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<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Manual</title>
<style type="text/css">
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</head>
<body>
<div class="title">
<h1>Thufir the Confessor</h1>
</div>
<div class="content">
<h2 id="introduction">Introduction</h2>
<p>Thufir is a barcode reader to receive files through a series of 2D barcodes.
The programs to send files are easy to port and even short enough to be typed
in.</p>
<p>Thufir's intended use is to copy files when access to a computer is limited
to a keyboard and display but accessing files and running programs are
possible. Currently there are senders for HTML5 browsers, Java, and Excel.</p>
<p>The steps to copy a file with Thufir are</p>
<ul>
<li>identify which senders can be run on the computer</li>
<li>type in or copy to the computer a sender</li>
<li>set the sender and receiver parameters</li>
<li>point the phone's camera to the computer's screen</li>
<li>start the sender</li>
<li>hold while the file is being received</li>
<li>the file should be in the folder
<span class="folder"><sdcard>/thufir/</span>.</li>
</ul>
<p>It's easier to try out Thufir first on a computer without restrictions.</p>
</div>
<div class="separator"></div>
<div class="toc">
<h2 id="Contents">Contents</h2>
<p><ul class="toc">
<li><a href="#introduction">Introduction</a></li>
<li><a href="#senders">Senders</a>
<ul>
<li><a href="#senders-settings">Settings</a></li>
<li><a href="#senders-html5">HTML5</a></li>
<li><a href="#senders-java">Java</a></li>
<li><a href="#senders-excel">Excel</a></li>
<li><a href="#senders-others">Others</a></li>
</ul></li>
<li><a href="#phone-settings">Phone settings</a></li>
<li><a href="#diagnostics">Diagnostics</a></li>
<li><a href="#protocol">Protocol</a></li>
<li><a href="#speed-up">Speed up</a></li>
<li><a href="#examples">Examples</a>
<ul>
<li><a href="#examples-correct">Correctly typed in program</a></li>
<li><a href="#examples-typo">Program with 2 typos checked by a correct
program</a></li>
<li><a href="#examples-incorrect">Program with 2 typos checked by
itself</a></li>
</ul></li>
<li><a href="#license">License</a>
</ul>
</div>
<div class="separator"></div>
<div class="content">
<h2 id="senders">Senders</h2>
<p>While all the senders are equally capable and the HTML5 one is the easiest
to use, the most important factor is which one can be run on the computer.</p>
<p>After the sender has been chosen it must be typed in or copied to the
computer. The sender can be typed in directly but it's error prone, so in the
vein of type-in programs of old computer magazines a shorter program is
provided to check the correctness of other programs. With this the CRC32 hash
of every line of the typed-in program is computed and can be compared to the
provided correct values. As the hashes are chained from the first line to the
last, matching hashes indicate likely correctness of the line of the hash and
all previous lines.
<a class="example" href="#examples-correct">example</a></p>
<p>With this chaining</p>
<ul>
<li>if the last hash of the typed in program matches the correct one,
the program is likely correct.</li>
<li>if there's at least one typo, all the hashes before the first typo
match, and the hashes of the first typo and all subsequent lines
likely mismatch.
<a class="example" href="#examples-typo">example</a></li>
<li>missing lines don't affect the hashes of preceding lines,
so partial programs can be checked after every line typed in.</li>
</ul>
<p>While the crc program can be checked by itself and all matching hashes mean
likely correctness, a crc program with errors in it may produce no or any
output, so incrementality likely doesn't hold on the crc program itself.
