The navigation bar for a winning entry now has a "_Original C_" link
(between the ✅ and the Inventory on the right hand side) so that one
may easily view the original C code that was submitted for IOCCC judging.
Ran `make www timestamp` to perform the above.
793 lines
32 KiB
HTML
793 lines
32 KiB
HTML
<!DOCTYPE html>
|
||
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
|
||
<!-- START: two lines up starts content from: inc/top.default.html -->
|
||
|
||
<!-- END: this line ends content from: inc/top.default.html -->
|
||
<!-- START: this line starts content from: inc/head.default.html -->
|
||
|
||
<head>
|
||
<link rel="stylesheet" href="../../ioccc.css">
|
||
<link href="https://fonts.googleapis.com/css2?family=Outfit:wght@100..900&display=swap" rel="stylesheet">
|
||
<meta charset="utf-8">
|
||
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
|
||
<title>1992/gson - Most humorous output</title>
|
||
<link rel="icon" type="image/x-icon" href="../../favicon.ico">
|
||
<meta name="description" content="1992 IOCCC entry gson - Most humorous output">
|
||
<meta name="keywords" content="IOCCC, 1992, IOCCC 1992, IOCCC entry, gson, Most humorous output">
|
||
</head>
|
||
|
||
<!-- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! -->
|
||
<!-- !!! DO NOT MODIFY THIS FILE - This file is generated by a tool !!! -->
|
||
<!-- !!! DO NOT MODIFY THIS FILE - This file is generated by a tool !!! -->
|
||
<!-- !!! DO NOT MODIFY THIS FILE - This file is generated by a tool !!! -->
|
||
<!-- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! -->
|
||
|
||
<!-- END: this line ends content from: inc/head.default.html -->
|
||
|
||
<!-- -->
|
||
<!-- This web page was formed via the tool: bin/readme2index.sh -->
|
||
<!-- The content of main section of this web page came from: 1992/gson/README.md -->
|
||
<!-- -->
|
||
|
||
<!-- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! -->
|
||
<!-- !!! Do not modify this web page, instead modify the file: 1992/gson/README.md !!! -->
|
||
<!-- !!! Do not modify this web page, instead modify the file: 1992/gson/README.md !!! -->
|
||
<!-- !!! Do not modify this web page, instead modify the file: 1992/gson/README.md !!! -->
|
||
<!-- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! -->
|
||
|
||
<!-- Markdown content was converted into HTML via the tool: bin/md2html.sh -->
|
||
|
||
<!-- START: this line starts content from: inc/body.default.html -->
|
||
|
||
<body>
|
||
|
||
<!-- END: this line ends content from: inc/body.default.html -->
|
||
<!-- START: this line starts content from: inc/topbar.default.html -->
|
||
|
||
<div class="theader">
|
||
<nav class="topbar">
|
||
<div class="container">
|
||
<div class="logo">
|
||
<a href="../../index.html" class="logo-link">
|
||
IOCCC
|
||
</a>
|
||
</div>
|
||
|
||
<div class="topbar-items">
|
||
<div class="item">
|
||
<span class="item-header">
|
||
Entries
|
||
</span>
|
||
|
||
<div class="sub-item">
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../years.html" class="sub-item-link">
|
||
Winning entries
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../authors.html" class="sub-item-link">
|
||
Winning authors
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../location.html" class="sub-item-link">
|
||
Location of authors
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../bugs.html" class="sub-item-link">
|
||
Bugs and (mis)features
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../faq.html#fix_an_entry" class="sub-item-link">
|
||
Fixing entries
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../faq.html#fix_author" class="sub-item-link">
|
||
Updating author info
|
||
</a>
|
||
</div>
|
||
|
||
</div>
|
||
</div>
|
||
|
||
<div class="item">
|
||
<span class="item-header">
|
||
Status
|
||
</span>
|
||
|
||
<div class="sub-item">
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../news.html" class="sub-item-link">
