From 5055ca747c4c0d635ed8f2ab272f493748c2f50a Mon Sep 17 00:00:00 2001
From: Naushir Patuck <naush@raspberrypi.com>
Date: Tue, 8 Jun 2021 12:03:32 +0100
Subject: libcamera: utils: Add helper class for std::chrono::duration

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 defined 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>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 include/libcamera/internal/utils.h | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

(limited to 'include')

diff --git a/include/libcamera/internal/utils.h b/include/libcamera/internal/utils.h
index 83dada7c..15beb0f4 100644
--- a/include/libcamera/internal/utils.h
+++ b/include/libcamera/internal/utils.h
@@ -316,8 +316,40 @@ 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>
+std::basic_ostream<CharT, Traits> &operator<<(std::basic_ostream<CharT, Traits> &os,
+					      const utils::Duration &d);
+#endif
+
 } /* namespace libcamera */
 
 #endif /* __LIBCAMERA_INTERNAL_UTILS_H__ */
-- 
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