[libcamera-devel] [PATCH v2 07/14] libcamera: controls: Allow read only access to control values

[Laurent Pinchart]

Hi Niklas,

Thank you for the patch.

On Fri, Aug 30, 2019 at 01:26:46AM +0200, Niklas Söderlund wrote:
> Allow the control values in a ControlList to be examined from a const
> environment.
> 
> Signed-off-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
> ---
>  include/libcamera/controls.h |  1 +
>  src/libcamera/controls.cpp   | 34 ++++++++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
> index fbb3a62274c64259..eee5ef87b8fd2633 100644
> --- a/include/libcamera/controls.h
> +++ b/include/libcamera/controls.h
> @@ -124,6 +124,7 @@ public:
>  	void clear() { controls_.clear(); }
>  
>  	ControlValue &operator[](ControlId id);
> +	const ControlValue &operator[](ControlId id) const;
>  	ControlValue &operator[](const ControlInfo *info) { return controls_[info]; }
>  
>  	void update(const ControlList &list);
> diff --git a/src/libcamera/controls.cpp b/src/libcamera/controls.cpp
> index 35861e27401d5241..12cbf778408ee8e7 100644
> --- a/src/libcamera/controls.cpp
> +++ b/src/libcamera/controls.cpp
> @@ -521,6 +521,40 @@ ControlValue &ControlList::operator[](ControlId id)
>  	return controls_[&iter->second];
>  }
>  
> +/**
> + * \brief Access a control specified by \a id

s/a control/the control/ to match the non-const version.

> + * \param[in] id The control ID
> + *
> + * This method returns a reference to the control identified by \a id, if it
> + * exists or an empty control if it does not.

s/, if it exists/ if it exists,/

I would actually not use "exist" as thats ambiguous (where does it
exist, in the control list or in the camera ?).

 * This method returns a const reference to the control identified by \a id. If
 * no such controls is present in the list, a const reference to an empty
 * control value is returned.

> + *
> + * The behaviour is undefined if the control \a id is not supported by the
> + * camera that the ControlList refers to.
> + *
> + * \return A reference to the value of the control identified by \a id

s/A reference/A const reference/

> + */
> +const ControlValue &ControlList::operator[](ControlId id) const
> +{
> +	const ControlInfoMap &controls = camera_->controls();
> +	static ControlValue empty;
> +
> +	const auto iter = controls.find(id);
> +	if (iter == controls.end()) {
> +		LOG(Controls, Error)
> +			<< "Camera " << camera_->name()
> +			<< " does not support control " << id;
> +		return empty;
> +	}

This is common to the non-const version of the function, so I wonder if
it should be moved to a separate private method. It could be a bit
overkill.

> +
> +	const auto it = controls_.find(&iter->second);

iter and it isn't a good idea, please use more explicit names.

> +	if (it == controls_.end()) {
> +		LOG(Controls, Error) << "list does not have control " << id;
> +		return empty;
> +	}
> +
> +	return it->second;
> +}
> +
>  /**
>   * \fn ControlList::operator[](const ControlInfo *info)
>   * \brief Access or insert the control specified by \a info

-- 
Regards,

Laurent Pinchart