Added a new implementation of the RealtimeBox with added best effort …

…behaviour (#139)

Co-authored-by: Lennart Nachtigall <[email protected]>
Co-authored-by: Lennart Nachtigall <[email protected]>
Co-authored-by: Christoph Froehlich <[email protected]>
Co-authored-by: Christoph Fröhlich <[email protected]>

CMakeLists.txt

@@ -9,6 +9,7 @@ set(THIS_PACKAGE_INCLUDE_DEPENDS
   rclcpp
   rclcpp_action
   Threads
+  rcpputils
 )
 
 find_package(ament_cmake REQUIRED)
@@ -45,6 +46,9 @@ if(BUILD_TESTING)
   ament_add_gmock(realtime_box_tests test/realtime_box_tests.cpp)
   target_link_libraries(realtime_box_tests realtime_tools)
 
+  ament_add_gmock(realtime_box_best_effort_tests test/realtime_box_best_effort_tests.cpp)
+  target_link_libraries(realtime_box_best_effort_tests realtime_tools)
+
   ament_add_gmock(realtime_buffer_tests test/realtime_buffer_tests.cpp)
   target_link_libraries(realtime_buffer_tests realtime_tools)
 

include/realtime_tools/realtime_box_best_effort.h

@@ -0,0 +1,232 @@
+// Copyright (c) 2024, Lennart Nachtigall
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+//    * Redistributions of source code must retain the above copyright
+//      notice, this list of conditions and the following disclaimer.
+//
+//    * Redistributions in binary form must reproduce the above copyright
+//      notice, this list of conditions and the following disclaimer in the
+//      documentation and/or other materials provided with the distribution.
+//
+//    * Neither the name of the Willow Garage, Inc. nor the names of its
+//      contributors may be used to endorse or promote products derived from
+//      this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+// Author: Lennart Nachtigall
+
+#ifndef REALTIME_TOOLS__REALTIME_BOX_BEST_EFFORT_H_
+#define REALTIME_TOOLS__REALTIME_BOX_BEST_EFFORT_H_
+
+#include <initializer_list>
+#include <mutex>
+#include <optional>
+#include <utility>
+
+#include <rcpputils/pointer_traits.hpp>
+
+namespace realtime_tools
+{
+
+template <typename T>
+constexpr auto is_ptr_or_smart_ptr = rcpputils::is_pointer<T>::value;
+
+/*!
+    A Box that ensures thread safe access to the boxed contents.
+    Access is best effort. If it can not lock it will return.
+
+    NOTE about pointers:
+    You can use pointers with this box but the access will be different.
+    Only use the get/set methods that take function pointer for accessing the internal value.
+*/
+template <class T, typename mutex_type = std::mutex>
+class RealtimeBoxBestEffort
+{
+  static_assert(
+    std::is_same_v<mutex_type, std::mutex> || std::is_same_v<mutex_type, std::recursive_mutex>);
+  static_assert(std::is_copy_constructible_v<T>, "Passed type must be copy constructible");
+
+public:
+  using mutex_t = mutex_type;
+  using type = T;
+  // Provide various constructors
+  constexpr explicit RealtimeBoxBestEffort(const T & init = T{}) : value_(init) {}
+  constexpr explicit RealtimeBoxBestEffort(const T && init) : value_(std::move(init)) {}
+
+  // Only enabled for types that can be constructed from an initializer list
+  template <typename U = T>
+  constexpr RealtimeBoxBestEffort(
+    const std::initializer_list<U> & init,
+    std::enable_if_t<std::is_constructible_v<U, std::initializer_list>>)
+  : value_(init)
+  {
+  }
+
+  /**
+   * @brief set a new content with best effort
+   * @return false if mutex could not be locked
+   * @note disabled for pointer types
+   */
+  template <typename U = T>
+  typename std::enable_if_t<!is_ptr_or_smart_ptr<U>, bool> trySet(const T & value)
+  {
+    std::unique_lock<mutex_t> guard(lock_, std::defer_lock);
+    if (!guard.try_lock()) {
+      return false;
+    }
+    value_ = value;
+    return true;
+  }
+  /**
+   * @brief access the content readable with best effort
+   * @return false if the mutex could not be locked
+   * @note only safe way to access pointer type content (rw)
+   */
+  bool trySet(const std::function<void(T &)> & func)
+  {
