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 */

src/libcamera/utils.cpp

@@ -7,6 +7,8 @@
 
 #include "utils.h"
 
+#include <iomanip>
+#include <sstream>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -93,6 +95,54 @@ char *secure_getenv(const char *name)
  * \return lo if v is less than lo, hi if v is greater than hi, otherwise v
  */
 
+/**
+ * \typedef clock
+ * \brief The libcamera clock (monotonic)
+ */
+
+/**
+ * \typedef duration
+ * \brief The libcamera duration related to libcamera::utils::clock
+ */
+
+/**
+ * \typedef time_point
+ * \brief The libcamera time point related to libcamera::utils::clock
+ */
+
+/**
+ * \brief Convert a duration to a timespec
+ * \param[in] value The duration
+ * \return A timespec expressing the duration
+ */
+struct timespec duration_to_timespec(const duration &value)
+{
+	uint64_t nsecs = std::chrono::duration_cast<std::chrono::nanoseconds>(value).count();
+	struct timespec ts;
+	ts.tv_sec = nsecs / 1000000000ULL;
+	ts.tv_nsec = nsecs % 1000000000ULL;
+	return ts;
+}
+
+/**
+ * \brief Convert a time point to a string representation
+ * \param[in] time The time point
+ * \return A string representing the time point in hh:mm:ss.nanoseconds format
+ */
+std::string time_point_to_string(const time_point &time)
+{
+	uint64_t nsecs = std::chrono::duration_cast<std::chrono::nanoseconds>(time.time_since_epoch()).count();
+	unsigned int secs = nsecs / 1000000000ULL;
+
+	std::ostringstream ossTimestamp;
+	ossTimestamp.fill('0');
+	ossTimestamp << secs / (60 * 60) << ":"
+		     << std::setw(2) << (secs / 60) % 60 << ":"
+		     << std::setw(2) << secs % 60 << "."
+		     << std::setw(9) << nsecs % 1000000000ULL;
+	return ossTimestamp.str();
+}
+
 } /* namespace utils */
 
 } /* namespace libcamera */