo-server.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

docker run --name mongo-server -p 27017:27017 -d mongo


================================================
FILE: mongo/wuid/coverage.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

go test -cover -coverprofile=c.out -v "$@" && go tool cover -html=c.out


================================================
FILE: mongo/wuid/vet.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

printImportantMessage "====== gofmt"
gofmt -w .

printImportantMessage "====== go vet"
go vet ./...

printImportantMessage "====== gocyclo"
gocyclo -over 15 .

printImportantMessage "====== ineffassign"
ineffassign ./...

printImportantMessage "====== misspell"
misspell *


================================================
FILE: mongo/wuid/wuid.go
================================================
package wuid

import (
	"context"
	"errors"
	"github.com/edwingeng/slog"
	"github.com/edwingeng/wuid/internal"
	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/mongo"
	"go.mongodb.org/mongo-driver/mongo/options"
	"go.mongodb.org/mongo-driver/mongo/readconcern"
	"go.mongodb.org/mongo-driver/mongo/readpref"
	"go.mongodb.org/mongo-driver/mongo/writeconcern"
	"time"
)

// WUID is an extremely fast universal unique identifier generator.
type WUID struct {
	w *internal.WUID
}

// NewWUID creates a new WUID instance.
func NewWUID(name string, logger slog.Logger, opts ...Option) *WUID {
	return &WUID{w: internal.NewWUID(name, logger, opts...)}
}

// Next returns a unique identifier.
func (w *WUID) Next() int64 {
	return w.w.Next()
}

type NewClient func() (client *mongo.Client, autoDisconnect bool, err error)

// LoadH28FromMongo adds 1 to a specific number in MongoDB and fetches its new value.
// The new value is used as the high 28 bits of all generated numbers. In addition, all the
// arguments passed in are saved for future renewal.
func (w *WUID) LoadH28FromMongo(newClient NewClient, dbName, coll, docID string) error {
	if len(dbName) == 0 {
		return errors.New("dbName cannot be empty")
	}
	if len(coll) == 0 {
		return errors.New("coll cannot be empty")
	}
	if len(docID) == 0 {
		return errors.New("docID cannot be empty")
	}

	client, autoDisconnect, err := newClient()
	if err != nil {
		return err
	}
	defer func() {
		if autoDisconnect {
			ctx2, cancel2 := context.WithTimeout(context.Background(), time.Second*5)
			defer cancel2()
			_ = client.Disconnect(ctx2)
		}
	}()

	ctx1, cancel1 := context.WithTimeout(context.Background(), time.Second*5)
	defer cancel1()
	if err := client.Ping(ctx1, readpref.Primary()); err != nil {
		return err
	}

	collOpts := &options.CollectionOptions{
		ReadConcern:    readconcern.Majority(),
		WriteConcern:   writeconcern.New(writeconcern.WMajority()),
		ReadPreference: readpref.Primary(),
	}

	var doc struct {
		N int32
	}

	filter := bson.D{
		{Key: "_id", Value: docID},
	}
	update := bson.D{
		{
			Key: "$inc",
			Value: bson.D{
				{Key: "n", Value: int32(1)},
			},
		},
	}

	var findOneAndUpdateOptions options.FindOneAndUpdateOptions
	findOneAndUpdateOptions.SetUpsert(true).SetReturnDocument(options.After)
	c := client.Database(dbName).Collection(coll, collOpts)
	err = c.FindOneAndUpdate(ctx1, filter, update, &findOneAndUpdateOptions).Decode(&doc)
	if err != nil {
		return err
	}
	h28 := int64(doc.N)
	if err = w.w.VerifyH28(h28); err != nil {
		return err
	}

	w.w.Reset(h28 << 36)
	w.w.Logger.Infof("<wuid> new h28: %d. name: %s", h28, w.w.Name)

	w.w.Lock()
	defer w.w.Unlock()

	if w.w.Renew != nil {
		return nil
	}
	w.w.Renew = func() error {
		return w.LoadH28FromMongo(newClient, dbName, coll, docID)
	}

	return nil
}

// RenewNow reacquires the high 28 bits immediately.
func (w *WUID) RenewNow() error {
	return w.w.RenewNow()
}

type Option = internal.Option

// WithH28Verifier adds an extra verifier for the high 28 bits.
func WithH28Verifier(cb func(h28 int64) error) Option {
	return internal.WithH28Verifier(cb)
}

// WithSection brands a section ID on each generated number. A section ID must be in between [0, 7].
func WithSection(section int8) Option {
	return internal.WithSection(section)
}

// WithStep sets the step and the floor for each generated number.
func WithStep(step int64, floor int64) Option {
	return internal.WithStep(step, floor)
}

// WithObfuscation enables number obfuscation.
func WithObfuscation(seed int) Option {
	return internal.WithObfuscation(seed)
}


