refactor: Decompose index func

internal/tape/read.go

@@ -0,0 +1,27 @@
+package tape
+
+import "os"
+
+func OpenTapeReadOnly(tape string) (f *os.File, isRegular bool, err error) {
+	fileDescription, err := os.Stat(tape)
+	if err != nil {
+		return nil, false, err
+	}
+
+	isRegular = fileDescription.Mode().IsRegular()
+	if isRegular {
+		f, err = os.Open(tape)
+		if err != nil {
+			return f, isRegular, err
+		}
+
+		return f, isRegular, nil
+	}
+
+	f, err = os.OpenFile(tape, os.O_RDONLY, os.ModeCharDevice)
+	if err != nil {
+		return f, isRegular, err
+	}
+
+	return f, isRegular, nil
+}