Add examples/basic/fileio/multiwriter/gzip_and_crc.go

Author: devlights

examples/basic/fileio/examples.go

@@ -3,6 +3,7 @@ package fileio
 import (
 	"github.com/devlights/try-golang/examples/basic/fileio/filesystem"
 	"github.com/devlights/try-golang/examples/basic/fileio/ja"
+	"github.com/devlights/try-golang/examples/basic/fileio/multiwriter"
 	"github.com/devlights/try-golang/examples/basic/fileio/readwrite"
 	"github.com/devlights/try-golang/examples/basic/fileio/stat"
 	"github.com/devlights/try-golang/examples/basic/fileio/stdinouterr"
@@ -27,4 +28,5 @@ func (r *register) Regist(m mapping.ExampleMapping) {
 	filesystem.NewRegister().Regist(m)
 	ja.NewRegister().Regist(m)
 	sync_and_close.NewRegister().Regist(m)
+	multiwriter.NewRegister().Regist(m)
 }

examples/basic/fileio/multiwriter/README.md

@@ -0,0 +1,7 @@
+# サンプルリスト
+
+このディレクトリには以下のサンプルがあります。
+
+| file            | example name                  | note                                                                           |
+| --------------- | ----------------------------- | ------------------------------------------------------------------------------ |
+| gzip_and_crc.go | fileio_multiwriter_gzipandcrc | io.MultiWriterを利用してgzip圧縮しながらCRCチェックサムも算出するサンプルです. |

examples/basic/fileio/multiwriter/examples.go

@@ -0,0 +1,21 @@
+package multiwriter
+
+import "github.com/devlights/try-golang/mapping"
+
+type (
+	register struct{}
+)
+
+var (
+	_ mapping.Register = (*register)(nil)
+)
+
+// NewRegister -- このパッケージ用のサンプルを登録する mapping.Register を生成します。
+func NewRegister() mapping.Register {
+	return new(register)
+}
+
+// Regist -- 登録します.
+func (r *register) Regist(m mapping.ExampleMapping) {
+	m["fileio_multiwriter_gzipandcrc"] = GzipAndCrc
+}

examples/basic/fileio/multiwriter/gzip_and_crc.go

@@ -0,0 +1,64 @@
+package multiwriter
+
+import (
+	"bytes"
+	"compress/gzip"
+	"encoding/hex"
+	"hash/crc32"
+	"io"
+	"os"
+
+	"github.com/devlights/gomy/output"
+)
+
+// GzipAndCrc は、io.MultiWriterを利用してgzip圧縮しながらCRCチェックサムも算出するサンプルです.
+//
+// # REFERENCES
+//
+//   - https://pkg.go.dev/io@go1.22.2#MultiWriter
+//   - https://pkg.go.dev/hash/crc32@go1.22.2#NewIEEE
+//   - https://pkg.go.dev/compress/gzip@go1.22.2#Writer
+//   - https://pkg.go.dev/encoding/hex@go1.22.2#Dumper
+func GzipAndCrc() error {
+	var (
+		data   = []byte("hello world こんにちは 世界")
+		buf    = new(bytes.Buffer)
+		gzipW  = gzip.NewWriter(buf)
+		crcW   = crc32.NewIEEE()
+		writer = io.MultiWriter(gzipW, crcW, hex.Dumper(os.Stdout))
+		err    error
+	)
+	defer gzipW.Close()
+
+	_, err = writer.Write(data)
+	if err != nil {
+		return err
+	}
+
+	output.Stdoutl("")
+	output.Stdoutf("[orig]", "%x\n", data)
+	output.Stdoutf("[gzip]", "%x\n", buf.Bytes())
+	output.Stdoutf("[crc ]", "%x\n", crcW.Sum32())
+
+	return nil
+
+	/*
+		$ task
+		task: [build] go build .
+		task: [run] ./try-golang -onetime
+
+		ENTER EXAMPLE NAME: fileio_multiwriter
+
+		[Name] "fileio_multiwriter_gzipandcrc"
+		00000000  68 65 6c 6c 6f 20 77 6f  72 6c 64 20 e3 81 93 e3  |hello world ....|
+		00000010  82 93 e3 81 ab e3 81 a1  e3 81 af 20 e4 b8 96 e7  |........... ....|
+		00000020  95 8c
+		[orig]               68656c6c6f20776f726c6420e38193e38293e381abe381a1e381af20e4b896e7958c
+		[gzip]               1f8b08000000000000ff
+		[crc ]               6535a281
+
+
+		[Elapsed] 343.1µs
+	*/
+
+}