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

[Laurent Pinchart]

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.

 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