MshMeshReader.cc

// -*- 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
//-----------------------------------------------------------------------------
/*---------------------------------------------------------------------------*/
/* MshMeshReader.cc                                            (C) 2000-2025 */
/*                                                                           */
/* Reading/Writing of an MSH format file.                                    */
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
#include "arcane/utils/Iostream.h"
#include "arcane/utils/StdHeader.h"
#include "arcane/utils/HashTableMap.h"
#include "arcane/utils/ValueConvert.h"
#include "arcane/utils/ITraceMng.h"
#include "arcane/utils/String.h"
#include "arcane/utils/IOException.h"
#include "arcane/utils/Collection.h"
#include "arcane/utils/Real3.h"
#include "arcane/utils/OStringStream.h"
 
#include "arcane/core/AbstractService.h"
#include "arcane/core/FactoryService.h"
#include "arcane/core/IMeshReader.h"
#include "arcane/core/IMesh.h"
#include "arcane/core/IMeshSubMeshTransition.h"
#include "arcane/core/IItemFamily.h"
#include "arcane/core/Item.h"
#include "arcane/core/ItemEnumerator.h"
#include "arcane/core/VariableTypes.h"
#include "arcane/core/IVariableAccessor.h"
#include "arcane/core/IParallelMng.h"
#include "arcane/core/MeshPartInfo.h"
#include "arcane/core/MeshUtils.h"
#include "arcane/core/ICaseMeshReader.h"
#include "arcane/core/IMeshBuilder.h"
#include "arcane/core/ItemPrinter.h"
 
// Element types in .msh file format, found in gmsh-2.0.4/Common/GmshDefines.h
#include "arcane/std/internal/IosFile.h"
#include "arcane/std/internal/IosGmsh.h"
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
// NOTE: Starting in July 2024 (version 3.13.8), the parallel version of the reader
// (MshParallelMshReader.cc) is used by default. This version will eventually be removed.
 
/*
 * NOTES:
 * - The `gmsh` library provides an 'open.py' script in the 'demos/api' directory
 *   that allows generating a '.msh' file from a '.geo'.
 * - It is also possible to use the 'gmsh' executable directly with
 *   the '-save-all' option to save a '.msh' file from a '.geo'
 *
 * TODO:
 * - read node tags (uniqueId())
 * - support partitions
 * - be able to use the 'gmsh' library directly.
 * - improve parallel reading by preventing all subdomains
 *   from reading the file (even if only subdomain 0 allocates entities)
 */
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
namespace Arcane
{
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/

class MshMeshReader
: public TraceAccessor
, public IMshMeshReader
{
 public:
 
  using eReturnType = typename IMeshReader::eReturnType;

  struct MeshV4ElementsBlock
  {
    Int32 index = 0; 
    Int32 nb_entity = 0; 
    Integer item_type = -1; 
    Int32 dimension = -1; 
    Int32 item_nb_node = 0; 
    Int32 entity_tag = -1;
    UniqueArray<Int64> uids;
    UniqueArray<Int64> connectivity;
  };

  struct MeshPhysicalName
  {
    MeshPhysicalName(Int32 _dimension, Int32 _tag, const String& _name)
    : dimension(_dimension)
    , tag(_tag)
    , name(_name)
    {}
    MeshPhysicalName() = default;
    bool isNull() const { return dimension == (-1); }
    Int32 dimension = -1;
    Int32 tag = -1;
    String name;
  };

  struct MeshPhysicalNameList
  {
    MeshPhysicalNameList()
    : m_physical_names(4)
    {}
    void add(Int32 dimension, Int32 tag, String name)
    {
      m_physical_names[dimension].add(MeshPhysicalName{ dimension, tag, name });
    }
    MeshPhysicalName find(Int32 dimension, Int32 tag) const
    {
      for (auto& x : m_physical_names[dimension])
        if (x.tag == tag)
          return x;
      return {};
    }
 
   private:
 
    UniqueArray<UniqueArray<MeshPhysicalName>> m_physical_names;
  };

  struct MeshV4EntitiesNodes
  {
    MeshV4EntitiesNodes(Int32 _tag, Int32 _physical_tag)
    : tag(_tag)
    , physical_tag(_physical_tag)
    {}
    Int32 tag;
    Int32 physical_tag;
  };

  struct MeshV4EntitiesWithNodes
  {
    MeshV4EntitiesWithNodes(Int32 _dim, Int32 _tag, Int32 _physical_tag)
    : dimension(_dim)
    , tag(_tag)
    , physical_tag(_physical_tag)
    {}
    Int32 dimension;
    Int32 tag;
    Int32 physical_tag;
  };
 
  struct MeshInfo
  {
   public:
 
    MeshInfo()
    : node_coords_map(5000, true)
    {}
 
   public:
 
    MeshV4EntitiesWithNodes* findEntities(Int32 dimension, Int32 tag)
    {
      for (auto& x : entities_with_nodes_list[dimension - 1])
        if (x.tag == tag)
          return &x;
      return nullptr;
    }
 
    MeshV4EntitiesNodes* findNodeEntities(Int32 tag)
    {
      for (auto& x : entities_nodes_list)
        if (x.tag == tag)
          return &x;
      return nullptr;
    }
 
   public:
 
    Integer nb_elements = 0;
    Integer nb_cell_node = 0;
    UniqueArray<Int32> cells_nb_node;
    UniqueArray<Int32> cells_type;
    UniqueArray<Int64> cells_uid;
    UniqueArray<Int64> cells_connectivity;
    UniqueArray<Real3> node_coords;
    HashTableMapT<Int64, Real3> node_coords_map;
    MeshPhysicalNameList physical_name_list;
    UniqueArray<MeshV4EntitiesNodes> entities_nodes_list;
    UniqueArray<MeshV4EntitiesWithNodes> entities_with_nodes_list[3];
    UniqueArray<MeshV4ElementsBlock> blocks;
  };
 
 public:
 
  explicit MshMeshReader(ITraceMng* tm)
  : TraceAccessor(tm)
  {}
 
  eReturnType readMeshFromMshFile(IMesh* mesh, const String& file_name, bool use_internal_partition) override;
 
 private:
 
