Add a note (#36)

* Refactoring

* Add functions to get ID elements

.github/workflows/test.yml

@@ -0,0 +1,24 @@
+on: [push, pull_request]
+name: Test
+jobs:
+  test:
+    strategy:
+      matrix:
+        go-version: [1.18.x, 1.19.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

.travis.yml

@@ -1,14 +0,0 @@
-language: go
-go:
-  - 1.10.x
-  - 1.11.x
-sudo: false
-before_install:
-  - go get -u golang.org/x/lint/golint
-  - go get github.com/axw/gocov/gocov
-  - go get github.com/mattn/goveralls
-script:
-  - test -z "`gofmt -l .`"
-  - test -z "`golint ./...`"
-  - $GOPATH/bin/goveralls -service=travis-ci
-  - cd example && ./linux64_build.sh

README.md

@@ -2,17 +2,27 @@ Sonyflake
 =========
 
 [![GoDoc](https://godoc.org/github.com/sony/sonyflake?status.svg)](http://godoc.org/github.com/sony/sonyflake)
-[![Build Status](https://travis-ci.org/sony/sonyflake.svg?branch=master)](https://travis-ci.org/sony/sonyflake)
-[![Coverage Status](https://coveralls.io/repos/sony/sonyflake/badge.svg?branch=master&service=github)](https://coveralls.io/github/sony/sonyflake?branch=master)
 [![Go Report Card](https://goreportcard.com/badge/github.com/sony/sonyflake)](https://goreportcard.com/report/github.com/sony/sonyflake)
 
 Sonyflake is a distributed unique ID generator inspired by [Twitter's Snowflake](https://blog.twitter.com/2010/announcing-snowflake).  
+
+Sonyflake focuses on lifetime and performance on many host/core environment.
+So it has a different bit assignment from 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
 
+As a result, Sonyflake has the following advantages and disadvantages:
+
+- The lifetime (174 years) is longer than that of Snowflake (69 years)
+- It can work in more distributed machines (2^16) than Snowflake (2^10)
+- It can generate 2^8 IDs per 10 msec at most in a single machine/thread (slower than Snowflake)
+
+However, if you want more generation rate in a single host,
+you can easily run multiple Sonyflake ID generators concurrently using goroutines.
+
 Installation
 ------------
 
@@ -61,6 +71,10 @@ func (sf *Sonyflake) NextID() (uint64, error)
 NextID can continue to generate IDs for about 174 years from StartTime.
 But after the Sonyflake time is over the limit, NextID returns an error.
 
+> **Note:**
+> Sonyflake currently does not use the most significant bit of IDs,
+> so you can convert Sonyflake IDs from `uint64` to `int64` safely.
+
 AWS VPC and Docker
 ------------------
 

go.mod

@@ -1,5 +1,3 @@
 module github.com/sony/sonyflake
 
-go 1.12
-
-require github.com/deckarep/golang-set v1.7.1
+go 1.13

go.sum

@@ -1,2 +0,0 @@
-github.com/deckarep/golang-set v1.7.1 h1:SCQV0S6gTtp6itiFrTqI+pfmJ4LN85S1YzhDf9rTHJQ=
-github.com/deckarep/golang-set v1.7.1/go.mod h1:93vsz/8Wt4joVM7c2AVqh+YRMiUSc14yDtF28KmMOgQ=

sonyflake.go

@@ -1,9 +1,10 @@
 // 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
+//
+//	39 bits for time in units of 10 msec
+//	 8 bits for a sequence number
+//	16 bits for a machine id
 package sonyflake
 
 import (
@@ -116,8 +117,8 @@ func currentElapsedTime(startTime int64) int64 {
 }
 
 func sleepTime(overtime int64) time.Duration {
-	return time.Duration(overtime)*10*time.Millisecond -
-		time.Duration(time.Now().UTC().UnixNano()%sonyflakeTimeUnit)*time.Nanosecond
+	return time.Duration(overtime*sonyflakeTimeUnit) -
+		time.Duration(time.Now().UTC().UnixNano()%sonyflakeTimeUnit)
 }
 
 func (sf *Sonyflake) toID() (uint64, error) {
@@ -164,15 +165,33 @@ func lower16BitPrivateIP() (uint16, error) {
 	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 {
-	const maskSequence = uint64((1<<BitLenSequence - 1) << BitLenMachineID)
-	const maskMachineID = uint64(1<<BitLenMachineID - 1)
-
 	msb := id >> 63
-	time := id >> (BitLenSequence + BitLenMachineID)
-	sequence := id & maskSequence >> BitLenMachineID
-	machineID := id & maskMachineID
+	time := elapsedTime(id)
+	sequence := SequenceNumber(id)
+	machineID := MachineID(id)
 	return map[string]uint64{
 		"id":         id,
 		"msb":        msb,

sonyflake_test.go

@@ -5,8 +5,6 @@ import (
 	"runtime"
 	"testing"
 	"time"
-
-	"github.com/deckarep/golang-set"
 )
 
 var sf *Sonyflake
@@ -38,34 +36,28 @@ func nextID(t *testing.T) uint64 {
 }
 
 func TestSonyflakeOnce(t *testing.T) {
-	sleepTime := uint64(50)
-	time.Sleep(time.Duration(sleepTime) * 10 * time.Millisecond)
+	sleepTime := time.Duration(50 * sonyflakeTimeUnit)
+	time.Sleep(sleepTime)
 
 	id := nextID(t)
-	parts := Decompose(id)
 
-	actualMSB := parts["msb"]
-	if actualMSB != 0 {
-		t.Errorf("unexpected msb: %d", actualMSB)
-	}
-
-	actualTime := parts["time"]
-	if actualTime < sleepTime || actualTime > sleepTime+1 {
+	actualTime := ElapsedTime(id)
+	if actualTime < sleepTime || actualTime > sleepTime+sonyflakeTimeUnit {
 		t.Errorf("unexpected time: %d", actualTime)
 	}
 
-	actualSequence := parts["sequence"]
+	actualSequence := SequenceNumber(id)
 	if actualSequence != 0 {
 		t.Errorf("unexpected sequence: %d", actualSequence)
 	}
 
-	actualMachineID := parts["machine-id"]
+	actualMachineID := MachineID(id)
 	if actualMachineID != machineID {
 		t.Errorf("unexpected machine id: %d", actualMachineID)
 	}
 
 	fmt.Println("sonyflake id:", id)
-	fmt.Println("decompose:", parts)
+	fmt.Println("decompose:", Decompose(id))
 }
 
 func currentTime() int64 {
@@ -139,16 +131,15 @@ func TestSonyflakeInParallel(t *testing.T) {
 		go generate()
 	}
 
-	set := mapset.NewSet()
+	set := make(map[uint64]struct{})
 	for i := 0; i < numID*numGenerator; i++ {
 		id := <-consumer
-		if set.Contains(id) {
+		if _, ok := set[id]; ok {
 			t.Fatal("duplicated id")
-		} else {
-			set.Add(id)
 		}
+		set[id] = struct{}{}
 	}
-	fmt.Println("number of id:", set.Cardinality())
+	fmt.Println("number of id:", len(set))
 }
 
 func TestNilSonyflake(t *testing.T) {
@@ -190,3 +181,9 @@ func TestNextIDError(t *testing.T) {
 		t.Errorf("time is not over")
 	}
 }
+
+func TestSonyflakeTimeUnit(t *testing.T) {
+	if time.Duration(sonyflakeTimeUnit) != 10*time.Millisecond {
+		t.Errorf("unexpected time unit")
+	}
+}