Add support for taking a sequence of messages

rcl/include/rcl/subscription.h

@@ -26,6 +26,8 @@ extern "C"
 #include "rcl/node.h"
 #include "rcl/visibility_control.h"
 
+#include "rmw/message_sequence.h"
+
 /// Internal rcl implementation struct.
 struct rcl_subscription_impl_t;
 
@@ -203,7 +205,7 @@ rcl_subscription_get_default_options(void);
 /// Take a ROS message from a topic using a rcl subscription.
 /**
  * It is the job of the caller to ensure that the type of the ros_message
- * argument and the type associate with the subscription, via the type
+ * argument and the type associated with the subscription, via the type
  * support, match.
  * Passing a different type to rcl_take produces undefined behavior and cannot
  * be checked by this function and therefore no deliberate error will occur.
@@ -227,7 +229,7 @@ rcl_subscription_get_default_options(void);
  * be allocated for a dynamically sized array in the target message, then the
  * allocator given in the subscription options is used.
  *
- * The rmw message_info struct contains meta information about this particular
+ * The rmw_message_info struct contains meta information about this particular
  * message instance, like what the GUID of the publisher which published it
  * originally or whether or not the message received from within the same
  * process.
@@ -248,7 +250,7 @@ rcl_subscription_get_default_options(void);
  * \param[inout] ros_message type-erased ptr to a allocated ROS message
  * \param[out] message_info rmw struct which contains meta-data for the message
  * \param[in] allocation structure pointer used for memory preallocation (may be NULL)
- * \return `RCL_RET_OK` if the message was published, or
+ * \return `RCL_RET_OK` if the message was taken, or
  * \return `RCL_RET_INVALID_ARGUMENT` if any arguments are invalid, or
  * \return `RCL_RET_SUBSCRIPTION_INVALID` if the subscription is invalid, or
  * \return `RCL_RET_BAD_ALLOC` if allocating memory failed, or
@@ -266,6 +268,58 @@ rcl_take(
   rmw_subscription_allocation_t * allocation
 );
 
+/// Take a sequence of messages from a topic using a rcl subscription.
+/**
+ * In contrast to `rcl_take`, this function can take multiple messages at
+ * the same time.
+ * It is the job of the caller to ensure that the type of the message_sequence
+ * argument and the type associated with the subscription, via the type
+ * support, match.
+ *
+ * The message_sequence pointer should point to an already allocated sequence
+ * of ROS messages of the correct type, into which the taken ROS messages will
+ * be copied if messages are available.
+ * The message_sequence `size` member will be set to the number of messages
+ * correctly taken.
+ *
+ * The rmw_message_info_sequence struct contains meta information about the
+ * corresponding message instance index.
+ * The message_info_sequence argument should be an already allocated
+ * rmw_message_info_sequence_t structure.
+ *
+ * <hr>
+ * Attribute          | Adherence
+ * ------------------ | -------------
+ * Allocates Memory   | Maybe [1]
+ * Thread-Safe        | No
+ * Uses Atomics       | No
+ * Lock-Free          | Yes
+ * <i>[1] only if storage in the serialized_message is insufficient</i>
+ *
+ * \param[in] subscription the handle to the subscription from which to take.
+ * \param[in] count number of messages to attempt to take.
+ * \param[inout] message_sequence pointer to a (pre-allocated) message sequence.
+ * \param[inout] message_info_sequence pointer to a (pre-allocated) message info sequence.
+ * \param[in] allocation structure pointer used for memory preallocation (may be NULL)
+ * \return `RCL_RET_OK` if one or more messages was taken, or
+ * \return `RCL_RET_INVALID_ARGUMENT` if any arguments are invalid, or
+ * \return `RCL_RET_SUBSCRIPTION_INVALID` if the subscription is invalid, or
+ * \return `RCL_RET_BAD_ALLOC` if allocating memory failed, or
+ * \return `RCL_RET_SUBSCRIPTION_TAKE_FAILED` if take failed but no error
+ *         occurred in the middleware, or
+ * \return `RCL_RET_ERROR` if an unspecified error occurs.
+ */
+RCL_PUBLIC
+RCL_WARN_UNUSED
+rcl_ret_t
+rcl_take_sequence(
+  const rcl_subscription_t * subscription,
+  size_t count,
+  rmw_message_sequence_t * message_sequence,
+  rmw_message_info_sequence_t * message_info_sequence,
+  rmw_subscription_allocation_t * allocation
+);
+
 /// Take a serialized raw message from a topic using a rcl subscription.
 /**
  * In contrast to `rcl_take`, this function stores the taken message in

