[libcamera-devel] [PATCH] libcamera: utils: Add arithmetic operators for struct timespec

[Shik Chen]

Hi Laurent,

On Wed, Jan 23, 2019 at 4:28 PM Laurent Pinchart <
laurent.pinchart at ideasonboard.com> wrote:
>
> Implement additions and subtraction of struct timespec through
> non-member operators to simplify timespec handling.

IIUC, operator overloading on types of other libs is banned by the style
guide :Q
https://google.github.io/styleguide/cppguide.html#Operator_Overloading

>
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>
> I wrote this code while working on EINTR handling for the event
> dispatcher, and later refactored the implementation in a way that
> doesn't make use of these operators anymore. I thought they could still
> be useful as reference for later use. This patch is thus not meant to be
> merged now, but can be picked up later if anyone needs it.
>
>  src/libcamera/include/utils.h |  6 +++++
>  src/libcamera/meson.build     |  1 +
>  src/libcamera/utils.cpp       | 46 +++++++++++++++++++++++++++++++++++
>  3 files changed, 53 insertions(+)
>  create mode 100644 src/libcamera/utils.cpp
>
> diff --git a/src/libcamera/include/utils.h b/src/libcamera/include/utils.h
> index 73fa2e69b029..7df20976f36f 100644
> --- a/src/libcamera/include/utils.h
> +++ b/src/libcamera/include/utils.h
> @@ -8,6 +8,7 @@
>  #define __LIBCAMERA_UTILS_H__
>
>  #include <memory>
> +#include <time.h>
>
>  #define ARRAY_SIZE(a)  (sizeof(a) / sizeof(a[0]))
>
> @@ -24,6 +25,11 @@ std::unique_ptr<T> make_unique(Args&&... args)
>
>  } /* namespace utils */
>
> +struct timespec &operator+=(struct timespec &lhs, const struct timespec
&rhs);
> +struct timespec operator+(struct timespec lhs, const struct timespec
&rhs);
> +struct timespec &operator-=(struct timespec &lhs, const struct timespec
&rhs);
> +struct timespec operator-(struct timespec lhs, const struct timespec
&rhs);
> +
>  } /* namespace libcamera */
>
>  #endif /* __LIBCAMERA_UTILS_H__ */
> diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
> index f9f25c0ecf15..72d4a194e19a 100644
> --- a/src/libcamera/meson.build
> +++ b/src/libcamera/meson.build
> @@ -11,6 +11,7 @@ libcamera_sources = files([
>      'pipeline_handler.cpp',
>      'signal.cpp',
>      'timer.cpp',
> +    'utils.cpp',
>      'v4l2_device.cpp',
>  ])
>
> diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
> new file mode 100644
> index 000000000000..5014b27d8c7d
> --- /dev/null
> +++ b/src/libcamera/utils.cpp
> @@ -0,0 +1,46 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2018, Google Inc.
> + *
> + * utils.cpp - Miscellaneous utility functions
> + */
> +
> +#include "utils.h"
> +
> +namespace libcamera {
> +
> +struct timespec &operator+=(struct timespec &lhs, const struct timespec
&rhs)
> +{
> +       lhs.tv_sec += rhs.tv_sec;
> +       lhs.tv_nsec += rhs.tv_nsec;
> +       if (lhs.tv_nsec >= 1000000000) {
> +               lhs.tv_sec++;
> +               lhs.tv_nsec -= 1000000000;
> +       }
> +
> +       return lhs;
> +}
> +
> +struct timespec operator+(struct timespec lhs, const struct timespec
&rhs)
> +{
> +       return lhs += rhs;
> +}
> +
> +struct timespec &operator-=(struct timespec &lhs, const struct timespec
&rhs)
> +{
> +       lhs.tv_sec -= rhs.tv_sec;
> +       lhs.tv_nsec -= rhs.tv_nsec;
> +       if (lhs.tv_nsec < 0) {
> +               lhs.tv_sec--;
> +               lhs.tv_nsec += 1000000000;
> +       }
> +
> +       return lhs;
> +}
> +
> +struct timespec operator-(struct timespec lhs, const struct timespec
&rhs)
> +{
> +       return lhs - rhs;
> +}
> +
> +} /* namespace libcamera */
> --
> Regards,
>
> Laurent Pinchart

Sincerely,
Shik
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