[PATCH v2 04/17] libcamera: vector: Add a Span based constructor

[Kieran Bingham]

Quoting Stefan Klug (2025-03-19 16:11:09)
> Now that Matrix has a Span based constructor, add the same for Vector.

Well, with that logic, someone else has a yacht - so I deserve one ...
:-)

I assume Vectors deserve span based constructors because it benefits
them directly?


> 
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> 
> ---
> 
> Changes in v2:
> - Added this patch
> ---
>  include/libcamera/internal/vector.h | 12 ++++++++----
>  src/libcamera/vector.cpp            |  8 ++++++++
>  2 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/include/libcamera/internal/vector.h b/include/libcamera/internal/vector.h
> index a67a09474204..66cc5ac988c2 100644
> --- a/include/libcamera/internal/vector.h
> +++ b/include/libcamera/internal/vector.h
> @@ -40,10 +40,14 @@ public:
>                 data_.fill(scalar);
>         }
>  
> -       constexpr Vector(const std::array<T, Rows> &data)
> +       Vector(const std::array<T, Rows> &data)
>         {
> -               for (unsigned int i = 0; i < Rows; i++)
> -                       data_[i] = data[i];
> +               std::copy(data.begin(), data.end(), data_.begin());
> +       }

This loses a constexpr ... what's the downside here? At least that
should be highlighted/discussed in the commit message.


> +
> +       Vector(const Span<const T, Rows> &data)
> +       {
> +               std::copy(data.begin(), data.end(), data_.begin());
>         }
>  
>         const T &operator[](size_t i) const
> @@ -285,7 +289,7 @@ private:
>                 return *this;
>         }
>  
> -       std::array<T, Rows> data_;
> +       std::array<T, Rows> data_{};

Is this just for initialisation ?

>  };
>  
>  template<typename T>
> diff --git a/src/libcamera/vector.cpp b/src/libcamera/vector.cpp
> index 85ca2208245a..435f2fc62f8b 100644
> --- a/src/libcamera/vector.cpp
> +++ b/src/libcamera/vector.cpp
> @@ -44,6 +44,14 @@ LOG_DEFINE_CATEGORY(Vector)
>   * The size of \a data must be equal to the dimension size Rows of the vector.
>   */
>  
> +/**
> + * \fn Vector::Vector(const Span<const T, Rows> &data)
> + * \brief Construct vector from supplied data
> + * \param data Data from which to construct a vector
> + *
> + * The size of \a data must be equal to the dimension size Rows of the vector.
> + */
> +
>  /**
>   * \fn T Vector::operator[](size_t i) const
>   * \brief Index to an element in the vector
> -- 
> 2.43.0
>