[libcamera-devel,v4,1/4] libcamera: utils: Add helper class for std::chrono::duration

12374 diff mbox series

A new utils::Duration class is defined to represent a
std::chrono::duration type with double precision nanosecond timebase.
Using a double minimises the loss of precision when converting timebases.
This helper class may be used by IPAs to represent variables such as frame
durations and exposure times.

An operator << overload is define to help with displaying
utils::Duration value in stream objects. Currently, this will display
the duration value in microseconds.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
---
 include/libcamera/internal/utils.h | 42 ++++++++++++++++++++++++++++++
 src/libcamera/utils.cpp            | 41 +++++++++++++++++++++++++++++
 2 files changed, 83 insertions(+)

Hi Naush,

On Mon, May 24, 2021 at 09:48:19AM +0100, Naushir Patuck wrote:
> A new utils::Duration class is defined to represent a
> std::chrono::duration type with double precision nanosecond timebase.
> Using a double minimises the loss of precision when converting timebases.
> This helper class may be used by IPAs to represent variables such as frame
> durations and exposure times.
>
> An operator << overload is define to help with displaying
> utils::Duration value in stream objects. Currently, this will display
> the duration value in microseconds.
>
> Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
> Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
> ---
>  include/libcamera/internal/utils.h | 42 ++++++++++++++++++++++++++++++
>  src/libcamera/utils.cpp            | 41 +++++++++++++++++++++++++++++
>  2 files changed, 83 insertions(+)
>
> diff --git a/include/libcamera/internal/utils.h b/include/libcamera/internal/utils.h
> index 83dada7cc16c..f536f2267d70 100644
> --- a/include/libcamera/internal/utils.h
> +++ b/include/libcamera/internal/utils.h
> @@ -316,8 +316,50 @@ auto enumerate(T (&iterable)[N]) -> details::enumerate_adapter<T *>
>  }
>  #endif
>
> +class Duration : public std::chrono::duration<double, std::nano>
> +{
> +	using BaseDuration = std::chrono::duration<double, std::nano>;
> +
> +public:
> +	Duration() = default;
> +
> +	template<typename Rep, typename Period>
> +	constexpr Duration(const std::chrono::duration<Rep, Period> &d)
> +		: BaseDuration(d)
> +	{
> +	}
> +
> +	template<typename Period>
> +	double get() const
> +	{
> +		auto const c = std::chrono::duration_cast<std::chrono::duration<double, Period>>(*this);
> +		return c.count();
> +	}
> +
> +	explicit constexpr operator bool() const
> +	{
> +		return *this != BaseDuration::zero();
> +	}
> +};
> +
>  } /* namespace utils */
>
> +#ifndef __DOXYGEN__
> +template<class CharT, class Traits>
> +static inline std::basic_ostream<CharT, Traits> &operator<<(std::basic_ostream<CharT, Traits> &os,
> +							    const utils::Duration &d)
> +{
> +	std::basic_ostringstream<CharT, Traits> s;
> +
> +	s.flags(os.flags());
> +	s.imbue(os.getloc());
> +	s.setf(std::ios_base::fixed, std::ios_base::floatfield);
> +	s.precision(2);
> +	s << d.get<std::micro>() << "us";
> +	return os << s.str();
> +}
> +#endif
> +
>  } /* namespace libcamera */
>
>  #endif /* __LIBCAMERA_INTERNAL_UTILS_H__ */
> diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
> index 826144d3c837..480284c6c2c9 100644
> --- a/src/libcamera/utils.cpp
> +++ b/src/libcamera/utils.cpp
> @@ -506,6 +506,47 @@ std::string libcameraSourcePath()
>   * loop, iterates over an indexed view of the \a iterable
>   */
>
> +/**
> + * \class Duration
> + * \brief Helper class for std::chrono::duration types

Helper class derived from std::chrono::duration that represents a time
duration in nanoseconds with double precision

> + */
> +
> +/**
> + * \typedef Duration::BaseDuration
> + * \brief Base struct for the \a Duration helper class
> + */

Isn't this private ? does it need documentation ? It's just a
syntactic sugar used in the class definition, isn't it ?