|
||
News
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../status.html" class="sub-item-link">
|
||
Contest status
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../next/rules.html" class="sub-item-link">
|
||
IOCCC rules
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../next/guidelines.html" class="sub-item-link">
|
||
IOCCC guidelines
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../markdown.html" class="sub-item-link">
|
||
Markdown guidelines
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../SECURITY.html" class="sub-item-link">
|
||
Security policy
|
||
</a>
|
||
</div>
|
||
|
||
</div>
|
||
</div>
|
||
|
||
<div class="item">
|
||
<span class="item-header">
|
||
FAQ
|
||
</span>
|
||
|
||
<div class="sub-item">
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../faq.html" class="sub-item-link">
|
||
Frequently asked questions
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../quick-start.html#enter" class="sub-item-link">
|
||
Enter the IOCCC
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../faq.html#compiling" class="sub-item-link">
|
||
Compiling entries
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../faq.html#running_entries" class="sub-item-link">
|
||
Running entries
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../faq.html#help" class="sub-item-link">
|
||
How to help
|
||
</a>
|
||
</div>
|
||
|
||
</div>
|
||
</div>
|
||
|
||
<div class="item">
|
||
<span class="item-header">
|
||
About
|
||
</span>
|
||
|
||
<div class="sub-item">
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../index.html" class="sub-item-link">
|
||
Home page
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../social.html" class="sub-item-link">
|
||
IOCCC social media
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../about.html" class="sub-item-link">
|
||
About the IOCCC
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../judges.html" class="sub-item-link">
|
||
The judges
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../thanks-for-help.html" class="sub-item-link">
|
||
Thanks for the help
|
||
</a>
|
||
</div>
|
||
|
||
<div class="outfit-font">
|
||
<a href="../../contact.html" class="sub-item-link">
|
||
Contact us
|
||
</a>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</nav>
|
||
|
||
<div class="header-mobile-menu">
|
||
<noscript>
|
||
<a href="../../nojs-menu.html" class="topbar-js-label">
|
||
Please Enable JavaScript
|
||
</a>
|
||
</noscript>
|
||
|
||
<button id="header-open-menu-button" class="topbar-mobile-menu">
|
||
<img
|
||
src="../../png/hamburger-icon-open.png"
|
||
alt="hamburger style menu icon - open state"
|
||
width=48
|
||
height=48>
|
||
</button>
|
||
|
||
<button id="header-close-menu-button" class="hide-content">
|
||
<img
|
||
src="../../png/hamburger-icon-closed.png"
|
||
alt="hamburger style menu icon - closed state"
|
||
width=48
|
||
height=48>
|
||
</button>
|
||
|
||
<div id="mobile-menu-panel" class="hide-content">
|
||
<div class="mobile-menu-container">
|
||
|
||
<div class="mobile-menu-wrapper">
|
||
<div class="mobile-menu-item">
|
||
Entries
|
||
</div>
|
||
<div class="mobile-submenu-wrapper">
|
||
|
||
<a class="mobile-submenu-item" href="../../years.html">
|
||
Winning entries
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../authors.html">
|
||
Winning authors
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../location.html">
|
||
Location of authors
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../bugs.html">
|
||
Bugs and (mis)features
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../faq.html#fix_an_entry">
|
||
Fixing entries
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../faq.html#fix_author">
|
||
Updating author info
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../thanks-for-help.html">
|
||
Thanks for the help
|
||
</a>
|
||
|
||
</div>
|
||
</div>
|
