[libcamera-devel] [PATCH/RFC 3/3] v4l2: Replace manual loop counters with utils::enumerate()

[Kieran Bingham]

Hi Laurent,

On 23/04/2021 03:09, Laurent Pinchart wrote:
> Use the newly introduced utils::enumerate() to replace manual loop
> counters. A local variable is needed, as utils::enumerate() requires an
> lvalue reference.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  src/v4l2/v4l2_compat_manager.cpp | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/src/v4l2/v4l2_compat_manager.cpp b/src/v4l2/v4l2_compat_manager.cpp
> index 90c0f0121a32..bf5bf8e3223d 100644
> --- a/src/v4l2/v4l2_compat_manager.cpp
> +++ b/src/v4l2/v4l2_compat_manager.cpp
> @@ -23,6 +23,7 @@
>  #include <libcamera/camera_manager.h>
>  
>  #include "libcamera/internal/log.h"
> +#include "libcamera/internal/utils.h"
>  
>  #include "v4l2_camera_file.h"
>  
> @@ -81,11 +82,11 @@ int V4L2CompatManager::start()
>  	 * For each Camera registered in the system, a V4L2CameraProxy gets
>  	 * created here to wrap a camera device.
>  	 */
> -	unsigned int index = 0;
> -	for (auto &camera : cm_->cameras()) {
> -		V4L2CameraProxy *proxy = new V4L2CameraProxy(index, camera);
> +	auto cameras = cm_->cameras();
> +	for (const auto camera : utils::enumerate(cameras)) {

Is it possible to used named scopes here like:

    for (const auto [index, camera] : utils::enumerate(cameras)) {
        V4L2CameraProxy *proxy = new V4L2CameraProxy(index, camera);

(note, I'm asking if your series makes this possible, not for you to
make this change)

Otherwise, I like that the index becomes part of the iteration.
I have a slight dislike to treating your iterated item as 'value' ...
but that's just the same dislike I have for std::pair, but at least in
this case it's not named first and second!

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



> +		V4L2CameraProxy *proxy = new V4L2CameraProxy(camera.index,
> +							     camera.value);
>  		proxies_.emplace_back(proxy);
> -		++index;
>  	}
>  
>  	return 0;
> @@ -117,11 +118,10 @@ int V4L2CompatManager::getCameraIndex(int fd)
>  	if (!target)
>  		return -1;
>  
> -	unsigned int index = 0;
> -	for (auto &camera : cm_->cameras()) {
> -		if (camera == target)
> -			return index;
> -		++index;
> +	auto cameras = cm_->cameras();
> +	for (const auto camera : utils::enumerate(cameras)) {
> +		if (camera.value == target)
> +			return camera.index;
>  	}
>  
>  	return -1;
> 

-- 
Regards
--
Kieran