Deno: Processing tar archive results in checksum error (Standard Library) - tar

Question

I would like to process a tar archive with help of tar.ts from Standard Library.
The archive can be written successfully to test.tar by following code:
import { Tar, Untar } from "https://deno.land/std/archive/tar.ts";
// create tar archive
const tar = new Tar();
const content = new TextEncoder().encode("hello tar world!");
await tar.append("output.txt", {
reader: new Deno.Buffer(content),
contentSize: content.byteLength,
});
await Deno.writeFile("./test.tar", tar.out);
However, reading the tar triggers an error:
error: Uncaught Error: checksum error
throw new Error("checksum error");
--------^
at Untar.extract (https://deno.land/std/archive/tar.ts:432:13)
at async file:///C:/Users/bela/Desktop/script/test.ts:23:16
The code:
// read from tar archive
const untar = new Untar(await Deno.open("./test.tar"));
const buf = new Deno.Buffer();
const result = await untar.extract(buf); // <-- this line triggers error
const untarText = new TextDecoder("utf-8").decode(buf.bytes());
Where did I miss a step?

Answer 1

You have to use tar.getReader() to get the correct tar content.
const tar = new Tar();
const content = new TextEncoder().encode("hello tar world!");
await tar.append("output.txt", {
reader: new Deno.Buffer(content),
contentSize: content.byteLength,
});
const writer = await Deno.open("./test.tar", { write: true, create: true });
await Deno.copy(tar.getReader(), writer);
const untar = new Untar(await Deno.open("./test.tar", { read: true }));
const buf = new Deno.Buffer();
const result = await untar.extract(buf); // <-- this line triggers error
const untarText = new TextDecoder("utf-8").decode(buf.bytes());
console.log(untarText);
tar.out is currently a zero-filled Uint8Array which appears to be a bug in the std code