Rely on std::filesystem for file_utils (#3042)

Co-authored-by: Andrew Johnson <git.vyveu@simplelogin.com>
Co-authored-by: Paul Romano <paul.k.romano@gmail.com>

include/openmc/file_utils.h

@@ -5,7 +5,10 @@
 
 namespace openmc {
 
-// TODO: replace with std::filesystem when switch to C++17 is made
+// NOTE: This is a thin wrapper over std::filesystem because we
+// pass strings around a lot. Objects like settings::path_input
+// are extern std::string to play with other libraries and languages
+
 //! Determine if a path is a directory
 //! \param[in] path Path to check
 //! \return Whether the path is a directory
@@ -18,7 +21,8 @@ bool file_exists(const std::string& filename);
 
 //! Determine directory containing given file
 //! \param[in] filename Path to file
-//! \return Name of directory containing file
+//! \return Name of directory containing file excluding the final directory
+//! separator
 std::string dir_name(const std::string& filename);
 
 // Gets the file extension of whatever string is passed in. This is defined as

src/cross_sections.cpp

@@ -23,6 +23,7 @@
 #include "pugixml.hpp"
 
 #include <cstdlib> // for getenv
+#include <filesystem>
 #include <unordered_set>
 
 namespace openmc {
@@ -282,15 +283,16 @@ void read_ce_cross_sections(const vector<vector<double>>& nuc_temps,
 void read_ce_cross_sections_xml()
 {
   // Check if cross_sections.xml exists
-  const auto& filename = settings::path_cross_sections;
-  if (dir_exists(filename)) {
+  std::filesystem::path filename(settings::path_cross_sections);
+  if (!std::filesystem::exists(filename)) {
+    fatal_error(
+      "Cross sections XML file '" + filename.string() + "' does not exist.");
+  }
+
+  if (std::filesystem::is_directory(filename)) {
     fatal_error("OPENMC_CROSS_SECTIONS is set to a directory. "
                 "It should be set to an XML file.");
   }
-  if (!file_exists(filename)) {
-    // Could not find cross_sections.xml file
-    fatal_error("Cross sections XML file '" + filename + "' does not exist.");
-  }
 
   write_message("Reading cross sections XML file...", 5);
 
@@ -309,15 +311,10 @@ void read_ce_cross_sections_xml()
   } else {
     // If no directory is listed in cross_sections.xml, by default select the
     // directory in which the cross_sections.xml file resides
-
-    // TODO: Use std::filesystem functionality when C++17 is adopted
-    auto pos = filename.rfind("/");
-    if (pos == std::string::npos) {
-      // No '\\' found, so the file must be in the same directory as
-      // materials.xml
-      directory = settings::path_input;
+    if (filename.has_parent_path()) {
+      directory = filename.parent_path().string();
     } else {
-      directory = filename.substr(0, pos);
+      directory = settings::path_input;
     }
   }
 

src/dagmc.cpp

@@ -17,6 +17,7 @@
 #include <fmt/core.h>
 
 #include <algorithm>
+#include <filesystem>
 #include <fstream>
 #include <sstream>
 #include <string>
@@ -56,7 +57,8 @@ DAGUniverse::DAGUniverse(pugi::xml_node node)
   if (check_for_node(node, "filename")) {
     filename_ = get_node_value(node, "filename");
     if (!starts_with(filename_, "/")) {
-      filename_ = dir_name(settings::path_input) + filename_;
+      std::filesystem::path d(dir_name(settings::path_input));
+      filename_ = (d / filename_).string();
     }
   } else {
     fatal_error("Must specify a file for the DAGMC universe");

src/file_utils.cpp

@@ -1,65 +1,42 @@
 #include "openmc/file_utils.h"
 
-#include <algorithm> // any_of
-#include <cctype>    // for isalpha
-#include <fstream>   // for ifstream
-#include <sys/stat.h>
+#include <filesystem>
 
 namespace openmc {
 
 bool dir_exists(const std::string& path)
 {
-  struct stat s;
-  if (stat(path.c_str(), &s) != 0)
-    return false;
-
-  return s.st_mode & S_IFDIR;
+  std::filesystem::path d(path);
+  return std::filesystem::is_directory(d);
 }
 
