[PATCH v1 1/3] libcamera: controls: Give name to the union containing storage

[Kieran Bingham]

Quoting Barnabás Pőcze (2025-04-17 12:35:37)
> In order to be able to copy the storage as one unit, regardless of
> which member is active give a name to the union member.
> 
> Signed-off-by: Barnabás Pőcze <barnabas.pocze at ideasonboard.com>

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> ---
>  include/libcamera/controls.h |  6 +++---
>  src/libcamera/controls.cpp   | 17 ++++++++---------
>  2 files changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
> index 4bfe9615c..1dc6ccffa 100644
> --- a/include/libcamera/controls.h
> +++ b/include/libcamera/controls.h
> @@ -238,9 +238,9 @@ private:
>         bool isArray_;
>         std::size_t numElements_ : 32;
>         union {
> -               uint64_t value_;
> -               void *storage_;
> -       };
> +               uint64_t internal;
> +               void *external;
> +       } storage_;
>  
>         void release();
>         void set(ControlType type, bool isArray, const void *data,
> diff --git a/src/libcamera/controls.cpp b/src/libcamera/controls.cpp
> index 70f6f6092..d384e1ef7 100644
> --- a/src/libcamera/controls.cpp
> +++ b/src/libcamera/controls.cpp
> @@ -10,6 +10,7 @@
>  #include <sstream>
>  #include <string.h>
>  #include <string>
> +#include <utility>
>  
>  #include <libcamera/base/log.h>
>  #include <libcamera/base/utils.h>
> @@ -122,10 +123,8 @@ void ControlValue::release()
>  {
>         std::size_t size = numElements_ * ControlValueSize[type_];
>  
> -       if (size > sizeof(value_)) {
> -               delete[] reinterpret_cast<uint8_t *>(storage_);
> -               storage_ = nullptr;
> -       }
> +       if (size > sizeof(storage_.internal))
> +               delete[] reinterpret_cast<uint8_t *>(std::exchange(storage_.external, nullptr));
>  }
>  
>  ControlValue::~ControlValue()
> @@ -192,9 +191,9 @@ ControlValue &ControlValue::operator=(const ControlValue &other)
>  Span<const uint8_t> ControlValue::data() const
>  {
>         std::size_t size = numElements_ * ControlValueSize[type_];
> -       const uint8_t *data = size > sizeof(value_)
> -                           ? reinterpret_cast<const uint8_t *>(storage_)
> -                           : reinterpret_cast<const uint8_t *>(&value_);
> +       const uint8_t *data = size > sizeof(storage_.internal)
> +                           ? reinterpret_cast<const uint8_t *>(storage_.external)
> +                           : reinterpret_cast<const uint8_t *>(&storage_.internal);
>         return { data, size };
>  }
>  
> @@ -391,8 +390,8 @@ void ControlValue::reserve(ControlType type, bool isArray, std::size_t numElemen
>         if (oldSize == newSize)
>                 return;
>  
> -       if (newSize > sizeof(value_))
> -               storage_ = reinterpret_cast<void *>(new uint8_t[newSize]);
> +       if (newSize > sizeof(storage_.internal))
> +               storage_.external = new uint8_t[newSize];
>  }
>  
>  /**
> -- 
> 2.49.0
>