Add v2

.github/workflows/test-v1.yml

@@ -0,0 +1,43 @@
+name: CI for v1 Module
+
+on:
+  push:
+    paths-ignore:
+      - 'v2/**'
+  pull_request:
+    paths-ignore:
+      - 'v2/**'
+
+jobs:
+  test-v1:
+    strategy:
+      matrix:
+        go-version: [1.23.x, 1.24.x]
+        os: [ubuntu-latest]
+
+    runs-on: ${{matrix.os}}
+
+    defaults:
+      run:
+        working-directory: ./
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{matrix.go-version}}
+
+      - name: gofmt
+        run: test -z "`gofmt -l .`"
+
+      - name: golint
+        run: test -z "`golint ./...`"
+
+      - name: go test
+        run: go test -v ./...
+
+      - name: Build example
+        run: cd example && ./linux64_build.sh

.github/workflows/test-v2.yml

@@ -0,0 +1,46 @@
+name: CI for v2 Module
+
+on:
+  push:
+    paths:
+      - 'v2/**'
+  pull_request:
+    paths:
+      - 'v2/**'
+
+jobs:
+  test-v2:
+    strategy:
+      matrix:
+        go-version: [1.23.x, 1.24.x]
+        os: [ubuntu-latest]
+
+    runs-on: ${{matrix.os}}
+
+    defaults:
+      run:
+        working-directory: ./v2
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: ./v2/go.mod
+
+      - name: Tidy modules
+        run: go mod tidy
+
+      - name: Run tests
+        run: go test ./... -v
+
+      - name: gofmt
+        run: test -z "`gofmt -l .`"
+
+      - name: golint
+        run: test -z "`golint ./...`"
+
+      - name: Build example
+        run: cd example && ./linux64_build.sh

.github/workflows/test.yml

@@ -1,24 +0,0 @@
-on: [push, pull_request]
-name: Test
-jobs:
-  test:
-    strategy:
-      matrix:
-        go-version: [1.23.x, 1.24.x]
-        os: [ubuntu-latest]
-    runs-on: ${{matrix.os}}
-    steps:
-    - name: Set up Go
-      uses: actions/setup-go@v2
-      with:
-        go-version: ${{matrix.go-version}}
-    - name: Checkout
-      uses: actions/checkout@v2
-    - name: gofmt
-      run: test -z "`gofmt -l .`"
-    - name: golint
-      run: test -z "`golint ./...`"
-    - name: go test
-      run: go test -v ./...
-    - name: Build example
-      run: cd example && ./linux64_build.sh

v2/awsutil/awsutil.go

@@ -0,0 +1,64 @@
+// Package awsutil provides utility functions for using Sonyflake on AWS.
+package awsutil
+
+import (
+	"errors"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"os/exec"
+	"regexp"
+	"strconv"
+	"time"
+)
+
+func amazonEC2PrivateIPv4() (net.IP, error) {
+	res, err := http.Get("http://169.254.169.254/latest/meta-data/local-ipv4")
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	ip := net.ParseIP(string(body))
+	if ip == nil {
+		return nil, errors.New("invalid ip address")
+	}
+	return ip.To4(), nil
+}
+
+// AmazonEC2MachineID retrieves the private IP address of the Amazon EC2 instance
+// and returns its lower 16 bits.
+// It works correctly on Docker as well.
+func AmazonEC2MachineID() (uint16, error) {
+	ip, err := amazonEC2PrivateIPv4()
+	if err != nil {
+		return 0, err
+	}
+
+	return uint16(ip[2])<<8 + uint16(ip[3]), nil
+}
+
+// TimeDifference returns the time difference between the localhost and the given NTP server.
+func TimeDifference(server string) (time.Duration, error) {
+	output, err := exec.Command("/usr/sbin/ntpdate", "-q", server).CombinedOutput()
+	if err != nil {
+		return time.Duration(0), err
+	}
+
+	re, _ := regexp.Compile("offset (.*) sec")
+	submatched := re.FindSubmatch(output)
+	if len(submatched) != 2 {
+		return time.Duration(0), errors.New("invalid ntpdate output")
+	}
+
+	f, err := strconv.ParseFloat(string(submatched[1]), 64)
+	if err != nil {
+		return time.Duration(0), err
+	}
+	return time.Duration(f*1000) * time.Millisecond, nil
+}