||
|
||
<div class="mobile-menu-wrapper">
|
||
|
||
<div class="mobile-menu-item">
|
||
Status
|
||
</div>
|
||
<div class="mobile-submenu-wrapper">
|
||
|
||
<a class="mobile-submenu-item" href="../../news.html">
|
||
News
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../status.html">
|
||
Contest status
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../next/rules.html">
|
||
IOCCC rules
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../next/guidelines.html">
|
||
IOCCC guidelines
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../markdown.html">
|
||
Markdown guidelines
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../SECURITY.html">
|
||
Security policy
|
||
</a>
|
||
|
||
</div>
|
||
</div>
|
||
|
||
<div class="mobile-menu-wrapper">
|
||
<div class="mobile-menu-item">
|
||
FAQ
|
||
</div>
|
||
<div class="mobile-submenu-wrapper">
|
||
|
||
<a class="mobile-submenu-item" href="../../faq.html">
|
||
Frequently asked questions
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../quick-start.html#enter">
|
||
Enter the IOCCC
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../faq.html#compiling">
|
||
Compiling entries
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../faq.html#running_entries">
|
||
Running entries
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../faq.html#help">
|
||
How to help
|
||
</a>
|
||
|
||
</div>
|
||
</div>
|
||
|
||
<div class="mobile-menu-wrapper">
|
||
<div class="mobile-menu-item">
|
||
About
|
||
</div>
|
||
<div class="mobile-submenu-wrapper">
|
||
|
||
<a class="mobile-submenu-item" href="../../index.html">
|
||
Home page
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../social.html">
|
||
IOCCC social media
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../about.html">
|
||
About the IOCCC
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../judges.html">
|
||
The judges
|
||
</a>
|
||
|
||
<a class="mobile-submenu-item" href="../../contact.html">
|
||
Contact us
|
||
</a>
|
||
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
|
||
</div>
|
||
|
||
<script>
|
||
var headerOpenMenuButton = document.getElementById("header-open-menu-button");
|
||
var headerCloseMenuButton = document.getElementById("header-close-menu-button");
|
||
var mobileMenuPanel = document.getElementById("mobile-menu-panel");
|
||
|
||
headerOpenMenuButton.addEventListener("click", () => {
|
||
headerOpenMenuButton.classList.remove("topbar-mobile-menu");
|
||
headerOpenMenuButton.classList.add("hide-content");
|
||
|
||
headerCloseMenuButton.classList.remove("hide-content");
|
||
headerCloseMenuButton.classList.add("topbar-mobile-menu");
|
||
|
||
mobileMenuPanel.classList.remove("hide-content");
|
||
mobileMenuPanel.classList.add("topbar-mobile-panel");
|
||
});
|
||
|
||
headerCloseMenuButton.addEventListener("click", () => {
|
||
headerCloseMenuButton.classList.remove("topbar-mobile-menu");
|
||
headerCloseMenuButton.classList.add("hide-content");
|
||
|
||
mobileMenuPanel.classList.add("hide-content");
|
||
mobileMenuPanel.classList.remove("topbar-mobile-panel");
|
||
|
||
headerOpenMenuButton.classList.add("topbar-mobile-menu");
|
||
headerOpenMenuButton.classList.remove("hide-content");
|
||
});
|
||
</script>
|
||
|
||
<!-- END: this line ends content from: inc/topbar.default.html -->
|
||
<!-- START: this line starts content from: inc/header.default.html -->
|
||
|
||
<div class="header">
|
||
<a href="../../2011/zucker/index.html">
|
||
<img src="../../png/ioccc.png"
|
||
alt="IOCCC image by Matt Zucker"
|
||
width=300
|
||
height=110>
|
||
</a>
|
||
<h1>The International Obfuscated C Code Contest</h1>
|
||
<h2>1992/gson - Most humorous output</h2>
|
||
<h3>anagram generator</h3>
|
||
</div>
|
||
|
||
<!-- END: this line ends content from: inc/header.default.html -->
|
||
<!-- START: this line starts content from: inc/navbar.mid.html -->
|
||
|
||
<div class="navbar">