================================================
FILE: mongo/wuid/wuid_test.go
================================================
package wuid

import (
	"context"
	"errors"
	"fmt"
	"github.com/edwingeng/slog"
	"github.com/edwingeng/wuid/internal"
	"go.mongodb.org/mongo-driver/mongo"
	"go.mongodb.org/mongo-driver/mongo/options"
	"math/rand"
	"strings"
	"sync/atomic"
	"testing"
	"time"
)

var (
	dumb = slog.NewDumbLogger()
)

var (
	cfg struct {
		addr   string
		dbName string
		coll   string
		docID  string
	}
)

func init() {
	cfg.addr = "127.0.0.1:27017"
	cfg.dbName = "test"
	cfg.coll = "wuid"
	cfg.docID = "default"
}

func connectMongodb() (*mongo.Client, error) {
	ctx1, cancel1 := context.WithTimeout(context.Background(), time.Second*3)
	defer cancel1()
	uri := fmt.Sprintf("mongodb://%s", cfg.addr)
	return mongo.Connect(ctx1, options.Client().ApplyURI(uri))
}

func TestWUID_LoadH28FromMongo(t *testing.T) {
	newClient := func() (*mongo.Client, bool, error) {
		client, err := connectMongodb()
		return client, true, err
	}

	w := NewWUID(cfg.docID, dumb)
	err := w.LoadH28FromMongo(newClient, cfg.dbName, cfg.coll, cfg.docID)
	if err != nil {
		t.Fatal(err)
	}

	initial := atomic.LoadInt64(&w.w.N)
	for i := 1; i < 100; i++ {
		if err := w.RenewNow(); err != nil {
			t.Fatal(err)
		}
		expected := ((initial >> 36) + int64(i)) << 36
		if atomic.LoadInt64(&w.w.N) != expected {
			t.Fatalf("w.w.N is %d, while it should be %d. i: %d", atomic.LoadInt64(&w.w.N), expected, i)
		}
		n := rand.Intn(10)
		for j := 0; j < n; j++ {
			w.Next()
		}
	}
}

func TestWUID_LoadH28FromMongo_Error(t *testing.T) {
	w := NewWUID(cfg.docID, dumb)
	if w.LoadH28FromMongo(nil, "", cfg.coll, cfg.docID) == nil {
		t.Fatal("dbName is not properly checked")
	}
	if w.LoadH28FromMongo(nil, cfg.dbName, "", cfg.docID) == nil {
		t.Fatal("coll is not properly checked")
	}
	if w.LoadH28FromMongo(nil, cfg.dbName, cfg.coll, "") == nil {
		t.Fatal("docID is not properly checked")
	}

	newErrorClient := func() (*mongo.Client, bool, error) {
		return nil, true, errors.New("beta")
	}
	if w.LoadH28FromMongo(newErrorClient, cfg.dbName, cfg.coll, cfg.docID) == nil {
		t.Fatal(`w.LoadH28FromMongo(newErrorClient, cfg.dbName, cfg.coll, cfg.docID) == nil`)
	}
}

func waitUntilNumRenewedReaches(t *testing.T, w *WUID, expected int64) {
	t.Helper()
	startTime := time.Now()
	for time.Since(startTime) < time.Second*3 {
		if atomic.LoadInt64(&w.w.Stats.NumRenewed) == expected {
			return
		}
		time.Sleep(time.Millisecond * 10)
	}
	t.Fatal("timeout")
}

func TestWUID_Renew(t *testing.T) {
	client, err := connectMongodb()
	if err != nil {
		t.Fatal(err)
	}
	newClient := func() (*mongo.Client, bool, error) {
		return client, false, err
	}

	w := NewWUID(cfg.docID, slog.NewScavenger())
	err = w.LoadH28FromMongo(newClient, cfg.dbName, cfg.coll, cfg.docID)
	if err != nil {
		t.Fatal(err)
	}

	h28 := atomic.LoadInt64(&w.w.N) >> 36
	atomic.StoreInt64(&w.w.N, (h28<<36)|internal.Bye)
	n1a := w.Next()
	if n1a>>36 != h28 {
		t.Fatal(`n1a>>36 != h28`)
	}

	waitUntilNumRenewedReaches(t, w, 1)
	n1b := w.Next()
	if n1b != (h28+1)<<36+1 {
		t.Fatal(`n1b != (h28+1)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+1)<<36)|internal.Bye)
	n2a := w.Next()
	if n2a>>36 != h28+1 {
		t.Fatal(`n2a>>36 != h28+1`)
	}

	waitUntilNumRenewedReaches(t, w, 2)
	n2b := w.Next()
	if n2b != (h28+2)<<36+1 {
		t.Fatal(`n2b != (h28+2)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+2)<<36)|internal.Bye)
	n3a := w.Next()
	if n3a>>36 != h28+2 {
		t.Fatal(`n3a>>36 != h28+2`)
	}

