feat(cpp-client): Add a cross-platform method to get the filename from a path (deephaven#5836)

We needed something functionally similar to the Linux `basename()`
method. We can behavior that meets our needs by using
`std::filesystem::path(p).filename().string()`

Author: kosak

cpp-client/deephaven/dhcore/include/public/deephaven/dhcore/utility/utility.h

@@ -187,6 +187,16 @@ TimePointToEpochMillis(
 TimePointToStr(
     std::chrono::time_point<std::chrono::system_clock> time_point);
 
+/**
+ * This is a method that simply invokes std::filesystem::path(path).filename().string().
+ * We put it here because it is sometimes useful, to provide functionality
+ * similar to the POSIX basename() call. We deliberately do not inline it
+ * because is generates a surprising amount of code.
+ * @param path The path
+ * @return The basename of the path, as returned by std::filesystem::path(path).filename().string()
+ */
+std::string Basename(std::string_view path);
+
 template <class T> [[nodiscard]] std::string
 TypeName(const T& t) {
   return demangle(typeid(t).name());

cpp-client/deephaven/dhcore/src/utility/utility.cc

@@ -3,6 +3,7 @@
  */
 #include "deephaven/dhcore/utility/utility.h"
 
+#include <filesystem>
 #include <ostream>
 #include <string>
 #include <vector>
@@ -144,6 +145,10 @@ TimePointToStr(
   return EpochMillisToStr(TimePointToEpochMillis(time_point));
 }
 
+std::string Basename(std::string_view path) {
+  return std::filesystem::path(path).filename().string();
+}
+
 #ifdef __GNUG__
 std::string demangle(const char *name) {
   int status = -1;

cpp-client/deephaven/tests/src/utility_test.cc

@@ -5,6 +5,7 @@
 #include "deephaven/dhcore/utility/utility.h"
 
 using deephaven::dhcore::utility::Base64Encode;
+using deephaven::dhcore::utility::Basename;
 using deephaven::dhcore::utility::EpochMillisToStr;
 using deephaven::dhcore::utility::ObjectId;
 
@@ -28,4 +29,16 @@ TEST_CASE("ObjectId", "[utility]") {
   auto id = ObjectId("hello", reinterpret_cast<void *>(p));
   CHECK(id == "hello(0xdeadbeef)");
 }
+
+TEST_CASE("Basename", "[utility]") {
+#ifdef __linux__
+  CHECK("file.txt" == Basename("/home/kosak/file.txt"));
+  CHECK(Basename("/home/kosak/").empty());
+#endif
+
+#ifdef _WIN32
+  CHECK("file.txt" == Basename(R"(C:\Users\kosak\file.txt)"));
+  CHECK(Basename(R"(C:\Users\kosak\)").empty());
+#endif
+}
 }  // namespace deephaven::client::tests