UniqueID.h

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#pragma once
 
#include "MantidNexus/DllConfig.h"
#include "MantidNexus/NexusFile_fwd.h"
 
// Forward declarations for needed HDF5 functions
// NOTE declare extern "C" to prevent conflict with actual declaration
// NOTE use MYH5DLL, set to match HDF5's H5_DLL, to allow Windows build
#if defined(_MSC_VER) // on Windows builds
#define MYH5DLL __declspec(dllimport)
#else
#define MYH5DLL // gcc and clang do not need a DLL specifier
#endif
extern "C" {
MYH5DLL herr_t H5Iis_valid(hid_t);
MYH5DLL herr_t H5Fclose(hid_t);
MYH5DLL herr_t H5garbage_collect();
}
 
namespace Mantid::Nexus {
 
template <herr_t (*const D)(hid_t)> class UniqueID {
protected:
  hid_t m_id;
 
private:
  UniqueID(UniqueID<D> const &uid) = delete;
  UniqueID &operator=(UniqueID<D> const &) = delete;
  void close();
 
public:
  // constructors / destructor
  UniqueID() : m_id(INVALID_ID) {}
  UniqueID(hid_t const id) : m_id(id) {}
  ~UniqueID() { close(); }
  UniqueID(UniqueID<D> &&uid) noexcept : m_id(uid.m_id) { uid.m_id = INVALID_ID; }
 
  // assignment
  UniqueID<D> &operator=(hid_t const id);
  UniqueID<D> &operator=(UniqueID<D> &&uid);
 
  // comparators
  bool operator==(int const id) const { return static_cast<int>(m_id) == id; }
  bool operator<=(int const id) const { return static_cast<int>(m_id) <= id; }
  bool operator<(int const id) const { return static_cast<int>(m_id) < id; }
 
  // using the id
  operator hid_t() const { return m_id; }
 
  hid_t get() const { return m_id; }
 
  hid_t release();
  void reset(hid_t const id = INVALID_ID);
  bool isValid() const;
 
  static hid_t constexpr INVALID_ID{-1};
};
 
template <herr_t (*const D)(hid_t)> inline bool UniqueID<D>::isValid() const {
  // fail early condition
  if (m_id < 0) {
    return false;
  } else {
    return H5Iis_valid(m_id) > 0;
  }
}
 
template <herr_t (*const deleter)(hid_t)> inline void UniqueID<deleter>::close() {
  if (isValid()) {
    deleter(this->m_id);
    this->m_id = INVALID_ID;
  }
}
 
template <> inline void UniqueID<&H5Fclose>::close() {
  if (isValid()) {
    H5Fclose(this->m_id);
    this->m_id = INVALID_ID;
    // call garbage collection to close any and all open objects on this file
    H5garbage_collect();
  }
}
 
template <herr_t (*const D)(hid_t)> inline hid_t UniqueID<D>::release() {
  hid_t tmp = m_id;
  m_id = INVALID_ID;
  return tmp;
}
 
template <herr_t (*const D)(hid_t)> inline void UniqueID<D>::reset(hid_t const id) {
  if (m_id != id) {
    close();
    m_id = id;
  }
}
 
template <herr_t (*const D)(hid_t)> inline UniqueID<D> &UniqueID<D>::operator=(hid_t const id) {
  reset(id);
  return *this;
}
 
template <herr_t (*const D)(hid_t)> inline UniqueID<D> &UniqueID<D>::operator=(UniqueID<D> &&uid) {
  if (this != &uid) {
    reset(uid.m_id);
    uid.m_id = INVALID_ID;
  }
  return *this;
}
 
} // namespace Mantid::Nexus