> +
> +/**
> + * \fn Duration::Duration(const std::chrono::duration<Rep, Period> &d)
> + * \brief Copy constructor from a \a std::chrono::duration type
> + * \param[in] d The std::chrono::duration object to convert from
> + *
> + * Constructs a \a Duration object from a \a std::chrono::duration object,
> + * internally converting the representation to \a Duration::BaseDuration type
> + */
> +
> +/**
> + * \fn Duration::get<Period>()
> + * \brief Retrieve the tick count, converted to the timebase provided by the
> + * template argument Period of type \a std::ratio
> + *
> + * A typical usage example is given below:
> + *
> + * \code{.cpp}
> + * utils::Duration d = 5s;
> + * double d_in_ms = d.get<std::milli>();
> + * \endcode
> + *
> + * \return The tick count of the Duration expressed in \a Period
> + */
> +
> +/**
> + * \fn Duration::operator bool()
> + * \brief Boolean operator to test if a \a Duration holds a non-zero time value.
> + *
> + * \return True if \a Duration is a non-zero time value, False otherwise.
> + */

All minor, which if not other comments, can be changed with your ack
when applying
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

Thanks
  j

> +
>  } /* namespace utils */
>
>  } /* namespace libcamera */
> --
> 2.25.1
>

Hi Jacopo,

Thank you for your review feedback.

On Mon, 24 May 2021 at 12:58, Jacopo Mondi <jacopo@jmondi.org> wrote:

> Hi Naush,
>
> On Mon, May 24, 2021 at 09:48:19AM +0100, Naushir Patuck wrote:
> > A new utils::Duration class is defined to represent a
> > std::chrono::duration type with double precision nanosecond timebase.
> > Using a double minimises the loss of precision when converting timebases.
> > This helper class may be used by IPAs to represent variables such as
> frame
> > durations and exposure times.
> >
> > An operator << overload is define to help with displaying
> > utils::Duration value in stream objects. Currently, this will display
> > the duration value in microseconds.
> >
> > Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
> > Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
> > ---
> >  include/libcamera/internal/utils.h | 42 ++++++++++++++++++++++++++++++
> >  src/libcamera/utils.cpp            | 41 +++++++++++++++++++++++++++++
> >  2 files changed, 83 insertions(+)
> >
> > diff --git a/include/libcamera/internal/utils.h
> b/include/libcamera/internal/utils.h
> > index 83dada7cc16c..f536f2267d70 100644
> > --- a/include/libcamera/internal/utils.h
> > +++ b/include/libcamera/internal/utils.h
> > @@ -316,8 +316,50 @@ auto enumerate(T (&iterable)[N]) ->
> details::enumerate_adapter<T *>
> >  }
> >  #endif
> >
> > +class Duration : public std::chrono::duration<double, std::nano>
> > +{
> > +     using BaseDuration = std::chrono::duration<double, std::nano>;
> > +
> > +public:
> > +     Duration() = default;
> > +
> > +     template<typename Rep, typename Period>
> > +     constexpr Duration(const std::chrono::duration<Rep, Period> &d)
> > +             : BaseDuration(d)
> > +     {
> > +     }
> > +
> > +     template<typename Period>
> > +     double get() const
> > +     {
> > +             auto const c =
> std::chrono::duration_cast<std::chrono::duration<double, Period>>(*this);
> > +             return c.count();
> > +     }
> > +
> > +     explicit constexpr operator bool() const
> > +     {
> > +             return *this != BaseDuration::zero();
> > +     }
> > +};
> > +
> >  } /* namespace utils */
> >
> > +#ifndef __DOXYGEN__
> > +template<class CharT, class Traits>
> > +static inline std::basic_ostream<CharT, Traits>
> &operator<<(std::basic_ostream<CharT, Traits> &os,
> > +                                                         const
> utils::Duration &d)
> > +{
> > +     std::basic_ostringstream<CharT, Traits> s;
> > +
> > +     s.flags(os.flags());
> > +     s.imbue(os.getloc());
> > +     s.setf(std::ios_base::fixed, std::ios_base::floatfield);
> > +     s.precision(2);
> > +     s << d.get<std::micro>() << "us";
> > +     return os << s.str();
> > +}
> > +#endif
> > +
> >  } /* namespace libcamera */
> >
> >  #endif /* __LIBCAMERA_INTERNAL_UTILS_H__ */
> > diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
> > index 826144d3c837..480284c6c2c9 100644
> > --- a/src/libcamera/utils.cpp
> > +++ b/src/libcamera/utils.cpp
> > @@ -506,6 +506,47 @@ std::string libcameraSourcePath()
> >   * loop, iterates over an indexed view of the \a iterable
> >   */
> >
> > +/**
> > + * \class Duration
> > + * \brief Helper class for std::chrono::duration types
>
> Helper class derived from std::chrono::duration that represents a time
> duration in nanoseconds with double precision
>

Ack.


