This is the Python version of the MD5 test program from the MD5
Internet Draft (Rivest and Dusse, The MD5 Message-Digest Algorithm, 10
July 1991).  The file "foo" contains the string "abc" with no trailing
newline.

When called without arguments, it acts as a filter.  When called with
"-x", it executes a self-test, and the output should literally match
the output given in the RFC.

Code by Jan-Hein B\"uhrman after the original in C.