| Message ID | 20241119103740.1919807-5-stefan.klug@ideasonboard.com |
|---|---|
| State | New |
| Headers | show |
| Series |
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| Related | show |
Hi Stefan, Thank you for the patch. On Tue, Nov 19, 2024 at 11:37:31AM +0100, Stefan Klug wrote: > Having an array based constructor gives us initialization via > initializer lists. This needs a bit more information. The Matrix constructor that takes a std::vector is meant and only used to initialize a Matrix from an initializer list. Using a std::vector is problematic for two reasons. First, it requires constructing a vector, copying the data from the initializer list, which is an expensive operation. Then, the vector size can't be verified at compile time, making the constructor unsafe. The first issue could be solved by replacing the vector with a std::initializer_list or a Span. The second issue would require checking the initializer list size with a static assertion, or restricting usage of the constructor to fixed-extent spans. Unfortunately, even if the size of initializer lists is always known at compile time, the std::initializer_list::size() function is a compile-time constant only for constant initializer lists. Using a span would work better, but construction of a fixed extent span from an initializer list must be explicit, making the API cumbersome. We can solve all those issues by passing an std::array to the constructor. Construction of an array from an initializer list can be implicit and doesn't involve a copy, and the array size is a template parameter and therefore guaranteed to be a compile-time constant. > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > --- > include/libcamera/internal/matrix.h | 2 +- > src/libcamera/matrix.cpp | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/libcamera/internal/matrix.h b/include/libcamera/internal/matrix.h > index 3701d0ee980b..7a71028c473a 100644 > --- a/include/libcamera/internal/matrix.h > +++ b/include/libcamera/internal/matrix.h > @@ -33,7 +33,7 @@ public: > data_.fill(static_cast<T>(0)); > } > > - Matrix(const std::vector<T> &data) > + Matrix(const std::array<T, Rows * Cols> &data) > { > std::copy(data.begin(), data.end(), data_.begin()); > } > diff --git a/src/libcamera/matrix.cpp b/src/libcamera/matrix.cpp > index 55359aa206ee..4d95a19bfbb9 100644 > --- a/src/libcamera/matrix.cpp > +++ b/src/libcamera/matrix.cpp > @@ -32,7 +32,7 @@ LOG_DEFINE_CATEGORY(Matrix) > */ > > /** > - * \fn Matrix::Matrix(const std::vector<T> &data) > + * \fn Matrix::Matrix(const std::array<T, Rows * Cols> &data) > * \brief Construct a matrix from supplied data > * \param[in] data Data from which to construct a matrix > *
diff --git a/include/libcamera/internal/matrix.h b/include/libcamera/internal/matrix.h index 3701d0ee980b..7a71028c473a 100644 --- a/include/libcamera/internal/matrix.h +++ b/include/libcamera/internal/matrix.h @@ -33,7 +33,7 @@ public: data_.fill(static_cast<T>(0)); } - Matrix(const std::vector<T> &data) + Matrix(const std::array<T, Rows * Cols> &data) { std::copy(data.begin(), data.end(), data_.begin()); } diff --git a/src/libcamera/matrix.cpp b/src/libcamera/matrix.cpp index 55359aa206ee..4d95a19bfbb9 100644 --- a/src/libcamera/matrix.cpp +++ b/src/libcamera/matrix.cpp @@ -32,7 +32,7 @@ LOG_DEFINE_CATEGORY(Matrix) */ /** - * \fn Matrix::Matrix(const std::vector<T> &data) + * \fn Matrix::Matrix(const std::array<T, Rows * Cols> &data) * \brief Construct a matrix from supplied data * \param[in] data Data from which to construct a matrix *
Having an array based constructor gives us initialization via initializer lists. Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com> --- include/libcamera/internal/matrix.h | 2 +- src/libcamera/matrix.cpp | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)