trans-shiftjis.go

package main

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"log"
	"os"

	"golang.org/x/text/encoding/japanese"
	"golang.org/x/text/transform"
)

func main() {
	if len(os.Args) < 2 {
		fmt.Printf("Usage: %s file\n", os.Args[0])
		return
	}
	filename := os.Args[1]

	f, err := os.Open(filename)
	if err != nil {
		log.Fatalf("failed to open: %v", err)
	}
	defer f.Close()

	r := transform.NewReader(f, japanese.ShiftJIS.NewDecoder())

	// Dump to STDOUT
	//_, err = io.Copy(os.Stdout, r)
	//if err != nil {
	//	log.Fatalf("failed to copy: %v\n", err)
	//}

	b, err := ioutil.ReadAll(r)
	if err != nil {
		log.Fatalf("failed to read: %v\n", err)
	}

	// Check replacement rune exists.
	// https://godoc.org/golang.org/x/text/encoding#Decoder
	n := bytes.Index(b, []byte("\ufffd"))
	if n != -1 {
		fmt.Printf("replacement rune found at %d\n", n)
	}
}