[libcamera-devel] [PATCH v2 2/4] v4l2: Replace manual loop counters with utils::enumerate()

[Kieran Bingham]

Hi Laurent,

On 15/05/2021 05:05, 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.

So this is not possible?

	for (auto [index, camera] : utils::enumerate(cm_->cameras()) {

I guess that's fine, but will it be obvious to someone trying to use it
that they need to move the thing to enumerate to a local variable if
it's not there?

I probably really don't want to know - but why does it need this?
It seems like an odd limitation, but if it's just a small corner case,
then I don't mind having it split out. It helps keep line lengths
shorter anyway...?

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


> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
> Changes since v1:
> 
> - Use structured bindings
> ---
>  src/v4l2/v4l2_compat_manager.cpp | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/src/v4l2/v4l2_compat_manager.cpp b/src/v4l2/v4l2_compat_manager.cpp
> index 90c0f0121a32..96dbcdf28f04 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 +82,10 @@ 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()) {
> +	auto cameras = cm_->cameras();
> +	for (auto [index, camera] : utils::enumerate(cameras)) {
>  		V4L2CameraProxy *proxy = new V4L2CameraProxy(index, camera);
>  		proxies_.emplace_back(proxy);
> -		++index;
>  	}
>  
>  	return 0;
> @@ -117,11 +117,10 @@ int V4L2CompatManager::getCameraIndex(int fd)
>  	if (!target)
>  		return -1;
>  
> -	unsigned int index = 0;
> -	for (auto &camera : cm_->cameras()) {
> +	auto cameras = cm_->cameras();
> +	for (auto [index, camera] : utils::enumerate(cameras)) {
>  		if (camera == target)
>  			return index;
> -		++index;
>  	}
>  
>  	return -1;
> 

-- 
Regards
--
Kieran