v2/example/Dockerfile

@@ -0,0 +1,6 @@
+FROM ubuntu:14.04
+
+ADD ./sonyflake_server /
+ENTRYPOINT ["/sonyflake_server"]
+
+EXPOSE 8080

v2/example/Dockerrun.aws.json

@@ -0,0 +1,8 @@
+{
+  "AWSEBDockerrunVersion": "1",
+  "Ports": [
+    {
+      "ContainerPort": "8080"
+    }
+  ]
+}

v2/example/README.md

@@ -0,0 +1,21 @@
+Example
+=======
+
+This example runs Sonyflake on AWS Elastic Beanstalk.
+
+Setup
+-----
+
+1. Build the cross compiler for linux/amd64 if using other platforms.
+
+  ```
+  cd $GOROOT/src && GOOS=linux GOARCH=amd64 ./make.bash
+  ```
+
+2. Build sonyflake_server in the example directory.
+
+  ```
+  ./linux64_build.sh
+  ```
+
+3. Upload the example directory to AWS Elastic Beanstalk.

v2/example/linux64_build.sh

@@ -0,0 +1,2 @@
+#!/bin/sh
+GOOS=linux GOARCH=amd64 go build sonyflake_server.go

v2/example/sonyflake_server.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/sony/sonyflake/v2"
+	"github.com/sony/sonyflake/v2/awsutil"
+)
+
+var sf *sonyflake.Sonyflake
+
+func init() {
+	var st sonyflake.Settings
+	st.MachineID = awsutil.AmazonEC2MachineID
+	sf = sonyflake.NewSonyflake(st)
+	if sf == nil {
+		panic("sonyflake not created")
+	}
+}
+
+func handler(w http.ResponseWriter, r *http.Request) {
+	id, err := sf.NextID()
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	body, err := json.Marshal(sonyflake.Decompose(id))
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	w.Header()["Content-Type"] = []string{"application/json; charset=utf-8"}
+	w.Write(body)
+}
+
+func main() {
+	http.HandleFunc("/", handler)
+	http.ListenAndServe(":8080", nil)
+}

v2/go.mod

@@ -0,0 +1,3 @@
+module github.com/sony/sonyflake/v2
+
+go 1.22

v2/mock/sonyflake_mock.go

@@ -0,0 +1,35 @@
+// Package mock offers implementations of interfaces defined in types.go
+// This allows complete control over input / output for any given method that consumes
+// a given type
+package mock
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/sony/sonyflake/v2/types"
+)
+
+// NewSuccessfulInterfaceAddrs returns a single private IP address
+func NewSuccessfulInterfaceAddrs() types.InterfaceAddrs {
+	ifat := make([]net.Addr, 0, 1)
+	ifat = append(ifat, &net.IPNet{IP: []byte{192, 168, 0, 1}, Mask: []byte{255, 0, 0, 0}})
+
+	return func() ([]net.Addr, error) {
+		return ifat, nil
+	}
+}
+
+// NewFailingInterfaceAddrs returns an error
+func NewFailingInterfaceAddrs() types.InterfaceAddrs {
+	return func() ([]net.Addr, error) {
+		return nil, fmt.Errorf("test error")
+	}
+}
+
+// NewFailingInterfaceAddrs returns an empty slice of addresses
+func NewNilInterfaceAddrs() types.InterfaceAddrs {
+	return func() ([]net.Addr, error) {
+		return []net.Addr{}, nil
+	}
+}