|
||
<a class="Left" href="../buzzard.2/index.html">← 1992/buzzard.2</a>
|
||
<a class="Left" href="../index.html">↑ 1992 ↑</a>
|
||
<a class="Left" href="../imc/index.html">1992/imc →</a>
|
||
<a class="Right" href="https://github.com/ioccc-src/winner/blob/master/1992/gson/gson.c">C code</a>
|
||
<a class="Right" href="https://github.com/ioccc-src/winner/blob/master/1992/gson/Makefile">Makefile</a>
|
||
<a class="Right" href="#inventory">Inventory</a>
|
||
<a class="Right" href="https://github.com/ioccc-src/winner/blob/master/1992/gson/gson.orig.c">Original C</a>
|
||
<a class="Right" href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fwww.ioccc.org%2F1992%2Fgson%2Findex.html">✓</a>
|
||
</div>
|
||
|
||
<!-- END: this line ends content from: inc/navbar.mid.html -->
|
||
<!-- START: this line starts content from: inc/before-content.default.html -->
|
||
|
||
<div class="content" id="content">
|
||
|
||
<!-- END: this line ends content from: inc/before-content.default.html -->
|
||
<!-- START: this line starts content for HTML phase 20 by: bin/output-index-author.sh via bin/md2html.sh -->
|
||
|
||
<!-- START: this line starts content generated by: bin/output-index-author.sh -->
|
||
|
||
<h2 id="author">Author:</h2>
|
||
<ul>
|
||
<li>Name: <a href="../../authors.html#Andreas_Gustafsson">Andreas Gustafsson</a><br>
|
||
Location: <a href="../../location.html#FI">FI</a> - <em>Republic of Finland </em> (<em>Finland</em>)</li>
|
||
</ul>
|
||
|
||
<!-- END: next line ends content generated by: bin/output-index-author.sh -->
|
||
|
||
<!-- END: this line ends content for HTML phase 20 by: bin/output-index-author.sh via bin/md2html.sh -->
|
||
<!-- START: this line starts content for HTML phase 21 by: bin/pandoc-wrapper.sh via bin/md2html.sh -->
|
||
|
||
<!-- BEFORE: 1st line of markdown file: 1992/gson/README.md -->
|
||
<h2 id="to-build">To build:</h2>
|
||
<pre><code> make all</code></pre>
|
||
<p><strong>NOTE</strong>: we <strong>FORCE DISABLE</strong> the optimiser because having it enabled causes
|
||
some invocations to crash in some systems.</p>
|
||
<h3 id="bugs-and-misfeatures">Bugs and (Mis)features:</h3>
|
||
<p>The current status of this entry is:</p>
|
||
<blockquote>
|
||
<p><strong>STATUS: uses gets() - change to fgets() if possible</strong><br>
|
||
<strong>STATUS: INABIAF - please DO NOT fix</strong></p>
|
||
</blockquote>
|
||
<p>For more detailed information see <a href="../../bugs.html#1992_gson">1992/gson in bugs.html</a>.</p>
|
||
<h2 id="to-use">To use:</h2>
|
||
<pre><code> ./ag word word2 word3 < dictionary | less</code></pre>
|
||
<h2 id="try">Try:</h2>
|
||
<pre><code> ./try.sh</code></pre>
|
||
<p>The script first will use the <a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/mkdict.sh">mkdict.sh</a> script to create
|
||
a dictionary file out of the files
|
||
<a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/README.md">README.md</a>,
|
||
<a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/try.sh">try.sh</a> (itself) and
|
||
<a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/Makefile">Makefile</a> runs the program with a number of
|
||
strings on that dictionary file.</p>
|
||
<p>Then the script will determine (or try and determine) where your system
|
||
dictionary is located and assuming that it can find one it’ll use that. It
|
||
checks the following locations though the last one is more ironic:</p>
|
||
<ul>
|
||
<li><code>/usr/share/dict/words</code></li>
|
||
<li><code>/usr/share/lib/spell/words</code></li>
|
||
<li><code>/usr/ucblib/dict/words</code></li>
|
||
<li><code>/dev/null</code> # <– for machines with nothing to say</li>
|
||
</ul>
|
||
<p>If a file is found then it will run the same process as above. The reason the
|
||
made up dictionary is used first is it provides shorter and a bit more fun
|
||
output.</p>
|
||
<h2 id="judges-remarks">Judges’ remarks:</h2>
|