	waitUntilNumRenewedReaches(t, w, 3)
	n3b := w.Next()
	if n3b != (h28+3)<<36+1 {
		t.Fatal(`n3b != (h28+3)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+2)<<36)+internal.Bye+1)
	for i := 0; i < 100; i++ {
		w.Next()
	}
	if atomic.LoadInt64(&w.w.Stats.NumRenewAttempts) != 3 {
		t.Fatal(`atomic.LoadInt64(&w.w.Stats.NumRenewAttempts) != 3`)
	}

	var num int
	sc := w.w.Logger.(*slog.Scavenger)
	sc.Filter(func(level, msg string) bool {
		if level == slog.LevelInfo && strings.Contains(msg, "renew succeeded") {
			num++
		}
		return true
	})
	if num != 3 {
		t.Fatal(`num != 3`)
	}
}

func Example() {
	newClient := func() (*mongo.Client, bool, error) {
		var client *mongo.Client
		// ...
		return client, true, nil
	}

	// Setup
	w := NewWUID("alpha", nil)
	err := w.LoadH28FromMongo(newClient, "test", "wuid", "default")
	if err != nil {
		panic(err)
	}

	// Generate
	for i := 0; i < 10; i++ {
		fmt.Printf("%#016x\n", w.Next())
	}
}


================================================
FILE: mysql/db.sql
================================================
CREATE DATABASE IF NOT EXISTS test;

use test;

CREATE TABLE IF NOT EXISTS `wuid` (
    `h` int(10) NOT NULL AUTO_INCREMENT,
    `x` tinyint(4) NOT NULL DEFAULT '0',
    PRIMARY KEY (`x`),
    UNIQUE KEY `h` (`h`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;


================================================
FILE: mysql/docker-mysql-client.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

docker run -it --rm mysql mysql -h host.docker.internal -u root -phello test


================================================
FILE: mysql/docker-mysql-server.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

docker run --name mysql-server -p 3306:3306 -e MYSQL_ROOT_PASSWORD=hello -d mysql
[[ $? -ne 0 ]] && exit 1

printImportantMessage "It may take quite a few seconds to get ready."
for ((i=0;i<1000;i++)); do
    docker run -it --rm mysql mysqladmin ping -h host.docker.internal --silent
    [[ $? -eq 0 ]] && echo "Ready." && break
    echo "Waiting $((i+1))..."
    sleep 1
done

sleep 1
docker run -v `pwd`/db.sql:/tmp/db.sql -it --rm mysql /bin/bash -c 'cat /tmp/db.sql | mysql -h host.docker.internal -u root -phello'
[[ $? -ne 0 ]] && exit 1

echo "Job done."


================================================
FILE: mysql/wuid/coverage.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

go test -cover -coverprofile=c.out -v "$@" && go tool cover -html=c.out


================================================
FILE: mysql/wuid/vet.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

printImportantMessage "====== gofmt"
gofmt -w .

printImportantMessage "====== go vet"
go vet ./...

printImportantMessage "====== gocyclo"
gocyclo -over 15 .

printImportantMessage "====== ineffassign"
ineffassign ./...

printImportantMessage "====== misspell"
misspell *


================================================
FILE: mysql/wuid/wuid.go
================================================
package wuid

import (
	"database/sql"
	"errors"
	"fmt"
	"github.com/edwingeng/slog"
	"github.com/edwingeng/wuid/internal"
	_ "github.com/go-sql-driver/mysql"
)

// WUID is an extremely fast universal unique identifier generator.
type WUID struct {
	w *internal.WUID
}

// NewWUID creates a new WUID instance.
func NewWUID(name string, logger slog.Logger, opts ...Option) *WUID {
	return &WUID{w: internal.NewWUID(name, logger, opts...)}
}

// Next returns a unique identifier.
func (w *WUID) Next() int64 {
	return w.w.Next()
}

type OpenDB func() (client *sql.DB, autoClose bool, err error)

// LoadH28FromMysql adds 1 to a specific number in MySQL and fetches its new value.
// The new value is used as the high 28 bits of all generated numbers. In addition, all the
// arguments passed in are saved for future renewal.
func (w *WUID) LoadH28FromMysql(openDB OpenDB, table string) error {
	if len(table) == 0 {
		return errors.New("table cannot be empty")
	}

	db, autoClose, err := openDB()
	if err != nil {
		return err
	}
	defer func() {
		if autoClose {
			_ = db.Close()
		}
	}()

	result, err := db.Exec(fmt.Sprintf("REPLACE INTO %s (x) VALUES (0)", table))
	if err != nil {
		return err
	}
	h28, err := result.LastInsertId()
	if err != nil {
		return err
	}
	if err = w.w.VerifyH28(h28); err != nil {
		return err
	}

	w.w.Reset(h28 << 36)
	w.w.Logger.Infof("<wuid> new h28: %d. name: %s", h28, w.w.Name)

	w.w.Lock()
	defer w.w.Unlock()

	if w.w.Renew != nil {
		return nil
	}
	w.w.Renew = func() error {
		return w.LoadH28FromMysql(openDB, table)
	}

	return nil
}

// RenewNow reacquires the high 28 bits immediately.
func (w *WUID) RenewNow() error {
	return w.w.RenewNow()
}

type Option = internal.Option

// WithH28Verifier adds an extra verifier for the high 28 bits.
func WithH28Verifier(cb func(h28 int64) error) Option {
	return internal.WithH28Verifier(cb)
}

