Merge pull request #233 from j8xixo12/gmsh_support

add Gmsh mesh file parser

cpp/modmesh/CMakeLists.txt

@@ -37,6 +37,7 @@ add_subdirectory(onedim)
 add_subdirectory(python)
 add_subdirectory(spacetime)
 add_subdirectory(view)
+add_subdirectory(inout)
 
 set(MODMESH_ROOT_HEADERS
     ${CMAKE_CURRENT_SOURCE_DIR}/modmesh.hpp
@@ -80,6 +81,7 @@ set(MODMESH_TERMINAL_FILES
     ${MODMESH_ONEDIM_FILES}
     ${MODMESH_SPACETIME_FILES}
     ${MODMESH_PYTHON_FILES}
+    ${MODMESH_INOUT_FILES}
     CACHE FILEPATH "" FORCE)
 
 set(MODMESH_GRAPHIC_FILES

cpp/modmesh/inout/CMakeLists.txt

@@ -0,0 +1,28 @@
+
+cmake_minimum_required(VERSION 3.16)
+
+set(MODMESH_INOUT_HEADERS
+    ${CMAKE_CURRENT_SOURCE_DIR}/inout.hpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/gmsh.hpp
+    CACHE FILEPATH "" FORCE)
+
+set(MODMESH_INOUT_SOURCES
+    ${CMAKE_CURRENT_SOURCE_DIR}/gmsh.cpp
+    CACHE FILEPATH "" FORCE)
+
+set(MODMESH_INOUT_PYMODHEADERS
+    ${CMAKE_CURRENT_SOURCE_DIR}/pymod/inout_pymod.hpp
+    CACHE FILEPATH "" FORCE)
+
+set(MODMESH_INOUT_PYMODSOURCES
+    ${CMAKE_CURRENT_SOURCE_DIR}/pymod/inout_pymod.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/pymod/wrap_Gmsh.cpp
+    CACHE FILEPATH "" FORCE)
+
+set(MODMESH_INOUT_FILES
+    ${MODMESH_INOUT_HEADERS}
+    ${MODMESH_INOUT_SOURCES}
+    ${MODMESH_INOUT_PYMODHEADERS}
+    ${MODMESH_INOUT_PYMODSOURCES}
+    CACHE FILEPATH "" FORCE)
+# vim: set ff=unix fenc=utf8 nobomb et sw=4 ts=4 sts=4:

cpp/modmesh/inout/gmsh.cpp

@@ -0,0 +1,96 @@
+#include <modmesh/inout/gmsh.hpp>
+#ifdef _WIN32
+#include <algorithm>
+#endif // _WIN32
+namespace modmesh
+{
+namespace inout
+{
+Gmsh::Gmsh(const std::string & data)
+{
+    bool meta_enter = false;
+    bool node_enter = false;
+    bool element_enter = false;
+    // clang-format off
+    std::unordered_map<std::string, std::function<void()>> keyword_handler = {
+        {"$MeshFormat", [this, &meta_enter]() { load_meta(); meta_enter = true; }},
+        {"$Nodes", [this, &node_enter]() { load_nodes(); node_enter = true; }},
+        {"$Elements", [this, &element_enter]() { load_elements(); element_enter = true; }},
+        {"$PhysicalNames", [this]() { load_physical(); }}};
+    // clang-format on
+
+    // String stream on windows need to remove \r for keyword comparison.
+    // DOS file newline character is CRLF, std::getline default using LF as delimeter
+    // therefore string seperated by std::getline will contain \r, it will cause
+    // keyword compare failed.
+    // TODO: Keyword comparison can use regular expression.
+#ifdef _WIN32
+    std::string data_copy = data;
+    data_copy.erase(std::remove(data_copy.begin(), data_copy.end(), '\r'), data_copy.end());
+    stream << data_copy;
+#else // _WIN32
+    stream << data;
+#endif // _WIN32
+
+    std::string line;
+    while (std::getline(stream, line))
+    {
+        // Using a finite state machine to check the input msh file format is valid or not.
+        // $ is a keyword to trigger state transition.
+        if (line.find('$') != std::string::npos)
+        {
+            auto it = keyword_handler.find(line);
+            if (it != keyword_handler.end())
+            {
+                if (is_valid_transition(it->first))
+                {
+                    it->second();
+                }
+                else
+                {
+                    break;
+                }
+            }
+            else
+            {
+                break;
+            }
+        }
+    }
+
+    // MeshFormat, Nodes and Elements section is mandatory in gmsh msh file,
+    // therefore need to check these sections are exist or not otherwise
+    // modmesh may crash during mesh processing.
+    if (!(meta_enter && node_enter && element_enter))
+    {
+        throw std::invalid_argument("Incorrect msh file format.");
+    }
+}
+
+std::shared_ptr<StaticMesh> Gmsh::to_block()
+{
+    std::shared_ptr<StaticMesh> block = StaticMesh::construct(m_eldim.max(), m_nds.shape(0), 0, m_elems.size());
+    build_interior(block);
+    return block;
+}
+
+void Gmsh::build_interior(const std::shared_ptr<StaticMesh> & blk)
+{
+    blk->cltpn().swap(m_cltpn);
+    blk->ndcrd().swap(m_nds);
+    for (size_t i = 0; i < m_elems.size(); ++i)
+    {
+        blk->clnds()(i, 0) = m_elems[i][0];
+        for (size_t j = 1; j <= m_elems[i][0]; ++j)
+        {
+            blk->clnds()(i, j) = m_elems[i][j];
+        }
+    }
+    blk->build_interior(true);
+    blk->build_boundary();
+    blk->build_ghost();
+}
+} /* end namespace inout */
+} /* end namespace modmesh */
+
+// vim: set ff=unix fenc=utf8 et sw=4 ts=4 sts=4: