Fix for issue 416: Impossible to retain transfer ids (#420)

- Introduced public `ITransferIdMap` and internal
`detail::ITransferIdStorage` interfaces.
- Presentation publisher and rpc client entities now...
- try initialize (at ctor) their transfer ids with the transfer id map
`getIdFor` method.
- try to store their next transfer ids into the map (using `setIdFor`).
- Extra unit tests and mocks to cover new transfer id map related
business logic.

Author: serges147

include/libcyphal/application/node/heartbeat_producer.hpp

@@ -169,7 +169,7 @@ class HeartbeatProducer final  // NOSONAR cpp:S3624
     void publishMessage(const TimePoint approx_now)
     {
         // Publishing of heartbeats makes sense only if the local node ID is known.
-        if (presentation_.transport().getLocalNodeId() == cetl::nullopt)
+        if (!presentation_.transport().getLocalNodeId().has_value())
         {
             return;
         }

include/libcyphal/presentation/client.hpp

@@ -237,8 +237,8 @@ class Client final : public detail::ClientBase
                 // For request (and the following response) we need to allocate a transfer ID,
                 // which will be in use to pair the request with the response.
                 //
-                auto& shared_client   = getSharedClient();
-                auto  opt_transfer_id = shared_client.nextTransferId();
+                auto&      shared_client   = getSharedClient();
+                const auto opt_transfer_id = shared_client.nextTransferId();
                 if (!opt_transfer_id)
                 {
                     return TooManyPendingRequestsError{};
@@ -325,8 +325,8 @@ class RawServiceClient final : public detail::ClientBase
         // 1. For request (and following response) we need to allocate a transfer ID,
         //    which will be in use to pair the request with the response.
         //
-        auto& shared_client   = getSharedClient();
-        auto  opt_transfer_id = shared_client.nextTransferId();
+        auto&      shared_client   = getSharedClient();
+        const auto opt_transfer_id = shared_client.nextTransferId();
         if (!opt_transfer_id)
         {
             return TooManyPendingRequestsError{};

include/libcyphal/presentation/client_impl.hpp

@@ -13,7 +13,7 @@
 #include "libcyphal/executor.hpp"
 #include "libcyphal/transport/errors.hpp"
 #include "libcyphal/transport/svc_sessions.hpp"
-#include "libcyphal/transport/transfer_id_generators.hpp"
+#include "libcyphal/transport/transfer_id_map.hpp"
 #include "libcyphal/transport/types.hpp"
 #include "libcyphal/types.hpp"
 
@@ -34,7 +34,9 @@ namespace presentation
 namespace detail
 {
 
-class SharedClient : public common::cavl::Node<SharedClient>, public SharedObject
+class SharedClient : public common::cavl::Node<SharedClient>,
+                     public SharedObject,
+                     protected transport::detail::ITransferIdStorage
 {
 public:
     using Node::remove;
@@ -134,17 +136,24 @@ class SharedClient : public common::cavl::Node<SharedClient>, public SharedObjec
         , svc_request_tx_session_{std::move(svc_request_tx_session)}
         , svc_response_rx_session_{std::move(svc_response_rx_session)}
         , response_rx_params_{svc_response_rx_session_->getParams()}
+        , next_transfer_id_{0}
         , nearest_deadline_{DistantFuture()}
     {
         CETL_DEBUG_ASSERT(svc_request_tx_session_ != nullptr, "");
         CETL_DEBUG_ASSERT(svc_response_rx_session_ != nullptr, "");
 
+        if (const auto* const transfer_id_map = delegate.getTransferIdMap())
+        {
+            const SessionSpec session_spec{response_rx_params_.service_id, response_rx_params_.server_node_id};
+            next_transfer_id_ = transfer_id_map->getIdFor(session_spec);
+        }
+
         // Override the default (2s) timeout value of the response session.
         // This is done to allow multiple overlapping responses to be handled properly.
         // Otherwise, the responses would be rejected (as "duplicates") if their transfer IDs are in order.
         // Real duplicates (f.e. caused by redundant transports) won't cause any issues
         // b/c shared RPC client expects/accepts only one response per transfer ID,
-        // and corresponding promise callback node will be removed after the first response.
+        // and the corresponding promise callback node will be removed after the first response.
         svc_response_rx_session_->setTransferIdTimeout({});
 
         svc_response_rx_session_->setOnReceiveCallback([this](const auto& arg) {
@@ -199,7 +208,7 @@ class SharedClient : public common::cavl::Node<SharedClient>, public SharedObjec
     {
         if (timeout_node.isTimeoutLinked())
         {
-            // Remove previous timeout node (if any),
+            // Remove the previous timeout node (if any),
             // and then reinsert the node with updated/given new deadline time.
             //
             timeout_nodes_by_deadline_.remove(&timeout_node);
@@ -240,9 +249,27 @@ class SharedClient : public common::cavl::Node<SharedClient>, public SharedObjec
 
     void destroy() noexcept override
     {
+        if (auto* const transfer_id_map = delegate_.getTransferIdMap())
+        {
+            const SessionSpec session_spec{response_rx_params_.service_id, response_rx_params_.server_node_id};
+            transfer_id_map->setIdFor(session_spec, next_transfer_id_);
+        }
+
         delegate_.forgetSharedClient(*this);
     }
 
+    // MARK: ITransferIdStorage
+
+    transport::TransferId load() const noexcept override
+    {
+        return next_transfer_id_;
+    }
+
+    void save(const transport::TransferId transfer_id) noexcept override
+    {
+        next_transfer_id_ = transfer_id;
+    }
+
 protected:
     virtual void insertNewCallbackNode(CallbackNode& callback_node)
     {
@@ -273,7 +300,8 @@ class SharedClient : public common::cavl::Node<SharedClient>, public SharedObjec
     }
 
 private:
-    using Schedule = IExecutor::Callback::Schedule;
+    using Schedule    = IExecutor::Callback::Schedule;
+    using SessionSpec = transport::ITransferIdMap::SessionSpec;
 
     static constexpr TimePoint DistantFuture()
     {
@@ -388,6 +416,7 @@ class SharedClient : public common::cavl::Node<SharedClient>, public SharedObjec
     const UniquePtr<transport::IRequestTxSession>  svc_request_tx_session_;
     const UniquePtr<transport::IResponseRxSession> svc_response_rx_session_;
     const transport::ResponseRxParams              response_rx_params_;
+    transport::TransferId                          next_transfer_id_;
     common::cavl::Tree<CallbackNode>               cb_nodes_by_transfer_id_;
     TimePoint                                      nearest_deadline_;
     common::cavl::Tree<TimeoutNode>                timeout_nodes_by_deadline_;
@@ -399,8 +428,8 @@ class SharedClient : public common::cavl::Node<SharedClient>, public SharedObjec
 
 /// @brief Defines a shared client implementation that uses a generic transfer ID generator.
 ///
-template <typename TransferIdGeneratorMixin>
-class ClientImpl final : public SharedClient, private TransferIdGeneratorMixin
+template <typename TransferIdGenerator>
+class ClientImpl final : public SharedClient
 {
 public:
     ClientImpl(IPresentationDelegate&                   delegate,
@@ -409,7 +438,7 @@ class ClientImpl final : public SharedClient, private TransferIdGeneratorMixin
                UniquePtr<transport::IResponseRxSession> svc_response_rx_session,
                const transport::TransferId              transfer_id_modulo)
         : SharedClient{delegate, executor, std::move(svc_request_tx_session), std::move(svc_response_rx_session)}
-        , TransferIdGeneratorMixin{transfer_id_modulo}
+        , transfer_id_generator_{transfer_id_modulo, *this}
     {
     }
 
@@ -424,40 +453,41 @@ class ClientImpl final : public SharedClient, private TransferIdGeneratorMixin
 private:
     using Base = SharedClient;
 
-    // MARK: SharedClient
-
-    CETL_NODISCARD cetl::optional<transport::TransferId> nextTransferId() noexcept override
-    {
-        return TransferIdGeneratorMixin::nextTransferId();
-    }
-
     void insertNewCallbackNode(CallbackNode& callback_node) override
     {
         SharedClient::insertNewCallbackNode(callback_node);
-        TransferIdGeneratorMixin::retainTransferId(callback_node.getTransferId());
+        transfer_id_generator_.retainTransferId(callback_node.getTransferId());
     }
 
     void removeCallbackNode(CallbackNode& callback_node) override
     {
-        TransferIdGeneratorMixin::releaseTransferId(callback_node.getTransferId());
+        transfer_id_generator_.releaseTransferId(callback_node.getTransferId());
         SharedClient::removeCallbackNode(callback_node);
     }
 
+    // MARK: SharedClient
+
+    CETL_NODISCARD cetl::optional<transport::TransferId> nextTransferId() noexcept override
+    {
+        return transfer_id_generator_.nextTransferId();
+    }
+
+    TransferIdGenerator transfer_id_generator_;
+
 };  // ClientImpl<TransferIdGeneratorMixin>
 
 /// @brief Defines a shared client specialization that uses a trivial transfer ID generator.
 ///
 template <>
-class ClientImpl<transport::detail::TrivialTransferIdGenerator> final
-    : public SharedClient,
-      private transport::detail::TrivialTransferIdGenerator
+class ClientImpl<transport::detail::TrivialTransferIdGenerator> final : public SharedClient
 {
 public:
     ClientImpl(IPresentationDelegate&                   delegate,
                IExecutor&                               executor,
                UniquePtr<transport::IRequestTxSession>  svc_request_tx_session,
                UniquePtr<transport::IResponseRxSession> svc_response_rx_session)
         : Base{delegate, executor, std::move(svc_request_tx_session), std::move(svc_response_rx_session)}
+        , transfer_id_generator_{*this}
     {
     }
 
@@ -476,9 +506,11 @@ class ClientImpl<transport::detail::TrivialTransferIdGenerator> final
 
     CETL_NODISCARD cetl::optional<transport::TransferId> nextTransferId() noexcept override
     {
-        return TrivialTransferIdGenerator::nextTransferId();
+        return transfer_id_generator_.nextTransferId();
     }
 
+    transport::detail::TrivialTransferIdGenerator transfer_id_generator_;
+
 };  // ClientImpl<TrivialTransferIdGenerator>
 
 }  // namespace detail