v2/sonyflake.go

@@ -0,0 +1,229 @@
+// Package sonyflake implements Sonyflake, a distributed unique ID generator inspired by Twitter's Snowflake.
+//
+// A Sonyflake ID is composed of
+//
+//	39 bits for time in units of 10 msec
+//	 8 bits for a sequence number
+//	16 bits for a machine id
+package sonyflake
+
+import (
+	"errors"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/sony/sonyflake/v2/types"
+)
+
+// These constants are the bit lengths of Sonyflake ID parts.
+const (
+	BitLenTime      = 39                               // bit length of time
+	BitLenSequence  = 8                                // bit length of sequence number
+	BitLenMachineID = 63 - BitLenTime - BitLenSequence // bit length of machine id
+)
+
+// Settings configures Sonyflake:
+//
+// StartTime is the time since which the Sonyflake time is defined as the elapsed time.
+// If StartTime is 0, the start time of the Sonyflake is set to "2014-09-01 00:00:00 +0000 UTC".
+// If StartTime is ahead of the current time, Sonyflake is not created.
+//
+// MachineID returns the unique ID of the Sonyflake instance.
+// If MachineID returns an error, Sonyflake is not created.
+// If MachineID is nil, default MachineID is used.
+// Default MachineID returns the lower 16 bits of the private IP address.
+//
+// CheckMachineID validates the uniqueness of the machine ID.
+// If CheckMachineID returns false, Sonyflake is not created.
+// If CheckMachineID is nil, no validation is done.
+type Settings struct {
+	StartTime      time.Time
+	MachineID      func() (uint16, error)
+	CheckMachineID func(uint16) bool
+}
+
+// Sonyflake is a distributed unique ID generator.
+type Sonyflake struct {
+	mutex       *sync.Mutex
+	startTime   int64
+	elapsedTime int64
+	sequence    uint16
+	machineID   uint16
+}
+
+var (
+	ErrStartTimeAhead   = errors.New("start time is ahead of now")
+	ErrNoPrivateAddress = errors.New("no private ip address")
+	ErrOverTimeLimit    = errors.New("over the time limit")
+	ErrInvalidMachineID = errors.New("invalid machine id")
+)
+
+var defaultInterfaceAddrs = net.InterfaceAddrs
+
+// New returns a new Sonyflake configured with the given Settings.
+// New returns an error in the following cases:
+// - Settings.StartTime is ahead of the current time.
+// - Settings.MachineID returns an error.
+// - Settings.CheckMachineID returns false.
+func New(st Settings) (*Sonyflake, error) {
+	if st.StartTime.After(time.Now()) {
+		return nil, ErrStartTimeAhead
+	}
+
+	sf := new(Sonyflake)
+	sf.mutex = new(sync.Mutex)
+	sf.sequence = uint16(1<<BitLenSequence - 1)
+
+	if st.StartTime.IsZero() {
+		sf.startTime = toSonyflakeTime(time.Date(2014, 9, 1, 0, 0, 0, 0, time.UTC))
+	} else {
+		sf.startTime = toSonyflakeTime(st.StartTime)
+	}
+
+	var err error
+	if st.MachineID == nil {
+		sf.machineID, err = lower16BitPrivateIP(defaultInterfaceAddrs)
+	} else {
+		sf.machineID, err = st.MachineID()
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	if st.CheckMachineID != nil && !st.CheckMachineID(sf.machineID) {
+		return nil, ErrInvalidMachineID
+	}
+
+	return sf, nil
+}
+
+// NewSonyflake returns a new Sonyflake configured with the given Settings.
+// NewSonyflake returns nil in the following cases:
+// - Settings.StartTime is ahead of the current time.
+// - Settings.MachineID returns an error.
+// - Settings.CheckMachineID returns false.