// WithSection brands a section ID on each generated number. A section ID must be in between [0, 7].
func WithSection(section int8) Option {
	return internal.WithSection(section)
}

// WithStep sets the step and the floor for each generated number.
func WithStep(step int64, floor int64) Option {
	return internal.WithStep(step, floor)
}

// WithObfuscation enables number obfuscation.
func WithObfuscation(seed int) Option {
	return internal.WithObfuscation(seed)
}


================================================
FILE: mysql/wuid/wuid_test.go
================================================
package wuid

import (
	"database/sql"
	"errors"
	"fmt"
	"github.com/edwingeng/slog"
	"github.com/edwingeng/wuid/internal"
	_ "github.com/go-sql-driver/mysql"
	"math/rand"
	"strings"
	"sync/atomic"
	"testing"
	"time"
)

var (
	dumb = slog.NewDumbLogger()
)

var (
	cfg struct {
		addr   string
		user   string
		pass   string
		dbName string
		table  string
	}
)

func init() {
	cfg.addr = "127.0.0.1:3306"
	cfg.user = "root"
	cfg.pass = "hello"
	cfg.dbName = "test"
	cfg.table = "wuid"
}

func connect() (*sql.DB, error) {
	dsn := cfg.user
	if len(cfg.pass) > 0 {
		dsn += ":" + cfg.pass
	}
	dsn += "@tcp(" + cfg.addr + ")/" + cfg.dbName
	return sql.Open("mysql", dsn)
}

func TestWUID_LoadH28FromMysql(t *testing.T) {
	openDB := func() (*sql.DB, bool, error) {
		db, err := connect()
		return db, true, err
	}
	w := NewWUID("alpha", dumb)
	err := w.LoadH28FromMysql(openDB, cfg.table)
	if err != nil {
		t.Fatal(err)
	}

	initial := atomic.LoadInt64(&w.w.N)
	for i := 1; i < 100; i++ {
		if err := w.RenewNow(); err != nil {
			t.Fatal(err)
		}
		expected := ((initial >> 36) + int64(i)) << 36
		if atomic.LoadInt64(&w.w.N) != expected {
			t.Fatalf("w.w.N is %d, while it should be %d. i: %d", atomic.LoadInt64(&w.w.N), expected, i)
		}
		n := rand.Intn(10)
		for j := 0; j < n; j++ {
			w.Next()
		}
	}
}

func TestWUID_LoadH28FromMysql_Error(t *testing.T) {
	w := NewWUID("alpha", dumb)
	if w.LoadH28FromMysql(nil, "") == nil {
		t.Fatal("table is not properly checked")
	}

	newErrorDB := func() (client *sql.DB, autoClose bool, err error) {
		return nil, true, errors.New("beta")
	}
	if w.LoadH28FromMysql(newErrorDB, "beta") == nil {
		t.Fatal(`w.LoadH28FromMysql(newErrorDB, "beta") == nil`)
	}
}

func waitUntilNumRenewedReaches(t *testing.T, w *WUID, expected int64) {
	t.Helper()
	startTime := time.Now()
	for time.Since(startTime) < time.Second*3 {
		if atomic.LoadInt64(&w.w.Stats.NumRenewed) == expected {
			return
		}
		time.Sleep(time.Millisecond * 10)
	}
	t.Fatal("timeout")
}

func TestWUID_Next_Renew(t *testing.T) {
	db, err := connect()
	if err != nil {
		t.Fatal(err)
	}
	openDB := func() (*sql.DB, bool, error) {
		return db, false, err
	}

	w := NewWUID("alpha", slog.NewScavenger())
	err = w.LoadH28FromMysql(openDB, cfg.table)
	if err != nil {
		t.Fatal(err)
	}

	h28 := atomic.LoadInt64(&w.w.N) >> 36
	atomic.StoreInt64(&w.w.N, (h28<<36)|internal.Bye)
	n1a := w.Next()
	if n1a>>36 != h28 {
		t.Fatal(`n1a>>36 != h28`)
	}

	waitUntilNumRenewedReaches(t, w, 1)
	n1b := w.Next()
	if n1b != (h28+1)<<36+1 {
		t.Fatal(`n1b != (h28+1)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+1)<<36)|internal.Bye)
	n2a := w.Next()
	if n2a>>36 != h28+1 {
		t.Fatal(`n2a>>36 != h28+1`)
	}

	waitUntilNumRenewedReaches(t, w, 2)
	n2b := w.Next()
	if n2b != (h28+2)<<36+1 {
		t.Fatal(`n2b != (h28+2)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+2)<<36)|internal.Bye)
	n3a := w.Next()
	if n3a>>36 != h28+2 {
		t.Fatal(`n3a>>36 != h28+2`)
	}