  Integer m_version = 0;
 
  eReturnType _readNodesFromAsciiMshV2File(IosFile&, Array<Real3>&);
  eReturnType _readNodesFromAsciiMshV4File(IosFile&, MeshInfo& mesh_info);
  eReturnType _readNodesFromBinaryMshFile(IosFile&, Array<Real3>&);
  Integer _readElementsFromAsciiMshV2File(IosFile&, MeshInfo& mesh_info);
  Integer _readElementsFromAsciiMshV4File(IosFile&, MeshInfo& mesh_info);
  eReturnType _readMeshFromNewMshFile(IMesh*, IosFile&);
  void _allocateCells(IMesh* mesh, MeshInfo& mesh_info, bool is_read_items);
  void _allocateGroups(IMesh* mesh, MeshInfo& mesh_info, bool is_read_items);
  void _addFaceGroup(IMesh* mesh, MeshV4ElementsBlock& block, const String& group_name);
  void _addCellGroup(IMesh* mesh, MeshV4ElementsBlock& block, const String& group_name);
  void _addNodeGroup(IMesh* mesh, MeshV4ElementsBlock& block, const String& group_name);
  Integer _switchMshType(Integer, Integer&);
  void _readPhysicalNames(IosFile& ios_file, MeshInfo& mesh_info);
  void _readEntitiesV4(IosFile& ios_file, MeshInfo& mesh_info);
};
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
extern "C++" Ref<IMshMeshReader>
createMshMeshReader(ITraceMng* tm)
{
  return makeRef<IMshMeshReader>(new MshMeshReader(tm));
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
Integer MshMeshReader::
_switchMshType(Integer mshElemType, Integer& nNodes)
{
  switch (mshElemType) {
  case (IT_NullType): // used to decode IT_NullType: IT_HemiHexa7|IT_Line9
    switch (nNodes) {
    case (7):
      return IT_HemiHexa7;
    default:
      info() << "Could not decode IT_NullType with nNodes=" << nNodes;
      throw IOException("_convertToMshType", "Could not decode IT_NullType with nNodes");
    }
    break;
  case (MSH_PNT):
    nNodes = 1;
    return IT_Vertex; //printf("1-node point");
  case (MSH_LIN_2):
    nNodes = 2;
    return IT_Line2; //printf("2-node line");
  case (MSH_TRI_3):
    nNodes = 3;
    return IT_Triangle3; //printf("3-node triangle");
  case (MSH_QUA_4):
    nNodes = 4;
    return IT_Quad4; //printf("4-node quadrangle");
  case (MSH_TET_4):
    nNodes = 4;
    return IT_Tetraedron4; //printf("4-node tetrahedron");
  case (MSH_HEX_8):
    nNodes = 8;
    return IT_Hexaedron8; //printf("8-node hexahedron");
  case (MSH_PRI_6):
    nNodes = 6;
    return IT_Pentaedron6; //printf("6-node prism");
  case (MSH_PYR_5):
    nNodes = 5;
    return IT_Pyramid5; //printf("5-node pyramid");
  case (MSH_TRI_10):
    nNodes = 10;
    return IT_Heptaedron10; //printf("10-node second order tetrahedron")
  case (MSH_TRI_12):
    nNodes = 12;
    return IT_Octaedron12; //printf("Unknown MSH_TRI_12");
 
  case (MSH_TRI_6):
  case (MSH_QUA_9):
  case (MSH_HEX_27):
  case (MSH_PRI_18):
  case (MSH_PYR_14):
  case (MSH_QUA_8):
  case (MSH_HEX_20):
  case (MSH_PRI_15):
  case (MSH_PYR_13):
  case (MSH_TRI_9):
  case (MSH_TRI_15):
  case (MSH_TRI_15I):
  case (MSH_TRI_21):
  default:
    ARCANE_THROW(NotSupportedException, "Unknown GMSH element type '{0}'", mshElemType);
  }
  return IT_NullType;
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
IMeshReader::eReturnType MshMeshReader::
_readNodesFromAsciiMshV2File(IosFile& ios_file, Array<Real3>& node_coords)
{
  // number-of-nodes & coords
  info() << "[_readNodesFromAsciiMshV2File] Looking for number-of-nodes";
  Integer nb_node = ios_file.getInteger();
  if (nb_node < 0)
    throw IOException(A_FUNCINFO, String("Invalid number of nodes: n=") + nb_node);
  info() << "[_readNodesFromAsciiMshV2File] nb_node=" << nb_node;
  for (Integer i = 0; i < nb_node; ++i) {
    // Must read the ID even if it is not used.
    [[maybe_unused]] Int32 id = ios_file.getInteger();
    Real nx = ios_file.getReal();
    Real ny = ios_file.getReal();
    Real nz = ios_file.getReal();
    node_coords.add(Real3(nx, ny, nz));
    //info() << "id_" << id << " xyz(" << nx << "," << ny << "," << nz << ")";
  }
  ios_file.getNextLine(); // Skip current \n\r
  return IMeshReader::RTOk;
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
IMeshReader::eReturnType MshMeshReader::
_readNodesFromAsciiMshV4File(IosFile& ios_file, MeshInfo& mesh_info)
{
  // First line of the file
  Integer nb_entity = ios_file.getInteger();
  Integer total_nb_node = ios_file.getInteger();
  Integer min_node_tag = ios_file.getInteger();
  Integer max_node_tag = ios_file.getInteger();
  ios_file.getNextLine(); // Skip current \n\r
  if (total_nb_node < 0)
    ARCANE_THROW(IOException, "Invalid number of nodes : '{0}'", total_nb_node);
  info() << "[Nodes] nb_entity=" << nb_entity
         << " total_nb_node=" << total_nb_node
         << " min_tag=" << min_node_tag
         << " max_tag=" << max_node_tag;
 
