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

[Kieran Bingham]

Hi Laurent,

On 23/01/2019 08:28, Laurent Pinchart wrote:
> Implement additions and subtraction of struct timespec through
> non-member operators to simplify timespec handling.
> 
> 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.


Thank you, I do foresee this being useful in the future when handling
buffer timestamps and such. Even if just for printing debug statements
and measuring durations between frames.

Most of the time the library itself shouldn't care too much about buffer
timestamps, but perhaps even that might change when we look at 3a.

Perhaps because of this I'd almost be tempted to add these utils anyway
if we wrapped a test that used them ? But then we're dragging unused
code around - so it can wait until it's necessary.

--
Kieran


>  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
--
Kieran