(experimental) pure-Go ROOT I/O (but just I, not O, and only for TFile,TKey and TDirectory)

From: Sebastien Binet <binet_at_cern.ch>
Date: Wed, 6 Jun 2012 17:19:48 +0200

hi there,

following CHEP and the JSRootIO presentation (reading ROOT files w/ JavaScript, w/o ROOT installed) I wondered if I could do the same with Go :)

so here it is:
 https://bitbucket.org/binet/go-root

not everything has been implemented, so it is more a proof of concept rather than anything else: right now, the main feature is the groot-ls executable which can (recursively) dump the hierarchical structure of any ROOT file (well, it worked on all the ROOT files I tested.)

I mainly got inspiration from:

• JSRootIO [0]
• java's hep.root.io [1]
• inexlib [2] (a pure C++ header library to read/write ROOT files)

The nice thing of go-root, besides not having to install ROOT, is that I don't need to:

• first create a C/C++ object to be filled by the ROOT I/O (via SWIG or Reflex)
• then fill pure Go structures from those objects (or "go-ify" these C/C++ objects, the same process than the "pythonization" in PyROOT)

ie: there is no additional buffering.

of course, reimplementing everything is cumbersome, not to mention error prone, so...

 would there be an option which would allow me to have my cake  and eat it ?

perhaps registering custom streamers which would indicate the ROOT I/O to de-serialize, say, the TTree payload directly into the Go equivalent structures, w/o having to pass thru additional "buffering" ?

e.g. instead of de-serializing the Event payload of a TTree which consists in:
class Event {
public:

 std::string name;
 std::vector<float> px;
 std::vector<float> py;

 //...
};

one would de-serialize it into a Go struct like that: type Event struct {
  Name string
  Px []float64
  Py []float64
}

(the memory layouts of a std::string and std::vector<T> don't necessarily match Go's string and []T...)

the end-game being to get rid of the context switches b/w Go and C++, and eventually being faster than ROOT I/O (by being concurrent and parallel)
 :)

-s

[0] http://root.cern.ch/viewvc/branches/dev/bellenot/JSRootIO/
[1] http://java.freehep.org/svn/repos/freehep/list/freehep/trunk/hepio/freehep-rootio/src/main/java/?revision=HEAD&bypassEmpty=true
[2] http://inexlib.lal.in2p3.fr/

-- 
#########################################
# Dr. Sebastien Binet
# Laboratoire de l'Accelerateur Lineaire
# Universite Paris-Sud XI
# Batiment 200
# 91898 Orsay
#########################################






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Received on Wed Jun 06 2012 - 17:20:02 CEST