||
<p>Recently some newspapers printed amusing anagrams of one of the
|
||
names listed above. Run this program to find the anagrams they
|
||
weren’t allowed to print!</p>
|
||
<p>The author provided an obfuscated script that can be used to construct
|
||
dictionaries which has been put in as <a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/mkdict.sh">mkdict.sh</a>. To use try:</p>
|
||
<pre><code> cat README.md | ./mkdict.sh > words</code></pre>
|
||
<p>Then try using the program <a href="#to-use">as shown above</a> with the file <code>words</code>.</p>
|
||
<h2 id="authors-remarks">Author’s remarks:</h2>
|
||
<p>The name of the game:</p>
|
||
<p><code>AG</code> is short for either <code>Anagram Generator</code> or simply <code>AnaGram</code>. It might also be
|
||
construed to mean <code>Alphabet Game</code>, and by pure coincidence it happens to be the
|
||
author’s initials.</p>
|
||
<h3 id="what-it-does">What it does</h3>
|
||
<p><code>AG</code> takes one or more words as arguments, and tries to find anagrams of those
|
||
words, i.e. words or sentences containing exactly the same letters.</p>
|
||
<h3 id="how-to-use-it">How to use it</h3>
|
||
<p>To run <code>AG</code>, you need a dictionary file consisting of distinct words in the
|
||
natural language of your choice, one word on each line. If your machine doesn’t
|
||
have one already, you can make your own dictionary by concatenating a few
|
||
hundred of your favourite Usenet articles and piping them through the following
|
||
obfuscated shell script:</p>
|
||
<pre><code> #!/bin/sh
|
||
z=a-z];tr [A-Z\] \[$z|sed s/[\^$z[\^$z*/_/g|tr _ \\012|grep ..|sort -u</code></pre>
|
||
<p>Using articles from <code>alt.folklore.computers</code> is likely to make
|
||
a more professional-looking dictionary than <code>rec.arts.erotica</code>.</p>
|
||
<p><code>AG</code> must be run with the dictionary file as standard input.</p>
|
||
<p>Because anagrams consisting of just a few words are generally more
|
||
meaningful than those consisting of dozens of very short words, the
|
||
number of words in the anagrams is limited to 3 by default. This
|
||
limit can be changed using a numeric command line option, as in
|
||
<code>./ag -4 international obfuscated c code contest </usr/dict/words</code>.</p>
|
||
<h3 id="bugs-and-limitations">Bugs and limitations</h3>
|
||
<ul>
|
||
<li>There is no error checking.</li>
|
||
<li>Standard input must be seekable, so you can’t pipe the dictionary into <code>AG</code>.</li>
|
||
<li>The input sentence and each line in the dictionary may contain at most 32
|
||
distinct letters, and each letter may occur at most 15 times.</li>
|
||
<li>Words in the dictionary may be at most 255 bytes long.</li>
|
||
<li><code>AG</code> cannot handle characters that sign-extend to negative values.</li>
|
||
<li>Although <code>AG</code> works on both 16-bit and 32-bit machines, the size of the problems
|
||
it can solve is severely limited on machines that limit the stack size to 64k or
|
||
less.</li>
|
||
</ul>
|
||
<h3 id="notice-to-those-who-wish-for-a-greater-challenge">NOTICE to those who wish for a greater challenge:</h3>
|
||
<p><strong>If you want a greater challenge, don’t read any further</strong>:
|
||
just try to understand the program via the source.</p>
|
||
<p>If you get stuck, come back and read below for additional hints and information.</p>
|
||
<h3 id="obfuscatory-notes">Obfuscatory notes</h3>
|
||
<p>As you can see, <code>AG</code> takes advantage of the new ‘92 whitespace rules’ to
|
||
achieve a clear, readable, self-documenting layout. The identifiers
|
||
have been chosen in a way appropriate for an alphabet game, and common
|
||
sources of bugs such as goto statements and malloc/free have been
|
||
eliminated. As <code>AG</code> also refrains from abusing the preprocessor, it
|
||
doesn’t really have much to offer in terms of “surface obfuscation”.
