https://github.com/hymkor/study-go-multi-writer
io.MultiWriter は遅いから、使わなくてもよい時は使わない方がよいというだけのリポート
https://github.com/hymkor/study-go-multi-writer
go golang multiwriter
Last synced: 24 days ago
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io.MultiWriter は遅いから、使わなくてもよい時は使わない方がよいというだけのリポート
- Host: GitHub
- URL: https://github.com/hymkor/study-go-multi-writer
- Owner: hymkor
- Created: 2023-06-12T08:18:17.000Z (almost 2 years ago)
- Default Branch: master
- Last Pushed: 2023-06-12T08:18:54.000Z (almost 2 years ago)
- Last Synced: 2025-02-10T15:50:56.535Z (3 months ago)
- Topics: go, golang, multiwriter
- Language: Go
- Homepage:
- Size: 1.95 KB
- Stars: 1
- Watchers: 1
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
io.MultiWriter は遅いから、使わなくてもよい時は使わない方がよいというだけのリポート
=====================
string とファイル（ここでは /dev/null）へ同じものを出力する
```main.go
package multi
import (
"bufio"
"io"
"strings"
)
// Multi1 - strings.Builder で string のインスタンスを作ったあと、それをファイルにも出力する
func Multi1(n int, w io.Writer) string {
var buffer strings.Builder
for i := 0; i < n; i++ {
buffer.WriteByte(byte(i))
}
s := buffer.String()
io.WriteString(w, s)
return s
}
// Multi2 - MultiWriter で、strings.Builder とファイルに同時出力
func Multi2(n int, w io.Writer) string {
var buffer strings.Builder
ww := io.MultiWriter(w, &buffer)
for i := 0; i < n; i++ {
ww.Write([]byte{byte(i)})
}
return buffer.String()
}
// Multi3 - Multi2 と同じだが、bufio でオーバーヘッドを軽減
func Multi3(n int, w io.Writer) string {
var buffer strings.Builder
bw := bufio.NewWriter(io.MultiWriter(w, &buffer))
for i := 0; i < n; i++ {
bw.WriteByte(byte(i))
}
bw.Flush()
return buffer.String()
}
```
```main_test.go
package multi_test
import (
"io"
"os"
"testing"
"github.com/hymkor/study-go-multi-writer"
)
func try(f func(int, io.Writer) string, n int) {
devNull, err := os.OpenFile(os.DevNull, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0666)
if err != nil {
panic(err.Error())
}
defer devNull.Close()
f(n, devNull)
}
func BenchmarkMulti1(b *testing.B) {
try(multi.Multi1, b.N)
}
func BenchmarkMulti2(b *testing.B) {
try(multi.Multi2, b.N)
}
func BenchmarkMulti3(b *testing.B) {
try(multi.Multi3, b.N)
}
```
### 「go test -bench . -benchmem」の結果
``` go test -bench . -benchmem |
goos: windows
goarch: amd64
pkg: github.com/hymkor/study-go-multi-writer
cpu: Intel(R) Core(TM) i5-6500T CPU @ 2.50GHz
BenchmarkMulti1-4 355637443 3.080 ns/op 5 B/op 0 allocs/op
BenchmarkMulti2-4 734821 1609 ns/op 6 B/op 1 allocs/op
BenchmarkMulti3-4 272213160 4.154 ns/op 5 B/op 0 allocs/op
PASS
ok github.com/hymkor/study-go-multi-writer 5.670s
```