Implementation of an alternative Builder which impl io::Read

[ph0llux]

Hi,

I have implemented an alternative Builder (I've named it "Streamer", but I'm not very good at such naming, so feel free to suggest something more appropriate 😄 ) which implements io::Read.

How does it work?

You build a streamer, then add your stuff (e.g. some paths to files) and then "read" the archive. You don't need an underlying writer, you can use it directly as a reader.
Here is a code example:

use std::path::PathBuf;
use std::fs;
use tar::Streamer;
use std::io;

fn main() {
    let mut streamer = Streamer::new();
    // Use the directory at one location, but insert it into the archive
    // with a different name.
    streamer.append_dir_all("my_download_dir", "/home/ph0llux/Downloads").unwrap();
    // Write the archive to the given path.
    let mut target_archive = fs::File::create("/home/ph0llux/my_downloads.tar").unwrap();
    io::copy(&mut streamer, &mut target_archive).unwrap();
}

The biggest question: Why?

Yes... my personal use case was the use of the Rocket-library - I had to build a TAR archive from some files which are on a web server and then offer that directly for download.
Since the files are very large, I always had to "write" the tar archive to the web server first and then I could offer it for download.
With the streamer I can offer it directly as a data stream and let it "build on-the-fly" during the download.
But there may be other use-cases, also.

When will I get an I/O error?

Mostly while reading the archive.

Additional Notes

• I tried to recreate the "public API" of the [Builder] as far as possible in the [Streamer]. I.e. if [Builder] provides an append_data(), [Streamer] does the same.
• No code review of a third person has occurred to yet.