tape/drive: add 'move_to_file' to TapeDriver trait

so that we can directly move to a specified file on the tape

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

src/tape/drive/lto/mod.rs

@@ -309,6 +309,10 @@ impl TapeDriver for LtoTapeHandle {
         Ok(())
     }
 
+    fn move_to_file(&mut self, file: u64) -> Result<(), Error> {
+        self.locate_file(file)
+    }
+
     fn rewind(&mut self) -> Result<(), Error> {
         self.sg_tape.rewind()
     }

src/tape/drive/mod.rs

@@ -80,6 +80,9 @@ pub trait TapeDriver {
     /// Move to last file
     fn move_to_last_file(&mut self) -> Result<(), Error>;
 
+    /// Move to given file nr
+    fn move_to_file(&mut self, file: u64) -> Result<(), Error>;
+
     /// Current file number
     fn current_file_number(&mut self) -> Result<u64, Error>;
 

src/tape/drive/virtual_tape.rs

@@ -261,6 +261,28 @@ impl TapeDriver for VirtualTapeHandle {
         Ok(())
     }
 
+    fn move_to_file(&mut self, file: u64) -> Result<(), Error> {
+        let mut status = self.load_status()?;
+        match status.current_tape {
+            Some(VirtualTapeStatus { ref name, ref mut pos }) => {
+
+                let index = self.load_tape_index(name)
+                    .map_err(|err| io::Error::new(io::ErrorKind::Other, err.to_string()))?;
+
+                if file as usize > index.files {
+                    bail!("invalid file nr");
+                }
+
+                *pos = file as usize;
+
+                self.store_status(&status)
+                    .map_err(|err| io::Error::new(io::ErrorKind::Other, err.to_string()))?;
+
+                Ok(())
+            }
+            None => bail!("drive is empty (no tape loaded)."),
+        }
+    }
 
     fn read_next_file(&mut self) -> Result<Box<dyn TapeRead>, BlockReadError> {
         let mut status = self.load_status()