+func NewSonyflake(st Settings) *Sonyflake {
+	sf, _ := New(st)
+	return sf
+}
+
+// NextID generates a next unique ID.
+// After the Sonyflake time overflows, NextID returns an error.
+func (sf *Sonyflake) NextID() (uint64, error) {
+	const maskSequence = uint16(1<<BitLenSequence - 1)
+
+	sf.mutex.Lock()
+	defer sf.mutex.Unlock()
+
+	current := currentElapsedTime(sf.startTime)
+	if sf.elapsedTime < current {
+		sf.elapsedTime = current
+		sf.sequence = 0
+	} else { // sf.elapsedTime >= current
+		sf.sequence = (sf.sequence + 1) & maskSequence
+		if sf.sequence == 0 {
+			sf.elapsedTime++
+			overtime := sf.elapsedTime - current
+			time.Sleep(sleepTime((overtime)))
+		}
+	}
+
+	return sf.toID()
+}
+
+const sonyflakeTimeUnit = 1e7 // nsec, i.e. 10 msec
+
+func toSonyflakeTime(t time.Time) int64 {
+	return t.UTC().UnixNano() / sonyflakeTimeUnit
+}
+
+func currentElapsedTime(startTime int64) int64 {
+	return toSonyflakeTime(time.Now()) - startTime
+}
+
+func sleepTime(overtime int64) time.Duration {
+	return time.Duration(overtime*sonyflakeTimeUnit) -
+		time.Duration(time.Now().UTC().UnixNano()%sonyflakeTimeUnit)
+}
+
+func (sf *Sonyflake) toID() (uint64, error) {
+	if sf.elapsedTime >= 1<<BitLenTime {
+		return 0, ErrOverTimeLimit
+	}
+
+	return uint64(sf.elapsedTime)<<(BitLenSequence+BitLenMachineID) |
+		uint64(sf.sequence)<<BitLenMachineID |
+		uint64(sf.machineID), nil
+}
+
+func privateIPv4(interfaceAddrs types.InterfaceAddrs) (net.IP, error) {
+	as, err := interfaceAddrs()
+	if err != nil {
+		return nil, err
+	}
+
+	for _, a := range as {
+		ipnet, ok := a.(*net.IPNet)
+		if !ok || ipnet.IP.IsLoopback() {
+			continue
+		}
+
+		ip := ipnet.IP.To4()
+		if isPrivateIPv4(ip) {
+			return ip, nil
+		}
+	}
+	return nil, ErrNoPrivateAddress
+}
+
+func isPrivateIPv4(ip net.IP) bool {
+	// Allow private IP addresses (RFC1918) and link-local addresses (RFC3927)
+	return ip != nil &&
+		(ip[0] == 10 || ip[0] == 172 && (ip[1] >= 16 && ip[1] < 32) || ip[0] == 192 && ip[1] == 168 || ip[0] == 169 && ip[1] == 254)
+}
+
+func lower16BitPrivateIP(interfaceAddrs types.InterfaceAddrs) (uint16, error) {
+	ip, err := privateIPv4(interfaceAddrs)
+	if err != nil {
+		return 0, err
+	}
+
+	return uint16(ip[2])<<8 + uint16(ip[3]), nil
+}
+
+// ElapsedTime returns the elapsed time when the given Sonyflake ID was generated.
+func ElapsedTime(id uint64) time.Duration {
+	return time.Duration(elapsedTime(id) * sonyflakeTimeUnit)
+}
+
+func elapsedTime(id uint64) uint64 {
+	return id >> (BitLenSequence + BitLenMachineID)
+}
+
+// SequenceNumber returns the sequence number of a Sonyflake ID.
+func SequenceNumber(id uint64) uint64 {
+	const maskSequence = uint64((1<<BitLenSequence - 1) << BitLenMachineID)
+	return id & maskSequence >> BitLenMachineID
+}
+
+// MachineID returns the machine ID of a Sonyflake ID.
+func MachineID(id uint64) uint64 {
+	const maskMachineID = uint64(1<<BitLenMachineID - 1)
+	return id & maskMachineID
+}
+
+// Decompose returns a set of Sonyflake ID parts.
+func Decompose(id uint64) map[string]uint64 {
+	msb := id >> 63
+	time := elapsedTime(id)
+	sequence := SequenceNumber(id)
+	machineID := MachineID(id)
+	return map[string]uint64{
+		"id":         id,
+		"msb":        msb,
+		"time":       time,
+		"sequence":   sequence,
+		"machine-id": machineID,
+	}
+}

