[libcamera-devel] [PATCH 2/2] libcamera: span: Provide and use helper variable templates for type traits

[Niklas Söderlund]

Hi Laurent,

Thanks for your work.

On 2020-10-26 21:52:09 +0200, Laurent Pinchart wrote:
> 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 at ideasonboard.com>

Reviewed-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>

> ---
>  include/libcamera/controls.h | 12 ++++++------
>  include/libcamera/span.h     | 22 ++++++++++++++--------
>  2 files changed, 20 insertions(+), 14 deletions(-)
> 
> diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
> index dc549a92f975..3634dc431618 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 d720adb81f89..e7ffef1255d4 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 (*)[]>,
> -- 
> Regards,
> 
> Laurent Pinchart
> 
> _______________________________________________
> libcamera-devel mailing list
> libcamera-devel at lists.libcamera.org
> https://lists.libcamera.org/listinfo/libcamera-devel

-- 
Regards,
Niklas Söderlund