  UniqueArray<Int32> nodes_uids;
  for (Integer i_entity = 0; i_entity < nb_entity; ++i_entity) {
    // Entity dimension (not useful)
    [[maybe_unused]] Integer entity_dim = ios_file.getInteger();
    // Entity tag (not useful)
    [[maybe_unused]] Integer entity_tag = ios_file.getInteger();
    Integer parametric_coordinates = ios_file.getInteger();
    Integer nb_node2 = ios_file.getInteger();
    ios_file.getNextLine();
 
    info(4) << "[Nodes] index=" << i_entity << " entity_dim=" << entity_dim << " entity_tag=" << entity_tag
            << " parametric=" << parametric_coordinates
            << " nb_node2=" << nb_node2;
    if (parametric_coordinates != 0)
      ARCANE_THROW(NotSupportedException, "Only 'parametric coordinates' value of '0' is supported (current={0})", parametric_coordinates);
    // It is possible that the number of nodes is 0.
    // In this case, we must directly proceed to the next line
    if (nb_node2 == 0)
      continue;
    nodes_uids.resize(nb_node2);
    for (Integer i = 0; i < nb_node2; ++i) {
      // Keep the node's uniqueId().
      nodes_uids[i] = ios_file.getInteger();
      //info() << "I=" << i << " ID=" << nodes_uids[i];
    }
    for (Integer i = 0; i < nb_node2; ++i) {
      Real nx = ios_file.getReal();
      Real ny = ios_file.getReal();
      Real nz = ios_file.getReal();
      Real3 xyz(nx, ny, nz);
      mesh_info.node_coords_map.add(nodes_uids[i], xyz);
      //info() << "I=" << i << " ID=" << nodes_uids[i] << " COORD=" << xyz;
    }
    ios_file.getNextLine(); // Skip current \n\r
  }
  return IMeshReader::RTOk;
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
Integer MshMeshReader::
_readElementsFromAsciiMshV2File(IosFile& ios_file, MeshInfo& mesh_info)
{
  Integer number_of_elements = ios_file.getInteger(); // is an integer equal to 0 in the ASCII file format, equal to 1 for the binary format
  if (number_of_elements < 0)
    ARCANE_THROW(IOException, String("Error with the number_of_elements=") + number_of_elements);
 
  info() << "nb_elements=" << number_of_elements;
 
  //elm-number elm-type number-of-tags < tag > ... node-number-list
  // Reading mesh and connectivity info
  // bool to check if we start from 0 or 1
  bool it_starts_at_zero = false;
  for (Integer i = 0; i < number_of_elements; ++i) {
    [[maybe_unused]] Integer elm_number = ios_file.getInteger(); // Index
    Integer elm_type = ios_file.getInteger(); // Type
    // info() << elm_number << " " << elm_type;
    // Now get tags in the case the number of nodes is encoded
    Integer number_of_tags = ios_file.getInteger();
    Integer lastTag = 0;
    for (Integer j = 0; j < number_of_tags; ++j)
      lastTag = ios_file.getInteger();
    Integer number_of_nodes = 0; // Set the number of nodes from the discovered type
    if (elm_type == IT_NullType) {
      number_of_nodes = lastTag;
      info() << "We hit the case the number of nodes is encoded (number_of_nodes=" << number_of_nodes << ")";
    }
    Integer cell_type = _switchMshType(elm_type, number_of_nodes);
    //#warning Skipping 2D lines & points
    // We skip 2-node lines and 1-node points
    if (number_of_nodes < 3) {
      for (Integer j = 0; j < number_of_nodes; ++j)
        ios_file.getInteger();
      continue;
    }
 
    mesh_info.cells_type.add(cell_type);
    mesh_info.cells_nb_node.add(number_of_nodes);
    mesh_info.cells_uid.add(i);
    info() << elm_number << " " << elm_type << " " << number_of_tags << " number_of_nodes=" << number_of_nodes;
    //    printf("%i %i %i %i %i (", elm_number, elm_type, reg_phys, reg_elem, number_of_nodes);
    for (Integer j = 0; j < number_of_nodes; ++j) {
      //      printf("%i ", node_number);
      Integer id = ios_file.getInteger();
      if (id == 0)
        it_starts_at_zero = true;
      mesh_info.cells_connectivity.add(id);
    }
    //    printf(")\n");
  }
  if (!it_starts_at_zero)
    for (Integer j = 0, max = mesh_info.cells_connectivity.size(); j < max; ++j)
      mesh_info.cells_connectivity[j] = mesh_info.cells_connectivity[j] - 1;
 
  ios_file.getNextLine(); // Skip current \n\r
 
  // Only 3D meshes are supported in this old format
  return 3;
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/

Integer MshMeshReader::
_readElementsFromAsciiMshV4File(IosFile& ios_file, MeshInfo& mesh_info)
{
  Integer nb_block = ios_file.getInteger();
 
  Integer number_of_elements = ios_file.getInteger(); // is an integer equal to 0 in the ASCII file format, equal to 1 for the binary format
  Integer min_element_tag = ios_file.getInteger();
  Integer max_element_tag = ios_file.getInteger();
  ios_file.getNextLine(); // Skip current \n\r
  info() << "[Elements] nb_block=" << nb_block
         << " nb_elements=" << number_of_elements
         << " min_element_tag=" << min_element_tag
         << " max_element_tag=" << max_element_tag;
 
  if (number_of_elements < 0)
    ARCANE_THROW(IOException, "Invalid number of elements: {0}", number_of_elements);
 
