Project Overview

Go4 (GSI Online Offline Object Oriented) is a C++ framework for experiment data processing, developed at the EE department of GSI Helmholtz Centre for Heavy Ion Research. It provides infrastructure for online and offline analysis of experimental physics data.

Version: v6.4.0 (build 60400), March 2025
License: GNU General Public License v2 or later
Language: C++ (.cxx / .h files)
Build System: CMake (minimum 3.10)
Dependencies: ROOT >= 6.28, Qt5 >= 5.12 or Qt6 >= 6.4
Total Source Files: ~965 (.cxx, .h, .cpp, .hpp)

Architecture

The project follows a modular library architecture with clear dependency layers:

Dependency Layers

Layer 1 (Base):     Go4LockGuard, Go4Log, Go4Exceptions, Go4CommandsBase, Go4StatusBase
                           ↓
Layer 2 (Core):     Go4Base (aggregates Layer 1 + ROOT dict)
                           ↓
Layer 3 (Thread):   Go4ThreadManager
                           ↓
Layer 4 (Task):     Go4Socket, Go4Queue, Go4TaskHandler, Go4CommandsTaskHandler
                           ↓
Layer 5 (AnalBase): Go4Event, Go4EventServer, Go4ConditionsBase, Go4DynamicList,
                    Go4StatusAnalysis, Go4Analysis, MbsAPIbase, Go4HDF5 (optional)
                           ↓
Layer 6 (Analysis): MbsAPI, RawAPI (optional), Go4HistogramServer,
                    Go4CommandsAnalysis, Go4AnalysisClient, Go4Http (optional)
                           ↓
Layer 7 (GUI):      Go4ObjectManager, Go4Display, Go4Proxies → qt4/

Key Directories

Directory	Purpose
Go4Base*	Foundation modules (logging, exceptions, commands, status)
Go4ThreadManager	Thread pool and task scheduling
Go4TaskHandler	Client-server task management via sockets
Go4Analysis*	Core analysis framework (steps, events, conditions)
Go4Commands*	Command pattern implementations for remote control
Go4ConditionsBase	Data visualization conditions (polygon, window, etc.)
Go4Dict	ROOT dictionary linkdef headers
qt4/	Qt GUI applications (go4gui, web interface)
Go4Example*/	Example analysis implementations
cmake/modules/	Custom CMake macros and modules
python/go4py/	Python bindings
MbsAPI/	MBS event format reader API

Coding Conventions

File Naming

Headers: TModule-name.h (e.g., TGo4AnalysisStep.h)
Sources: TModule-name.cxx (e.g., TGo4AnalysisStep.cxx)
Class names match header file names with T prefix convention

Class Naming

All Go4 classes prefixed with TGo4 (e.g., TGo4Analysis, TGo4Command)
Inheritance naming: append role descriptor (e.g., TGo4AnalysisImp, TGo4AnalysisManager)
Commander pattern: TGo4Com<action> (e.g., TGo4ComStart, TGo4ComQuit)

Header Style

Include guard format: TMODULENAME_H (uppercase)
Go4 header includes use bare names: #include "TGo4Log.h" (no path)
All headers are copied to ${BUILD_DIR}/include/ during build

File Header Block

Every source and header file starts with:

// $Id$
//-----------------------------------------------------------------------
//       The GSI Online Offline Object Oriented (Go4) Project
//         Experiment Data Processing at EE department, GSI
//-----------------------------------------------------------------------
// Copyright (C) 2000- GSI Helmholtzzentrum fuer Schwerionenforschung GmbH
//                     Planckstr. 1, 64291 Darmstadt, Germany
// Contact:            http://go4.gsi.de
//-----------------------------------------------------------------------
// This software can be used under the license agreements as stated
// in Go4License.txt file which is part of the distribution.
//-----------------------------------------------------------------------

Code Style

Tabs for indentation
Opening braces on same line for functions/classes
Pointer/reference with type: const char* ptr, int& ref
No trailing semicolons after namespace blocks

Build System

CMake Macros (from cmake/modules/Go4Macros.cmake)

Macro	Purpose
GO4_SOURCES(libname HEADERS h1 SOURCES s1)	Register source/header files for a library
GO4_STANDARD_LIBRARY(name LINKDEF ... DEPENDENCIES ...)	Create a Go4 shared library with ROOT dictionary
GO4_USER_ANALYSIS(HEADERS h1 SOURCES s1 LINKDEF l)	Build user analysis library
GO4_INSTALL_HEADERS(h1 h2 ...)	Copy headers to build include directory
GO4_LINK_LIBRARY(name SOURCES s1 LIBRARIES l1 DEFINITIONS d1)	Create a shared library without ROOT dict

Common CMake Options

cmake - Dhdf5=ON    # Enable HDF5 support
cmake -Dqt6=ON      # Use Qt6 instead of Qt5
cmake -Dgui=ON      # Build GUI components
cmake -Dexamples=ON # Build example projects
cmake -Ddabc=ON     # Enable DABC integration

Build Commands

mkdir build && cd build
cmake <path_to_source>
make -j$(nproc)
source go4login        # Set environment variables

Development Guidelines

Adding a New Module

Create directory Go4<Name>/ with CMakeLists.txt
Add Module.mk for legacy Make support
Use GO4_SOURCES to register files in the parent CMakeLists.txt
Include in appropriate layer's library build

Adding a New Command

Create TGo4Com<action>.h and TGo4Com<action>.cxx in appropriate Go4Commands*/ directory
Inherit from TGo4Command base class
Override Execute() method
Register in command list's CreateCommands() method

Adding a New Analysis Step

Create step class inheriting TGo4AnalysisStep
Override Init(), FillData(), ResetLoop(), ResetResults()
Register in user analysis library's CMakeLists.txt

ROOT Dictionary Generation

Headers included in LINKDEF files get dictionary generation via ROOT_GENERATE_DICTIONARY. All public API headers that need interpreter access must be listed in the corresponding Go4Dict/Go4*LinkDef.h.

Platform Support

Platform	Status
openSUSE Leap/Tumbleweed	Primary development
Debian 7-11	Supported
macOS 10.14+	Supported (requires qt5web)
Windows (VS2019)	Supported
GCC 10-13	Tested

Key Environment Variables

After running source go4login:

GO4SYS — Go4 installation/build directory
GO4INC — Go4 include directory
GO4BIN — Go4 binaries directory
GO4LIB — Go4 libraries directory

Git Remotes

origin: git@g.nosp@m.ithu.nosp@m.b.com:gsi-ee/go4.git

Useful Paths

Path	Content
docs/	PDF manuals (Go4Introduction, Go4Reference, Go4FitTutorial)
etc/	Configuration files and startup scripts
macros/	ROOT macro files (.C)
html/, html5/	Web interface assets
data/test.lmd	Test data file
docker/	Docker configurations for various distros