libcamera: utils: Add clock helpers

In preparation for standardisation of the std::chrono::steady_clock as
the libcamera default clock, define aliases for the clock, duration and
time point, and add helper functions to convert a duration to a timespec
and a time point to a string. More helpers will be added later as
needed.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/libcamera/include/utils.h

@@ -8,7 +8,10 @@
 #define __LIBCAMERA_UTILS_H__
 
 #include <algorithm>
+#include <chrono>
 #include <memory>
+#include <string>
+#include <sys/time.h>
 
 #define ARRAY_SIZE(a)	(sizeof(a) / sizeof(a[0]))
 
@@ -53,6 +56,13 @@ const T& clamp(const T& v, const T& lo, const T& hi)
 	return std::max(lo, std::min(v, hi));
 }
 
+using clock = std::chrono::steady_clock;
+using duration = std::chrono::steady_clock::duration;
+using time_point = std::chrono::steady_clock::time_point;
+
+struct timespec duration_to_timespec(const duration &value);
+std::string time_point_to_string(const time_point &time);
+
 } /* namespace utils */
 
 } /* namespace libcamera */