BmnDataReader.h

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/*
    BM@N alignment routine
    BM@N experiment at NICA complex, JINR, 2025
 
    Department: Math & Soft Group of HEP lab
    Author:     Igor Polev, polev@jinr.ru
 
    BmnDataReader class header-only implementation
    Stadard interface for reading data from set of ROOT files
*/
 
#ifndef BMNDATAREADER_H
#define BMNDATAREADER_H
 
#include "TChain.h"
#include "TString.h"
#include "TTreeReader.h"
 
#include <fstream>
#include <string>
 
#define BMN_TREE_NAME_DEFAULT "bmndata"
 
class BmnDataReader
{
  public:
    BmnDataReader() = delete;
    BmnDataReader(const char* filesListPath, const char* treeName = nullptr);
    BmnDataReader(const std::string& filesListPath, const char* treeName = nullptr)
        : BmnDataReader(filesListPath.c_str(), treeName) {};
    BmnDataReader(const TString& filesListPath, const char* treeName = nullptr)
        : BmnDataReader(filesListPath.Data(), treeName) {};
    ~BmnDataReader()
    {
        if (fpDataChain)
            delete fpDataChain;
        if (fpReader)
            delete fpReader;
    }
 
    TChain& Chain() { return *fpDataChain; }
    TTreeReader& Reader() { return *fpReader; }
 
  private:
    TChain* fpDataChain{nullptr};
    TTreeReader* fpReader{nullptr};
};
 
inline BmnDataReader::BmnDataReader(const char* filePathList, const char* treeName)
{
    const char* treeNameFinal{treeName ? treeName : BMN_TREE_NAME_DEFAULT};
 
    // collect .root files into chain
    std::ifstream file(filePathList);
    if (!file.is_open())
        throw std::runtime_error(std::string("BmnDataReader: failed to open ROOT list file ") + filePathList);
    fpDataChain = new TChain(treeNameFinal);
    std::string filePath;
    while (getline(file, filePath))
        if (!fpDataChain->Add(filePath.c_str(), 0)) {
            delete fpDataChain;
            throw std::runtime_error(std::string("BmnDataReader: failed to access file ") + filePath + " or tree "
                                     + treeNameFinal + " not found");
        }
    file.close();
 
    // init reader
    fpReader = new TTreeReader{fpDataChain};
    if (-1 == fpReader->GetEntries()) {
        delete fpReader;
        delete fpDataChain;
        throw std::runtime_error(std::string("BmnDataReader: failed to init reader for ") + treeNameFinal);
    }
}
 
#endif   // BMNDATAREADER_H