pub fn into_inner(self) -> R { self.inner }
}
+impl<R: Seek> BufReader<R> {
+ /// Seeks relative to the current position. If the new position lies within the buffer,
+ /// the buffer will not be flushed, allowing for more efficient seeks.
+ /// This method does not return the location of the underlying reader, so the caller
+ /// must track this information themselves if it is required.
+ #[unstable(feature = "bufreader_seek_relative", issue = "31100")]
+ pub fn seek_relative(&mut self, offset: i64) -> io::Result<()> {
+ let pos = self.pos as u64;
+ if offset < 0 {
+ if let Some(new_pos) = pos.checked_sub((-offset) as u64) {
+ self.pos = new_pos as usize;
+ return Ok(())
+ }
+ } else {
+ if let Some(new_pos) = pos.checked_add(offset as u64) {
+ if new_pos <= self.cap as u64 {
+ self.pos = new_pos as usize;
+ return Ok(())
+ }
+ }
+ }
+ self.seek(SeekFrom::Current(offset)).map(|_|())
+ }
+}
+
#[stable(feature = "rust1", since = "1.0.0")]
impl<R: Read> Read for BufReader<R> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
assert_eq!(reader.seek(SeekFrom::Current(-2)).ok(), Some(3));
}
+ #[test]
+ fn test_buffered_reader_seek_relative() {
+ let inner: &[u8] = &[5, 6, 7, 0, 1, 2, 3, 4];
+ let mut reader = BufReader::with_capacity(2, io::Cursor::new(inner));
+
+ assert!(reader.seek_relative(3).is_ok());
+ assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..]));
+ assert!(reader.seek_relative(0).is_ok());
+ assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..]));
+ assert!(reader.seek_relative(1).is_ok());
+ assert_eq!(reader.fill_buf().ok(), Some(&[1][..]));
+ assert!(reader.seek_relative(-1).is_ok());
+ assert_eq!(reader.fill_buf().ok(), Some(&[0, 1][..]));
+ assert!(reader.seek_relative(2).is_ok());
+ assert_eq!(reader.fill_buf().ok(), Some(&[2, 3][..]));
+ }
+
#[test]
fn test_buffered_reader_seek_underflow() {
// gimmick reader that yields its position modulo 256 for each byte