This method updates compressed stream position exactly when the
client of this code has read off at least one byte passed any BZip2
end of block marker.
This mechanism is very helpful to deal with data level record
boundaries. Please see constructor and next methods of
org.apache.hadoop.mapred.LineRecordReader as an example usage of this
feature. We elaborate it with an example in the following:
Assume two different scenarios of the BZip2 compressed stream, where
[m] represent end of block, \n is line delimiter and . represent compressed
Assume that end is right after [m]. In the first case the reading
will stop at \n and there is no need to read one more line. (To see the
reason of reading one more line in the next() method is explained in LineRecordReader.)
While in the second example LineRecordReader needs to read one more line
(till the second \n). Now since BZip2Codecs only update position
at least one byte passed a maker, so it is straight forward to differentiate
between the two cases mentioned.