in-memory tar in Go

tar_reader.go

package main

import (
	"archive/tar"
	"fmt"
	"io"
	"os"
	"strings"
	"testing/fstest"
)

func MustReadTar(content string) fstest.MapFS {
	contentReader := strings.NewReader(content)
	tarReader := tar.NewReader(contentReader)
	fs := make(fstest.MapFS)
	for {
		file, err := tarReader.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			panic(err)
		}
		if file.Typeflag != tar.TypeReg {
			continue
		}
		data, err := io.ReadAll(tarReader)
		if err != nil {
			panic(err)
		}
		fs[file.Name] = &fstest.MapFile{Data: data}
	}
	return fs
}

func main() {
	// open tar-example.tar
	file, err := os.Open("tar-example.tar")
	if err != nil {
		panic(err)
	}
	defer file.Close()
	// read file content as string
	content, err := io.ReadAll(file)
	if err != nil {
		panic(err)
	}
	fs := MustReadTar(string(content))
	fmt.Println(fs)
	hello, err := fs.ReadFile("tar-example/subdirectory/hello.txt")
	if err != nil {
		panic(err)
	}
	fmt.Println(string(hello))
}

test-tar-reader.sh

#!/usr/bin/env bash

mkdir -p tar-example/subdirectory
tar cf tar-example.tar tar-example
go run tar_reader.go