|
||
Instead, it tries to achieve both its speed and its obscurity through a
|
||
careful choice of algorithms. Some of the finer points of those
|
||
algorithms are outlined the section below.</p>
|
||
<h3 id="how-this-entry-works">How this entry works:</h3>
|
||
<p>Here follows a description of some of the data structures and
|
||
algorithms used by <code>AG</code>. It is by no means complete, but it may help
|
||
you get an idea about the general principles.</p>
|
||
<hr style="width:10%;text-align:left;margin-left:0">
|
||
<p>Internally, <code>AG</code> represents words and sentences as arrays of 32
|
||
4-bit integer elements. Each element represents the number of
|
||
times a letter occurs in the word/sentence. There are 32 elements
|
||
because 32 is a convenient power of two larger than the number of
|
||
letters in most western alphabets, and the elements are 4 bits
|
||
each because the same letter is unlikely to occur more than 15
|
||
times in a practical anagram generation problem.</p>
|
||
<p>These <code>32*4</code>-bit arrays are actually stored in memory in a
|
||
“bit-transposed” format, as arrays of four <code>long</code> values. It is
|
||
assumed that a <code>long</code> is at least 32 bits. The first 4-bit letter
|
||
count is formed by the least significant (<code>2^0</code>) bit in each of the
|
||
four <code>long</code>s, the next one is formed by the <code>2^1</code> bits, etc.</p>
|
||
<p>This storage format makes it possible to add or subtract two such
|
||
vectors of 32 4-bit values in parallel by simulating a set of 32
|
||
binary full adders in software using bitwise logical operations.
|
||
E.g., all the LSBs of the result are formed in parallel by taking
|
||
the exclusive OR of the LSBs in each summand, and 32 carry bits
|
||
are formed in parallel in a similar way using a logical AND.
|
||
Thus, 32 independent 4-bit additions can be performed by just four
|
||
iterations of a loop containing some 32-bit bitwise logical
|
||
operations, but no arithmetic operations other than those implied
|
||
by array indexing.</p>
|
||
<p>Subtraction works similarly, and in fact <code>AG</code> only implements
|
||
subtraction directly, handling addition by means of the identity
|
||
<code>a+b = a-(0-b)</code>.</p>
|
||
<p>In addition to this <code>32*4</code>-bit representation, <code>AG</code> also forms a so-called
|
||
“signature” that is the bitwise OR of the four <code>long</code>s, which is
|
||
equivalent to saying that the signature of a word contains a logical 1
|
||
in the bit positions corresponding to letters occurring at least once
|
||
in that word.</p>
|
||
<p>The first thing <code>AG</code> does is to construct a lookup table of 256
|
||
<code>long</code>s, one for each 8-bit character value. The entry for a
|
||
character will be zero if that character doesn’t appear in the
|
||
sentence given on the command line, or it will have a single bit
|
||
set if the character does appear in the sentence. By adding
|
||
together the bit masks for all the letters in the input sentence
|
||
using the transpose addition method described above, <code>AG</code> forms the
|
||
<code>32*4</code> bit array representation of the input sentence.</p>
|
||
<p>The next action performed is reading the dictionary. Those words that
|
||
contain letters not in the input sentence are immediately discarded.
|
||
Words containing the right letters but in excessive numbers are
|
||
eliminated in a separate check involving the <code>32*4</code> bit array.</p>
|
||
<p>The remaining words, which will be referred to as “candidate words”,
|
||
are stored in <code>32*4</code>-bit representation, together with their signatures
|
||
and offsets into the dictionary file so that the plain-text version of
|
||
a word can later be found for printing. This information is kept in a
|
||
local <code>struct</code> in the dictionary-reading function, and memory is
|
||
allocated for each candidate word simply by making another recursive
|
||
call to that function.</p>
|
||
<p>Each <code>struct</code> so allocated is linked into a fixed-size hash table of
|
||
4096 entries indexed by the 12 low bits of the word’s signature.