rcl/src/rcl/subscription.c

@@ -283,6 +283,52 @@ rcl_take(
   return RCL_RET_OK;
 }
 
+rcl_ret_t
+rcl_take_sequence(
+  const rcl_subscription_t * subscription,
+  size_t count,
+  rmw_message_sequence_t * message_sequence,
+  rmw_message_info_sequence_t * message_info_sequence,
+  rmw_subscription_allocation_t * allocation
+)
+{
+  // Set the sizes to zero to indicate that there are no valid messages
+  message_sequence->size = 0u;
+  message_info_sequence->size = 0u;
+
+  RCUTILS_LOG_DEBUG_NAMED(ROS_PACKAGE_NAME, "Subscription taking %zu messages", count);
+  if (!rcl_subscription_is_valid(subscription)) {
+    return RCL_RET_SUBSCRIPTION_INVALID;  // error message already set
+  }
+  RCL_CHECK_ARGUMENT_FOR_NULL(message_sequence, RCL_RET_INVALID_ARGUMENT);
+  RCL_CHECK_ARGUMENT_FOR_NULL(message_info_sequence, RCL_RET_INVALID_ARGUMENT);
+
+  if (message_sequence->capacity < count) {
+    RCL_SET_ERROR_MSG("Insufficient message sequence capacity for requested count");
+    return RCL_RET_INVALID_ARGUMENT;
+  }
+
+  if (message_info_sequence->capacity < count) {
+    RCL_SET_ERROR_MSG("Insufficient message info sequence capacity for requested count");
+    return RCL_RET_INVALID_ARGUMENT;
+  }
+
+  size_t taken = 0u;
+  rmw_ret_t ret = rmw_take_sequence(
+    subscription->impl->rmw_handle, count, message_sequence, message_info_sequence, &taken,
+    allocation);
+  if (ret != RMW_RET_OK) {
+    RCL_SET_ERROR_MSG(rmw_get_error_string().str);
+    return rcl_convert_rmw_ret_to_rcl_ret(ret);
+  }
+  RCUTILS_LOG_DEBUG_NAMED(
+    ROS_PACKAGE_NAME, "Subscription took %zu messages", taken);
+  if (0u == taken) {
+    return RCL_RET_SUBSCRIPTION_TAKE_FAILED;
+  }
+  return RCL_RET_OK;
+}
+
 rcl_ret_t
 rcl_take_serialized_message(
   const rcl_subscription_t * subscription,

