Merge pull request #681 from devlights/add-sync-oncevalue-example

Add sync.OnceValue example

Author: devlights

examples/basic/syncs/README.md

@@ -15,3 +15,4 @@
 |use\_mutex.go|syncs\_use\_mutex|sync.Mutex のサンプルです|
 |use\_once.go|syncs\_use\_once|sync.Onceのサンプルです|
 |use\_oncefunc.go|syncs\_use\_oncefunc|Go 1.21 で追加された sync.OnceFunc() のサンプルです|
+|use\_oncevalue.go|syncs\_use\_oncevalue|Go 1.21 で追加された sync.OnceValue() のサンプルです|

examples/basic/syncs/examples.go

@@ -24,4 +24,5 @@ func (r *register) Regist(m mapping.ExampleMapping) {
 	m["syncs_use_map"] = UseMap
 	m["syncs_use_once"] = UseOnce
 	m["syncs_use_oncefunc"] = UseOnceFunc
+	m["syncs_use_oncevalue"] = UseOnceValue
 }

examples/basic/syncs/use_oncefunc.go

@@ -45,4 +45,35 @@ func UseOnceFunc() error {
 	output.Stdoutl("[after]", v)
 
 	return nil
+
+	/*
+	   $ task
+	   task: [build] go build .
+	   task: [run] ./try-golang -onetime
+
+	   ENTER EXAMPLE NAME: syncs_use_oncefunc
+
+	   [Name] "syncs_use_oncefunc"
+	   [before]             0
+	   [done]               goroutine-15
+	   [done]               goroutine-10
+	   [done]               goroutine-3
+	   [done]               goroutine-0
+	   [done]               goroutine-11
+	   [done]               goroutine-14
+	   [done]               goroutine-6
+	   [done]               goroutine-1
+	   [done]               goroutine-2
+	   [done]               goroutine-5
+	   [done]               goroutine-12
+	   [done]               goroutine-4
+	   [done]               goroutine-7
+	   [done]               goroutine-8
+	   [done]               goroutine-9
+	   [done]               goroutine-13
+	   [after]              1
+
+
+	   [Elapsed] 563.92µs
+	*/
 }

examples/basic/syncs/use_oncevalue.go

@@ -0,0 +1,81 @@
+package syncs
+
+import (
+	"runtime"
+	"sync"
+
+	"github.com/devlights/gomy/output"
+)
+
+// UseOnceValue は、Go 1.21 で追加された sync.OnceValue() のサンプルです。
+//
+// # REFERENCES
+//   - https://pkg.go.dev/sync@go1.21.4#OnceValue
+func UseOnceValue() error {
+	//
+	// Go 1.21 にて、sync.OnceValue() が追加された
+	// 元々存在していた、sync.Once を使いやすくした感じ
+	// 値を返却する関数を使える
+	//
+
+	var (
+		v = 0
+		f = sync.OnceValue(func() int {
+			v++
+			return v
+		})
+	)
+	output.Stdoutl("[before]", v)
+
+	var (
+		numCpu = runtime.NumCPU()
+		done   = make(chan bool, numCpu)
+	)
+	for i := 0; i < numCpu; i++ {
+		i := i
+		go func() {
+			result := f()
+			done <- true
+			output.Stderrf("[done]", "result=%d\tgoroutine-%d\n", result, i)
+		}()
+	}
+
+	for i := 0; i < numCpu; i++ {
+		<-done
+	}
+
+	output.Stdoutl("[after]", v)
+
+	return nil
+
+	/*
+		$ task
+		task: [build] go build .
+		task: [run] ./try-golang -onetime
+
+		ENTER EXAMPLE NAME: syncs_use_oncevalue
+
+		[Name] "syncs_use_oncevalue"
+		[before]             0
+		[done]               result=1   goroutine-5
+		[done]               result=1   goroutine-11
+		[done]               result=1   goroutine-4
+		[done]               result=1   goroutine-3
+		[done]               result=1   goroutine-2
+		[done]               result=1   goroutine-12
+		[done]               result=1   goroutine-14
+		[done]               result=1   goroutine-7
+		[done]               result=1   goroutine-6
+		[done]               result=1   goroutine-8
+		[done]               result=1   goroutine-0
+		[done]               result=1   goroutine-1
+		[done]               result=1   goroutine-9
+		[done]               result=1   goroutine-13
+		[done]               result=1   goroutine-15
+		[done]               result=1   goroutine-10
+		[after]              1
+
+
+		[Elapsed] 640.98µs
+	*/
+}