Issue 650: add Custom to DriverID enum (#665)

* add Custom to DriverID enum

* add tests

* remove DLL_EXPORT

Author: jkotan

src/h5cpp/file/driver.hpp

@@ -48,6 +48,7 @@ namespace file
 //!
 enum class DriverID : unsigned
 {
+  Custom = 0,
   Posix = 1,
   Direct = 2,
   Memory = 3,

test/file/driver_test.cpp

@@ -34,6 +34,18 @@
 
 using namespace hdf5;
 
+
+class MyPosixDriver : public hdf5::file::PosixDriver
+{
+  public:
+  MyPosixDriver() {}
+
+  virtual hdf5::file::DriverID id() const noexcept override{
+    return hdf5::file::DriverID::Custom;
+  }
+};
+
+
 SCENARIO("Construction of a memory driver instance", "[file,h5cpp,driver]") {
   GIVEN("a default constructed instance") {
     file::MemoryDriver m;
@@ -99,6 +111,11 @@ SECTION("the posix driver") {
   REQUIRE(m.id() == file::DriverID::Posix);
 }
 
+ SECTION("the custom driver") {
+  MyPosixDriver m;
+  REQUIRE(m.id() == file::DriverID::Custom);
+}
+
 #ifdef H5CPP_WITH_MPI
 
 SECTION("the MPI driver") {