Communicator.h

// -*- tab-width: 2; indent-tabs-mode: nil; coding: utf-8-with-signature -*-
//-----------------------------------------------------------------------------
// Copyright 2000-2026 CEA (www.cea.fr) IFPEN (www.ifpenergiesnouvelles.com)
// See the top-level COPYRIGHT file for details.
// SPDX-License-Identifier: Apache-2.0
//-----------------------------------------------------------------------------
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/* Communicator.h                                              (C) 2000-2025 */
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/* Communicator for message exchange.                                        */
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#ifndef ARCCORE_MESSAGEPASSING_COMMUNICATOR_H
#define ARCCORE_MESSAGEPASSING_COMMUNICATOR_H
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#include "arccore/message_passing/MessagePassingGlobal.h"
#include "arccore/base/Ref.h"
 
#include <cstddef>
#include <iosfwd>
 
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namespace Arcane::MessagePassing
{
 
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/*!
 * \brief Communicator for message exchange.
 *
 * This class is an abstraction of the communicator found
 * in the MPI standard under the type 'MPI_Comm'.
 *
 * This class allows generically storing a communicator without
 * knowing its exact type (for example MPI_Comm with the MPI standard). We use
 * a union for this purpose.
 *
 * Before using an instance of this class, the null communicator must be set
 * by calling the static method setNullCommunicator() with the null communicator
 * value for the implementation used.
 */
class ARCCORE_MESSAGEPASSING_EXPORT Communicator
{
  union _Communicator
  {
    int i;
    long l;
    std::size_t st;
    void* v;
    const void* cv;
  };
 
  enum Type
  {
    T_Int,
    T_Long,
    T_SizeT,
    T_Ptr,
    T_Null
  };
 
 public:
 
  Communicator()
  {
    m_type = T_Null;
    m_communicator = null_communicator;
  }
 
 public:
 
  explicit Communicator(void* acommunicator)
  {
    m_type = T_Ptr;
    m_communicator.v = acommunicator;
  }
 
  explicit Communicator(const void* acommunicator)
  {
    m_type = T_Ptr;
    m_communicator.cv = acommunicator;
  }
 
  explicit Communicator(int acommunicator)
  {
    m_type = T_Int;
    m_communicator.i = acommunicator;
  }
 
  explicit Communicator(long acommunicator)
  {
    m_type = T_Long;
    m_communicator.l = acommunicator;
  }
 
  explicit Communicator(std::size_t acommunicator)
  {
    m_type = T_SizeT;
    m_communicator.st = acommunicator;
  }
 
 public:
 
  template <typename T>
  operator const T*() const { return (const T*)m_communicator.cv; }
  template <typename T>
  operator T*() const { return (T*)m_communicator.v; }
  operator int() const { return m_communicator.i; }
  operator long() const { return m_communicator.l; }
  operator size_t() const { return m_communicator.st; }
  void* communicatorAddress() { return &m_communicator; }
 
 public:
 
  /*!
   * \brief Indicates if the communicator is valid.
   *
   * A communicator is valid if it is different from the null communicator.
   */
  bool isValid() const
  {
    if (m_type == T_Null)
      return false;
    // If the request type is different from the null request type,
    // then the request is considered valid.
    if (m_type != null_communicator_type)
      return true;
    if (m_type == T_Int)
      return m_communicator.i != null_communicator.i;
    if (m_type == T_Long)
      return m_communicator.l != null_communicator.l;
    if (m_type == T_SizeT)
      return m_communicator.st != null_communicator.st;
    if (m_type == T_Ptr)
      return m_communicator.cv != null_communicator.cv;
    return false;
  }
 
  static void setNullCommunicator(Communicator r)
  {
    null_communicator = r.m_communicator;
    null_communicator_type = r.m_type;
  }
 
  void reset()
  {
    m_communicator = null_communicator;
    m_type = T_Null;
  }
 
  void print(std::ostream& o) const;
 
  friend inline std::ostream& operator<<(std::ostream& o, const Communicator& pcommunicator)
  {
    pcommunicator.print(o);
    return o;
  }
 
  //! \internal
  Int32 _type() const { return m_type; }
 
 private:
 
  int m_type = T_Null;
  _Communicator m_communicator;
  static _Communicator null_communicator;
  static int null_communicator_type;
};
 
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} // namespace Arcane::MessagePassing
 
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#endif