Add function rcl_names_and_types_init (#403)

This wraps the rmw function just like the finalize function.

Signed-off-by: Jacob Perron <jacob@openrobotics.org>

rcl/include/rcl/graph.h

@@ -292,6 +292,37 @@ rcl_get_service_names_and_types(
   rcl_allocator_t * allocator,
   rcl_names_and_types_t * service_names_and_types);
 
+/// Initialize a rcl_names_and_types_t object.
+/**
+ * This function initializes the string array for the names and allocates space
+ * for all the string arrays for the types according to the given size, but
+ * it does not initialize the string array for each set of types.
+ * However, the string arrays for each set of types is zero initialized.
+ *
+ * <hr>
+ * Attribute          | Adherence
+ * ------------------ | -------------
+ * Allocates Memory   | Yes
+ * Thread-Safe        | No
+ * Uses Atomics       | No
+ * Lock-Free          | Yes
+ *
+ * \param[inout] names_and_types object to be initialized
+ * \param[in] size the number of names and sets of types to be stored
+ * \param[in] allocator to be used to allocate and deallocate memory
+ * \returns `RCL_RET_OK` on success, or
+ * \returns `RCL_RET_INVALID_ARGUMENT` if any arguments are invalid, or
+ * \returns `RCL_BAD_ALLOC` if memory allocation fails, or
+ * \returns `RCL_RET_ERROR` when an unspecified error occurs.
+ */
+RCL_PUBLIC
+RCL_WARN_UNUSED
+rcl_ret_t
+rcl_names_and_types_init(
+  rcl_names_and_types_t * names_and_types,
+  size_t size,
+  rcl_allocator_t * allocator);
+
 /// Finalize a rcl_names_and_types_t object.
 /**
  * The object is populated when given to one of the rcl_get_*_names_and_types()

rcl/src/rcl/graph.c

@@ -193,6 +193,17 @@ rcl_get_service_names_and_types(
   return rcl_convert_rmw_ret_to_rcl_ret(rmw_ret);
 }
 
+rcl_ret_t
+rcl_names_and_types_init(
+  rcl_names_and_types_t * names_and_types,
+  size_t size,
+  rcl_allocator_t * allocator)
+{
+  RCL_CHECK_ARGUMENT_FOR_NULL(names_and_types, RCL_RET_INVALID_ARGUMENT);
+  rmw_ret_t rmw_ret = rmw_names_and_types_init(names_and_types, size, allocator);
+  return rcl_convert_rmw_ret_to_rcl_ret(rmw_ret);
+}
+
 rcl_ret_t
 rcl_names_and_types_fini(rcl_names_and_types_t * topic_names_and_types)
 {

rcl/test/rcl/test_graph.cpp

@@ -170,6 +170,41 @@ TEST_F(
   EXPECT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
 }
 
+/* Test the rcl_names_and_types_init function.
+ */
+TEST_F(
+  CLASSNAME(TestGraphFixture, RMW_IMPLEMENTATION),
+  test_rcl_names_and_types_init
+) {
+  rcl_ret_t ret;
+  rcl_allocator_t allocator = rcl_get_default_allocator();
+  rcl_names_and_types_t nat = rcl_get_zero_initialized_names_and_types();
+  // invalid names and types
+  ret = rcl_names_and_types_init(nullptr, 10, &allocator);
+  EXPECT_EQ(RCL_RET_INVALID_ARGUMENT, ret) << rcl_get_error_string().str;
+  rcl_reset_error();
+  // invalid allocator
+  ret = rcl_names_and_types_init(&nat, 10, nullptr);
+  EXPECT_EQ(RCL_RET_INVALID_ARGUMENT, ret) << rcl_get_error_string().str;
+  rcl_reset_error();
+  // zero size
+  ret = rcl_names_and_types_init(&nat, 0, &allocator);
+  EXPECT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+  EXPECT_EQ(nat.names.size, 0u);
+  ret = rcl_names_and_types_fini(&nat);
+  ASSERT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+  // non-zero size
+  size_t num_names = 10u;
+  ret = rcl_names_and_types_init(&nat, num_names, &allocator);
+  EXPECT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+  EXPECT_EQ(nat.names.size, num_names);
+  for (size_t i = 0; i < num_names; i++) {
+    EXPECT_EQ(nat.types[i].size, 0u);
+  }
+  ret = rcl_names_and_types_fini(&nat);
+  EXPECT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+}
+
 /* Test the rcl_count_publishers function.
  *
  * This does not test content the response.