  UniqueArray<MeshV4ElementsBlock>& blocks = mesh_info.blocks;
  blocks.resize(nb_block);
 
  {
    // Number the blocks (for debugging)
    Integer index = 0;
    for (MeshV4ElementsBlock& block : blocks) {
      block.index = index;
      ++index;
    }
  }
  for (MeshV4ElementsBlock& block : blocks) {
    Integer entity_dim = ios_file.getInteger();
    Integer entity_tag = ios_file.getInteger(); // is an integer equal to 0 in the ASCII file format, equal to 1 for the binary format
    Integer entity_type = ios_file.getInteger();
    Integer nb_entity_in_block = ios_file.getInteger();
 
    Integer item_nb_node = 0;
    Integer item_type = _switchMshType(entity_type, item_nb_node);
 
    info(4) << "[Elements] index=" << block.index << " entity_dim=" << entity_dim
            << " entity_tag=" << entity_tag
            << " entity_type=" << entity_type << " nb_in_block=" << nb_entity_in_block
            << " item_type=" << item_type << " item_nb_node=" << item_nb_node;
 
    block.nb_entity = nb_entity_in_block;
    block.item_type = item_type;
    block.item_nb_node = item_nb_node;
    block.dimension = entity_dim;
    block.entity_tag = entity_tag;
 
    if (entity_type == MSH_PNT) {
      // If the type is a point, the processing seems
      // a bit particular. In this case, there are
      // two integers in the next line:
      // - an integer that doesn't seem
      // - the unique node number we are interested in
      [[maybe_unused]] Int64 unused_id = ios_file.getInt64();
      Int64 item_unique_id = ios_file.getInt64();
      info(4) << "Adding unique node uid=" << item_unique_id;
      block.uids.add(item_unique_id);
    }
    else {
      for (Integer i = 0; i < nb_entity_in_block; ++i) {
        Int64 item_unique_id = ios_file.getInt64();
        block.uids.add(item_unique_id);
        for (Integer j = 0; j < item_nb_node; ++j)
          block.connectivity.add(ios_file.getInt64());
      }
    }
    ios_file.getNextLine(); // Skip current \n\r
  }
  // Now that we have all the blocks, the mesh dimension is
  // the largest dimension of the blocks
  Integer mesh_dimension = -1;
  for (MeshV4ElementsBlock& block : blocks)
    mesh_dimension = math::max(mesh_dimension, block.dimension);
  if (mesh_dimension < 0)
    ARCANE_FATAL("Invalid computed mesh dimension '{0}'", mesh_dimension);
  if (mesh_dimension != 2 && mesh_dimension != 3)
    ARCANE_THROW(NotSupportedException, "mesh dimension '{0}'. Only 2D or 3D meshes are supported", mesh_dimension);
  info() << "Computed mesh dimension = " << mesh_dimension;
 
  // We only keep blocks of our dimension
  // to create the cells
  for (MeshV4ElementsBlock& block : blocks) {
    if (block.dimension != mesh_dimension)
      continue;
 
    info(4) << "Keeping block index=" << block.index;
 
    Integer item_type = block.item_type;
    Integer item_nb_node = block.item_nb_node;
 
    for (Integer i = 0; i < block.nb_entity; ++i) {
      mesh_info.cells_type.add(item_type);
      mesh_info.cells_nb_node.add(item_nb_node);
      mesh_info.cells_uid.add(block.uids[i]);
      auto v = block.connectivity.subView(i * item_nb_node, item_nb_node);
      mesh_info.cells_connectivity.addRange(v);
    }
  }
 
  return mesh_dimension;
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
/*
 * nodes-binary is the list of nodes in binary form, i.e., a array of
 * number-of-nodes *(4+3*data-size) bytes. For each node, the first 4 bytes
 * contain the node number and the next (3*data-size) bytes contain the three
 * floating point coordinates.
 */
IMeshReader::eReturnType MshMeshReader::
_readNodesFromBinaryMshFile(IosFile& ios_file, Array<Real3>& node_coords)
{
  ARCANE_UNUSED(ios_file);
  ARCANE_UNUSED(node_coords);
  return IMeshReader::RTError;
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void MshMeshReader::
_allocateCells(IMesh* mesh, MeshInfo& mesh_info, bool is_read_items)
{
  Integer nb_elements = mesh_info.cells_type.size();
  info() << "nb_of_elements=cells_type.size()=" << nb_elements;
  Integer nb_cell_node = mesh_info.cells_connectivity.size();
  info() << "nb_cell_node=cells_connectivity.size()=" << nb_cell_node;
 
  // Creating the cells
  info() << "Building cells, nb_cell=" << nb_elements << " nb_cell_node=" << nb_cell_node;
  // Info for cell creation
  // per cell: 1 for its unique id,
  //             1 for its type,
  //             1 for each node
  UniqueArray<Int64> cells_infos;
  Integer connectivity_index = 0;
  UniqueArray<Real3> local_coords;
  for (Integer i = 0; i < nb_elements; ++i) {
    Integer current_cell_nb_node = mesh_info.cells_nb_node[i];
    Integer cell_type = mesh_info.cells_type[i];
    Int64 cell_uid = mesh_info.cells_uid[i];
    cells_infos.add(cell_type);
    cells_infos.add(cell_uid); //cell_unique_id
 
    ArrayView<Int64> local_info(current_cell_nb_node, &mesh_info.cells_connectivity[connectivity_index]);
    cells_infos.addRange(local_info);
    connectivity_index += current_cell_nb_node;
  }
 
