Prevent fallback to slow path when the source file is completely empty

Signed-off-by: Sven Wiltink <sven@wiltink.dev>
svenwiltink · Aug 22, 2023 · bae7011 · bae7011
1 parent f1005bf
commit bae7011
Showing 1 changed file with 8 additions and 0 deletions.
diff --git a/sparse_unix.go b/sparse_unix.go
@@ -51,6 +51,14 @@ func detectDataSection(file *os.File, offset int64) (start int64, end int64, err
 
 func supportsSeekHole(file *os.File) bool {
 	_, err := file.Seek(0, SEEK_DATA)
+	var syserr syscall.Errno
+
+	// when a file is completely empty SEEK_DATA fails with ENXIO indicating an EOF.
+	if errors.As(err, &syserr) {
+		if syserr == syscall.ENXIO {
+			return true
+		}
+	}
 	return err == nil
 }