Added tests for mixed C and C++ code

Also added delete_c_struct function, which is needed as the struct
FdpDataPipeline is an incomplete type.

Author: LiamPattinson

include/fdp/fdp.h

@@ -186,12 +186,17 @@ DataPipeline::sptr from_c_struct(FdpDataPipeline *data_pipeline);
  *
  * If the pipeline is set up using the C++ method DataPipeline::construct, this may be
  * used to generate a C-compatible struct. Note that this uses 'new' to allocate the
- * returned pointer, so the user should 'delete` the pointer after use to avoid memory
+ * returned pointer, so the user should 'delete_c_struct` after use to avoid memory
  * leaks. It is not recommended to mix usage of the C and C++ APIs for init and finalise
  * functions.
  */
 FdpDataPipeline* to_c_struct(DataPipeline::sptr data_pipeline);
 
+/**
+ * @brief Function to clean up FdpDataPipeline created by to_c_struct
+ */
+void delete_c_struct(FdpDataPipeline *data_pipeline);
+
 } // close namespace FairDataPipeline
 
 #endif

src/fdp_c_api.cxx

@@ -28,6 +28,11 @@ FdpDataPipeline* FDP::to_c_struct(FDP::DataPipeline::sptr data_pipeline){
     return new FdpDataPipeline{data_pipeline};
 }
 
+
+void FDP::delete_c_struct(FdpDataPipeline *data_pipeline){
+    delete data_pipeline;
+}
+
 /** 
  * @brief Utility method, calls exception-raising function and returns error codes
  *
@@ -116,7 +121,7 @@ FdpError fdp_init(
         std::string(script_file_path),
         token_str
     );
-    *data_pipeline = to_c_struct(cpp_data_pipeline);
+    *data_pipeline = FDP::to_c_struct(cpp_data_pipeline);
     return err;
 }
 
@@ -129,7 +134,7 @@ FdpError fdp_finalise(FdpDataPipeline **data_pipeline){
         [](FDP::DataPipeline::sptr pipeline){pipeline->finalise();},
         (*data_pipeline)->_pipeline
     );
-    delete *data_pipeline;
+    FDP::delete_c_struct(*data_pipeline);
     *data_pipeline = nullptr;
     return err;
 }

test/test_c_api.cxx

@@ -31,6 +31,7 @@ std::string home_dir(){
 
 TEST(CTest, link_read_write){
   fdp_set_log_level(FDP_LOG_DEBUG);
+  char buf[512];
 
   // Initialise
   FdpDataPipeline* pipeline;
@@ -48,7 +49,6 @@ TEST(CTest, link_read_write){
     ),
     FDP_ERR_NONE
   );
-  char buf[512];
 
   // Test link write
   buf[0] = '\0'; // Ensure strlen of output buffer is 0
@@ -82,6 +82,79 @@ TEST(CTest, link_read_write){
   EXPECT_EQ(fdp_finalise(&pipeline), FDP_ERR_NONE);
 }
 
+TEST(CTest, cpp_to_c){
+  fdp_set_log_level(FDP_LOG_DEBUG);
+  char buf[512];
+
+  // Initialise using C++
+  fs::path config = fs::path(TESTDIR) / "data" / "write_csv.yaml";
+  fs::path script = fs::path(TESTDIR) / "test_script.sh";
+  std::string token = fdp::read_token(
+    fs::path(home_dir()) / ".fair" / "registry" / "token"
+  );
+  auto cpp_pipeline = fdp::DataPipeline::construct(
+    config.string(), script.string(), token
+  );
+
+  // Switch to C API, use temporary FdpDataPipeline
+  FdpDataPipeline *c_pipeline = fdp::to_c_struct(cpp_pipeline);
+
+  // Test link write
+  buf[0] = '\0'; // Ensure strlen of output buffer is 0
+  EXPECT_EQ(fdp_link_write(c_pipeline, "test/csv", buf), FDP_ERR_NONE);
+  EXPECT_GT(strlen(buf), 1);
+
+  // Write to new path
+  std::ofstream fstream(buf);
+  fstream << "Test";
+  fstream.close();
+
+  // Finish working in C, delete FdpDataPipeline
+  fdp::delete_c_struct(c_pipeline);
+
+  // Finalise in C++
+  cpp_pipeline->finalise();
+}
+
+TEST(CTest, c_to_cpp){
+  fdp_set_log_level(FDP_LOG_DEBUG);
+
+  // Initialise using C
+  FdpDataPipeline* c_pipeline;
+  fs::path config = fs::path(TESTDIR) / "data" / "write_csv.yaml";
+  fs::path script = fs::path(TESTDIR) / "test_script.sh";
+  std::string token = fdp::read_token(
+    fs::path(home_dir()) / ".fair" / "registry" / "token"
+  );
+  ASSERT_EQ(
+    fdp_init(
+        &c_pipeline,
+        config.string().c_str(),
+        script.string().c_str(),
+        token.c_str()
+    ),
+    FDP_ERR_NONE
+  );
+
+  // Switch to C++ API
+  auto cpp_pipeline = fdp::from_c_struct(c_pipeline);
+
+  // Test link write
+  std::string data_product = "test/csv";
+  fs::path currentLink = fs::path(cpp_pipeline->link_write(data_product));
+  EXPECT_GT(currentLink.string().size(), 1);
+
+  // Write to new path
+  std::ofstream fstream(currentLink);
+  fstream << "Test";
+  fstream.close();
+
+  // Finish working in C++
+  cpp_pipeline = nullptr;
+
+  // Finalise in C
+  EXPECT_EQ(fdp_finalise(&c_pipeline), FDP_ERR_NONE);
+}
 
 TEST(CTest, log_levels){
     fdp_set_log_level(FDP_LOG_INFO);