>
> > + */
> > +
> > +/**
> > + * \typedef Duration::BaseDuration
> > + * \brief Base struct for the \a Duration helper class
> > + */
>
> Isn't this private ? does it need documentation ? It's just a
> syntactic sugar used in the class definition, isn't it ?
>

It is private/syntactic sugar - I was not sure what the rule was for
private members with regards to documentation.  I can remove
it.


>
>
> > +
> > +/**
> > + * \fn Duration::Duration(const std::chrono::duration<Rep, Period> &d)
> > + * \brief Copy constructor from a \a std::chrono::duration type
> > + * \param[in] d The std::chrono::duration object to convert from
> > + *
> > + * Constructs a \a Duration object from a \a std::chrono::duration
> object,
> > + * internally converting the representation to \a
> Duration::BaseDuration type
> > + */
> > +
> > +/**
> > + * \fn Duration::get<Period>()
> > + * \brief Retrieve the tick count, converted to the timebase provided
> by the
> > + * template argument Period of type \a std::ratio
> > + *
> > + * A typical usage example is given below:
> > + *
> > + * \code{.cpp}
> > + * utils::Duration d = 5s;
> > + * double d_in_ms = d.get<std::milli>();
> > + * \endcode
> > + *
> > + * \return The tick count of the Duration expressed in \a Period
> > + */
> > +
> > +/**
> > + * \fn Duration::operator bool()
> > + * \brief Boolean operator to test if a \a Duration holds a non-zero
> time value.
> > + *
> > + * \return True if \a Duration is a non-zero time value, False
> otherwise.
> > + */
>
> All minor, which if not other comments, can be changed with your ack
> when applying
> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
>

Thank's for the tag.  I will submit a v5 revision with the updates once you
and
others have a chance to comment on  all the other patches in the series.

Regards,
Naush


>
> Thanks
>   j
>
> > +
> >  } /* namespace utils */
> >
> >  } /* namespace libcamera */
> > --
> > 2.25.1
> >
>

