Best Use of Flags

Glyn Anderson
Jl. Raya Serang KM 18.2
Desa Bojong
Cikupa, Tangerang, 15710
Indonesia

To build:

make

To use:

echo something | ./anderson

Try:

echo Obfuscate | ./anderson

Judges' remarks:

This small program might be a nice addition to a digital personal organizer; just in case you are stranded on a desert island and need to signal your distress to passing ships.

The obfuscation in this program is truly masterful. The program is very cleverly obscured without the use of a single #define! Reformatting this program by hand :-) is the easiest way to understand what is going on.

Author's remarks:

This program is a simple filter that translates ASCII text into semaphore code. It reads from standard input and converts all alphanumeric characters to their corresponding semaphore codes. Consecutive whitespace is translated as a single 'break' code. Newlines also cause the next code to be output on a new line. All other characters are ignored. The codes themselves are written to standard output as a depiction of a person holding two flags, using only ASCII characters (semaphore smileys, if you will). For example, given the input "Hello, world!", the output will be:

	      <>       <>       <>    <>                  <>     <>
  _()       ()/      ()/      ()/     _\)       ()       (/_     _\)
[] /^      |^^      /^^      /^^    [] ^^      |^^|      ^^ [] [] ^^
  <>[      [][     <>][     <>][       ][      [][]      ][       ][


	      <>    []
  _()_      ()/     |()       ()
[] ^^ []   /^^       ^^|     |^^|
   ][     <>][       ][]     [][]

The program is obfuscated without the use of the preprocessor or any special compilation parameters. In fact, the program doesn't even bother using any keywords, save the single 'char' at the beginning. This program was crafted using only operator precedence rules, short-circuit evaluation and recursion. Each function contains a single, non-empty statement. (I did have to add a couple of empty statements to format the code properly.) There is a single string constant which encodes the flag positions and other data needed for drawing the semaphore codes.

The preprocessor will provide no help in de-obfuscating this code, and a C beautifier won't get you very far either. You just have to crunch through it.

An ANSI C compiler will generate several warnings when it compiles this program, as none of the functions declare their return type, nor do they return anything. This was necessary to keep the program free of keywords. It's valid in K&R C, and compiles in ANSI C. There are also warnings about conversion from 'int' to 'char' and the resulting loss of data. Again, if it's OK with K&R, it's OK with me.

This program is a great teaching tool for learning the semaphore code; and if you don't have any flags handy you can just use two copies of the source file.

Copyright and CC BY-SA 4.0 License:

Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)

For more information, see: https://creativecommons.org/licenses/by-sa/4.0/