tape: add TapeDriver::move_to_last_file

src/tape/drive/linux_tape.rs

@@ -467,6 +467,23 @@ impl TapeDriver for LinuxTapeHandle {
         Ok(())
     }
 
+    fn move_to_last_file(&mut self) -> Result<(), Error> {
+
+        let cmd = mtop { mt_op: MTCmd::MTEOM, mt_count: 1, };
+
+        unsafe {
+            mtioctop(self.file.as_raw_fd(), &cmd)
+        }.map_err(|err| format_err!("MTEOM failed - {}", err))?;
+
+        let cmd = mtop { mt_op: MTCmd::MTBSFM, mt_count: 2, };
+
+        unsafe {
+            mtioctop(self.file.as_raw_fd(), &cmd)
+        }.map_err(|err| format_err!("MTBSFM failed - {}", err))?;
+
+        Ok(())
+    }
+
     fn rewind(&mut self) -> Result<(), Error> {
 
         let cmd = mtop { mt_op: MTCmd::MTREW, mt_count: 1, };

src/tape/drive/mod.rs

@@ -87,6 +87,9 @@ pub trait TapeDriver {
     /// We assume this flushes the tape write buffer.
     fn move_to_eom(&mut self) -> Result<(), Error>;
 
+    /// Move to last file
+    fn move_to_last_file(&mut self) -> Result<(), Error>;
+
     /// Current file number
     fn current_file_number(&mut self) -> Result<u64, Error>;
 

src/tape/drive/virtual_tape.rs

@@ -305,6 +305,29 @@ impl TapeDriver for VirtualTapeHandle {
         }
     }
 
+    fn move_to_last_file(&mut self) -> 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 index.files == 0 {
+                    bail!("move_to_last_file failed - media contains no data");
+                }
+
+                *pos = index.files - 1;
+
+                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 rewind(&mut self) -> Result<(), Error> {
         let mut status = self.load_status()?;
         match status.current_tape {