Difference between revisions of "Serializing and deserializing root objects"

Revision as of 14:22, 30 June 2009

Introduction

ROOT objects can be serialized to a byte array or reconstructed from the byte array quite easily. One reason to do this might be to store or transport ROOT objects in a way not supported by ROOT itself. An example is transport of a ROOT histogram from a producer to a consumer program via the cMsg package, a publish/subscribe messaging system that will be used extensively in the Hall D online monitoring system (see section on Example Programs below).

Serialize

ROOT TMessage objects can hold serialized ROOT objects. They are filled via the write() method:

#include "TH1F.h"
#include "TMessage.h"

// create TMessage object capable of holding serialized ROOT object
TMessage *tm = new TMessage(kMESS_OBJECT);

// fill internal buffer with serialized version of some ROOT object
tm->WriteObject(some_root_object);

// get pointer to internal buffer and length
char *buffer     = tm->Buffer();
int bufferLength = tm->Length());    // in bytes

Deserialize

Example Programs

cMsgRootProducer.cc,cMsgRootConsumer.cc,Makefile Examples demonstrate transport via cMsg package.