Requested updates to source

Rename sample_source -> sample.
Use std::string as type of argument to openmc_create_source.
Use reinterpret_cast when accessing dlsym.
Also moves check for dlerror to be before the attempt to create the
source (avoids null reference if fails) and capture error message
before dlclose, so that the error message is still available.
Formatting updates and some refactoring for examples and tests.

examples/custom_source/source_ring.cpp

@@ -7,7 +7,7 @@
 
 class Source : public openmc::CustomSource
 {
-  openmc::Particle::Bank sample_source(uint64_t* seed)
+  openmc::Particle::Bank sample(uint64_t* seed)
   {
     openmc::Particle::Bank particle;
     // wgt
@@ -30,7 +30,7 @@ class Source : public openmc::CustomSource
 // A function to create a unique pointer to an instance of this class when generated
 // via a plugin call using dlopen/dlsym.
 // You must have external C linkage here otherwise dlopen will not find the file
-extern "C" std::unique_ptr<Source> openmc_create_source()
+extern "C" std::unique_ptr<Source> openmc_create_source(std::string parameters)
 {
-  return std::unique_ptr<Source> (new Source());
+  return std::make_unique<Source>();
 }

examples/parameterized_custom_source/parameterized_source_ring.cpp

@@ -8,25 +8,12 @@
 
 class Source : public openmc::CustomSource
 {
-  protected:
-    double radius_;
-    double energy_;
-
-    // Protect the constructor as we only want the class to be created by the from_string method.
-    Source(double radius, double energy)
-    {
-      radius_ = radius;
-      energy_ = energy;
-    }
-
   public:
-    // Getters for the values that we want to use in sampling.
-    double radius() { return radius_; }
-    double energy() { return energy_; }
+    Source(double radius, double energy) : radius_(radius), energy_(energy) { }
 
     // Defines a function that can create a unique pointer to a new instance of this class
     // by extracting the parameters from the provided string.
-    static std::unique_ptr<Source> from_string(const char* parameters)
+    static std::unique_ptr<Source> from_string(std::string parameters)
     {
       std::unordered_map<std::string, std::string> parameter_mapping;
 
@@ -39,13 +26,13 @@ class Source : public openmc::CustomSource
         parameter_mapping[key] = value;
       }
 
-      return std::unique_ptr<Source> (
-        new Source(std::stod(parameter_mapping["radius"]), std::stod(parameter_mapping["energy"]))
-      );
+      double radius = std::stod(parameter_mapping["radius"]);
+      double energy = std::stod(parameter_mapping["energy"]);
+      return std::make_unique<Source>(radius, energy);
     }
 
     // Samples from an instance of this class.
-    openmc::Particle::Bank sample_source(uint64_t* seed)
+    openmc::Particle::Bank sample(uint64_t* seed)
     {
       openmc::Particle::Bank particle;
       // wgt
@@ -53,23 +40,27 @@ class Source : public openmc::CustomSource
       particle.wgt = 1.0;
       // position
       double angle = 2.0 * M_PI * openmc::prn(seed);
-      double radius = this->radius();
+      double radius = this->radius_;
       particle.r.x = radius * std::cos(angle);
       particle.r.y = radius * std::sin(angle);
       particle.r.z = 0.0;
       // angle
       particle.u = {1.0, 0.0, 0.0};
-      particle.E = this->energy();
+      particle.E = this->energy_;
       particle.delayed_group = 0;
 
       return particle;
     }
+
+  private:
+    double radius_;
+    double energy_;
 };
 
 // A function to create a unique pointer to an instance of this class when generated
 // via a plugin call using dlopen/dlsym.
 // You must have external C linkage here otherwise dlopen will not find the file
-extern "C" std::unique_ptr<Source> openmc_create_source(const char* parameters)
+extern "C" std::unique_ptr<Source> openmc_create_source(std::string parameters)
 {
   return Source::from_string(parameters);
 }

include/openmc/source.h

@@ -63,10 +63,10 @@ class CustomSource {
   public:
     virtual ~CustomSource() {}
 
-    virtual Particle::Bank sample_source(uint64_t* seed) = 0;
+    virtual Particle::Bank sample(uint64_t* seed) = 0;
 };
 
-typedef std::unique_ptr<CustomSource> create_custom_source_t(const char* parameters);
+typedef std::unique_ptr<CustomSource> create_custom_source_t(std::string parameters);
 