	waitUntilNumRenewedReaches(t, w, 3)
	n3b := w.Next()
	if n3b != (h28+3)<<36+1 {
		t.Fatal(`n3b != (h28+3)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+2)<<36)+internal.Bye+1)
	for i := 0; i < 100; i++ {
		w.Next()
	}
	if atomic.LoadInt64(&w.w.Stats.NumRenewAttempts) != 3 {
		t.Fatal(`atomic.LoadInt64(&w.w.Stats.NumRenewAttempts) != 3`)
	}

	var num int
	sc := w.w.Logger.(*slog.Scavenger)
	sc.Filter(func(level, msg string) bool {
		if level == slog.LevelInfo && strings.Contains(msg, "renew succeeded") {
			num++
		}
		return true
	})
	if num != 3 {
		t.Fatal(`num != 3`)
	}
}

func Example() {
	openDB := func() (*sql.DB, bool, error) {
		var db *sql.DB
		// ...
		return db, true, nil
	}

	// Setup
	w := NewWUID("alpha", nil)
	err := w.LoadH28FromMysql(openDB, "wuid")
	if err != nil {
		panic(err)
	}

	// Generate
	for i := 0; i < 10; i++ {
		fmt.Printf("%#016x\n", w.Next())
	}
}


================================================
FILE: redis/docker-redis-client.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

docker run -it --rm redis redis-cli -h host.docker.internal


================================================
FILE: redis/docker-redis-server.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

docker run --name redis-server -d -p 6379-6383:6379 redis


================================================
FILE: redis/v8/wuid/coverage.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

go test -cover -coverprofile=c.out -v "$@" && go tool cover -html=c.out


================================================
FILE: redis/v8/wuid/vet.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

printImportantMessage "====== gofmt"
gofmt -w .

printImportantMessage "====== go vet"
go vet ./...

printImportantMessage "====== gocyclo"
gocyclo -over 15 .

printImportantMessage "====== ineffassign"
ineffassign ./...

printImportantMessage "====== misspell"
misspell *


================================================
FILE: redis/v8/wuid/wuid.go
================================================
package wuid

import (
	"context"
	"errors"
	"github.com/edwingeng/slog"
	"github.com/edwingeng/wuid/internal"
	"github.com/go-redis/redis/v8"
	"time"
)

// WUID is an extremely fast universal unique identifier generator.
type WUID struct {
	w *internal.WUID
}

// NewWUID creates a new WUID instance.
func NewWUID(name string, logger slog.Logger, opts ...Option) *WUID {
	return &WUID{w: internal.NewWUID(name, logger, opts...)}
}

// Next returns a unique identifier.
func (w *WUID) Next() int64 {
	return w.w.Next()
}

type NewClient func() (client redis.UniversalClient, autoClose bool, err error)

// LoadH28FromRedis adds 1 to a specific number in Redis and fetches its new value.
// The new value is used as the high 28 bits of all generated numbers. In addition, all the
// arguments passed in are saved for future renewal.
func (w *WUID) LoadH28FromRedis(newClient NewClient, key string) error {
	if len(key) == 0 {
		return errors.New("key cannot be empty")
	}

	client, autoClose, err := newClient()
	if err != nil {
		return err
	}
	defer func() {
		if autoClose {
			_ = client.Close()
		}
	}()

	ctx1, cancel1 := context.WithTimeout(context.Background(), time.Second*5)
	defer cancel1()
	h28, err := client.Incr(ctx1, key).Result()
	if err != nil {
		return err
	}
	if err = w.w.VerifyH28(h28); err != nil {
		return err
	}

	w.w.Reset(h28 << 36)
	w.w.Logger.Infof("<wuid> new h28: %d. name: %s", h28, w.w.Name)

	w.w.Lock()
	defer w.w.Unlock()

	if w.w.Renew != nil {
		return nil
	}
	w.w.Renew = func() error {
		return w.LoadH28FromRedis(newClient, key)
	}

	return nil
}

// RenewNow reacquires the high 28 bits immediately.
func (w *WUID) RenewNow() error {
	return w.w.RenewNow()
}

type Option = internal.Option

// WithH28Verifier adds an extra verifier for the high 28 bits.
func WithH28Verifier(cb func(h28 int64) error) Option {
	return internal.WithH28Verifier(cb)
}

// WithSection brands a section ID on each generated number. A section ID must be in between [0, 7].
func WithSection(section int8) Option {
	return internal.WithSection(section)
}

// WithStep sets the step and the floor for each generated number.
func WithStep(step int64, floor int64) Option {
	return internal.WithStep(step, floor)
}

// WithObfuscation enables number obfuscation.
func WithObfuscation(seed int) Option {
	return internal.WithObfuscation(seed)
}