Hi Naush,

On Mon, May 24, 2021 at 01:30:20PM +0100, Naushir Patuck wrote:
> Hi Jacopo,
>
> Thank you for your review feedback.
>
> On Mon, 24 May 2021 at 12:58, Jacopo Mondi <jacopo@jmondi.org> wrote:
>
> > Hi Naush,
> >
> > On Mon, May 24, 2021 at 09:48:19AM +0100, Naushir Patuck wrote:
> > > A new utils::Duration class is defined to represent a
> > > std::chrono::duration type with double precision nanosecond timebase.
> > > Using a double minimises the loss of precision when converting timebases.
> > > This helper class may be used by IPAs to represent variables such as
> > frame
> > > durations and exposure times.
> > >
> > > An operator << overload is define to help with displaying
> > > utils::Duration value in stream objects. Currently, this will display
> > > the duration value in microseconds.
> > >
> > > Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
> > > Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
> > > ---
> > >  include/libcamera/internal/utils.h | 42 ++++++++++++++++++++++++++++++
> > >  src/libcamera/utils.cpp            | 41 +++++++++++++++++++++++++++++
> > >  2 files changed, 83 insertions(+)
> > >
> > > diff --git a/include/libcamera/internal/utils.h
> > b/include/libcamera/internal/utils.h
> > > index 83dada7cc16c..f536f2267d70 100644
> > > --- a/include/libcamera/internal/utils.h
> > > +++ b/include/libcamera/internal/utils.h
> > > @@ -316,8 +316,50 @@ auto enumerate(T (&iterable)[N]) ->
> > details::enumerate_adapter<T *>
> > >  }
> > >  #endif
> > >
> > > +class Duration : public std::chrono::duration<double, std::nano>
> > > +{
> > > +     using BaseDuration = std::chrono::duration<double, std::nano>;
> > > +
> > > +public:
> > > +     Duration() = default;
> > > +
> > > +     template<typename Rep, typename Period>
> > > +     constexpr Duration(const std::chrono::duration<Rep, Period> &d)
> > > +             : BaseDuration(d)
> > > +     {
> > > +     }
> > > +
> > > +     template<typename Period>
> > > +     double get() const
> > > +     {
> > > +             auto const c =
> > std::chrono::duration_cast<std::chrono::duration<double, Period>>(*this);
> > > +             return c.count();
> > > +     }
> > > +
> > > +     explicit constexpr operator bool() const
> > > +     {
> > > +             return *this != BaseDuration::zero();
> > > +     }
> > > +};
> > > +
> > >  } /* namespace utils */
> > >
> > > +#ifndef __DOXYGEN__
> > > +template<class CharT, class Traits>
> > > +static inline std::basic_ostream<CharT, Traits>
> > &operator<<(std::basic_ostream<CharT, Traits> &os,
> > > +                                                         const
> > utils::Duration &d)
> > > +{
> > > +     std::basic_ostringstream<CharT, Traits> s;
> > > +
> > > +     s.flags(os.flags());
> > > +     s.imbue(os.getloc());
> > > +     s.setf(std::ios_base::fixed, std::ios_base::floatfield);
> > > +     s.precision(2);
> > > +     s << d.get<std::micro>() << "us";
> > > +     return os << s.str();
> > > +}
> > > +#endif
> > > +
> > >  } /* namespace libcamera */
> > >
> > >  #endif /* __LIBCAMERA_INTERNAL_UTILS_H__ */
> > > diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
> > > index 826144d3c837..480284c6c2c9 100644
> > > --- a/src/libcamera/utils.cpp
> > > +++ b/src/libcamera/utils.cpp
> > > @@ -506,6 +506,47 @@ std::string libcameraSourcePath()
> > >   * loop, iterates over an indexed view of the \a iterable
> > >   */
> > >
> > > +/**
> > > + * \class Duration
> > > + * \brief Helper class for std::chrono::duration types
> >
> > Helper class derived from std::chrono::duration that represents a time
> > duration in nanoseconds with double precision
> >
>
> Ack.
>
>
> >
> > > + */
> > > +
> > > +/**
> > > + * \typedef Duration::BaseDuration
> > > + * \brief Base struct for the \a Duration helper class
> > > + */
> >
> > Isn't this private ? does it need documentation ? It's just a
> > syntactic sugar used in the class definition, isn't it ?
> >
>
> It is private/syntactic sugar - I was not sure what the rule was for
> private members with regards to documentation.  I can remove
> it.

As long as Doxygen does not complain, I think you can leave it out.
However, I see you reference BaseDuration in other parts of the
documentation

>
>
> >
> >
> > > +
> > > +/**
> > > + * \fn Duration::Duration(const std::chrono::duration<Rep, Period> &d)
> > > + * \brief Copy constructor from a \a std::chrono::duration type
> > > + * \param[in] d The std::chrono::duration object to convert from
> > > + *
> > > + * Constructs a \a Duration object from a \a std::chrono::duration
> > object,
> > > + * internally converting the representation to \a
> > Duration::BaseDuration type

here

If this creates issue I think you could drop it here (or keep the
documentation for BaseDuration, up to you :)

Thanks
  j

> > > + */
> > > +
> > > +/**
> > > + * \fn Duration::get<Period>()
> > > + * \brief Retrieve the tick count, converted to the timebase provided
> > by the
> > > + * template argument Period of type \a std::ratio
> > > + *
> > > + * A typical usage example is given below:
> > > + *
> > > + * \code{.cpp}
> > > + * utils::Duration d = 5s;
> > > + * double d_in_ms = d.get<std::milli>();
> > > + * \endcode
> > > + *
> > > + * \return The tick count of the Duration expressed in \a Period
> > > + */
> > > +
> > > +/**
> > > + * \fn Duration::operator bool()
> > > + * \brief Boolean operator to test if a \a Duration holds a non-zero
> > time value.
> > > + *
> > > + * \return True if \a Duration is a non-zero time value, False
> > otherwise.
> > > + */
> >
> > All minor, which if not other comments, can be changed with your ack
> > when applying
> > Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
> >
>
> Thank's for the tag.  I will submit a v5 revision with the updates once you
> and
> others have a chance to comment on  all the other patches in the series.
>
> Regards,
> Naush
>
>
> >
> > Thanks
> >   j
> >
> > > +
> > >  } /* namespace utils */
> > >
> > >  } /* namespace libcamera */
> > > --
> > > 2.25.1
> > >
> >