pkg/system: rename maxTime and re-use, define unixEpochTime, update GoDoc

This more closely matches to how it's used everywhere. Also move the comment
describing "what" ChTimes() does inside its GoDoc.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

pkg/system/chtimes.go

@@ -8,9 +8,10 @@ import (
 )
 
 // Used by Chtimes
-var maxTime time.Time
+var unixEpochTime, unixMaxTime time.Time
 
 func init() {
+	unixEpochTime = time.Unix(0, 0)
 	if unsafe.Sizeof(syscall.Timespec{}.Nsec) == 8 {
 		// This is a 64 bit timespec
 		// os.Chtimes limits time to the following
@@ -18,28 +19,24 @@ func init() {
 		// Note that this intentionally sets nsec (not sec), which sets both sec
 		// and nsec internally in time.Unix();
 		// https://github.com/golang/go/blob/go1.19.2/src/time/time.go#L1364-L1380
-		maxTime = time.Unix(0, 1<<63-1)
+		unixMaxTime = time.Unix(0, 1<<63-1)
 	} else {
 		// This is a 32 bit timespec
-		maxTime = time.Unix(1<<31-1, 0)
+		unixMaxTime = time.Unix(1<<31-1, 0)
 	}
 }
 
-// Chtimes changes the access time and modified time of a file at the given path
+// Chtimes changes the access time and modified time of a file at the given path.
+// If the modified time is prior to the Unix Epoch (unixMinTime), or after the
+// end of Unix Time (unixEpochTime), os.Chtimes has undefined behavior. In this
+// case, Chtimes defaults to Unix Epoch, just in case.
 func Chtimes(name string, atime time.Time, mtime time.Time) error {
-	unixMinTime := time.Unix(0, 0)
-	unixMaxTime := maxTime
-
-	// If the modified time is prior to the Unix Epoch, or after the
-	// end of Unix Time, os.Chtimes has undefined behavior
-	// default to Unix Epoch in this case, just in case
-
-	if atime.Before(unixMinTime) || atime.After(unixMaxTime) {
-		atime = unixMinTime
+	if atime.Before(unixEpochTime) || atime.After(unixMaxTime) {
+		atime = unixEpochTime
 	}
 
-	if mtime.Before(unixMinTime) || mtime.After(unixMaxTime) {
-		mtime = unixMinTime
+	if mtime.Before(unixEpochTime) || mtime.After(unixMaxTime) {
+		mtime = unixEpochTime
 	}
 
 	if err := os.Chtimes(name, atime, mtime); err != nil {

pkg/system/chtimes_linux_test.go

@@ -12,10 +12,8 @@ func TestChtimesLinux(t *testing.T) {
 	file, dir := prepareTempFile(t)
 	defer os.RemoveAll(dir)
 
-	beforeUnixEpochTime := time.Unix(0, 0).Add(-100 * time.Second)
-	unixEpochTime := time.Unix(0, 0)
-	afterUnixEpochTime := time.Unix(100, 0)
-	unixMaxTime := maxTime
+	beforeUnixEpochTime := unixEpochTime.Add(-100 * time.Second)
+	afterUnixEpochTime := unixEpochTime.Add(100 * time.Second)
 
 	// Test both aTime and mTime set to Unix Epoch
 	Chtimes(file, unixEpochTime, unixEpochTime)

pkg/system/chtimes_test.go

@@ -26,10 +26,8 @@ func TestChtimes(t *testing.T) {
 	file, dir := prepareTempFile(t)
 	defer os.RemoveAll(dir)
 
-	beforeUnixEpochTime := time.Unix(0, 0).Add(-100 * time.Second)
-	unixEpochTime := time.Unix(0, 0)
-	afterUnixEpochTime := time.Unix(100, 0)
-	unixMaxTime := maxTime
+	beforeUnixEpochTime := unixEpochTime.Add(-100 * time.Second)
+	afterUnixEpochTime := unixEpochTime.Add(100 * time.Second)
 
 	// Test both aTime and mTime set to Unix Epoch
 	Chtimes(file, unixEpochTime, unixEpochTime)

pkg/system/chtimes_windows_test.go

@@ -15,10 +15,8 @@ func TestChtimesWindows(t *testing.T) {
 	file, dir := prepareTempFile(t)
 	defer os.RemoveAll(dir)
 
-	beforeUnixEpochTime := time.Unix(0, 0).Add(-100 * time.Second)
-	unixEpochTime := time.Unix(0, 0)
-	afterUnixEpochTime := time.Unix(100, 0)
-	unixMaxTime := maxTime
+	beforeUnixEpochTime := unixEpochTime.Add(-100 * time.Second)
+	afterUnixEpochTime := unixEpochTime.Add(100 * time.Second)
 
 	// Test both aTime and mTime set to Unix Epoch
 	Chtimes(file, unixEpochTime, unixEpochTime)