Merge pull request #767 from devlights/add-binary-to-struct-example

Author: devlights

examples/singleapp/cast_bytearray_to_struct/README.md

@@ -0,0 +1,3 @@
+# これは何？
+
+C言語のようにバイト配列を構造体にキャストするサンプルです。

examples/singleapp/cast_bytearray_to_struct/Taskfile.yml

@@ -0,0 +1,8 @@
+# https://taskfile.dev
+
+version: '3'
+
+tasks:
+  default:
+    cmds:
+      - go run main.go

examples/singleapp/cast_bytearray_to_struct/main.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+	"unsafe"
+)
+
+type ST struct {
+	V1    int32
+	V2    uint32
+	V3    [10]byte
+	Dummy [6]byte
+}
+
+func (me *ST) String() string {
+	return fmt.Sprintf("V1=%d, V2=%d, V3=%s, Dummy=%v\n", me.V1, me.V2, string(me.V3[:]), me.Dummy)
+}
+
+func main() {
+	//
+	// バイト列を作成
+	//
+	var (
+		buf bytes.Buffer
+		bin []byte
+	)
+
+	binary.Write(&buf, binary.LittleEndian, int32(127))
+	binary.Write(&buf, binary.LittleEndian, uint32(255))
+	buf.WriteString("helloworld")
+	buf.Write(make([]byte, 6))
+
+	bin = buf.Bytes()
+	fmt.Println(hex.Dump(bin))
+
+	//
+	// 構造体にキャスト
+	//
+	var (
+		ptr unsafe.Pointer
+		st  *ST
+	)
+
+	ptr = unsafe.Pointer(&bin[0])
+	st = (*ST)(ptr)
+
+	fmt.Printf("%v\n", st)
+
+	/*
+	   00000000  7f 00 00 00 ff 00 00 00  68 65 6c 6c 6f 77 6f 72  |........hellowor|
+	   00000010  6c 64 00 00 00 00 00 00                           |ld......|
+
+	   V1=127, V2=255, V3=helloworld, Dummy=[0 0 0 0 0 0]
+	*/
+
+}