rcl/test/rcl/test_subscription.cpp

@@ -278,3 +278,155 @@ TEST_F(CLASSNAME(TestSubscriptionFixture, RMW_IMPLEMENTATION), test_subscription
     ASSERT_EQ(std::string(test_string), std::string(msg.string_value.data, msg.string_value.size));
   }
 }
+
+/* Basic nominal test of a subscription taking a sequence.
+ */
+TEST_F(
+  CLASSNAME(
+    TestSubscriptionFixture,
+    RMW_IMPLEMENTATION), test_subscription_nominal_string_sequence) {
+  rcl_ret_t ret;
+  rcl_publisher_t publisher = rcl_get_zero_initialized_publisher();
+  const rosidl_message_type_support_t * ts =
+    ROSIDL_GET_MSG_TYPE_SUPPORT(test_msgs, msg, Strings);
+  const char * topic = "rcl_test_subscription_nominal_string_sequence_chatter";
+  rcl_publisher_options_t publisher_options = rcl_publisher_get_default_options();
+  ret = rcl_publisher_init(&publisher, this->node_ptr, ts, topic, &publisher_options);
+  ASSERT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+  OSRF_TESTING_TOOLS_CPP_SCOPE_EXIT(
+  {
+    rcl_ret_t ret = rcl_publisher_fini(&publisher, this->node_ptr);
+    EXPECT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+  });
+  rcl_subscription_t subscription = rcl_get_zero_initialized_subscription();
+  rcl_subscription_options_t subscription_options = rcl_subscription_get_default_options();
+  ret = rcl_subscription_init(&subscription, this->node_ptr, ts, topic, &subscription_options);
+  ASSERT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+  OSRF_TESTING_TOOLS_CPP_SCOPE_EXIT(
+  {
+    rcl_ret_t ret = rcl_subscription_fini(&subscription, this->node_ptr);
+    EXPECT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+  });
+  // TODO(wjwwood): add logic to wait for the connection to be established
+  //                probably using the count_subscriptions busy wait mechanism
+  //                until then we will sleep for a short period of time
+  std::this_thread::sleep_for(std::chrono::milliseconds(1000));
+  const char * test_string = "testing";
+  {
+    test_msgs__msg__Strings msg;
+    test_msgs__msg__Strings__init(&msg);
+    ASSERT_TRUE(rosidl_runtime_c__String__assign(&msg.string_value, test_string));
+    ret = rcl_publish(&publisher, &msg, nullptr);
+    ret = rcl_publish(&publisher, &msg, nullptr);
+    ret = rcl_publish(&publisher, &msg, nullptr);
+    test_msgs__msg__Strings__fini(&msg);
+    ASSERT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+  }
+  bool success;
+  wait_for_subscription_to_be_ready(&subscription, context_ptr, 10, 100, success);
+  ASSERT_TRUE(success);
+  auto allocator = rcutils_get_default_allocator();
+  {
+    size_t size = 1;
+    rmw_message_info_sequence_t message_infos;
+    rmw_message_info_sequence_init(&message_infos, size, &allocator);
+
+    rmw_message_sequence_t messages;
+    rmw_message_sequence_init(&messages, size, &allocator);
+
+    auto seq = test_msgs__msg__Strings__Sequence__create(size);
+
+    for (size_t ii = 0; ii < size; ++ii) {
+      messages.data[ii] = &seq->data[ii];
+    }
+
+    OSRF_TESTING_TOOLS_CPP_SCOPE_EXIT(
+    {
+      rmw_message_info_sequence_fini(&message_infos);
+      rmw_message_sequence_fini(&messages);
+      test_msgs__msg__Strings__Sequence__destroy(seq);
+    });
+
+    // Attempt to take more than capacity allows.
+    ret = rcl_take_sequence(&subscription, 5, &messages, &message_infos, nullptr);
+    ASSERT_EQ(RCL_RET_INVALID_ARGUMENT, ret) << rcl_get_error_string().str;
+
+    ASSERT_EQ(0u, messages.size);
+    ASSERT_EQ(0u, message_infos.size);
+  }
+
+  {
+    size_t size = 5;
+    rmw_message_info_sequence_t message_infos;
+    rmw_message_info_sequence_init(&message_infos, size, &allocator);
+
+    rmw_message_sequence_t messages;
+    rmw_message_sequence_init(&messages, size, &allocator);
+
+    auto seq = test_msgs__msg__Strings__Sequence__create(size);
+
+    for (size_t ii = 0; ii < size; ++ii) {
+      messages.data[ii] = &seq->data[ii];
+    }
+
+    OSRF_TESTING_TOOLS_CPP_SCOPE_EXIT(
+    {
+      rmw_message_info_sequence_fini(&message_infos);
+      rmw_message_sequence_fini(&messages);
+      test_msgs__msg__Strings__Sequence__destroy(seq);
+    });
+
+    ret = rcl_take_sequence(&subscription, 5, &messages, &message_infos, nullptr);
+    ASSERT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+    ASSERT_EQ(3u, messages.size);
+    ASSERT_EQ(3u, message_infos.size);
+  }
+
+  {
+    test_msgs__msg__Strings msg;
+    test_msgs__msg__Strings__init(&msg);
+    ASSERT_TRUE(rosidl_runtime_c__String__assign(&msg.string_value, test_string));
+    ret = rcl_publish(&publisher, &msg, nullptr);
+    ret = rcl_publish(&publisher, &msg, nullptr);
+    ret = rcl_publish(&publisher, &msg, nullptr);
+    ret = rcl_publish(&publisher, &msg, nullptr);
+    ret = rcl_publish(&publisher, &msg, nullptr);
+    test_msgs__msg__Strings__fini(&msg);
+    ASSERT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+  }
+
+  // Give a brief moment for publications to go through.
+  std::this_thread::sleep_for(std::chrono::milliseconds(500));
+  // Take fewer messages than are available in the subscription
+  {
+    size_t size = 3;
+    rmw_message_info_sequence_t message_infos;
+    rmw_message_info_sequence_init(&message_infos, size, &allocator);
+
+    rmw_message_sequence_t messages;
+    rmw_message_sequence_init(&messages, size, &allocator);
+
+    auto seq = test_msgs__msg__Strings__Sequence__create(size);
+
+    for (size_t ii = 0; ii < size; ++ii) {
+      messages.data[ii] = &seq->data[ii];
+    }
+
+    OSRF_TESTING_TOOLS_CPP_SCOPE_EXIT(
+    {
+      rmw_message_info_sequence_fini(&message_infos);
+      rmw_message_sequence_fini(&messages);
+      test_msgs__msg__Strings__Sequence__destroy(seq);
+    });
+
+    ret = rcl_take_sequence(&subscription, 3, &messages, &message_infos, nullptr);
+
+    ASSERT_EQ(RCL_RET_OK, ret) << rcl_get_error_string().str;
+    ASSERT_EQ(3u, messages.size);
+    ASSERT_EQ(3u, message_infos.size);
+
+    ASSERT_EQ(
+      std::string(test_string),
+      std::string(seq->data[0].string_value.data, seq->data[0].string_value.size));
+  }
+}