HepMC3/src/HepMC3Metadata.cpp

0001 // This file is part of the ACTS project.
0002 //
0003 // Copyright (C) 2016 CERN for the benefit of the ACTS project
0004 //
0005 // This Source Code Form is subject to the terms of the Mozilla Public
0006 // License, v. 2.0. If a copy of the MPL was not distributed with this
0007 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
0008
0009 #include "ActsExamples/Io/HepMC3/HepMC3Metadata.hpp"
0010
0011 #include "Acts/Utilities/Logger.hpp"
0012
0013 #include <fstream>
0014
0015 #include <nlohmann/json.hpp>
0016
0017 namespace ActsExamples::HepMC3Metadata {
0018
0019 static const std::string kEventCountKey = "num_events";
0020
0021 std::filesystem::path getSidecarPath(const std::filesystem::path& hepmc3File) {
0022   return hepmc3File.string() + ".json";
0023 }
0024
0025 std::optional<HepMC3Metadata> readSidecar(
0026     const std::filesystem::path& hepmc3File) {
0027   auto sidecarPath = getSidecarPath(hepmc3File);
0028
0029   if (!std::filesystem::exists(sidecarPath)) {
0030     return std::nullopt;
0031   }
0032
0033   try {
0034     std::ifstream file(sidecarPath);
0035     if (!file.is_open()) {
0036       return std::nullopt;
0037     }
0038
0039     nlohmann::json j;
0040     file >> j;
0041
0042     if (!j.contains(kEventCountKey) ||
0043         !j[kEventCountKey].is_number_unsigned()) {
0044       return std::nullopt;
0045     }
0046
0047     return HepMC3Metadata{.numEvents = j[kEventCountKey].get<std::size_t>()};
0048   } catch (...) {
0049     // Any error reading or parsing the file
0050     return std::nullopt;
0051   }
0052 }
0053
0054 bool writeSidecar(const std::filesystem::path& hepmc3File,
0055                   const HepMC3Metadata& metadata, const Acts::Logger& logger) {
0056   auto sidecarPath = getSidecarPath(hepmc3File);
0057   ACTS_DEBUG("Writing HepMC3 sidecar metadata to " << sidecarPath);
0058
0059   try {
0060     nlohmann::json j;
0061     j[kEventCountKey] = metadata.numEvents;
0062
0063     std::ofstream file(sidecarPath);
0064     if (!file.is_open()) {
0065       ACTS_DEBUG("Failed to open sidecar file for writing: " << sidecarPath);
0066       return false;
0067     }
0068
0069     file << j.dump(2);  // Pretty print with 2-space indent
0070     return file.good();
0071   } catch (...) {
0072     ACTS_DEBUG("Failed to write sidecar metadata file: " << sidecarPath);
0073     // Silent failure - directory might not be writable
0074     return false;
0075   }
0076 }
0077
0078 }  // namespace ActsExamples::HepMC3Metadata