Add public facing API for validating rcl_wait_set_t (ros2#538)

I've exposed the existing function as public API and added documentation and unit tests.

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

rcl/include/rcl/wait.h

@@ -459,6 +459,29 @@ RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait(rcl_wait_set_t * wait_set, int64_t timeout);
 
+/// Return `true` if the wait set is valid, else `false`.
+/**
+ * A wait set is invalid if:
+ *   - the implementation is `NULL` (rcl_wait_set_init not called or failed)
+ *   - the wait set has been finalized with rcl_wait_set_fini
+ *
+ * Also return `false` if the wait set pointer is `NULL`.
+ *
+ * <hr>
+ * Attribute          | Adherence
+ * ------------------ | -------------
+ * Allocates Memory   | No
+ * Thread-Safe        | No
+ * Uses Atomics       | No
+ * Lock-Free          | Yes
+ *
+ * \param[in] wait_set the rcl_wait_set_t to be validated
+ * \return `true` if the wait_set is valid, otherwise `false`.
+ */
+RCL_PUBLIC
+bool
+rcl_wait_set_is_valid(const rcl_wait_set_t * wait_set);
+
 #ifdef __cplusplus
 }
 #endif

rcl/src/rcl/wait.c

@@ -79,8 +79,8 @@ rcl_get_zero_initialized_wait_set()
   return null_wait_set;
 }
 
-static bool
-__wait_set_is_valid(const rcl_wait_set_t * wait_set)
+bool
+rcl_wait_set_is_valid(const rcl_wait_set_t * wait_set)
 {
   return wait_set && wait_set->impl;
 }
@@ -118,7 +118,7 @@ rcl_wait_set_init(
 
   RCL_CHECK_ALLOCATOR_WITH_MSG(&allocator, "invalid allocator", return RCL_RET_INVALID_ARGUMENT);
   RCL_CHECK_ARGUMENT_FOR_NULL(wait_set, RCL_RET_INVALID_ARGUMENT);
-  if (__wait_set_is_valid(wait_set)) {
+  if (rcl_wait_set_is_valid(wait_set)) {
     RCL_SET_ERROR_MSG("wait_set already initialized, or memory was uninitialized.");
     return RCL_RET_ALREADY_INIT;
   }
@@ -173,7 +173,7 @@ rcl_wait_set_init(
   }
   return RCL_RET_OK;
 fail:
-  if (__wait_set_is_valid(wait_set)) {
+  if (rcl_wait_set_is_valid(wait_set)) {
     rmw_ret_t ret = rmw_destroy_wait_set(wait_set->impl->rmw_wait_set);
     if (ret != RMW_RET_OK) {
       fail_ret = RCL_RET_WAIT_SET_INVALID;
@@ -189,7 +189,7 @@ rcl_wait_set_fini(rcl_wait_set_t * wait_set)
   rcl_ret_t result = RCL_RET_OK;
   RCL_CHECK_ARGUMENT_FOR_NULL(wait_set, RCL_RET_INVALID_ARGUMENT);
 
-  if (__wait_set_is_valid(wait_set)) {
+  if (rcl_wait_set_is_valid(wait_set)) {
     rmw_ret_t ret = rmw_destroy_wait_set(wait_set->impl->rmw_wait_set);
     if (ret != RMW_RET_OK) {
       RCL_SET_ERROR_MSG(rmw_get_error_string().str);
@@ -204,7 +204,7 @@ rcl_ret_t
 rcl_wait_set_get_allocator(const rcl_wait_set_t * wait_set, rcl_allocator_t * allocator)
 {
   RCL_CHECK_ARGUMENT_FOR_NULL(wait_set, RCL_RET_INVALID_ARGUMENT);
-  if (!__wait_set_is_valid(wait_set)) {
+  if (!rcl_wait_set_is_valid(wait_set)) {
     RCL_SET_ERROR_MSG("wait set is invalid");
     return RCL_RET_WAIT_SET_INVALID;
   }
@@ -215,7 +215,7 @@ rcl_wait_set_get_allocator(const rcl_wait_set_t * wait_set, rcl_allocator_t * al
 
 #define SET_ADD(Type) \
   RCL_CHECK_ARGUMENT_FOR_NULL(wait_set, RCL_RET_INVALID_ARGUMENT); \
-  if (!__wait_set_is_valid(wait_set)) { \
+  if (!rcl_wait_set_is_valid(wait_set)) { \
     RCL_SET_ERROR_MSG("wait set is invalid"); \
     return RCL_RET_WAIT_SET_INVALID; \
   } \
@@ -515,7 +515,7 @@ rcl_ret_t
 rcl_wait(rcl_wait_set_t * wait_set, int64_t timeout)
 {
   RCL_CHECK_ARGUMENT_FOR_NULL(wait_set, RCL_RET_INVALID_ARGUMENT);
-  if (!__wait_set_is_valid(wait_set)) {
+  if (!rcl_wait_set_is_valid(wait_set)) {
     RCL_SET_ERROR_MSG("wait set is invalid");
     return RCL_RET_WAIT_SET_INVALID;
   }

rcl/test/rcl/test_wait.cpp

@@ -65,6 +65,26 @@ class CLASSNAME (WaitSetTestFixture, RMW_IMPLEMENTATION) : public ::testing::Tes
   }
 };
 
+TEST_F(CLASSNAME(WaitSetTestFixture, RMW_IMPLEMENTATION), wait_set_is_valid) {
+  // null pointers are invalid
+  EXPECT_FALSE(rcl_wait_set_is_valid(nullptr));
+
+  // uninitialized wait set is invalid
+  rcl_wait_set_t wait_set = rcl_get_zero_initialized_wait_set();
+  EXPECT_FALSE(rcl_wait_set_is_valid(&wait_set));
+
+  // initialized wait set is valid
+  rcl_ret_t ret =
+    rcl_wait_set_init(&wait_set, 1, 1, 1, 1, 1, 0, context_ptr, rcl_get_default_allocator());
+  EXPECT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+  EXPECT_TRUE(rcl_wait_set_is_valid(&wait_set));
+
+  // finalized wait set is invalid
+  ret = rcl_wait_set_fini(&wait_set);
+  EXPECT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+  EXPECT_FALSE(rcl_wait_set_is_valid(&wait_set));
+}
+
 TEST_F(CLASSNAME(WaitSetTestFixture, RMW_IMPLEMENTATION), test_resize_to_zero) {
   // Initialize a wait set with a subscription and then resize it to zero.
   rcl_wait_set_t wait_set = rcl_get_zero_initialized_wait_set();