 //==============================================================================
 // Functions

src/source.cpp

@@ -46,7 +46,7 @@ std::vector<SourceDistribution> external_sources;
 namespace {
 
 void* custom_source_library;
-std::string custom_source_parameters = "";
+std::string custom_source_parameters;
 std::unique_ptr<CustomSource> custom_source;
 
 }
@@ -373,18 +373,20 @@ void load_custom_source_library()
   dlerror();
 
   // get the function to create the CustomSource from the library
-  create_custom_source_t* create_custom_source = (create_custom_source_t*) dlsym(custom_source_library, "openmc_create_source");
-
-  // create a pointer to an instance of the CustomSource
-  custom_source = create_custom_source(custom_source_parameters.c_str());
+  auto create_custom_source = reinterpret_cast<create_custom_source_t*>(
+    dlsym(custom_source_library, "openmc_create_source"));
 
   // check for any dlsym errors
   auto dlsym_error = dlerror();
   if (dlsym_error) {
+    std::string error_msg = fmt::format("Couldn't open the openmc_create_source symbol: {}", dlsym_error);
     dlclose(custom_source_library);
-    fatal_error(fmt::format("Couldn't open the sample_source symbol: {}", dlsym_error));
+    fatal_error(error_msg);
   }
 
+  // create a pointer to an instance of the CustomSource
+  custom_source = create_custom_source(custom_source_parameters);
+
 #else
   fatal_error("Custom source libraries have not yet been implemented for "
     "non-POSIX systems");
@@ -409,7 +411,7 @@ void close_custom_source_library()
 Particle::Bank sample_custom_source_library(uint64_t* seed)
 {
   // sample from the instance of the CustomSource
-  return custom_source->sample_source(seed);
+  return custom_source->sample(seed);
 }
 
 void fill_source_bank_custom_source()

tests/regression_tests/source_dlopen/source_sampling.cpp

@@ -7,7 +7,7 @@
 
 class Source : openmc::CustomSource
 {
-  openmc::Particle::Bank sample_source(uint64_t *seed)
+  openmc::Particle::Bank sample(uint64_t *seed)
   {
     openmc::Particle::Bank particle;
     // wgt
@@ -29,7 +29,7 @@ class Source : openmc::CustomSource
 // A function to create a unique pointer to an instance of this class when generated
 // via a plugin call using dlopen/dlsym.
 // You must have external C linkage here otherwise dlopen will not find the file
-extern "C" std::unique_ptr<Source> openmc_create_source()
+extern "C" std::unique_ptr<Source> openmc_create_source(std::string parameters)
 {
-  return std::unique_ptr<Source> (new Source());
+  return std::make_unique<Source>();
 }

tests/regression_tests/source_parameterized_dlopen/parameterized_source_sampling.cpp

@@ -1,18 +1,12 @@
 #include "openmc/source.h"
 #include "openmc/particle.h"
 
-class Source : public openmc::CustomSource
-{
+class Source : public openmc::CustomSource {
   public:
-    double energy;
-
-    Source(double energy)
-    {
-      this->energy = energy;
-    }
+    Source(double energy) : energy_(energy) { }
 
     // Samples from an instance of this class.
-    openmc::Particle::Bank sample_source(uint64_t* seed)
+    openmc::Particle::Bank sample(uint64_t* seed)
     {
       openmc::Particle::Bank particle;
       // wgt
@@ -24,17 +18,21 @@ class Source : public openmc::CustomSource
       particle.r.z = 0.0;
       // angle
       particle.u = {1.0, 0.0, 0.0};
-      particle.E = this->energy;
+      particle.E = this->energy_;
       particle.delayed_group = 0;
 
       return particle;
     }
+
+  private:
+    double energy_;
 };
 
 // A function to create a unique pointer to an instance of this class when generated
 // via a plugin call using dlopen/dlsym.
 // You must have external C linkage here otherwise dlopen will not find the file
-extern "C" std::unique_ptr<Source> openmc_create_source(const char* parameter)
+extern "C" std::unique_ptr<Source> openmc_create_source(std::string parameter)
 {
-  return std::unique_ptr<Source> (new Source(atof(parameter)));
+  double energy = std::stod(parameter);
+  return std::make_unique<Source>(energy);
 }