[libcamera-devel] [PATCH] libcamera: v4l2_device: Return const std::string

[Laurent Pinchart]

Hi Jacopo,

On Mon, Jan 21, 2019 at 10:20:20AM +0100, Jacopo Mondi wrote:
> Make getter functions of V4L2Device return std::string as the rest of
> the library does.

This is something that has been discussed during the review of Kieran's
original patch I believe. The question was whether it would be more
efficient to use const char * or a an std::string, and the answer to
that question depends on the expected usage of those methods. If all
users need an std::string, then I agree that the methods below can as
well construct one. On the other hand, if some users need a const char
*, it is a bit pointless to convert from const char * to std::string and
then back to const char * using c_str(). This is why we have opted for
const char * here.

This is a generic question that we should ask ourselves through the
library. Anyone with free time to analyze the problem ? :-)

> Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> ---
>  src/libcamera/include/v4l2_device.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/src/libcamera/include/v4l2_device.h b/src/libcamera/include/v4l2_device.h
> index 474c05b..5fe3d82 100644
> --- a/src/libcamera/include/v4l2_device.h
> +++ b/src/libcamera/include/v4l2_device.h
> @@ -45,9 +45,9 @@ public:
>  	bool isOpen() const;
>  	void close();
> 
> -	const char *driverName() const { return caps_.driver(); }
> -	const char *deviceName() const { return caps_.card(); }
> -	const char *busName() const { return caps_.bus_info(); }
> +	const std::string driverName() const { return std::string(caps_.driver()); }
> +	const std::string deviceName() const { return std::string(caps_.card()); }
> +	const std::string busName() const { return std::string(caps_.bus_info()); }

If we wanted to return an std::string, we should drop the const as the
string is returned by value.

> 
>  private:
>  	std::string devnode_;

-- 
Regards,

Laurent Pinchart