<a class="example" href="#examples-incorrect">example</a></p>
<h3 id="senders-settings">Settings</h3>
<p>The senders all have common parameters but usually only the
<span class="parameter">from</span> and the
<span class="parameter">file</span> can be set easily at every execution,
the rest must be set in the source code, and must be recompiled if that's
applicable. As the programs are easily made incorrect by small mistakes,
it's advised to make backup copies of known correct programs before
modifying them.</p>
<ul>
<li><span class="parameter">from</span>:
file offset to start the transmission from. Thufir can continue
the reception of interrupted transmissions and this specifies how much
has been already received. For new files specify 0, for partially
received files use the value shown on the progress bar.</li>
<li><span class="parameter">file</span>: file to send.</li>
<li><span class="parameter">br</span> and
<span class="parameter">da</span>: bright and dark colors of the
barcodes. Some displays and cameras may have better response to an
inverted color scheme, or more specific colors.</li>
<li><span class="parameter">tw</span> and
<span class="parameter">th</span>: width and height of the individual
outer tracking cells. Larger tracking cells are easier to find on an
image and provide more precision.</li>
<li><span class="parameter">cw</span> and
<span class="parameter">ch</span>: width and height of the individual
inner data cells.</li>
<li><span class="parameter">dw</span> and
<span class="parameter">dh</span>: width and height of all the data
cells, expressed as 16x16 data blocks.</li>
<li><span class="parameter">de</span>:
delay in ms between barcodes shown.</li>
<li><span class="parameter">id</span>:
delay in ms to wait after the sender started to show the first
barcode, to allow time to move the phone into position.</li>
<li><span class="parameter">xx</span> and
<span class="parameter">yy</span>: java only parameters to control the
position of the barcodes on the screen.</li>
</ul>
<p>Every barcode contains <span class="formula">28*dw*dh-1</span> bytes of
data, so the speed of the transmission is
<span class="formula">1000*(28*dw*dh-1)/de</span> bytes per second.</p>
<h3 id="senders-html5">HTML5</h3>
<p>These are most likely the easiest senders to use as they only require a
text editor and a compatible browser, which are commonly available.</p>
<p>There are the <a href="html5/crc.html">crc.html</a> and 2 senders
</p>
<ul>
<li><a href="html5/canvas.html">canvas.html</a> exposes only
parameters <span class="parameter">file</span> and
<span class="parameter">from</span> on the user interface</li>
<li><a href="html5/canvas-ui.html">canvas-ui.html</a> has all
the parameters on the interface for easy experimentation.</li>
</ul>
<h3 id="senders-java">Java</h3>
<p>To run the java sender a java compiler and runtime environment must be
available. Supported versions are standard edition 1.2 and up. To check their
versions run <span class="command">java -version</span>
and <span class="command">javac -version</span>.</p>
<p>There are the <a href="java/Crc.java">Crc</a> and 3 senders</p>
<ul>
<li><a href="java/AnsiStdOut.java">AnsiStdOut</a>: for
character terminals with ANSI escape code support</li>
<li><a href="java/Awt.java">Awt</a>: for graphical
terminals</li>
<li><a href="java/StdOut.java">StdOut</a>: for character
terminals without ANSI escape code support</li>
</ul>
<p>To compile one of the programs run
<span class="command">javac [file.java]</span>.</p>
<p>To check crc on a file run
<span class="command">java Crc [file.java]</span>.</p>
<p>To send a file run
<span class="command">java [AnsiStdOut|Awt|StdOut] [from] [file]</span>.</p>
<h3 id="senders-excel">Excel</h3>
<p>The <a href="excel/Excel.bas">Excel</a> sender is the cruftiest of
them. To run this an Excel with macros enabled is needed. There's only one
source file in this sender and it contains the crc as well. If all the lines
before the comment <span class="source">Rem sender</span> has been typed
in, running the <span class="source">sub crc</span> will copy the hashes of
all the lines from Module1 to the first sheet.</p>
<p>After all the lines are typed in</p>
<ul>
<li>go to the second sheet</li>
<li>use the cell A1 as the parameter
<span class="parameter">from</span></li>
<li>use A2 to hold the path to the
<span class="parameter">file</span></li>
<li>create two buttons in the first line</li>
<li>assign one button to the sub sf to select files</li>
<li>assign the other button to the sub st to start sending</li>
<li>press a lot of escapes to stop it before it runs down</li>
</ul>
<h3 id="senders-others">Others</h3>
<p>Other sources can be shown on Thufir's internal crc checker. Files put into
the folder <span class="folder"><sdcard>/thufir/sources/</span> show up
in the type-in menu.</p>
</div>
<div class="separator"></div>
<div class="content">
<h2 id="phone-settings">Phone settings</h2>
<p>The settings on the receiving side are grouped into two. Camera settings
are provided by the phone, and they vary. Program settings affect how images
are taken and processed, and the look of the program.</p>
<p>Settings in red are available, but not recommended.</p>
<p>The more important camera settings are</p>
<ul>
<li><span class="parameter">Camera</span>:
camera to use, mainly back and front</li>
<li><span class="parameter">Picture size</span>:
resolution of pictures taken</li>
<li><span class="parameter">Preview FPS</span>:
frame rate of the preview</li>
<li><span class="parameter">Preview size</span>:
resolution of the preview.</li>
</ul>
<p>Program settings are</p>
<ul>
<li><span class="parameter">Blob size</span>:
method to measure blobs.