================================================
FILE: redis/v8/wuid/wuid_test.go
================================================
package wuid

import (
	"errors"
	"flag"
	"fmt"
	"github.com/edwingeng/slog"
	"github.com/edwingeng/wuid/internal"
	"github.com/go-redis/redis/v8"
	"math/rand"
	"strings"
	"sync/atomic"
	"testing"
	"time"
)

var redisCluster = flag.Bool("cluster", false, "")

var (
	dumb = slog.NewDumbLogger()
)

var (
	cfg struct {
		addrs    []string
		password string
		key      string
	}
)

func init() {
	cfg.addrs = []string{"127.0.0.1:6379", "127.0.0.1:6380", "127.0.0.1:6381"}
	cfg.key = "v8:wuid"
}

func connect() redis.UniversalClient {
	if *redisCluster {
		return redis.NewClusterClient(&redis.ClusterOptions{
			Addrs:    cfg.addrs,
			Password: cfg.password,
		})
	} else {
		return redis.NewClient(&redis.Options{
			Addr:     cfg.addrs[0],
			Password: cfg.password,
		})
	}
}

func TestWUID_LoadH28FromRedis(t *testing.T) {
	newClient := func() (redis.UniversalClient, bool, error) {
		return connect(), true, nil
	}
	w := NewWUID("alpha", dumb)
	err := w.LoadH28FromRedis(newClient, cfg.key)
	if err != nil {
		t.Fatal(err)
	}

	initial := atomic.LoadInt64(&w.w.N)
	for i := 1; i < 100; i++ {
		if err := w.RenewNow(); err != nil {
			t.Fatal(err)
		}
		expected := ((initial >> 36) + int64(i)) << 36
		if atomic.LoadInt64(&w.w.N) != expected {
			t.Fatalf("w.w.N is %d, while it should be %d. i: %d", atomic.LoadInt64(&w.w.N), expected, i)
		}
		n := rand.Intn(10)
		for j := 0; j < n; j++ {
			w.Next()
		}
	}
}

func TestWUID_LoadH28FromRedis_Error(t *testing.T) {
	w := NewWUID("alpha", dumb)
	if w.LoadH28FromRedis(nil, "") == nil {
		t.Fatal("key is not properly checked")
	}

	newErrorClient := func() (redis.UniversalClient, bool, error) {
		return nil, true, errors.New("beta")
	}
	if w.LoadH28FromRedis(newErrorClient, "beta") == nil {
		t.Fatal(`w.LoadH28FromRedis(newErrorClient, "beta") == nil`)
	}
}

func waitUntilNumRenewedReaches(t *testing.T, w *WUID, expected int64) {
	t.Helper()
	startTime := time.Now()
	for time.Since(startTime) < time.Second*3 {
		if atomic.LoadInt64(&w.w.Stats.NumRenewed) == expected {
			return
		}
		time.Sleep(time.Millisecond * 10)
	}
	t.Fatal("timeout")
}

func TestWUID_Next_Renew(t *testing.T) {
	client := connect()
	newClient := func() (redis.UniversalClient, bool, error) {
		return client, false, nil
	}

	w := NewWUID("alpha", slog.NewScavenger())
	err := w.LoadH28FromRedis(newClient, cfg.key)
	if err != nil {
		t.Fatal(err)
	}

	h28 := atomic.LoadInt64(&w.w.N) >> 36
	atomic.StoreInt64(&w.w.N, (h28<<36)|internal.Bye)
	n1a := w.Next()
	if n1a>>36 != h28 {
		t.Fatal(`n1a>>36 != h28`)
	}

	waitUntilNumRenewedReaches(t, w, 1)
	n1b := w.Next()
	if n1b != (h28+1)<<36+1 {
		t.Fatal(`n1b != (h28+1)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+1)<<36)|internal.Bye)
	n2a := w.Next()
	if n2a>>36 != h28+1 {
		t.Fatal(`n2a>>36 != h28+1`)
	}

	waitUntilNumRenewedReaches(t, w, 2)
	n2b := w.Next()
	if n2b != (h28+2)<<36+1 {
		t.Fatal(`n2b != (h28+2)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+2)<<36)|internal.Bye)
	n3a := w.Next()
	if n3a>>36 != h28+2 {
		t.Fatal(`n3a>>36 != h28+2`)
	}

	waitUntilNumRenewedReaches(t, w, 3)
	n3b := w.Next()
	if n3b != (h28+3)<<36+1 {
		t.Fatal(`n3b != (h28+3)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+2)<<36)+internal.Bye+1)
	for i := 0; i < 100; i++ {
		w.Next()
	}
	if atomic.LoadInt64(&w.w.Stats.NumRenewAttempts) != 3 {
		t.Fatal(`atomic.LoadInt64(&w.w.Stats.NumRenewAttempts) != 3`)
	}

	var num int
	sc := w.w.Logger.(*slog.Scavenger)
	sc.Filter(func(level, msg string) bool {
		if level == slog.LevelInfo && strings.Contains(msg, "renew succeeded") {
			num++
		}
		return true
	})
	if num != 3 {
		t.Fatal(`num != 3`)
	}
}

func Example() {
	newClient := func() (redis.UniversalClient, bool, error) {
		var client redis.UniversalClient
		// ...
		return client, true, nil
	}

