From b9315017119d1650141da00f71f3a8a4dacb0d8a Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Fri, 23 Oct 2020 20:12:03 -0400
Subject: [PATCH] add utils::path_dirname() to complement
 utils::path_basename()

---
 src/utils.cpp                 | 16 ++++++++++++++++
 src/utils.h                   |  7 +++++++
 unittest/utils/test_utils.cpp | 15 +++++++++++++++
 3 files changed, 38 insertions(+)

diff --git a/src/utils.cpp b/src/utils.cpp
index 40fc87ca01..5ae76ed00d 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -772,6 +772,22 @@ std::string utils::path_basename(const std::string &path) {
   return path.substr(start);
 }
 
+/* ----------------------------------------------------------------------
+   Return only the leading part of a path, return just the directory
+------------------------------------------------------------------------- */
+
+std::string utils::path_dirname(const std::string &path) {
+#if defined(_WIN32)
+  size_t start = path.find_last_of("/\\");
+#else
+  size_t start = path.find_last_of("/");
+#endif
+
+  if (start == std::string::npos) return ".";
+
+  return path.substr(0,start);
+}
+
 /* ----------------------------------------------------------------------
    join two paths
 ------------------------------------------------------------------------- */
diff --git a/src/utils.h b/src/utils.h
index 7515f1f21b..52f7933caf 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -291,6 +291,13 @@ namespace LAMMPS_NS {
 
     std::string path_basename(const std::string &path);
 
+    /** Return the directory part of a path. Return "." if empty
+     *
+     * \param path file path
+     * \return directory name */
+
+    std::string path_dirname(const std::string &path);
+
     /** Join two pathname segments
      *
      * This uses the forward slash '/' character unless LAMMPS is compiled
diff --git a/unittest/utils/test_utils.cpp b/unittest/utils/test_utils.cpp
index 796ce0f8c7..2c3da7b9df 100644
--- a/unittest/utils/test_utils.cpp
+++ b/unittest/utils/test_utils.cpp
@@ -525,11 +525,26 @@ TEST(Utils, path_basename)
 {
 #if defined(_WIN32)
     ASSERT_THAT(utils::path_basename("c:\\parent\\folder\\filename"), Eq("filename"));
+    ASSERT_THAT(utils::path_basename("folder\\"), Eq(""));
+    ASSERT_THAT(utils::path_basename("c:/parent/folder/filename"), Eq("filename"));
 #else
     ASSERT_THAT(utils::path_basename("/parent/folder/filename"), Eq("filename"));
+    ASSERT_THAT(utils::path_basename("/parent/folder/"), Eq(""));
 #endif
 }
 
+TEST(Utils, path_dirname)
+{
+#if defined(_WIN32)
+    ASSERT_THAT(utils::path_dirname("c:/parent/folder/filename"), Eq("c:/parent/folder"));
+    ASSERT_THAT(utils::path_dirname("c:\\parent\\folder\\filename"), Eq("c:\\parent\\folder"));
+    ASSERT_THAT(utils::path_dirname("c:filename"), Eq("."));
+#else
+    ASSERT_THAT(utils::path_dirname("/parent/folder/filename"), Eq("/parent/folder"));
+#endif
+    ASSERT_THAT(utils::path_dirname("filename"), Eq("."));
+}
+
 TEST(Utils, getsyserror)
 {
 #if defined(__linux__)