<span class="parameter">area</span> is more precise,
<span class="parameter">perimeter</span> is faster</li>
<li><span class="parameter">Brightness scheme</span>:
barcode colors to look for:
<span class="parameter">bright on dark</span> looks for bright
barcodes on a dark background,
<span class="parameter">dark on bright</span> for dark barcodes on a
bright background,
<span class="parameter">auto</span> for both, which is slower</li>
<li><span class="parameter">Buttons' position</span>:
corner to put buttons in</li>
<li><span class="parameter">Diagnostics</span>:
turns on-screen diagnostics on and off</li>
<li><span class="parameter">Distortion correction</span>:
Larger barcodes with small data cells may be read more reliably
with distortion correction, but it can be quite slow, so it may
not help with overall transmission rate.
<span class="parameter">no</span> only corrects perspective.
<span class="parameter">some</span> tries to correct some lens
distortion.
<span class="parameter">some-s</span> is single threaded,
while <span class="parameter">some-ml</span>,
<span class="parameter">some-mm</span>, and
<span class="parameter">some-mlm</span> are multithreaded with
increasing parallelisation.</li>
<li><span class="parameter">Filter</span>:
whole-image filter to apply before any image processing. These may
help on character terminals. Max filters replace every pixel with the
brightest pixel in its neighborhood, to be used with bright on dark
barcodes. Similarly min filters choose the darkest pixels, and are
intended for dark on bright barcodes. The dimensions specify the size
of the neighborhood</li>
<li><span class="parameter">Image source</span>:
<span class="parameter">picture</span> takes pictures, which has
better quality, <span class="parameter">preview</span> uses the
viewfinder preview, which has a higher frame rate</li>
<li><span class="parameter">Parallelism</span>: number of threads to
process the images</li>
<li><span class="parameter">Threshold</span>: brightness to use in
partitioning the image. Brightness values less than threshold are
classified as dark, all else as bright</li>
<li><span class="parameter">Threshold mode</span>:
<span class="parameter">manual</span> mode partitions the images by
value of the setting <span class="parameter">threshold</span>, which
is faster, and <span class="parameter">auto</span> mode ignores the
setting <span class="parameter">threshold</span>, and a threshold
is calculated for every image based on its brightness histogram.</li>
</ul>
</div>
<div class="separator"></div>
<div class="content">
<h2 id="diagnostics">Diagnostics</h2>
<p>The on-screen diagnostics show some raw measurements to help find the
correct settings.</p>
<p>Running the diagnostics have a similar effect to receiving files, the
screen is forced on, and pictures are taken, and processed.</p>
<p>Some measurements are performed below and around the cross-hair on the
image overlay, and with diagnostics turned on, the cross-hair is movable by
touch.</p>
<p>The measurements are:</p>
<ul>
<li><span class="parameter">min. frame</span>,
<span class="parameter">avg. frame</span>,
<span class="parameter">max. frame</span>:
aggregates of times between two pictures taken by the camera</li>
<li><span class="parameter">dropped frames</span>:
ratio of images dropped per images take</li>
<li><span class="parameter">min. proc.</span>,
<span class="parameter">avg. proc.</span>,
<span class="parameter">max. proc.</span>:
aggregates of image processing times</li>
<li><span class="parameter">threshold</span>:
running average of the thresholds used in the partitioning</li>
<li><span class="parameter">brightness</span>:
brightness of the pixel under the cross-hair, and its
classification</li>
<li><span class="parameter">contrast</span>:
contrast around the cross-hair.</li>
</ul>
</div>
<div class="separator"></div>
<div class="content">
<h2 id="protocol">Protocol</h2>
<p>Thufir transmits a single file through a series of barcodes. Every barcode
contains data and CRC32 hashes. The data is concatenated to form the file,
while the hashes are used to check its integrity. The hashes are chained to
order the barcodes.</p>
<p>The data stream is the concatenation of</p>
<ul>
<li>the length of the name of the file as 1 byte</li>
<li>every ASCII code of the file name as a byte</li>
<li>the size of the file as 4 bytes</li>
<li>the content of the file</li>
<li>padding to make the length of the stream divisible by the data
size a the barcodes.</li>
</ul>
<p>Every barcode have two parts, the outer tracking, and the inner data
cells. The tracking cells identify the barcode in the image, determine the
amount of data it contains, and locate the data cells. Data cells are further
differentiated into 3 types:</p>
<ul>
<li>clock cells at the corners and the middle of the sides ensure
different consecutive barcodes</li>
<li>hash cells for integrity</li>
<li>actual data cells of the stream.</li>
</ul>
<p>The parameters <span class="parameter">dw</span> and
<span class="parameter">dh</span> specify how wide and tall barcodes should
be, set in 16x16 blocks of data cells. For every 28 bytes of clock and data
there are 4 bytes of crc, which added together is a complete data block.
