[libcamera-devel] [PATCH v3 03/33] libcamera: utils: Add exchange()

[Niklas Söderlund]

C++11 does not support std::exchange(), add a custom implementation in
utils.

Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 src/libcamera/include/utils.h | 9 +++++++++
 src/libcamera/utils.cpp       | 8 ++++++++
 2 files changed, 17 insertions(+)

diff --git a/src/libcamera/include/utils.h b/src/libcamera/include/utils.h
index badc77533fa15f09..6470cadc2c6c1234 100644
--- a/src/libcamera/include/utils.h
+++ b/src/libcamera/include/utils.h
@@ -67,6 +67,15 @@ const T& clamp(const T& v, const T& lo, const T& hi)
 	return std::max(lo, std::min(v, hi));
 }
 
+/* C++11 doesn't provide std::exchange */
+template<class T, class U = T>
+T exchange(T &obj, U &&new_value)
+{
+	T old_value = std::move(obj);
+	obj = std::forward<U>(new_value);
+	return old_value;
+}
+
 using clock = std::chrono::steady_clock;
 using duration = std::chrono::steady_clock::duration;
 using time_point = std::chrono::steady_clock::time_point;
diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
index 5de9e4813353b23c..a7e573ac45aec914 100644
--- a/src/libcamera/utils.cpp
+++ b/src/libcamera/utils.cpp
@@ -95,6 +95,14 @@ char *secure_getenv(const char *name)
  * \return lo if v is less than lo, hi if v is greater than hi, otherwise v
  */
 
+/**
+ * \fn libcamera::utils::exchange(T &obj, U &&new_value)
+ * \brief Replace the value of \a obj with \a new_value and return the old value
+ * \param[inout] obj Object whose value to replace
+ * \param[in] new_value The value to assign to obj
+ * \return The old value of \a obj
+ */
+
 /**
  * \typedef clock
  * \brief The libcamera clock (monotonic)
-- 
2.24.1