LammpsLoader.h

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/*
** This file is part of eOn.
**
** SPDX-License-Identifier: BSD-3-Clause
**
** Copyright (c) 2010--present, eOn Development Team
** All rights reserved.
**
** Repo:
** https://github.com/TheochemUI/eOn
*/
#pragma once

 
#include "eon/DynLib.h"
 
#include <stdexcept>
#include <string>
 
#ifdef EONMPI
#include <mpi.h>
#endif
 
namespace eonc {
 
// ---------------------------------------------------------------------------
// LammpsLoader: singleton that loads liblammps function pointers at runtime
// ---------------------------------------------------------------------------
class LammpsLoader {
public:
  // LAMMPS C API function pointer types (from library.h)
  using open_no_mpi_fn = void *(*)(int, char **, void **);
  using close_fn = void (*)(void *);
  using command_fn = char *(*)(void *, const char *);
  using file_fn = void (*)(void *, const char *);
  using scatter_atoms_fn = void (*)(void *, const char *, int, int, void *);
  using extract_var_fn = void *(*)(void *, const char *, const char *);
#ifdef EONMPI
  using open_mpi_fn = void *(*)(int, char **, MPI_Comm, void **);
#endif

  static LammpsLoader &instance();
 
  // Loaded function pointers (null if library not found)
  open_no_mpi_fn open_no_mpi{nullptr};
  close_fn close{nullptr};
  command_fn command{nullptr};
  file_fn file{nullptr};
  scatter_atoms_fn scatter_atoms{nullptr};
  extract_var_fn extract_variable{nullptr};
#ifdef EONMPI
  open_mpi_fn open_mpi{nullptr};
#endif

  [[nodiscard]] bool is_loaded() const noexcept { return m_loaded; }

  [[nodiscard]] bool available() const;

  void require_loaded();
 
  LammpsLoader(const LammpsLoader &) = delete;
  LammpsLoader &operator=(const LammpsLoader &) = delete;
 
private:
  LammpsLoader() = default;
  ~LammpsLoader();
 
  void ensure_loaded();
 
  bool m_loaded{false};
  bool m_tried{false};
  dynlib::Handle m_handle{};

  template <typename Fn> Fn load_sym(const char *name) {
    return reinterpret_cast<Fn>(dynlib::sym(m_handle, name));
  }
};
 
} // namespace eonc