v2/sonyflake_test.go

@@ -0,0 +1,314 @@
+package sonyflake
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"runtime"
+	"testing"
+	"time"
+
+	"github.com/sony/sonyflake/v2/mock"
+	"github.com/sony/sonyflake/v2/types"
+)
+
+var sf *Sonyflake
+
+var startTime int64
+var machineID uint64
+
+func init() {
+	var st Settings
+	st.StartTime = time.Now()
+
+	sf = NewSonyflake(st)
+	if sf == nil {
+		panic("sonyflake not created")
+	}
+
+	startTime = toSonyflakeTime(st.StartTime)
+
+	ip, _ := lower16BitPrivateIP(defaultInterfaceAddrs)
+	machineID = uint64(ip)
+}
+
+func nextID(t *testing.T) uint64 {
+	id, err := sf.NextID()
+	if err != nil {
+		t.Fatal("id not generated")
+	}
+	return id
+}
+
+func TestNew(t *testing.T) {
+	genError := fmt.Errorf("an error occurred while generating ID")
+
+	tests := []struct {
+		name     string
+		settings Settings
+		err      error
+	}{
+		{
+			name: "failure: time ahead",
+			settings: Settings{
+				StartTime: time.Now().Add(time.Minute),
+			},
+			err: ErrStartTimeAhead,
+		},
+		{
+			name: "failure: machine ID",
+			settings: Settings{
+				MachineID: func() (uint16, error) {
+					return 0, genError
+				},
+			},
+			err: genError,
+		},
+		{
+			name: "failure: invalid machine ID",
+			settings: Settings{
+				CheckMachineID: func(uint16) bool {
+					return false
+				},
+			},
+			err: ErrInvalidMachineID,
+		},
+		{
+			name:     "success",
+			settings: Settings{},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			sonyflake, err := New(test.settings)
+
+			if !errors.Is(err, test.err) {
+				t.Fatalf("unexpected value, want %#v, got %#v", test.err, err)
+			}
+
+			if sonyflake == nil && err == nil {
+				t.Fatal("unexpected value, sonyflake should not be nil")
+			}
+		})
+	}
+}
+
+func TestSonyflakeOnce(t *testing.T) {
+	sleepTime := time.Duration(50 * sonyflakeTimeUnit)
+	time.Sleep(sleepTime)
+
+	id := nextID(t)
+
+	actualTime := ElapsedTime(id)
+	if actualTime < sleepTime || actualTime > sleepTime+sonyflakeTimeUnit {
+		t.Errorf("unexpected time: %d", actualTime)
+	}
+
+	actualSequence := SequenceNumber(id)
+	if actualSequence != 0 {
+		t.Errorf("unexpected sequence: %d", actualSequence)
+	}
+
+	actualMachineID := MachineID(id)
+	if actualMachineID != machineID {
+		t.Errorf("unexpected machine id: %d", actualMachineID)
+	}
+
+	fmt.Println("sonyflake id:", id)
+	fmt.Println("decompose:", Decompose(id))
+}
+
+func currentTime() int64 {
+	return toSonyflakeTime(time.Now())
+}
+
+func TestSonyflakeFor10Sec(t *testing.T) {
+	var numID uint32
+	var lastID uint64
+	var maxSequence uint64
+
+	initial := currentTime()
+	current := initial
+	for current-initial < 1000 {
+		id := nextID(t)
+		parts := Decompose(id)
+		numID++
+
+		if id == lastID {
+			t.Fatal("duplicated id")
+		}
+		if id < lastID {
+			t.Fatal("must increase with time")
+		}
+		lastID = id
+
+		current = currentTime()
+
+		actualMSB := parts["msb"]
+		if actualMSB != 0 {
+			t.Errorf("unexpected msb: %d", actualMSB)
+		}
+
+		actualTime := int64(parts["time"])
+		overtime := startTime + actualTime - current
+		if overtime > 0 {
+			t.Errorf("unexpected overtime: %d", overtime)
+		}
+
+		actualSequence := parts["sequence"]
+		if maxSequence < actualSequence {
+			maxSequence = actualSequence
+		}
+
+		actualMachineID := parts["machine-id"]
+		if actualMachineID != machineID {
+			t.Errorf("unexpected machine id: %d", actualMachineID)
+		}
+	}
+
+	if maxSequence != 1<<BitLenSequence-1 {
+		t.Errorf("unexpected max sequence: %d", maxSequence)
+	}
+	fmt.Println("max sequence:", maxSequence)
+	fmt.Println("number of id:", numID)
+}
+
+func TestSonyflakeInParallel(t *testing.T) {