|
||
When the dictionary-reading function encounters end-of-file, all the
|
||
candidate words have been stored in nested activation records on the
|
||
stack, accessible through the hash table.</p>
|
||
<p>Generating the anagrams is then done by traversing the hash table and
|
||
subtracting the letters of each word in the hash table from the
|
||
“current sentence”, which initially is the sentence given on the
|
||
command line.</p>
|
||
<p>The subtraction is performed in parallel on the 4-bit letter counts
|
||
as described above, and if all 32 results are zero, an anagram has
|
||
been found. If the result is negative for one or more of the letters
|
||
(as indicated by one or more <code>1</code>s in a vector of 32 borrow bits
|
||
returned by the subtraction routine), the word did not match the
|
||
current sentence and is ignored. Finally, if the result contained
|
||
only non-negative letter counts, we have found a partial anagram:
|
||
a word containing some, but not all, of the letters in the current
|
||
sentence. In this case we recursively try to find an anagram of the
|
||
remaining letters. The depth of the recursion is limited to the
|
||
maximum number of words in the anagram, as specified by the user.</p>
|
||
<p>When the deepest recursion level has been reached, an optimization can
|
||
be applied: because no further recursion will be done, there is no
|
||
need to look for partial anagrams, and therefore <code>AG</code> only needs to
|
||
check for words that contain exactly the same letters as the current
|
||
sentence. Those words can be found simply by indexing the hash table
|
||
with the signature of the current sentence.</p>
|
||
<p>Even when not on the deepest recursion level, <code>AG</code> generally avoids
|
||
examining all the entries of the hash table. The idea is that we are
|
||
not interested in hash buckets whose words contain any letters not
|
||
in the current sentence; these buckets are exactly those whose index
|
||
has a logical one in a bit position where the signature of the current
|
||
sentence has a zero. Put another way, we want to loop through only
|
||
those hash bucket indices <code>i</code> that contain zeroes in all the bit
|
||
positions where the signature <code>s</code> of the current sentence contains
|
||
a zero; this can be expressed in C as (<code>i & ~s == 0</code>).</p>
|
||
<p>It is possible to loop through all such numbers in an efficient way by
|
||
taking advantage of certain properties of binary arithmetic: by
|
||
forcing the bits corresponding to zeroes in <code>s</code> to ones, we can make
|
||
the carries generated in incrementing <code>i</code> propagate straight across
|
||
those bits that should remain zero. For example, the following
|
||
program prints all those 16-bit integers that contain zeroes in all
|
||
even bit positions:</p>
|
||
<pre><code> main(){int i=0,s=0xAAAA;do{printf("%04x\t",i);}while(i=((i|~s)+1)&s);}</code></pre>
|
||
<p><code>AG</code> uses a similar method but works in the opposite direction, finding
|
||
the next lower value with zeroes in given bit positions by propagating
|
||
borrows across those bits. Some additional adjustments are made
|
||
to the hash table index when initiating a recursive search, using
|
||
similar bit-twiddling techniques.</p>
|
||
<p>Whenever an anagram has been found, it is printed by traversing a
|
||
linked list formed by <code>struct</code>s in the activation records of the
|
||
recursive invocations of the search function, seeking to the beginning
|
||
of the word matched by that invocation, and copying the characters of
|
||
the word directly from standard input to standard output.</p>
|
||
<!--
|
||
|
||
Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
|
||
|
||
You are free to share and adapt this file under the terms of this 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/
|
||
|
||
-->
|
||
<!-- AFTER: last line of markdown file: 1992/gson/README.md -->
|
||
|
||
<!-- END: this line ends content for HTML phase 21 by: bin/pandoc-wrapper.sh via bin/md2html.sh -->
|
||
<!-- START: this line starts content for HTML phase 22 by: bin/output-index-inventory.sh via bin/md2html.sh -->
|
||
|
||
<!-- START: this line starts content generated by: bin/output-index-inventory.sh -->
|
||
|
||
<div id="inventory">
|
||
<h1 id="inventory-for-1992gson">Inventory for 1992/gson</h1>
