Add a serialisation test

Add a test that
  - takes an object (e.g. an std::vector),
  - uses ROOT to serialise it to a buffer,
  - copies the buffer,
  - uses ROOT to deserialise the buffer into a new object.

Author: fwyzard

HeterogeneousCore/MPICore/test/BuildFile.xml

@@ -2,3 +2,7 @@
     <use name="openmpi"/>
     <flags TEST_RUNNER_CMD="mpirun -np 4 testMPI -s 1000 -r 12345 -n 10"/>
 </bin>
+
+<bin name="testSerialisation" file="testSerialisation.cc">
+    <use name="root"/>
+</bin>

HeterogeneousCore/MPICore/test/testSerialisation.cc

@@ -0,0 +1,79 @@
+// C++ headers
+#include <iomanip>
+#include <ios>
+#include <iostream>
+#include <vector>
+
+// ROOT headers
+#include <TBufferFile.h>
+#include <TClass.h>
+
+template <typename T>
+void print_vector(std::vector<T> const& v) {
+  if (v.empty()) {
+    std::cout << "{}";
+    return;
+  }
+
+  std::cout << "{ " << v[0];
+  for (unsigned int i = 1; i < v.size(); ++i) {
+    std::cout << ", " << v[i];
+  }
+  std::cout << " }";
+}
+
+void print_buffer(const char* buffer, int size) {
+  auto flags = std::cout.flags();
+  for (int i = 0; i < size; ++i) {
+    if (i % 16 == 0)
+      std::cout << '\t';
+    unsigned char value = buffer[i];
+    std::cout << "0x" << std::hex << std::setw(2) << std::setfill('0') << (unsigned int)value;
+    std::cout << ((i % 16 == 15 or i == size - 1) ? '\n' : ' ');
+  }
+  std::cout.flags(flags);
+}
+
+int main() {
+  // Type of the object to serialise and deserialise
+  using Type = std::vector<float>;
+
+  // Original vector to serialize
+  Type send_object = {1.1, 2.2, 3.3, 4.4, 5.5};
+
+  // Display the contents of the original vector
+  std::cout << "Original object:     ";
+  print_vector(send_object);
+  std::cout << "\n";
+
+  // Create a buffer for serialization
+  TBufferFile send_buffer(TBuffer::kWrite);
+
+  // Get the TClass for the type to serialise
+  //TClass* type = TClass::GetClass<Type>();
+  TClass* type = TClass::GetClass(typeid(Type));
+
+  // Serialize the vector into the buffer
+  send_buffer.WriteObjectAny((void*)&send_object, type, false);
+  int size = send_buffer.Length();
+
+  // Display the contents of the buffer
+  std::cout << "Serialised object is " << size << " bytes long:\n";
+  print_buffer(send_buffer.Buffer(), size);
+
+  // Create a new buffer for deserialization
+  TBufferFile recv_buffer(TBuffer::kRead, size);
+
+  // Copy the buffer
+  std::memcpy(recv_buffer.Buffer(), send_buffer.Buffer(), size);
+
+  // Deserialize into a new vector
+  std::unique_ptr<Type> recv_object{reinterpret_cast<Type*>(recv_buffer.ReadObjectAny(type))};
+
+  // Display the contents of the new vector
+  std::cout << "Deserialized object: ";
+  print_vector(*recv_object);
+  std::cout << "\n";
+
+  return 0;
+}