[Hadoop-common-user] Reading a block of data in Map function

I am wondering how to read a block of data in Map. I have a file with a
single number on every line and I wish to calculate some statistics.

Once the file is divided into blocks and sent to different nodes by hadoop,
is it possible to read a chunk of the data in each map function? Right now
each map is reading one number at a time.

Thanks,
Akshaya