+	numCPU := runtime.NumCPU()
+	runtime.GOMAXPROCS(numCPU)
+	fmt.Println("number of cpu:", numCPU)
+
+	consumer := make(chan uint64)
+
+	const numID = 10000
+	generate := func() {
+		for i := 0; i < numID; i++ {
+			consumer <- nextID(t)
+		}
+	}
+
+	const numGenerator = 10
+	for i := 0; i < numGenerator; i++ {
+		go generate()
+	}
+
+	set := make(map[uint64]struct{})
+	for i := 0; i < numID*numGenerator; i++ {
+		id := <-consumer
+		if _, ok := set[id]; ok {
+			t.Fatal("duplicated id")
+		}
+		set[id] = struct{}{}
+	}
+	fmt.Println("number of id:", len(set))
+}
+
+func pseudoSleep(period time.Duration) {
+	sf.startTime -= int64(period) / sonyflakeTimeUnit
+}
+
+func TestNextIDError(t *testing.T) {
+	year := time.Duration(365*24) * time.Hour
+	pseudoSleep(time.Duration(174) * year)
+	nextID(t)
+
+	pseudoSleep(time.Duration(1) * year)
+	_, err := sf.NextID()
+	if err == nil {
+		t.Errorf("time is not over")
+	}
+}
+
+func TestPrivateIPv4(t *testing.T) {
+	testCases := []struct {
+		description    string
+		expected       net.IP
+		interfaceAddrs types.InterfaceAddrs
+		error          string
+	}{
+		{
+			description:    "InterfaceAddrs returns an error",
+			expected:       nil,
+			interfaceAddrs: mock.NewFailingInterfaceAddrs(),
+			error:          "test error",
+		},
+		{
+			description:    "InterfaceAddrs returns an empty or nil list",
+			expected:       nil,
+			interfaceAddrs: mock.NewNilInterfaceAddrs(),
+			error:          "no private ip address",
+		},
+		{
+			description:    "InterfaceAddrs returns one or more IPs",
+			expected:       net.IP{192, 168, 0, 1},
+			interfaceAddrs: mock.NewSuccessfulInterfaceAddrs(),
+			error:          "",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			actual, err := privateIPv4(tc.interfaceAddrs)
+
+			if (err != nil) && (tc.error == "") {
+				t.Errorf("expected no error, but got: %s", err)
+				return
+			} else if (err != nil) && (tc.error != "") {
+				return
+			}
+
+			if net.IP.Equal(actual, tc.expected) {
+				return
+			} else {
+				t.Errorf("error: expected: %s, but got: %s", tc.expected, actual)
+			}
+		})
+	}
+}
+
+func TestLower16BitPrivateIP(t *testing.T) {
+	testCases := []struct {
+		description    string
+		expected       uint16
+		interfaceAddrs types.InterfaceAddrs
+		error          string
+	}{
+		{
+			description:    "InterfaceAddrs returns an empty or nil list",
+			expected:       0,
+			interfaceAddrs: mock.NewNilInterfaceAddrs(),
+			error:          "no private ip address",
+		},
+		{
+			description:    "InterfaceAddrs returns one or more IPs",
+			expected:       1,
+			interfaceAddrs: mock.NewSuccessfulInterfaceAddrs(),
+			error:          "",
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			actual, err := lower16BitPrivateIP(tc.interfaceAddrs)
+
+			if (err != nil) && (tc.error == "") {
+				t.Errorf("expected no error, but got: %s", err)
+				return
+			} else if (err != nil) && (tc.error != "") {
+				return
+			}
+
+			if actual == tc.expected {
+				return
+			} else {
+				t.Errorf("error: expected: %v, but got: %v", tc.expected, actual)
+			}
+		})
+	}
+}
+
+func TestSonyflakeTimeUnit(t *testing.T) {
+	if time.Duration(sonyflakeTimeUnit) != 10*time.Millisecond {
+		t.Errorf("unexpected time unit")
+	}
+}

v2/types/types.go

@@ -0,0 +1,8 @@
+// Package Types defines type signatures used throughout SonyFlake. This allows for
+// fine-tuned control over imports, and the ability to mock out imports as well
+package types
+
+import "net"
+
+// InterfaceAddrs defines the interface used for retrieving network addresses
+type InterfaceAddrs func() ([]net.Addr, error)