[libcamera-devel] [PATCH 1/4] ipa: raspberrypi: Add helper macros for std::chrono::duration

[David Plowman]

Hi Naush

On Wed, 19 May 2021 at 11:50, Naushir Patuck <naush at raspberrypi.com> wrote:
>
> Hi David,
>
> Thank you for your review feedback.
>
> On Wed, 19 May 2021 at 11:38, David Plowman <david.plowman at raspberrypi.com> wrote:
>>
>> Hi Naush
>>
>> Thank you for this patch.
>>
>> On Tue, 18 May 2021 at 11:09, Naushir Patuck <naush at raspberrypi.com> wrote:
>> >
>> > A new RPiController::Duration typedef is defined to represent a
>> > std::chrono::duration type with double precision nanosecond timebase
>> > that will be used throughout. This minimises the loss of precision when
>> > converting timebases. A function for returning the duration count in any
>> > timebase is also provided.
>> >
>> > An operator << overload is define to help with displaying
>> > RPiController::Duration value in stream objects.
>> >
>> > Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
>> > ---
>> >  src/ipa/raspberrypi/controller/duration.hpp | 33 +++++++++++++++++++++
>> >  1 file changed, 33 insertions(+)
>> >  create mode 100644 src/ipa/raspberrypi/controller/duration.hpp
>> >
>> > diff --git a/src/ipa/raspberrypi/controller/duration.hpp b/src/ipa/raspberrypi/controller/duration.hpp
>> > new file mode 100644
>> > index 000000000000..98aa3d78f52f
>> > --- /dev/null
>> > +++ b/src/ipa/raspberrypi/controller/duration.hpp
>> > @@ -0,0 +1,33 @@
>> > +/* SPDX-License-Identifier: BSD-2-Clause */
>> > +/*
>> > + * Copyright (C) 2021, Raspberry Pi (Trading) Limited
>> > + *
>> > + * duration.hpp - Helper macros for std::chrono::duration handling.
>> > + */
>> > +#pragma once
>> > +
>> > +#include <chrono>
>> > +#include <iomanip>
>> > +#include <iostream>
>> > +
>> > +namespace RPiController {
>> > +
>> > +using Duration = std::chrono::duration<double, std::nano>;
>> > +
>> > +// Helper to convert and return the count of any std::chrono::duration type to
>> > +// another timebase.  Use a double rep type to try and preserve precision.
>> > +template <typename P, typename T>
>> > +static constexpr double DurationValue(T const &d)
>> > +{
>> > +       return std::chrono::duration_cast<std::chrono::duration<double, P>>(d).count();
>> > +};
>> > +
>> > +static inline std::ostream &operator<<(std::ostream &os, const Duration &duration)
>> > +{
>> > +        std::streamsize ss = os.precision();
>> > +        os << std::fixed << std::setprecision(2) << DurationValue<std::micro>(duration) << " us";
>>
>> I suppose I wonder slightly why we change the precision, I assume the
>> output is just a bit tidier like that? And a space before the "us"? I
>> guess, why not!
>
>
> Yes, I did not want more than 2 decimal places of precision in the output.  I can remove the space
> before the "us" in the next revision.

It's OK... I don't mind the space!

David

>
> Regards,
> Naush
>
>>
>>
>> Reviewed-by: David Plowman <david.plowman at raspberrypi.com>
>>
>> Thanks
>> David
>>
>> > +        os << std::setprecision(ss) << std::defaultfloat;
>> > +        return os;
>> > +}
>> > +
>> > +} // namespace RPiController
>> > --
>> > 2.25.1
>> >