@Override
    public void mark(int unused) {
        abortIfNeeded();
        try {
            markPos = fileChannel.position();
        } catch (IOException e) {
            throw new SdkClientException("Failed to mark the file position", e);
        }
        if (log.isTraceEnabled())
            log.trace("File input stream marked at position " + markPos);
    }
Marks the current position in this input stream. A subsequent call to
the <code>reset</code> method repositions this stream at the last marked
position so that subsequent reads re-read the same bytes.
This method works as long as the underlying file has not been closed.
<p>
Note the creation of a {@link ResettableInputStream} would entail
physically opening a file. If the opened file is meant to be closed only
(in a finally block) by the very same code block that created it, then it
is necessary that the release method must not be called while the
execution is made in other stack frames.

In such case, as other stack frames may inadvertently or indirectly call
the close method of the stream, the creator of the stream would need to
explicitly disable the accidental closing via
{@link ResettableInputStream#disableClose()}, so that the release method
becomes the only way to truly close the opened file.

@param _
           ignored
aws-java-sdk-core/src/main/java/com/amazonaws/internal/ResettableInputStream.java