Hashing for unique-objects-container to use external MD5 function (#1652

)

* md5 hash w/wo mex

* add getmd5 dir

* separate class for hash function

* fix CI, warnings

* move to c++

* const in gcc

* tests

* restore mex to stored

* review responses

* fix comment position

* disambiguate constant

_LowLevelCode/cpp/CMakeLists.txt

@@ -8,6 +8,7 @@ else()
 endif()
 
 set(MEX_FUNCTIONS
+    "GetMD5"
     "cpp_communicator"
     "get_ascii_file"
     "serialiser"

_LowLevelCode/cpp/GetMD5/CMakeLists.txt

@@ -0,0 +1,24 @@
+set(
+    SRC_FILES
+    "GetMD5.cpp"
+)
+
+set(
+    HDR_FILES
+)
+
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+    # On GCC you must pass OpenMP_CXX_FLAGS to the linker
+    set(LIBS "${OpenMP_CXX_FLAGS}")
+endif()
+
+set(MEX_NAME "GetMD5")
+pace_add_mex(
+    NAME "${MEX_NAME}"
+    SRC "${SRC_FILES}" "${HDR_FILES}"
+    LINK_TO "${LIBS}"
+)
+if(${OPENMP_FOUND})
+    target_compile_options("${MEX_NAME}" PRIVATE ${OpenMP_CXX_FLAGS})
+    target_link_options("${MEX_NAME}" PRIVATE ${OpenMP_EXE_LINKER_FLAGS})
+endif()