From 975cf14a3d54a37f533d5fd1c63fe4de7aa1cc0a Mon Sep 17 00:00:00 2001
From: Yaroslav Kolomiiets <yrk@meta.com>
Date: Tue, 22 Oct 2024 02:30:19 +0100
Subject: [PATCH] unix: add unix.TimeToPtpClockTime on Linux

Add time conversion helpers for PtpClockTime similar to those
existing for Timespec and Timeval.

Allows to use the maths of the standard time package while avoiding
the boilerplate:
write "ptpt.Time()" instead of "time.Unix(ptpt.Sec, int64(ptpt.Nsec))",
and "unix.TimeToPtpClockTime(t)" instead of
"unix.PtpClockTime{Sec: t.Unix(), Nsec: uint32(t.Nanosecond())}".
---
 unix/timestruct_linux.go      | 26 ++++++++++++++++++++++
 unix/timestruct_linux_test.go | 42 +++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)
 create mode 100644 unix/timestruct_linux.go
 create mode 100644 unix/timestruct_linux_test.go

diff --git a/unix/timestruct_linux.go b/unix/timestruct_linux.go
new file mode 100644
index 000000000..19875897d
--- /dev/null
+++ b/unix/timestruct_linux.go
@@ -0,0 +1,26 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux
+
+package unix
+
+import "time"
+
+// TimeToPtpClockTime returns t as PtpClockTime
+func TimeToPtpClockTime(t time.Time) PtpClockTime {
+	sec := t.Unix()
+	nsec := uint32(t.Nanosecond())
+	return PtpClockTime{Sec: sec, Nsec: nsec}
+}
+
+// Time returns PTPClockTime as time.Time
+func (t *PtpClockTime) Time() time.Time {
+	return time.Unix(t.Sec, int64(t.Nsec))
+}
+
+// Unix returns the time stored in t as seconds plus nanoseconds.
+func (t *PtpClockTime) Unix() (sec int64, nsec int64) {
+	return t.Sec, int64(t.Nsec)
+}
diff --git a/unix/timestruct_linux_test.go b/unix/timestruct_linux_test.go
new file mode 100644
index 000000000..0a7249927
--- /dev/null
+++ b/unix/timestruct_linux_test.go
@@ -0,0 +1,42 @@
+// Copyright 2024 The Go Authors. All right reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux
+
+package unix_test
+
+import (
+	"testing"
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+func TestTimeToPtpClockTime(t *testing.T) {
+	testcases := []struct {
+		time  time.Time
+	}{
+		{time.Unix(0, 0)},
+		{time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)},
+		{time.Date(2262, time.December, 31, 23, 0, 0, 0, time.UTC)},
+		{time.Unix(0x7FFFFFFF, 0)},
+		{time.Unix(0x80000000, 0)},
+		{time.Unix(0x7FFFFFFF, 1000000000)},
+		{time.Unix(0x7FFFFFFF, 999999999)},
+		{time.Unix(-0x80000000, 0)},
+		{time.Unix(-0x80000001, 0)},
+		{time.Date(2038, time.January, 19, 3, 14, 7, 0, time.UTC)},
+		{time.Date(2038, time.January, 19, 3, 14, 8, 0, time.UTC)},
+		{time.Date(1901, time.December, 13, 20, 45, 52, 0, time.UTC)},
+		{time.Date(1901, time.December, 13, 20, 45, 51, 0, time.UTC)},
+	}
+
+	for _, tc := range testcases {
+		ts := unix.TimeToPtpClockTime(tc.time)
+		tstime := time.Unix(int64(ts.Sec), int64(ts.Nsec))
+		if !tstime.Equal(tc.time) {
+			t.Errorf("TimeToPtpClockTime(%v) is the time %v", tc.time, tstime)
+		}
+	}
+}