Category : C Source Code
Archive : OBFUSC89.ZIP
Filename : WESTLEY.HIN
Output of file : WESTLEY.HIN contained in archive : OBFUSC89.ZIP
Merlyn LeRoy (Brian Westley)
Starfire Consulting
1026 Blair Ave.
St. Paul, MN
55104
USA
Judges notes:
There is a secret way to get ONE of the versions to print out
"Hello, world!\n". Can you find how to do it?
Try the following commands:
westley < westley.c > ver0.c
westley 1 < westley.c > ver1.c
westley 1 2 < westley.c > ver2.c
westley 1 2 3 < westley.c > ver3.c
Try compiling and running the 4 resulting programs.
Selected notes from the author:
This is a filter. If it is run with no arguments, it copies
stdin to stdout. With one argument, it ROT13's stdin to
stdout. With two arguments, it reverses stdin to stdout. With
three arguments, it does both. It requires the ASCII character
set, with all characters being in 0..255, and EOF must be -1.
Also requires two's complement (I think).
The source code will run if ROT13'ed and/or reversed, using a
different algorithm for each version (hereafter referred to as
ver0 (original), ver1 (ROT13), ver2 (reversed), and ver3
(ROT13 and reversed)).
When compiling these versions, one needs to define 'trgpune'
in the compile line. Example:
cc -Dtrgpune=putchar ver3.c -o ver3
"trgpune" is the ROT13 of getchar(), so getchar() and putchar()
are exchanged in the ROT13 counterpart. It is easy to see that
this is unavoidable. I must have a #define for a library
function; otherwise I would have an unidentifed extern for the
ROT13 version. If I then define this function, it won't link
in the library version for the ORIGINAL code, since my
definition will supercede the library function. Hence, the
compiler option gives me putchar(), and allows me to use
getchar(). I pass a dummy argument to getchar() to eliminate
"variable number of args" from lint (unless it checks against
the library). Otherwise, all versions lint reasonably (main
returns random value & constant in conditional context [when I
check for ROT13 version] is all it complains about).
ver0 and ver1 use a range check and a calculation to do ROT13,
while ver2 and ver3 use table lookup. All versions contain
main() and it's ROT13 fn, znva(). ver0/ver1 [ver2/ver3] are
(of course) syntactically identical, since the syntax is in the
non-alphabetic characters. However, since one program starts
at main() while it's ROT13 counterpart starts at znva(), znva()
calls main (znva() is also used for output).
All versions use recursion to work. If the program is NOT
reversing it's output, it prints out the (possibly ROT13'd)
character before recursing, otherwise it prints it out
afterward (or doesn't recurse at all when EOF is reached).
Since most of this code is identical, it is put into znva() and
called with a first parameter of 0 as a flag (as "main()", it's
first argument (argc) must be at least one).
I can't use any flow control. If I used if(), I would have a
function vs() to define in the ROT13 version. But a function
called vs() turns into a function called if() in the original,
so it can't be done. Therefore, I do:
expr1 && expr2 && (expr3=etc);
which is the same as:
if (expr1 && expr2) expr3=etc;
A/UX on the Macintosh doesn't get this right; it evaluates ALL
expressions if they aren't in an assignment or conditional
statement. This might warrant a warning, since other compilers
may do this. I found MANY compilers botched:
expr1 && (expr2,expr3);
expr2 was OFTEN evaluated even if expr1 was false. I removed
such statements to make it more portable.
The variable names are worth noting:
'irk' and 'vex' are ROT13 pairs and are synonyms.
'Near' and 'Arne' are ROT13 pairs and are anagrams.
'NOON' and 'ABBA' are ROT13 pairs and are palindromes.
'tang' and 'gnat' are both ROT13 and palindrome pairs!
Normally (!), a reversible C program is done thus:
/**/ forward code /*/ edoc drawkcab /**/
If your compiler nests comments, it will get this wrong.
However, I have made some bits of the code palindromic,
(or different, but reversible) so it is more like:
/**/forward/*//**/ palindromic /**//*/drawkcab/**/
The code can therefore be interlaced. There are eight
such palindromic bits. You can find them within the
/*//**/ /**//*/ pairs.
The body of the code of ver0 and ver1 is a large lumpy 'K' (for
Kernighan); the code of ver2 and ver3 is a flat-topped and
lumpier 'R' (for Ritchie). Judicious use of spaces and tabs
helped here. It barely fits on an 80x24 screen. Squint. Note
that the code must start with a blank line, or the reversed version
will lack a terminating newline.
Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!
This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.
But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: http://www.os2museum.com/wp/mtswslnk/