  IPrimaryMesh* pmesh = mesh->toPrimaryMesh();
  info() << "## Allocating ##";
 
  if (is_read_items)
    pmesh->allocateCells(nb_elements, cells_infos, false);
  else
    pmesh->allocateCells(0, UniqueArray<Int64>(0), false);
 
  info() << "## Ending ##";
  pmesh->endAllocate();
  info() << "## Done ##";
 
  // Positioning the coordinates
  {
    VariableNodeReal3& nodes_coord_var(pmesh->nodesCoordinates());
    bool has_map = mesh_info.node_coords.empty();
    if (has_map) {
      ENUMERATE_NODE (i, mesh->ownNodes()) {
        Node node = *i;
        nodes_coord_var[node] = mesh_info.node_coords_map.lookupValue(node.uniqueId().asInt64());
      }
      nodes_coord_var.synchronize();
    }
    else {
      ENUMERATE_NODE (node, mesh->allNodes()) {
        nodes_coord_var[node] = mesh_info.node_coords.item(node->uniqueId().asInt32());
      }
    }
  }
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void MshMeshReader::
_allocateGroups(IMesh* mesh, MeshInfo& mesh_info, bool is_read_items)
{
  Int32 mesh_dim = mesh->dimension();
  Int32 face_dim = mesh_dim - 1;
  for (MeshV4ElementsBlock& block : mesh_info.blocks) {
    Int32 block_index = block.index;
    Int32 block_dim = block.dimension;
    // Allocate a group if it has an associated physical name.
    // For this, it must already be associated with an entity.
    Int32 block_entity_tag = block.entity_tag;
    if (block_entity_tag < 0) {
      info(5) << "[Groups] Skipping block index=" << block_index << " because it has no entity";
      continue;
    }
    MeshPhysicalName physical_name;
    // For now, we do not process clouds
    if (block_dim == 0) {
      MeshV4EntitiesNodes* entity = mesh_info.findNodeEntities(block_entity_tag);
      if (!entity) {
        info(5) << "[Groups] Skipping block index=" << block_index
                << " because entity tag is invalid";
        continue;
      }
      Int32 entity_physical_tag = entity->physical_tag;
      physical_name = mesh_info.physical_name_list.find(block_dim, entity_physical_tag);
    }
    else {
      MeshV4EntitiesWithNodes* entity = mesh_info.findEntities(block_dim, block_entity_tag);
      if (!entity) {
        info(5) << "[Groups] Skipping block index=" << block_index
                << " because entity tag is invalid";
        continue;
      }
      Int32 entity_physical_tag = entity->physical_tag;
      physical_name = mesh_info.physical_name_list.find(block_dim, entity_physical_tag);
    }
    if (physical_name.isNull()) {
      info(5) << "[Groups] Skipping block index=" << block_index
              << " because entity physical tag is invalid";
      continue;
    }
    info(4) << "[Groups] Block index=" << block_index << " dim=" << block_dim
            << " name='" << physical_name.name << "'";
    if (block_dim == mesh_dim) {
      if (is_read_items)
        _addCellGroup(mesh, block, physical_name.name);
      else
        mesh->cellFamily()->findGroup(physical_name.name, true);
    }
    else if (block_dim == face_dim) {
      if (is_read_items)
        _addFaceGroup(mesh, block, physical_name.name);
      else
        mesh->faceFamily()->findGroup(physical_name.name, true);
    }
    else {
      if (is_read_items)
        _addNodeGroup(mesh, block, physical_name.name);
      else
        mesh->nodeFamily()->findGroup(physical_name.name, true);
    }
  }
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void MshMeshReader::
_addFaceGroup(IMesh* mesh, MeshV4ElementsBlock& block, const String& group_name)
{
  const Int32 nb_entity = block.nb_entity;
 
  // There may be several blocks for the same group.
  // We retrieve the group if it already exists.
  FaceGroup face_group = mesh->faceFamily()->findGroup(group_name, true);
 
  UniqueArray<Int32> faces_id(nb_entity); // Face number in the mesh \a mesh
 
  const Int32 item_nb_node = block.item_nb_node;
  const Int32 face_nb_node = nb_entity * item_nb_node;
 
  UniqueArray<Int64> faces_first_node_unique_id(nb_entity);
  UniqueArray<Int32> faces_first_node_local_id(nb_entity);
  UniqueArray<Int64> faces_nodes_unique_id(face_nb_node);
  Integer faces_nodes_unique_id_index = 0;
 
  UniqueArray<Int64> orig_nodes_id(item_nb_node);
  UniqueArray<Integer> face_nodes_index(item_nb_node);
 
  IItemFamily* node_family = mesh->nodeFamily();
  NodeInfoListView mesh_nodes(node_family);
 
  // Reorder face IDs to conform to Arcane and find
  // the face in the mesh
  for (Integer i_face = 0; i_face < nb_entity; ++i_face) {
    for (Integer z = 0; z < item_nb_node; ++z)
      orig_nodes_id[z] = block.connectivity[faces_nodes_unique_id_index + z];
 
    mesh_utils::reorderNodesOfFace2(orig_nodes_id, face_nodes_index);
    for (Integer z = 0; z < item_nb_node; ++z)
      faces_nodes_unique_id[faces_nodes_unique_id_index + z] = orig_nodes_id[face_nodes_index[z]];
    faces_first_node_unique_id[i_face] = orig_nodes_id[face_nodes_index[0]];
    faces_nodes_unique_id_index += item_nb_node;
  }
 
  node_family->itemsUniqueIdToLocalId(faces_first_node_local_id, faces_first_node_unique_id);
 
