Encodes and decodes Ascii85.
Ascii85, also called Base85, is a form of binary-to-text encoding developed by Paul E. Rutter.
It uses five ASCII characters to represent four bytes of binary data (making the encoded size 1⁄4 larger than the original, assuming eight bits per ASCII character).
For encoder:
$ gcc encasc85.c -o encasc85
For decoder:
$ gcc decasc85.c -o decasc85
For encoding example.txt:
$ ./encasc85 < example.txt
For decoding example.txt:
$ ./decasc85 < example.txt