	// Setup
	w := NewWUID("alpha", nil)
	err := w.LoadH28FromRedis(newClient, "wuid")
	if err != nil {
		panic(err)
	}

	// Generate
	for i := 0; i < 10; i++ {
		fmt.Printf("%#016x\n", w.Next())
	}
}


================================================
FILE: redis/wuid/coverage.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

go test -cover -coverprofile=c.out -v "$@" && go tool cover -html=c.out


================================================
FILE: redis/wuid/vet.sh
================================================
#!/usr/bin/env bash

[[ "$TRACE" ]] && set -x
pushd `dirname "$0"` > /dev/null
trap __EXIT EXIT

colorful=false
tput setaf 7 > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
    colorful=true
fi

function __EXIT() {
    popd > /dev/null
}

function printError() {
    $colorful && tput setaf 1
    >&2 echo "Error: $@"
    $colorful && tput setaf 7
}

function printImportantMessage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

function printUsage() {
    $colorful && tput setaf 3
    >&2 echo "$@"
    $colorful && tput setaf 7
}

printImportantMessage "====== gofmt"
gofmt -w .

printImportantMessage "====== go vet"
go vet ./...

printImportantMessage "====== gocyclo"
gocyclo -over 15 .

printImportantMessage "====== ineffassign"
ineffassign ./...

printImportantMessage "====== misspell"
misspell *


================================================
FILE: redis/wuid/wuid.go
================================================
package wuid

import (
	"errors"
	"github.com/edwingeng/slog"
	"github.com/edwingeng/wuid/internal"
	"github.com/go-redis/redis"
)

// WUID is an extremely fast universal unique identifier generator.
type WUID struct {
	w *internal.WUID
}

// NewWUID creates a new WUID instance.
func NewWUID(name string, logger slog.Logger, opts ...Option) *WUID {
	return &WUID{w: internal.NewWUID(name, logger, opts...)}
}

// Next returns a unique identifier.
func (w *WUID) Next() int64 {
	return w.w.Next()
}

type NewClient func() (client redis.UniversalClient, autoClose bool, err error)

// LoadH28FromRedis adds 1 to a specific number in Redis and fetches its new value.
// The new value is used as the high 28 bits of all generated numbers. In addition, all the
// arguments passed in are saved for future renewal.
func (w *WUID) LoadH28FromRedis(newClient NewClient, key string) error {
	if len(key) == 0 {
		return errors.New("key cannot be empty")
	}

	client, autoClose, err := newClient()
	if err != nil {
		return err
	}
	defer func() {
		if autoClose {
			_ = client.Close()
		}
	}()

	h28, err := client.Incr(key).Result()
	if err != nil {
		return err
	}
	if err = w.w.VerifyH28(h28); err != nil {
		return err
	}

	w.w.Reset(h28 << 36)
	w.w.Logger.Infof("<wuid> new h28: %d. name: %s", h28, w.w.Name)

	w.w.Lock()
	defer w.w.Unlock()

	if w.w.Renew != nil {
		return nil
	}
	w.w.Renew = func() error {
		return w.LoadH28FromRedis(newClient, key)
	}

	return nil
}

// RenewNow reacquires the high 28 bits immediately.
func (w *WUID) RenewNow() error {
	return w.w.RenewNow()
}

type Option = internal.Option

// WithH28Verifier adds an extra verifier for the high 28 bits.
func WithH28Verifier(cb func(h28 int64) error) Option {
	return internal.WithH28Verifier(cb)
}

// WithSection brands a section ID on each generated number. A section ID must be in between [0, 7].
func WithSection(section int8) Option {
	return internal.WithSection(section)
}

// WithStep sets the step and the floor for each generated number.
func WithStep(step int64, floor int64) Option {
	return internal.WithStep(step, floor)
}

// WithObfuscation enables number obfuscation.
func WithObfuscation(seed int) Option {
	return internal.WithObfuscation(seed)
}


================================================
FILE: redis/wuid/wuid_test.go
================================================
package wuid

import (
	"errors"
	"flag"
	"fmt"
	"github.com/edwingeng/slog"
	"github.com/edwingeng/wuid/internal"
	"github.com/go-redis/redis"
	"math/rand"
	"strings"
	"sync/atomic"
	"testing"
	"time"
)

var redisCluster = flag.Bool("cluster", false, "")

var (
	dumb = slog.NewDumbLogger()
)

var (
	cfg struct {
		addrs    []string
		password string
		key      string
	}
)

func init() {
	cfg.addrs = []string{"127.0.0.1:6379", "127.0.0.1:6380", "127.0.0.1:6381"}
	cfg.key = "wuid"
}