  faces_nodes_unique_id_index = 0;
  for (Integer i_face = 0; i_face < nb_entity; ++i_face) {
    const Integer n = item_nb_node;
    Int64ConstArrayView face_nodes_id(item_nb_node, &faces_nodes_unique_id[faces_nodes_unique_id_index]);
    Node current_node(mesh_nodes[faces_first_node_local_id[i_face]]);
    Face face = mesh_utils::getFaceFromNodesUnique(current_node, face_nodes_id);
 
    if (face.null()) {
      OStringStream ostr;
      ostr() << "(Nodes:";
      for (Integer z = 0; z < n; ++z)
        ostr() << ' ' << face_nodes_id[z];
      ostr() << " - " << current_node.localId() << ")";
      ARCANE_FATAL("INTERNAL: MeshMeshReader face index={0} with nodes '{1}' is not in node/face connectivity",
                   i_face, ostr.str());
    }
    faces_id[i_face] = face.localId();
 
    faces_nodes_unique_id_index += n;
  }
  info(4) << "Adding " << faces_id.size() << " faces from block index=" << block.index
          << " to group '" << face_group.name() << "'";
  face_group.addItems(faces_id);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void MshMeshReader::
_addCellGroup(IMesh* mesh, MeshV4ElementsBlock& block, const String& group_name)
{
  const Int32 nb_entity = block.nb_entity;
 
  // There may be several blocks for the same group.
  // We retrieve the group if it already exists.
  IItemFamily* cell_family = mesh->cellFamily();
  CellGroup cell_group = cell_family->findGroup(group_name, true);
 
  UniqueArray<Int32> cells_id(nb_entity); // Cell number in the mesh \a mesh
 
  cell_family->itemsUniqueIdToLocalId(cells_id, block.uids);
 
  info(4) << "Adding " << cells_id.size() << " cells from block index=" << block.index
          << " to group '" << cell_group.name() << "'";
  cell_group.addItems(cells_id);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
void MshMeshReader::
_addNodeGroup(IMesh* mesh, MeshV4ElementsBlock& block, const String& group_name)
{
  const Int32 nb_entity = block.nb_entity;
 
  // There may be several blocks for the same group.
  // We retrieve the group if it already exists.
  IItemFamily* node_family = mesh->nodeFamily();
  NodeGroup node_group = node_family->findGroup(group_name, true);
 
  UniqueArray<Int32> nodes_id(nb_entity);
 
  node_family->itemsUniqueIdToLocalId(nodes_id, block.uids);
 
  info(4) << "Adding " << nodes_id.size() << " nodes from block index=" << block.index
          << " to group '" << node_group.name() << "'";
 
  if (nb_entity < 10) {
    info(4) << "Nodes UIDS=" << block.uids;
    info(4) << "Nodes LIDS=" << nodes_id;
  }
  node_group.addItems(nodes_id);
 
  if (nb_entity < 10) {
    VariableNodeReal3& coords(mesh->nodesCoordinates());
    ENUMERATE_ (Node, inode, node_group) {
      info(4) << "Node id=" << ItemPrinter(*inode) << " coord=" << coords[inode];
    }
  }
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
/*
 * $PhysicalNames // same as MSH version 2
 *    numPhysicalNames(ASCII int)
 *    dimension(ASCII int) physicalTag(ASCII int) "name"(127 characters max)
 *    ...
 * $EndPhysicalNames
 */
void MshMeshReader::
_readPhysicalNames(IosFile& ios_file, MeshInfo& mesh_info)
{
  String quote_mark = "\"";
  Int32 nb_name = ios_file.getInteger();
  info() << "nb_physical_name=" << nb_name;
  ios_file.getNextLine();
  for (Int32 i = 0; i < nb_name; ++i) {
    Int32 dim = ios_file.getInteger();
    Int32 tag = ios_file.getInteger();
    String s = ios_file.getNextLine();
    if (dim < 0 || dim > 3)
      ARCANE_FATAL("Invalid value for physical name dimension dim={0}", dim);
    // Group names may start with spaces and contain quotes that must be removed.
    s = String::collapseWhiteSpace(s);
    if (s.startsWith(quote_mark))
      s = s.substring(1);
    if (s.endsWith(quote_mark))
      s = s.substring(0, s.length() - 1);
    mesh_info.physical_name_list.add(dim, tag, s);
    info(4) << "[PhysicalName] index=" << i << " dim=" << dim << " tag=" << tag << " name='" << s << "'";
  }
  StringView s = ios_file.getNextLine();
  if (s != "$EndPhysicalNames")
    ARCANE_FATAL("found '{0}' and expected '$EndPhysicalNames'", s);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/

void MshMeshReader::
_readEntitiesV4(IosFile& ios_file, MeshInfo& mesh_info)
{
  Int32 nb_dim_item[4];
  nb_dim_item[0] = ios_file.getInteger();
  nb_dim_item[1] = ios_file.getInteger();
  nb_dim_item[2] = ios_file.getInteger();
  nb_dim_item[3] = ios_file.getInteger();
  info(4) << "[Entities] nb_0d=" << nb_dim_item[0] << " nb_1d=" << nb_dim_item[1]
          << " nb_2d=" << nb_dim_item[2] << " nb_3d=" << nb_dim_item[3];
  // After the format, entities may be present, but this is optional.
  // If they are present, we read the file until the end of this section.
  StringView next_line = ios_file.getNextLine();
  for (Int32 i = 0; i < nb_dim_item[0]; ++i) {
    Int32 tag = ios_file.getInteger();
    Real x = ios_file.getReal();
    Real y = ios_file.getReal();
    Real z = ios_file.getReal();
    Int32 num_physical_tag = ios_file.getInteger();
    if (num_physical_tag > 1)
      ARCANE_FATAL("NotImplemented numPhysicalTag>1 (n={0})", num_physical_tag);
    Int32 physical_tag = -1;
    if (num_physical_tag == 1)
      physical_tag = ios_file.getInteger();
    info(4) << "[Entities] point tag=" << tag << " x=" << x << " y=" << y << " z=" << z << " phys_tag=" << physical_tag;
    mesh_info.entities_nodes_list.add(MeshV4EntitiesNodes(tag, physical_tag));
    next_line = ios_file.getNextLine();
  }
 