|
||
</div>
|
||
<h2 id="primary-files">Primary files</h2>
|
||
<ul>
|
||
<li><a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/gson.c">gson.c</a> - entry source code</li>
|
||
<li><a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/Makefile">Makefile</a> - entry Makefile</li>
|
||
<li><a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/gson.orig.c">gson.orig.c</a> - original source code</li>
|
||
<li><a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/try.sh">try.sh</a> - script to try entry</li>
|
||
<li><a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/mkdict.sh">mkdict.sh</a> - author supplied obfuscated script to make a dictionary</li>
|
||
</ul>
|
||
<h2 id="secondary-files">Secondary files</h2>
|
||
<ul>
|
||
<li><a href="1992_gson.tar.bz2">1992_gson.tar.bz2</a> - download entry tarball</li>
|
||
<li><a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/README.md">README.md</a> - markdown source for this web page</li>
|
||
<li><a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/.entry.json">.entry.json</a> - entry summary and manifest in JSON</li>
|
||
<li><a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/.gitignore">.gitignore</a> - list of files that should not be committed under git</li>
|
||
<li><a href="https://github.com/ioccc-src/winner/blob/master/1992/gson/.path">.path</a> - directory path from top level directory</li>
|
||
<li><a href="index.html">index.html</a> - this web page</li>
|
||
</ul>
|
||
<hr style="width:10%;text-align:left;margin-left:0">
|
||
<h4>
|
||
Jump to: <a href="#">top</a>
|
||
</h4>
|
||
|
||
<!-- END: next line ends content generated by: bin/output-index-inventory.sh -->
|
||
|
||
<!-- END: this line ends content for HTML phase 22 by: bin/output-index-inventory.sh via bin/md2html.sh -->
|
||
<!-- START: this line starts content from: inc/after-content.default.html -->
|
||
|
||
</div>
|
||
|
||
<!-- END: this line ends content from: inc/after-content.default.html -->
|
||
<!-- START: this line starts content from: inc/footer.inventory.html -->
|
||
|
||
<!--
|
||
|
||
Copyright © 1984-2025 by Landon Curt Noll. All Rights Reserved.
|
||
|
||
You are free to share and adapt this file under the terms of this 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/
|
||
|
||
-->
|
||
|
||
<div class="footer">
|
||
|
||
<div id="copyright"><h3>Copyright © 1984-2025 by Landon Curt Noll:
|
||
<a href="https://creativecommons.org/faq/#what-does-some-rights-reserved-mean"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">Some Rights Reserved</a></h3>
|
||
<p>
|
||
This work is <b>licensed by Landon Curt Noll</b> under
|
||
<b><a href="https://creativecommons.org/licenses/by-sa/4.0/?ref=chooser-v1"
|
||
target="_blank"
|
||
rel="license noopener noreferrer"
|
||
style="display:inline-block;">CC BY-SA 4.0</a></b>.
|
||
<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
||
src="../../png/cc.png"
|
||
alt="cc inside circle symbol">
|
||
<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
||
src="../../png/by.png"
|
||
alt="person inside circle symbol">
|
||
<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
||
src="../../png/sa.png"
|
||
alt="arrow looping back on itself inside circle symbol"><br>
|
||
You should <b>carefully review</b> the
|
||
<b><a href="https://creativecommons.org/licenses/by-sa/4.0/legalcode.en"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">CC BY-SA 4.0 LEGAL CODE</a></b>
|
||
before using the licensed material.<br>
|
||
You may wish to review the
|
||
<b><a href="../../license.html"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">highlights of some of the key features and terms</a></b>
|
||
of <b>CC BY-SA 4.0</b>.<br>
|
||
</p>
|
||
</div>
|
||
|
||
<div id="coda"><h3>Coda</h3>
|
||
<p>
|
||
<a href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fwww.ioccc.org%2F1992%2Fgson%2Findex.html" rel="nofollow">Nu HTML check this web page</a><br>
|
||
<a href="#top">Jump to top</a> <a href="#content">Jump to Content</a> <a href="#inventory">Jump to Inventory</a><br>
|
||
</p>
|
||
</div>
|
||
|
||
</div>
|
||
|
||
<!-- END: this line ends content from: inc/footer.inventory.html -->
|
||
<!-- START: this line starts content from: inc/bottom.default.html -->
|
||
|
||
</body>
|
||
</html>
|
||
|
||
<!-- END: this line ends content from: inc/bottom.default.html -->
|