func connect() redis.UniversalClient {
	if *redisCluster {
		return redis.NewClusterClient(&redis.ClusterOptions{
			Addrs:    cfg.addrs,
			Password: cfg.password,
		})
	} else {
		return redis.NewClient(&redis.Options{
			Addr:     cfg.addrs[0],
			Password: cfg.password,
		})
	}
}

func TestWUID_LoadH28FromRedis(t *testing.T) {
	newClient := func() (redis.UniversalClient, bool, error) {
		return connect(), true, nil
	}
	w := NewWUID("alpha", dumb)
	err := w.LoadH28FromRedis(newClient, cfg.key)
	if err != nil {
		t.Fatal(err)
	}

	initial := atomic.LoadInt64(&w.w.N)
	for i := 1; i < 100; i++ {
		if err := w.RenewNow(); err != nil {
			t.Fatal(err)
		}
		expected := ((initial >> 36) + int64(i)) << 36
		if atomic.LoadInt64(&w.w.N) != expected {
			t.Fatalf("w.w.N is %d, while it should be %d. i: %d", atomic.LoadInt64(&w.w.N), expected, i)
		}
		n := rand.Intn(10)
		for j := 0; j < n; j++ {
			w.Next()
		}
	}
}

func TestWUID_LoadH28FromRedis_Error(t *testing.T) {
	w := NewWUID("alpha", dumb)
	if w.LoadH28FromRedis(nil, "") == nil {
		t.Fatal("key is not properly checked")
	}

	newErrorClient := func() (redis.UniversalClient, bool, error) {
		return nil, true, errors.New("beta")
	}
	if w.LoadH28FromRedis(newErrorClient, "beta") == nil {
		t.Fatal(`w.LoadH28FromRedis(newErrorClient, "beta") == nil`)
	}
}

func waitUntilNumRenewedReaches(t *testing.T, w *WUID, expected int64) {
	t.Helper()
	startTime := time.Now()
	for time.Since(startTime) < time.Second*3 {
		if atomic.LoadInt64(&w.w.Stats.NumRenewed) == expected {
			return
		}
		time.Sleep(time.Millisecond * 10)
	}
	t.Fatal("timeout")
}

func TestWUID_Next_Renew(t *testing.T) {
	client := connect()
	newClient := func() (redis.UniversalClient, bool, error) {
		return client, false, nil
	}

	w := NewWUID("alpha", slog.NewScavenger())
	err := w.LoadH28FromRedis(newClient, cfg.key)
	if err != nil {
		t.Fatal(err)
	}

	h28 := atomic.LoadInt64(&w.w.N) >> 36
	atomic.StoreInt64(&w.w.N, (h28<<36)|internal.Bye)
	n1a := w.Next()
	if n1a>>36 != h28 {
		t.Fatal(`n1a>>36 != h28`)
	}

	waitUntilNumRenewedReaches(t, w, 1)
	n1b := w.Next()
	if n1b != (h28+1)<<36+1 {
		t.Fatal(`n1b != (h28+1)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+1)<<36)|internal.Bye)
	n2a := w.Next()
	if n2a>>36 != h28+1 {
		t.Fatal(`n2a>>36 != h28+1`)
	}

	waitUntilNumRenewedReaches(t, w, 2)
	n2b := w.Next()
	if n2b != (h28+2)<<36+1 {
		t.Fatal(`n2b != (h28+2)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+2)<<36)|internal.Bye)
	n3a := w.Next()
	if n3a>>36 != h28+2 {
		t.Fatal(`n3a>>36 != h28+2`)
	}

	waitUntilNumRenewedReaches(t, w, 3)
	n3b := w.Next()
	if n3b != (h28+3)<<36+1 {
		t.Fatal(`n3b != (h28+3)<<36+1`)
	}

	atomic.StoreInt64(&w.w.N, ((h28+2)<<36)+internal.Bye+1)
	for i := 0; i < 100; i++ {
		w.Next()
	}
	if atomic.LoadInt64(&w.w.Stats.NumRenewAttempts) != 3 {
		t.Fatal(`atomic.LoadInt64(&w.w.Stats.NumRenewAttempts) != 3`)
	}

	var num int
	sc := w.w.Logger.(*slog.Scavenger)
	sc.Filter(func(level, msg string) bool {
		if level == slog.LevelInfo && strings.Contains(msg, "renew succeeded") {
			num++
		}
		return true
	})
	if num != 3 {
		t.Fatal(`num != 3`)
	}
}

func Example() {
	newClient := func() (redis.UniversalClient, bool, error) {
		var client redis.UniversalClient
		// ...
		return client, true, nil
	}

	// Setup
	w := NewWUID("alpha", nil)
	err := w.LoadH28FromRedis(newClient, "wuid")
	if err != nil {
		panic(err)
	}

	// Generate
	for i := 0; i < 10; i++ {
		fmt.Printf("%#016x\n", w.Next())
	}
}


================================================
FILE: wuid.go
================================================
package wuid

type WUID interface {
	Next() int64
}