  for (Int32 dim = 1; dim <= 3; ++dim) {
    for (Int32 i = 0; i < nb_dim_item[dim]; ++i) {
      Int32 tag = ios_file.getInteger();
      Real min_x = ios_file.getReal();
      Real min_y = ios_file.getReal();
      Real min_z = ios_file.getReal();
      Real max_x = ios_file.getReal();
      Real max_y = ios_file.getReal();
      Real max_z = ios_file.getReal();
      Int32 num_physical_tag = ios_file.getInteger();
      if (num_physical_tag > 1)
        ARCANE_FATAL("NotImplemented numPhysicalTag>1 (n={0})", num_physical_tag);
      Int32 physical_tag = -1;
      if (num_physical_tag == 1)
        physical_tag = ios_file.getInteger();
      Int32 num_bounding_group = ios_file.getInteger();
      for (Int32 k = 0; k < num_bounding_group; ++k) {
        [[maybe_unused]] Int32 group_tag = ios_file.getInteger();
      }
      mesh_info.entities_with_nodes_list[dim - 1].add(MeshV4EntitiesWithNodes(dim, tag, physical_tag));
      info(4) << "[Entities] dim=" << dim << " tag=" << tag
              << " min_x=" << min_x << " min_y=" << min_y << " min_z=" << min_z
              << " max_x=" << max_x << " max_y=" << max_y << " max_z=" << max_z
              << " phys_tag=" << physical_tag;
      next_line = ios_file.getNextLine();
    }
  }
  StringView s = ios_file.getNextLine();
  if (s != "$EndEntities")
    ARCANE_FATAL("found '{0}' and expected '$EndEntities'", s);
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
IMeshReader::eReturnType MshMeshReader::
_readMeshFromNewMshFile(IMesh* mesh, IosFile& ios_file)
{
  const char* func_name = "MshMeshReader::_readMeshFromNewMshFile()";
  info() << "[_readMeshFromNewMshFile] New native mesh file format detected";
  MeshInfo mesh_info;
#define MSH_BINARY_TYPE 1
 
  Real version = ios_file.getReal();
  if (version == 2.0)
    m_version = 2;
  else if (version == 4.1)
    m_version = 4;
  else
    ARCANE_THROW(IOException, "Wrong msh file version '{0}'. Only versions '2.0' or '4.1' are supported", version);
  info() << "Msh mesh_major_version=" << m_version;
  Integer file_type = ios_file.getInteger(); // is an integer equal to 0 in the ASCII file format, equal to 1 for the binary format
  if (file_type == MSH_BINARY_TYPE)
    ARCANE_THROW(IOException, "Binary mode is not supported!");
 
  Integer data_size = ios_file.getInteger(); // is an integer equal to the size of the floating point numbers used in the file
  ARCANE_UNUSED(data_size);
 
  if (file_type == MSH_BINARY_TYPE) {
    (void)ios_file.getInteger(); // is an integer of value 1 written in binary form
  }
  ios_file.getNextLine(); // Skip current \n\r
 
  // $EndMeshFormat
  if (!ios_file.lookForString("$EndMeshFormat"))
    ARCANE_THROW(IOException, "$EndMeshFormat not found");
 
  // TODO: The different sections ($Nodes, $Entities, ...) can
  // be in any order (except $Nodes which must be before $Elements)
  // Implement a method that handles this.
 
  StringView next_line = ios_file.getNextLine();
  // Group names
  if (next_line == "$PhysicalNames") {
    _readPhysicalNames(ios_file, mesh_info);
    next_line = ios_file.getNextLine();
  }
  // After the format, entities may be present, but this is optional.
  // If they are present, we read the file until the end of this section.
  if (next_line == "$Entities") {
    _readEntitiesV4(ios_file, mesh_info);
    next_line = ios_file.getNextLine();
  }
  // $Nodes
  if (next_line != "$Nodes")
    ARCANE_THROW(IOException, "Unexpected string '{0}'. Valid values are '$Nodes'", next_line);
 
  // Fetch nodes number and the coordinates
  if (file_type != MSH_BINARY_TYPE) {
    if (m_version == 2) {
      if (_readNodesFromAsciiMshV2File(ios_file, mesh_info.node_coords) != IMeshReader::RTOk)
        ARCANE_THROW(IOException, "Ascii nodes coords error");
    }
    else if (m_version == 4) {
      if (_readNodesFromAsciiMshV4File(ios_file, mesh_info) != IMeshReader::RTOk)
        ARCANE_THROW(IOException, "Ascii nodes coords error");
    }
  }
  else {
    if (_readNodesFromBinaryMshFile(ios_file, mesh_info.node_coords) != IMeshReader::RTOk)
      ARCANE_THROW(IOException, "Binary nodes coords error");
  }
  // $EndNodes
  if (!ios_file.lookForString("$EndNodes"))
    ARCANE_THROW(IOException, "$EndNodes not found");
 
  // $Elements
  Integer mesh_dimension = -1;
  {
    if (!ios_file.lookForString("$Elements"))
      ARCANE_THROW(IOException, "$Elements not found");
 
    if (m_version == 2)
      mesh_dimension = _readElementsFromAsciiMshV2File(ios_file, mesh_info);
    else if (m_version == 4)
      mesh_dimension = _readElementsFromAsciiMshV4File(ios_file, mesh_info);
 