 bool file_exists(const std::string& filename)
 {
-  // rule out file being a path to a directory
-  if (dir_exists(filename))
+  std::filesystem::path p(filename);
+  if (!std::filesystem::exists(p)) {
     return false;
-
-  std::ifstream s {filename};
-  return s.good();
+  }
+  if (std::filesystem::is_directory(p)) {
+    return false;
+  }
+  return true;
 }
 
 std::string dir_name(const std::string& filename)
 {
-  size_t pos = filename.find_last_of("\\/");
-  return (std::string::npos == pos) ? "" : filename.substr(0, pos + 1);
+  std::filesystem::path p(filename);
+  return (p.parent_path()).string();
 }
 
 std::string get_file_extension(const std::string& filename)
 {
-  // try our best to work on windows...
-#if defined(_WIN32) || defined(_WIN64)
-  const char sep_char = '\\';
-#else
-  const char sep_char = '/';
-#endif
-
-  // check that at least one letter is present
-  const auto last_period_pos = filename.find_last_of('.');
-  const auto last_sep_pos = filename.find_last_of(sep_char);
-
-  // no file extension. In the first case, we are only given
-  // a file name. In the second, we have been given a file path.
-  // If that's the case, periods are allowed in directory names,
-  // but have the interpretation as preceding a file extension
-  // after the last separator.
-  if (last_period_pos == std::string::npos ||
-      (last_sep_pos < std::string::npos && last_period_pos < last_sep_pos))
+  std::filesystem::path p(filename);
+  auto ext = p.extension();
+  if (!ext.empty()) {
+    // path::extension includes the period
+    return ext.string().substr(1);
+  }
   return "";
-
-  const std::string ending = filename.substr(last_period_pos + 1);
-
-  // check that at least one character is present.
-  const bool has_alpha = std::any_of(ending.begin(), ending.end(),
-    [](char x) { return static_cast<bool>(std::isalpha(x)); });
-  return has_alpha ? ending : "";
 }
 
 } // namespace openmc

src/simulation.cpp

@@ -446,10 +446,9 @@ void finalize_batch()
 
     // Write a continously-overwritten source point if requested.
     if (settings::source_latest) {
-      // note: correct file extension appended automatically
       auto filename = settings::path_output + "source";
       gsl::span<SourceSite> bankspan(simulation::source_bank);
-      write_source_point(filename.c_str(), bankspan, simulation::work_index,
+      write_source_point(filename, bankspan, simulation::work_index,
         settings::source_mcpl_write);
     }
   }

src/state_point.cpp

@@ -52,9 +52,7 @@ extern "C" int openmc_statepoint_write(const char* filename, bool* write_source)
 
   // If a file name was specified, ensure it has .h5 file extension
   const auto extension = get_file_extension(filename_);
-  if (extension == "") {
-    filename_.append(".h5");
-  } else if (extension != "h5") {
+  if (extension != "h5") {
     warning("openmc_statepoint_write was passed a file extension differing "
             "from .h5, but an hdf5 file will be written.");
   }
@@ -578,8 +576,10 @@ void write_source_point(std::string filename, gsl::span<SourceSite> source_bank,
 
   // Dispatch to appropriate function based on file type
   if (use_mcpl) {
+    filename.append(".mcpl");
     write_mcpl_source_point(filename.c_str(), source_bank, bank_index);
   } else {
+    filename.append(".h5");
     write_h5_source_point(filename.c_str(), source_bank, bank_index);
   }
 }
@@ -602,9 +602,7 @@ void write_h5_source_point(const char* filename,
 
   std::string filename_(filename);
   const auto extension = get_file_extension(filename_);
-  if (extension == "") {
-    filename_.append(".h5");
-  } else if (extension != "h5") {
+  if (extension != "h5") {
     warning("write_source_point was passed a file extension differing "
             "from .h5, but an hdf5 file will be written.");
   }

tests/cpp_unit_tests/test_file_utils.cpp

@@ -30,3 +30,12 @@ TEST_CASE("Test file_exists")
   // Note: not clear how to portably test where a file should exist.
   REQUIRE(!file_exists("./should_not_exist/really_do_not_make_this_please"));
 }
+
+TEST_CASE("Test dir_name")
+{
+  REQUIRE(dir_name("") == "");
+  REQUIRE(dir_name("/") == "/");
+  REQUIRE(dir_name("hello") == "");
+  REQUIRE(dir_name("hello/world") == "hello");
+  REQUIRE(dir_name("/path/to/dir/") == "/path/to/dir");
+}