[libcamera-devel] [PATCH 10/31] libcamera: controls: Return control by value in ControlList::get()

[Laurent Pinchart]

The ControlList::get() and ControlValue::get() methods return the
control value by reference. This requires the ControlValue class to
store the control value in the same form as the one returned by those
functions. For compound controls that are soon to be added, the
ControlValue class would need to store a span<> instance in addition to
the control value itself, which would increase the required storage
space.

Prepare for support of compound controls by returning from get() by
value. As all control values are 8 bytes at most, this doesn't affect
efficiency negatively.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 include/libcamera/controls.h | 10 ++++------
 src/libcamera/controls.cpp   | 10 +++++-----
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
index 9d93064c11b2..3b6b231c7c64 100644
--- a/include/libcamera/controls.h
+++ b/include/libcamera/controls.h
@@ -42,7 +42,7 @@ public:
 	}
 
 	template<typename T>
-	const T &get() const;
+	T get() const;
 	template<typename T>
 	void set(const T &value);
 
@@ -212,13 +212,11 @@ public:
 	bool contains(unsigned int id) const;
 
 	template<typename T>
-	const T &get(const Control<T> &ctrl) const
+	T get(const Control<T> &ctrl) const
 	{
 		const ControlValue *val = find(ctrl.id());
-		if (!val) {
-			static T t(0);
-			return t;
-		}
+		if (!val)
+			return T{};
 
 		return val->get<T>();
 	}
diff --git a/src/libcamera/controls.cpp b/src/libcamera/controls.cpp
index a136ebd2653b..6a0d66fbea8d 100644
--- a/src/libcamera/controls.cpp
+++ b/src/libcamera/controls.cpp
@@ -160,7 +160,7 @@ bool ControlValue::operator==(const ControlValue &other) const
  */
 
 /**
- * \fn template<typename T> const T &ControlValue::get() const
+ * \fn template<typename T> T ControlValue::get() const
  * \brief Get the control value
  *
  * The control value type shall match the type T, otherwise the behaviour is
@@ -177,7 +177,7 @@ bool ControlValue::operator==(const ControlValue &other) const
 
 #ifndef __DOXYGEN__
 template<>
-const bool &ControlValue::get<bool>() const
+bool ControlValue::get<bool>() const
 {
 	ASSERT(type_ == ControlTypeBool);
 
@@ -185,7 +185,7 @@ const bool &ControlValue::get<bool>() const
 }
 
 template<>
-const int32_t &ControlValue::get<int32_t>() const
+int32_t ControlValue::get<int32_t>() const
 {
 	ASSERT(type_ == ControlTypeInteger32);
 
@@ -193,7 +193,7 @@ const int32_t &ControlValue::get<int32_t>() const
 }
 
 template<>
-const int64_t &ControlValue::get<int64_t>() const
+int64_t ControlValue::get<int64_t>() const
 {
 	ASSERT(type_ == ControlTypeInteger64);
 
@@ -720,7 +720,7 @@ bool ControlList::contains(unsigned int id) const
 }
 
 /**
- * \fn template<typename T> const T &ControlList::get(const Control<T> &ctrl) const
+ * \fn template<typename T> T ControlList::get(const Control<T> &ctrl) const
  * \brief Get the value of control \a ctrl
  * \param[in] ctrl The control
  *
-- 
Regards,

Laurent Pinchart