[PATCH v1 4/4] libcamera: controls: Simplify ControlValue::{ControlValue, get, set}

[Barnabás Pőcze]

Whether or not the control has an array type can be determined from the
static information in `detail::control_type<T>`, so use that and
`if constexpr` to deduplicate the constructor, get, and set functions.

Signed-off-by: Barnabás Pőcze <barnabas.pocze at ideasonboard.com>
---
 include/libcamera/controls.h | 75 ++++++++++--------------------------
 1 file changed, 20 insertions(+), 55 deletions(-)

diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
index 85c724ec1..22b5e3d96 100644
--- a/include/libcamera/controls.h
+++ b/include/libcamera/controls.h
@@ -136,28 +136,14 @@ public:
 	ControlValue();
 
 #ifndef __DOXYGEN__
-	template<typename T, std::enable_if_t<!details::is_span<T>::value &&
-					      details::control_type<T>::value &&
-					      !std::is_same<std::string, std::remove_cv_t<T>>::value,
-					      std::nullptr_t> = nullptr>
-	ControlValue(const T &value)
-		: type_(ControlTypeNone), numElements_(0)
-	{
-		set(details::control_type<std::remove_cv_t<T>>::value, false,
-		    &value, 1, sizeof(T));
-	}
-
-	template<typename T, std::enable_if_t<details::is_span<T>::value ||
-					      std::is_same<std::string, std::remove_cv_t<T>>::value,
-					      std::nullptr_t> = nullptr>
+	template<typename T, typename = std::void_t<decltype(details::control_type<T>::value)>>
 #else
 	template<typename T>
 #endif
 	ControlValue(const T &value)
-		: type_(ControlTypeNone), numElements_(0)
+		: type_(ControlTypeNone), isArray_(false), numElements_(0)
 	{
-		set(details::control_type<std::remove_cv_t<T>>::value, true,
-		    value.data(), value.size(), sizeof(typename T::value_type));
+		set(value);
 	}
 
 	~ControlValue();
@@ -180,54 +166,33 @@ public:
 		return !(*this == other);
 	}
 
-#ifndef __DOXYGEN__
-	template<typename T, std::enable_if_t<!details::is_span<T>::value &&
-					      !std::is_same<std::string, std::remove_cv_t<T>>::value,
-					      std::nullptr_t> = nullptr>
-	T get() const
-	{
-		assert(type_ == details::control_type<std::remove_cv_t<T>>::value);
-		assert(!isArray_);
-
-		return *reinterpret_cast<const T *>(data().data());
-	}
-
-	template<typename T, std::enable_if_t<details::is_span<T>::value ||
-					      std::is_same<std::string, std::remove_cv_t<T>>::value,
-					      std::nullptr_t> = nullptr>
-#else
 	template<typename T>
-#endif
 	T get() const
 	{
-		assert(type_ == details::control_type<std::remove_cv_t<T>>::value);
-		assert(isArray_);
+		using TypeInfo = details::control_type<std::remove_cv_t<T>>;
 
-		using V = typename T::value_type;
-		const V *value = reinterpret_cast<const V *>(data().data());
-		return T{ value, numElements_ };
-	}
+		assert(type_ == TypeInfo::value);
+		assert(isArray_ == (TypeInfo::size > 0));
 
-#ifndef __DOXYGEN__
-	template<typename T, std::enable_if_t<!details::is_span<T>::value &&
-					      !std::is_same<std::string, std::remove_cv_t<T>>::value,
-					      std::nullptr_t> = nullptr>
-	void set(const T &value)
-	{
-		set(details::control_type<std::remove_cv_t<T>>::value, false,
-		    reinterpret_cast<const void *>(&value), 1, sizeof(T));
+		if constexpr (TypeInfo::size > 0)
+			return T(reinterpret_cast<const typename T::value_type *>(data().data()), numElements_);
+		else
+			return *reinterpret_cast<const T *>(data().data());
 	}
 
-	template<typename T, std::enable_if_t<details::is_span<T>::value ||
-					      std::is_same<std::string, std::remove_cv_t<T>>::value,
-					      std::nullptr_t> = nullptr>
-#else
 	template<typename T>
-#endif
 	void set(const T &value)
 	{
-		set(details::control_type<std::remove_cv_t<T>>::value, true,
-		    value.data(), value.size(), sizeof(typename T::value_type));
+		using TypeInfo = details::control_type<std::remove_cv_t<T>>;
+		constexpr auto type = TypeInfo::value;
+
+		if constexpr (TypeInfo::size > 0) {
+			static_assert(std::is_trivially_copyable_v<typename T::value_type>);
+			set(type, true, value.data(), value.size(), sizeof(typename T::value_type));
+		} else {
+			static_assert(std::is_trivially_copyable_v<T>);
+			set(type, false, reinterpret_cast<const void *>(&value), 1, sizeof(T));
+		}
 	}
 
 	void reserve(ControlType type, bool isArray = false,
-- 
2.49.0