Example 2:
Adding a checksum.

All you have to do is to replace the typedef-statement
typedef HuffmanCoder Coder;
in Example 1 by
typedef CoderPipe2<MD5SumCoder, HuffmanCoder> Coder;

The class CoderPipe2 combines the two L E D A coders MD5SumCoder (the checksummer) and HuffmanCoder into a single coder. If the pipe is used for encoding, then the MD5SumCoder is used first and the HuffmanCoder is applied
to its output. In decoding mode the situation is reversed.

The standard behaviour of a checksummer like MD5SumCoder is as follows:

In encoding mode it reads the input stream and computes a checksum;
the output data basically consists of the input data with the checksum appended.
In decoding mode, the checksum is stripped from the input data and verified.
If the input is corrupted, the failure flag of the coder is set to indicate this.