odbtest/test/shm/shm_r.go

package main
 
import(
	"fmt"
	"time"
	"unsafe"
	//"strings"
	"github.com/hidez8891/shm"
)

const SHM_NAME = "my_shm"
const SHM_SIZE = 4 * 1000 * 1000

type MyData struct {
    ss 		string
	ii		int
}

//https://stackoverflow.com/questions/16330490/in-go-how-can-i-convert-a-struct-to-a-byte-array

func main() {

	/*w, err := shm.Create("aaa", 64)
	if err != nil {
		fmt.Printf("fail: create shared memroy %v", err)
	}
	
	data := []byte( strings.Repeat("a", 63) )
	n, err := w.WriteAt(data, 0)
	if err != nil {
		fmt.Printf("fail: write shared memroy %v", err)
	}
	
	fmt.Println("wn==>%d", n)*/
	
	r, err := shm.Open(SHM_NAME, SHM_SIZE)
	if err != nil {
		fmt.Printf("fail: open shared memroy %v", err)
	}
	
	const sz = int( unsafe.Sizeof( MyData{} ) )
	
	buf := make([]byte, sz)
	n, err := r.ReadAt(buf, 0)
	if err != nil {
		fmt.Printf("fail: read shared memroy %v", err)
	}
	
	data := *(**MyData)(unsafe.Pointer(&buf))
	fmt.Printf("n==> %d, ss==>%s, ii==>%d \n", n, data.ss, data.ii)
	
	r.Close()
	
	time.Sleep(time.Duration(30)*time.Second)
	
	//w.Close()
	
}