+    std::unique_lock<mutex_t> guard(lock_, std::defer_lock);
+    if (!guard.try_lock()) {
+      return false;
+    }
+
+    func(value_);
+    return true;
+  }
+  /**
+   * @brief get the content with best effort
+   * @return std::nullopt if content could not be access, otherwise the content is returned
+   */
+  template <typename U = T>
+  [[nodiscard]] typename std::enable_if_t<!is_ptr_or_smart_ptr<U>, std::optional<U>> tryGet() const
+  {
+    std::unique_lock<mutex_t> guard(lock_, std::defer_lock);
+    if (!guard.try_lock()) {
+      return std::nullopt;
+    }
+    return value_;
+  }
+  /**
+   * @brief access the content (r) with best effort
+   * @return false if the mutex could not be locked
+   * @note only safe way to access pointer type content (r)
+   */
+  bool tryGet(const std::function<void(const T &)> & func)
+  {
+    std::unique_lock<mutex_t> guard(lock_, std::defer_lock);
+    if (!guard.try_lock()) {
+      return false;
+    }
+
+    func(value_);
+    return true;
+  }
+
+  /**
+   * @brief set the content and wait until the mutex could be locked (RealtimeBox behavior)
+   * @return true
+   */
+  template <typename U = T>
+  typename std::enable_if_t<!is_ptr_or_smart_ptr<U>, void> set(const T & value)
+  {
+    std::lock_guard<mutex_t> guard(lock_);
+    // cppcheck-suppress missingReturn
+    value_ = value;
+  }
+  /**
+   * @brief access the content (rw) and wait until the mutex could locked
+   */
+  void set(const std::function<void(T &)> & func)
+  {
+    std::lock_guard<mutex_t> guard(lock_);
+    func(value_);
+  }
+
+  /**
+   * @brief get the content and wait until the mutex could be locked (RealtimeBox behaviour)
+   * @return copy of the value
+   */
+  template <typename U = T>
+  [[nodiscard]] typename std::enable_if_t<!is_ptr_or_smart_ptr<U>, U> get() const
+  {
+    std::lock_guard<mutex_t> guard(lock_);
+    return value_;
+  }
+  /**
+   * @brief get the content and wait until the mutex could be locked
+   * @note same signature as in the existing RealtimeBox<T>
+   */
+  template <typename U = T>
+  typename std::enable_if_t<!is_ptr_or_smart_ptr<U>, void> get(T & in) const
+  {
+    std::lock_guard<mutex_t> guard(lock_);
+    // cppcheck-suppress missingReturn
+    in = value_;
+  }
+  /**
+   * @brief access the content (r) and wait until the mutex could be locked
+   * @note only safe way to access pointer type content (r)
+   * @note same signature as in the existing RealtimeBox<T>
+   */
+  void get(const std::function<void(const T &)> & func)
+  {
+    std::lock_guard<mutex_t> guard(lock_);
+    func(value_);
+  }
+
+  /**
+   * @brief provide a custom assignment operator for easier usage
+   * @note only to be used from non-RT!
+   */
+  template <typename U = T>
+  typename std::enable_if_t<!is_ptr_or_smart_ptr<U>, void> operator=(const T & value)
+  {
+    set(value);
+  }
+
+  /**
+   * @brief provide a custom conversion operator
+   * @note Can only be used from non-RT!
+   */
+  template <typename U = T, typename = typename std::enable_if_t<!is_ptr_or_smart_ptr<U>>>
+  [[nodiscard]] operator T() const
+  {
+    // Only makes sense with the getNonRT method otherwise we would return an std::optional
+    return get();
+  }
+  /**
+   * @brief provide a custom conversion operator
+   * @note Can be used from non-RT and RT contexts
+   */
+  template <typename U = T, typename = typename std::enable_if_t<!is_ptr_or_smart_ptr<U>>>
+  [[nodiscard]] operator std::optional<T>() const
+  {
+    return tryGet();
+  }
+
+  // In case one wants to actually use a pointer
+  // in this implementation we allow accessing the lock directly.
+  // Note: Be careful with lock.unlock().
+  // It may only be called from the thread that locked the mutex!
+  [[nodiscard]] const mutex_t & getMutex() const { return lock_; }
+  [[nodiscard]] mutex_t & getMutex() { return lock_; }
+
+private:
+  T value_;
+  mutable mutex_t lock_;
+};
+}  // namespace realtime_tools
+
+#endif  // REALTIME_TOOLS__REALTIME_BOX_BEST_EFFORT_H_