Author:

• Name: Stephen Dolan
  Location: IE - Republic of Ireland (Ireland)

To build:

    make all

To use:

    echo {10-hex-digits} | ./prog > out.pbm

Try:

    md5sum prog.c | ./prog | display -

Judges’ remarks:

There are no magic numbers in the program, and bits of the input map to pixels of the output in a regular way, yet it outputs a nice icon for itself, if given the MD5 hash of its own source. How?

Author’s remarks:

This program is a decoder for a very compact icon format, producing 80x80 pixel pbm images based on small bitmapped icons:

    echo faf6bdafe6 | ./prog | display -   # calendar
    echo f843928fe0 | ./prog | display -   # mail
    echo f0b42d0bd8 | ./prog | display -   # battery
    echo f39ce33bc0 | ./prog | display -   # 1
    echo f0aced1bc0 | ./prog | display -   # 2
    echo f1b4ed1bc0 | ./prog | display -   # 3
    echo 4010881098 | ./prog | display -   # ?
    echo c6018c7398 | ./prog | display -   # !
    echo de848d2c3c | ./prog | display -   # the tetrominos

NOTE: The use of | display - is optional. If omitted, just view the resulting output in a terminal with a small font size.

NOTE: Else if do not have ImageMagick’s display(1) tool installed the use pbm image viewing tool of your choice.

Effort has been made to reduce the size of the program text to a single longish line (135 characters, including newline). Regrettably, this left no space in which to store the program’s own icon, a picture of a computer screen displaying ‘C’.

Accordingly, the program’s icon is instead stored in the program’s MD5 hash:

    md5sum prog.c | ./prog | display -

NOTE: On machines without md5sum(1), try md5 or openssl md5 -r.

Notes

• While terseness was preferred over obscurity, this program hopefully still lives down to IOCCC’s usual standards of clarity.

  The program should be readable to any C programmer familiar with its less common operators, including French-quoted literals (<<5>>), the interrobang (?!) and the wink (^-).

• To fit on one line, the program commits two anachronistic sins: it assumes an implicit int return type for main, and it uses several stdlib functions without including the relevant header.

  It can be compiled by switching to -std=c89 (remembering a time when such crimes were let off with a warning), or by covering up the crimes with -Dmain='int main' -include stdio.h, at which point it is valid under any version of C.

• Even with these compiler options, Clang and GCC with -Wall also issue a warning complaining that the program correctly uses weird parts of the C operator precedence table. No apology is made for this one.

• Several variants of this program were considered. Several.

• The icon format is compressed, not just bit-packed: there are more pixels in the output than bits in the input.

• By an astonishing coincidence, the number of bits in the input format is approximately the log2 of the number of MD5 evaluations that a five-year-old GPU can do in an hour.

Primary files

• prog.c - entry source code
• Makefile - entry Makefile
• prog.orig.c - original source code
• try.sh - script to try entry

Secondary files

• 2024_stedolan.tar.bz2 - download entry tarball
• README.md - markdown source for this web page
• .entry.json - entry summary and manifest in JSON
• .gitignore - list of files that should not be committed under git
• .path - directory path from top level directory
• index.html - this web page

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