refactor: Inject mtio package to allow for remote implementation

pkg/config/config.go

@@ -28,6 +28,8 @@ type BackendConfig struct {
 
 	GetReader   func() (DriveReaderConfig, error)
 	CloseReader func() error
+
+	MagneticTapeIO MagneticTapeIO
 }
 
 type Header struct {
@@ -96,3 +98,11 @@ type FileConfig struct {
 	Path    string
 	Link    string
 }
+
+type MagneticTapeIO interface {
+	GetCurrentRecordFromTape(fd uintptr) (int64, error)
+	GoToEndOfTape(fd uintptr) error
+	GoToNextFileOnTape(fd uintptr) error
+	EjectTape(fd uintptr) error
+	SeekToRecordOnTape(fd uintptr, record int32) error
+}

pkg/config/constants.go

@@ -34,6 +34,8 @@ const (
 
 	WriteCacheTypeMemory = "memory"
 	WriteCacheTypeFile   = "file"
+
+	MagneticTapeBlockSize = 512
 )
 
 var (