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Subject: Re: [PATCH 8/8] v4l2-utils: turn prefixes to a constexpr array
To:     Rosen Penev <rosenp@gmail.com>, linux-media@vger.kernel.org
References: <20210421072035.4188497-1-rosenp@gmail.com>
 <20210421072035.4188497-8-rosenp@gmail.com>
From:   Hans Verkuil <hverkuil@xs4all.nl>
Message-ID: <566ba9fe-509c-26b4-19a3-845a45093ba1@xs4all.nl>
Date:   Wed, 21 Apr 2021 10:06:44 +0200
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On 21/04/2021 09:20, Rosen Penev wrote:
> Allows usage of a single any_of instead of a raw loop.
> 
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>  utils/v4l2-ctl/v4l2-ctl-common.cpp | 24 +++++-------------------
>  1 file changed, 5 insertions(+), 19 deletions(-)
> 
> diff --git a/utils/v4l2-ctl/v4l2-ctl-common.cpp b/utils/v4l2-ctl/v4l2-ctl-common.cpp
> index 17ad488dd..2b6dd6d13 100644
> --- a/utils/v4l2-ctl/v4l2-ctl-common.cpp
> +++ b/utils/v4l2-ctl/v4l2-ctl-common.cpp
> @@ -116,28 +116,14 @@ void common_usage()
>  	       );
>  }
>  
> -static const char *prefixes[] = {
> -	"video",
> -	"radio",
> -	"vbi",
> -	"swradio",
> -	"v4l-subdev",
> -	"v4l-touch",
> -	"media",
> -	nullptr
> +static constexpr std::array<const char *, 7> prefixes{
> +	"video", "radio", "vbi", "swradio", "v4l-subdev", "v4l-touch", "media",
>  };
>  
>  static bool is_v4l_dev(const char *name)
>  {
> -	for (unsigned i = 0; prefixes[i]; i++) {
> -		unsigned l = strlen(prefixes[i]);
> -
> -		if (!memcmp(name, prefixes[i], l)) {
> -			if (isdigit(name[l]))
> -				return true;
> -		}
> -	}
> -	return false;
> +	return std::any_of(prefixes.begin(), prefixes.end(),
> +			   [=](const char *prefix) { return !strcmp(name, prefix) && isdigit(name[strlen(prefix)]); });

Yuck. Besides, it is wrong AFAIKS since strcmp is not the same as memcmp.

I like the original code, easier to understand than the replacement. So sue me :-)

Regards,

	Hans

>  }
>  
>  static int calc_node_val(const char *s)
> @@ -146,7 +132,7 @@ static int calc_node_val(const char *s)
>  
>  	s = std::strrchr(s, '/') + 1;
>  
> -	for (unsigned i = 0; prefixes[i]; i++) {
> +	for (size_t i = 0; i < prefixes.size(); i++) {
>  		unsigned l = strlen(prefixes[i]);
>  
>  		if (!memcmp(s, prefixes[i], l)) {
>