[PATCH weston v2 2/6] shared: Add timespec_to_proto helper function

[Alexandros Frantzis]

Add helper function to convert from struct timespec values to tv_sec_hi,
tv_sec_lo, tv_nsec triplets used for sending high-resolution timestamp
data over the wayland protocol. Replace existing conversion code with
the helper function.

Signed-off-by: Alexandros Frantzis <alexandros.frantzis at collabora.com>
---

Changes in v2:
 - New patch, previously part of [PATCH weston 2/8].
 - Make normalized and non-negative input timespecs a precondition
   of timespec_to_proto (use assert() to check).
 - Simplify extracting the high and low bytes from the seconds part
   of the timespec in timespec_to_proto.
 - Remove test cases that are now unsupported.

 libweston/compositor.c |  9 +++++----
 shared/timespec-util.h | 24 ++++++++++++++++++++++++
 tests/timespec-test.c  | 29 +++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/libweston/compositor.c b/libweston/compositor.c
index 7d7a17ed..083664fd 100644
--- a/libweston/compositor.c
+++ b/libweston/compositor.c
@@ -341,7 +341,9 @@ weston_presentation_feedback_present(
 {
 	struct wl_client *client = wl_resource_get_client(feedback->resource);
 	struct wl_resource *o;
-	uint64_t secs;
+	uint32_t tv_sec_hi;
+	uint32_t tv_sec_lo;
+	uint32_t tv_nsec;
 
 	wl_resource_for_each(o, &output->resource_list) {
 		if (wl_resource_get_client(o) != client)
@@ -350,10 +352,9 @@ weston_presentation_feedback_present(
 		wp_presentation_feedback_send_sync_output(feedback->resource, o);
 	}
 
-	secs = ts->tv_sec;
+	timespec_to_proto(ts, &tv_sec_hi, &tv_sec_lo, &tv_nsec);
 	wp_presentation_feedback_send_presented(feedback->resource,
-						secs >> 32, secs & 0xffffffff,
-						ts->tv_nsec,
+						tv_sec_hi, tv_sec_lo, tv_nsec,
 						refresh_nsec,
 						seq >> 32, seq & 0xffffffff,
 						flags | feedback->psf_flags);
diff --git a/shared/timespec-util.h b/shared/timespec-util.h
index 5184d281..5f4b2b9e 100644
--- a/shared/timespec-util.h
+++ b/shared/timespec-util.h
@@ -147,6 +147,30 @@ timespec_to_usec(const struct timespec *a)
 	return (int64_t)a->tv_sec * 1000000 + a->tv_nsec / 1000;
 }
 
+/* Convert timespec to protocol data
+ *
+ * \param a timespec
+ * \param tv_sec_hi[out] the high bytes of the seconds part
+ * \param tv_sec_lo[out] the low bytes of the seconds part
+ * \param tv_nsec[out] the nanoseconds part
+ *
+ * The input timespec must be normalized (the nanoseconds part should
+ * be less than 1 second) and non-negative.
+ */
+static inline void
+timespec_to_proto(const struct timespec *a, uint32_t *tv_sec_hi,
+                  uint32_t *tv_sec_lo, uint32_t *tv_nsec)
+{
+	assert(a->tv_sec >= 0);
+	assert(a->tv_nsec >= 0 && a->tv_nsec < NSEC_PER_SEC);
+
+	uint64_t sec64 = a->tv_sec;
+
+	*tv_sec_hi = sec64 >> 32;
+	*tv_sec_lo = sec64 & 0xffffffff;
+	*tv_nsec = a->tv_nsec;
+}
+
 /* Convert nanoseconds to timespec
  *
  * \param a timespec
diff --git a/tests/timespec-test.c b/tests/timespec-test.c
index a4d8dcfb..54230f89 100644
--- a/tests/timespec-test.c
+++ b/tests/timespec-test.c
@@ -79,6 +79,35 @@ ZUC_TEST(timespec_test, timespec_to_msec)
 	ZUC_ASSERT_EQ(timespec_to_msec(&a), (4000ULL) + 4);
 }
 
+ZUC_TEST(timespec_test, timespec_to_proto)
+{
+	struct timespec a;
+	uint32_t tv_sec_hi;
+	uint32_t tv_sec_lo;
+	uint32_t tv_nsec;
+
+	a.tv_sec = 0;
+	a.tv_nsec = 0;
+	timespec_to_proto(&a, &tv_sec_hi, &tv_sec_lo, &tv_nsec);
+	ZUC_ASSERT_EQ(0, tv_sec_hi);
+	ZUC_ASSERT_EQ(0, tv_sec_lo);
+	ZUC_ASSERT_EQ(0, tv_nsec);
+
+	a.tv_sec = 1234;
+	a.tv_nsec = NSEC_PER_SEC - 1;
+	timespec_to_proto(&a, &tv_sec_hi, &tv_sec_lo, &tv_nsec);
+	ZUC_ASSERT_EQ(0, tv_sec_hi);
+	ZUC_ASSERT_EQ(1234, tv_sec_lo);
+	ZUC_ASSERT_EQ(NSEC_PER_SEC - 1, tv_nsec);
+
+	a.tv_sec = (time_t)0x7000123470005678LL;
+	a.tv_nsec = 1;
+	timespec_to_proto(&a, &tv_sec_hi, &tv_sec_lo, &tv_nsec);
+	ZUC_ASSERT_EQ((uint64_t)a.tv_sec >> 32, tv_sec_hi);
+	ZUC_ASSERT_EQ(0x70005678, tv_sec_lo);
+	ZUC_ASSERT_EQ(1, tv_nsec);
+}
+
 ZUC_TEST(timespec_test, millihz_to_nsec)
 {
 	ZUC_ASSERT_EQ(millihz_to_nsec(60000), 16666666);
-- 
2.14.1