libcamera: span: Provide and use helper variable templates for type traits

Following the C++17 practice, provide is_array_v<T> and is_span_v<T>
helper variable templates as shorter versions of is_array<T>::value and
is_span<T>::value, and use them through the code.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

2 files changed, 20 insertions, 14 deletions

diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
index dc549a92..3634dc43 100644
--- a/include/libcamera/controls.h
+++ b/include/libcamera/controls.h
@@ -96,7 +96,7 @@ public:
 	ControlValue();
 
 #ifndef __DOXYGEN__
-	template<typename T, typename std::enable_if_t<!details::is_span<T>::value &&
+	template<typename T, typename std::enable_if_t<!details::is_span_v<T> &&
 						       details::control_type<T>::value &&
 						       !std::is_same_v<std::string, std::remove_cv_t<T>>,
 						       std::nullptr_t> = nullptr>
@@ -107,7 +107,7 @@ public:
 		    &value, 1, sizeof(T));
 	}
 
-	template<typename T, typename std::enable_if_t<details::is_span<T>::value ||
+	template<typename T, typename std::enable_if_t<details::is_span_v<T> ||
 						       std::is_same_v<std::string, std::remove_cv_t<T>>,
 						       std::nullptr_t> = nullptr>
 #else
@@ -141,7 +141,7 @@ public:
 	}
 
 #ifndef __DOXYGEN__
-	template<typename T, typename std::enable_if_t<!details::is_span<T>::value &&
+	template<typename T, typename std::enable_if_t<!details::is_span_v<T> &&
 						       !std::is_same_v<std::string, std::remove_cv_t<T>>,
 						       std::nullptr_t> = nullptr>
 	T get() const
@@ -152,7 +152,7 @@ public:
 		return *reinterpret_cast<const T *>(data().data());
 	}
 
-	template<typename T, typename std::enable_if_t<details::is_span<T>::value ||
+	template<typename T, typename std::enable_if_t<details::is_span_v<T> ||
 						       std::is_same_v<std::string, std::remove_cv_t<T>>,
 						       std::nullptr_t> = nullptr>
 #else
@@ -169,7 +169,7 @@ public:
 	}
 
 #ifndef __DOXYGEN__
-	template<typename T, typename std::enable_if_t<!details::is_span<T>::value &&
+	template<typename T, typename std::enable_if_t<!details::is_span_v<T> &&
 						       !std::is_same_v<std::string, std::remove_cv_t<T>>,
 						       std::nullptr_t> = nullptr>
 	void set(const T &value)
@@ -178,7 +178,7 @@ public:
 		    reinterpret_cast<const void *>(&value), 1, sizeof(T));
 	}
 
-	template<typename T, typename std::enable_if_t<details::is_span<T>::value ||
+	template<typename T, typename std::enable_if_t<details::is_span_v<T> ||
 						       std::is_same_v<std::string, std::remove_cv_t<T>>,
 						       std::nullptr_t> = nullptr>
 #else
diff --git a/include/libcamera/span.h b/include/libcamera/span.h
index d720adb8..e7ffef12 100644
--- a/include/libcamera/span.h
+++ b/include/libcamera/span.h
@@ -31,6 +31,9 @@ template<typename U, std::size_t N>
 struct is_array<std::array<U, N>> : public std::true_type {
 };
 
+template<typename T>
+inline constexpr bool is_array_v = is_array<T>::value;
+
 template<typename U>
 struct is_span : public std::false_type {
 };
@@ -39,6 +42,9 @@ template<typename U, std::size_t Extent>
 struct is_span<Span<U, Extent>> : public std::true_type {
 };
 
+template<typename T>
+inline constexpr bool is_span_v = is_span<T>::value;
+
 } /* namespace details */
 
 namespace utils {
@@ -155,8 +161,8 @@ public:
 
 	template<class Container>
 	explicit constexpr Span(Container &cont,
-				std::enable_if_t<!details::is_span<Container>::value &&
-						 !details::is_array<Container>::value &&
+				std::enable_if_t<!details::is_span_v<Container> &&
+						 !details::is_array_v<Container> &&
 						 !std::is_array_v<Container> &&
 						 std::is_convertible_v<std::remove_pointer_t<decltype(utils::data(cont))> (*)[],
 								       element_type (*)[]>,
@@ -167,8 +173,8 @@ public:
 
 	template<class Container>
 	explicit constexpr Span(const Container &cont,
-				std::enable_if_t<!details::is_span<Container>::value &&
-						 !details::is_array<Container>::value &&
+				std::enable_if_t<!details::is_span_v<Container> &&
+						 !details::is_array_v<Container> &&
 						 !std::is_array_v<Container> &&
 						 std::is_convertible_v<std::remove_pointer_t<decltype(utils::data(cont))> (*)[],
 								       element_type (*)[]>,
@@ -317,8 +323,8 @@ public:
 
 	template<class Container>
 	constexpr Span(Container &cont,
-		       std::enable_if_t<!details::is_span<Container>::value &&
-					!details::is_array<Container>::value &&
+		       std::enable_if_t<!details::is_span_v<Container> &&
+					!details::is_array_v<Container> &&
 					!std::is_array_v<Container> &&
 					std::is_convertible_v<std::remove_pointer_t<decltype(utils::data(cont))> (*)[],
 							      element_type (*)[]>,
@@ -329,8 +335,8 @@ public:
 
 	template<class Container>
 	constexpr Span(const Container &cont,
-		       std::enable_if_t<!details::is_span<Container>::value &&
-					!details::is_array<Container>::value &&
+		       std::enable_if_t<!details::is_span_v<Container> &&
+					!details::is_array_v<Container> &&
 					!std::is_array_v<Container> &&
 					std::is_convertible_v<std::remove_pointer_t<decltype(utils::data(cont))> (*)[],
 							      element_type (*)[]>,