    // $EndElements
    if (!ios_file.lookForString("$EndElements"))
      throw IOException(func_name, "$EndElements not found");
  }
 
  info() << "Computed mesh dimension = " << mesh_dimension;
 
  IPrimaryMesh* pmesh = mesh->toPrimaryMesh();
  pmesh->setDimension(mesh_dimension);
 
  IParallelMng* pm = mesh->parallelMng();
  bool is_parallel = pm->isParallel();
  Int32 rank = mesh->meshPartInfo().partRank();
  // In parallel, only rank 0 reads the mesh
  bool is_read_items = !(is_parallel && rank != 0);
  _allocateCells(mesh, mesh_info, is_read_items);
  _allocateGroups(mesh, mesh_info, is_read_items);
  return IMeshReader::RTOk;
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
IMeshReader::eReturnType MshMeshReader::
readMeshFromMshFile(IMesh* mesh, const String& filename, bool use_internal_partition)
{
  info() << "Trying to read 'msh' file '" << filename << "'"
         << " use_internal_partition=" << use_internal_partition;
 
  std::ifstream ifile(filename.localstr());
  if (!ifile) {
    error() << "Unable to read file '" << filename << "'";
    return IMeshReader::RTError;
  }
  IosFile ios_file(&ifile);
  String mesh_format_str = ios_file.getNextLine(); // Comments do not seem to be implemented in .msh files
  if (IosFile::isEqualString(mesh_format_str, "$MeshFormat"))
    return _readMeshFromNewMshFile(mesh, ios_file);
  info() << "The file does not begin with '$MeshFormat' returning RTError";
  return IMeshReader::RTError;
}
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
extern "C++" Ref<IMshMeshReader>
createMshParallelMeshReader(ITraceMng* tm);
 
namespace
{
 
  Ref<IMshMeshReader>
  _internalCreateReader(ITraceMng* tm)
  {
    bool use_new_reader = true;
    if (auto v = Convert::Type<Int32>::tryParseFromEnvironment("ARCANE_USE_PARALLEL_MSH_READER", true))
      use_new_reader = (v.value() != 0);
    Ref<IMshMeshReader> reader;
    if (use_new_reader)
      reader = createMshParallelMeshReader(tm);
    else
      reader = createMshMeshReader(tm);
    return reader;
  }
 
} // namespace
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
class MshMeshReaderService
: public AbstractService
, public IMeshReader
{
 public:
 
  explicit MshMeshReaderService(const ServiceBuildInfo& sbi)
  : AbstractService(sbi)
  {
  }
 
 public:
 
  void build() override {}
 
  bool allowExtension(const String& str) override { return str == "msh"; }
 
  eReturnType readMeshFromFile(IPrimaryMesh* mesh, const XmlNode& mesh_node,
                               const String& file_name, const String& dir_name,
                               bool use_internal_partition) override
  {
    ARCANE_UNUSED(dir_name);
    ARCANE_UNUSED(mesh_node);
 
    Ref<IMshMeshReader> reader = _internalCreateReader(traceMng());
    return reader->readMeshFromMshFile(mesh, file_name, use_internal_partition);
  }
};
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
// Obsolete. Use 'MshMeshReader' instead
ARCANE_REGISTER_SERVICE(MshMeshReaderService,
                        ServiceProperty("MshNewMeshReader", ST_SubDomain),
                        ARCANE_SERVICE_INTERFACE(IMeshReader));
 
ARCANE_REGISTER_SERVICE(MshMeshReaderService,
                        ServiceProperty("MshMeshReader", ST_SubDomain),
                        ARCANE_SERVICE_INTERFACE(IMeshReader));
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
class MshCaseMeshReader
: public AbstractService
, public ICaseMeshReader
{
 public:
 
  class Builder
  : public IMeshBuilder
  {
   public:
 
    explicit Builder(ITraceMng* tm, const CaseMeshReaderReadInfo& read_info)
    : m_trace_mng(tm)
    , m_read_info(read_info)
    , m_use_internal_partition(read_info.isParallelRead())
    {}
 
   public:
 
    void fillMeshBuildInfo(MeshBuildInfo& build_info) override
    {
      ARCANE_UNUSED(build_info);
    }
    void allocateMeshItems(IPrimaryMesh* pm) override
    {
      Ref<IMshMeshReader> reader = _internalCreateReader(m_trace_mng);
      String fname = m_read_info.fileName();
      m_trace_mng->info() << "Msh Reader (ICaseMeshReader) file_name=" << fname;
      IMeshReader::eReturnType ret = reader->readMeshFromMshFile(pm, fname, m_use_internal_partition);
      if (ret != IMeshReader::RTOk)
        ARCANE_FATAL("Can not read MSH File");
    }
 
   private:
 
    ITraceMng* m_trace_mng;
    CaseMeshReaderReadInfo m_read_info;
    bool m_use_internal_partition = false;
  };
 
 public:
 
  explicit MshCaseMeshReader(const ServiceBuildInfo& sbi)
  : AbstractService(sbi)
  {}
 
 public:
 
  Ref<IMeshBuilder> createBuilder(const CaseMeshReaderReadInfo& read_info) const override
  {
    IMeshBuilder* builder = nullptr;
    if (read_info.format() == "msh")
      builder = new Builder(traceMng(), read_info);
    return makeRef(builder);
  }
};
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
ARCANE_REGISTER_SERVICE(MshCaseMeshReader,
                        ServiceProperty("MshCaseMeshReader", ST_SubDomain),
                        ARCANE_SERVICE_INTERFACE(ICaseMeshReader));
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
} // End namespace Arcane
 
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/