Seek trait provides a cursor which can be moved within a stream of
The stream typically has a fixed size, allowing seeking relative to either end or the current offset.
Seek to an offset, in bytes, in a stream.
A seek beyond the end of a stream is allowed, but behavior is defined by the implementation.
If the seek operation completed successfully,
this method returns the new position from the start of the stream.
That position can be used later with
Seeking to a negative offset is considered an error.
fn stream_len(&mut self) -> Result<u64>
Returns the length of this stream (in bytes).
This method is implemented using up to three seek operations. If this method returns successfully, the seek position is unchanged (i.e. the position before calling this method is the same as afterwards). However, if this method returns an error, the seek position is unspecified.
If you need to obtain the length of many streams and you don't care
about the seek position afterwards, you can reduce the number of seek
operations by simply calling
seek(SeekFrom::End(0)) and using its
return value (it is also the stream length).
Note that length of a stream can change over time (for example, when data is appended to a file). So calling this method multiple times does not necessarily return the same length each time.
fn stream_position(&mut self) -> Result<u64>
Returns the current seek position from the start of the stream.
This is equivalent to
Seek to an offset, in bytes, in the underlying reader.
The position used for seeking with
SeekFrom::Current(_) is the
position the underlying reader would be at if the
BufReader<R> had no
Seeking always discards the internal buffer, even if the seek position
would otherwise fall within it. This guarantees that calling
.into_inner() immediately after a seek yields the underlying reader
at the same position.
To seek without discarding the internal buffer, use
std::io::Seek for more details.
Note: In the edge case where you're seeking with
n minus the internal buffer length overflows an
seeks will be performed instead of one. If the second seek returns
Err, the underlying reader will be left at the same position it would
have if you called