Release v0.14.0

Release v0.14.0 is fresh from the oven.

This release is the result of some massive work in the xrootd package thanks to Mikhail Ivchenko (a.k.a @EgorMatirov), our Google Summer of Code 2018 student.

While GSoC-2018 is now over, it's time to reflect on what Mikhail wrote:

• an almost complete xrootd client, compatible with the C++ implementation;
• xrd-fuse, a command to mount the contents of a remote XRootD server, locally;
• the beginnings of an xrootd server.

Most notably, the client package allowed to:

• to create the xrd-cp and xrd-ls commands that copy and list the contents of a remote XRootD server,
• to seamlessly read ROOT files over XRootD.

The client package handles authentication with the unix and kerberos protocols.
Unfortunately, authentication via GSI couldn't be implemented because there were no publicly available specifications for that protocol, see xrootd/xrootd#757 for more details.

Here is the final report of this year's GSoC:

• https://gist.github.com/EgorMatirov/303e4019606677d1838677a5a7145420

Thanks a lot Mikhail, hope we'll see you around :)

Another big new feature is the ability to write ROOT files, directly with go-hep/rootio.
This is still very much a work in progress, though, as only writing "empty" ROOT files or writing ROOT files with TObjStrings have been explicitly tested.
Next release should see explicit support for writing histograms and graphs.

Lastly, improvements on the build and continuous integration procedure have been applied during this release cycle:

• added AppVeyor CI, for Windows:
• added code coverage, with codecov.io:

Code coverage improvements

The following packages have been updated, with additional tests, to improve their code coverage:

• brio, csvutil, csvutil/csvdriver,
• fit, fmom,
• heppdt, hepmc, hepevt,
• hbook/ntup, hplot,
• lcio, lhef,
• rootio, sio,
• xrootd.

Still some more work is needed to bring code coverage to a saner level (from ~55% to ~70-80%.)
Help more than welcome: it's "just" a matter of creating examples and tests.

hepevt

• AsciiEncoder was renamed into simply Encoder
• AsciiDecoder was renamed into simply Decoder

rootio

As noted above, it is now possible to create ROOT files.
The rootio package has a couple of examples:

• create an empty file
• create a file with a TObjString

Here is how you would create a ROOT file with one TObjString in it:

package main

import (
	"fmt"
	"log"

	"go-hep.org/x/hep/rootio"
)

func main() {
	w, err := rootio.Create(fname)
	if err != nil {
	    log.Fatal(err)
	}
	defer w.Close()

	var (
	    k   = "my-objstring"
	    v   = rootio.NewObjString("Hello World from Go-HEP!")
	)

	err = w.Put(k, v)
	if err != nil {
	    log.Fatal(err)
	}

	fmt.Printf("wkeys: %d\n", len(w.Keys()))
	
	err = w.Close()
	if err != nil {
	    log.Fatalf("could not close file: %v", err)
	}
}

It is quite possible the API may change as we gain experience with what it ought to look like in a Go world.
e.g. it is possible that rootio.Directory.Put would get clever enough to automatically translate a Go builtin, like string, in the ROOT equivalent, say TObjString, on the fly.
Still pondering on that...

Again, still a lot of work to do on the writing side of things:

• support for TH1x,
• support for TH2x,
• support for TGraph, TGraphErrors, TGraphAsymErrors
• support for TTree (this will take some time)
• support for user-provided types.

xrootd

The xrootd/server package ships with support for the following XRootD requests:

• open, read, close,
• write, stat, truncate, sync, rename.

There is no authentication support (yet) on the server: DO NOT RUN THIS ON PUBLICLY ACCESSIBLE MACHINES :)

The xrootd package gained a new sub-command:

• xrootd/cmd/xrd-srv

$> xrd-srv -h
xrd-srv serves data from a local filesystem over the XRootD protocol. 

Usage:

 $> xrd-srv [OPTIONS] <base-dir>

Example:

 $> xrd-srv /tmp
 $> xrd-srv -addr=0.0.0.0:1094 /tmp

Options:
  -addr string
    	listen to the provided address (default "0.0.0.0:1094")

AOB

Support for Go-1.6 and Go-1.7 has been dropped.
Please upgrade to the latest and finest Go version (1.11 is around the corner, with support for Go modules.)

Another interesting possible development avenue: exposing ROOT TTrees as Apache Arrow Arrays.
This would allow for a better interoperability with that ecosystem and the tools it provides for data science and data analysis in general.
Help wanted!