read and write tar files/archives

tar_example.go

package main

import (
	"archive/tar"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"os"
)

// test dataset
var data = map[string]interface{}{
	"foo_1": map[string]interface{}{"id": 1, "prefix": "foo", "active": false, "link": []int{0, 2}},
	"foo_2": map[string]interface{}{"id": 2, "prefix": "foo", "active": true, "link": []int{1, 3}},
	"foo_3": map[string]interface{}{"id": 3, "prefix": "foo", "active": false, "link": []int{2, 4}},
	"foo_4": map[string]interface{}{"id": 4, "prefix": "foo", "active": true, "link": []int{3, 5}},
	"foo_5": map[string]interface{}{"id": 5, "prefix": "foo", "active": false, "link": []int{4}},
}

// write tar
func DumpTar(name string, dat map[string]interface{}) {
	fd, err := os.OpenFile(name, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0755)
	if err != nil {
		log.Fatalln(err)
	}
	tw := tar.NewWriter(fd)
	for name, contents := range dat {
		body, err := json.MarshalIndent(contents, "", "    ")
		if err != nil {
			log.Fatalln(err)
		}
		hdr := &tar.Header{
			Name: name,
			Size: int64(len(body)),
		}
		if err := tw.WriteHeader(hdr); err != nil {
			log.Fatalln(err)
		}
		if _, err := tw.Write(body); err != nil {
			log.Fatalln(err)
		}
	}
	if err := tw.Close(); err != nil {
		log.Fatalln(err)
	}
	if err := fd.Close(); err != nil {
		log.Fatal(err)
	}
}

func LoadTar(name string) map[string]interface{} {
	fd, err := os.OpenFile(name, os.O_RDONLY, 0755)
	if err != nil {
		log.Fatalln(err)
	}
	tr := tar.NewReader(fd)
	var dat = make(map[string]interface{})
	for {
		hdr, err := tr.Next()
		if err == io.EOF {
			break
		} else if err != nil {
			log.Fatalln(err)
		}
		var body interface{}
		if err := json.NewDecoder(tr).Decode(&body); err != nil {
			log.Fatalln(err)
		}
		dat[hdr.Name] = body
	}
	return dat
}

func main() {

	DumpTar("data.tar", data)
	fmt.Println("dump tar: complete")
	hmm := LoadTar("data.tar")
	fmt.Println("load tar: complete")
	fmt.Println(hmm["foo_3"])
}