And there are 8 clock cells in a barcode. So a barcode contains
<span class="formula">28*dw*dh-1</span> bytes of data.</p>
<h3>Anatomy of a barcode</h3>
<div style="position: relative; width: 50%">
<div style="padding-bottom: 66.66666667%">
<div style="background: white; bottom: 0; left: 0; position: absolute; right: 0; top: 0">
<div style="background: black; bottom: 90%; left: 3.33333333%; position: absolute; right: 93.33333333%; top: 5%"></div>
<div style="background: black; bottom: 90%; left: 10%; position: absolute; right: 86.66666667%; top: 5%"></div>
<div style="background: black; bottom: 80%; left: 3.33333333%; position: absolute; right: 93.33333333%; top: 15%"></div>
<div style="background: black; bottom: 90%; left: 86.66666667%; position: absolute; right: 10%; top: 5%"></div>
<div style="background: black; bottom: 90%; left: 93.33333333%; position: absolute; right: 3.33333333%; top: 5%"></div>
<div style="background: black; bottom: 5%; left: 3.33333333%; position: absolute; right: 93.33333333%; top: 90%"></div>
<div style="background: black; bottom: 5%; left: 93.33333333%; position: absolute; right: 3.33333333%; top: 90%"></div>
<div style="background: silver; bottom: 90%; left: 16.66666667%; position: absolute; right: 80%; top: 5%"></div>
<div style="background: silver; bottom: 90%; left: 23.33333333%; position: absolute; right: 73.33333333%; top: 5%"></div>
<div style="background: silver; bottom: 70%; left: 3.33333333%; position: absolute; right: 93.33333333%; top: 25%"></div>
<div style="background: blue; bottom: 5%; left: 10%; position: absolute; right: 10%; top: 15%"></div>
<div style="background: red; bottom: 82.5%; left: 10%; position: absolute; right: 88.33333333%; top: 15%"></div>
<div style="background: red; bottom: 82.5%; left: 50%; position: absolute; right: 48.33333333%; top: 15%"></div>
<div style="background: red; bottom: 82.5%; left: 88.33333333%; position: absolute; right: 10%; top: 15%"></div>
<div style="background: red; bottom: 42.5%; left: 10%; position: absolute; right: 88.33333333%; top: 55%"></div>
<div style="background: red; bottom: 42.5%; left: 88.33333333%; position: absolute; right: 10%; top: 55%"></div>
<div style="background: red; bottom: 5%; left: 10%; position: absolute; right: 88.33333333%; top: 92.5%"></div>
<div style="background: red; bottom: 5%; left: 50%; position: absolute; right: 48.33333333%; top: 92.5%"></div>
<div style="background: red; bottom: 5%; left: 88.33333333%; position: absolute; right: 10%; top: 92.5%"></div>
<div style="background: lime; bottom: 72.5%; left: 55%; position: absolute; right: 10%; top: 25%"></div>
<div style="background: lime; bottom: 70%; left: 10%; position: absolute; right: 71.66666667%; top: 27.5%"></div>
<div style="background: lime; bottom: 60%; left: 81.66666667%; position: absolute; right: 10%; top: 37.5%"></div>
<div style="background: lime; bottom: 57.5%; left: 10%; position: absolute; right: 45%; top: 40%"></div>
<div style="background: lime; bottom: 45%; left: 28.33333333%; position: absolute; right: 18.33333333%; top: 52.5%"></div>
<div style="background: lime; bottom: 32.5%; left: 58.33333333%; position: absolute; right: 10%; top: 65%"></div>
<div style="background: lime; bottom: 30%; left: 10%; position: absolute; right: 68.33333333%; top: 67.5%"></div>
<div style="background: lime; bottom: 20%; left: 85%; position: absolute; right: 10%; top: 77.5%"></div>
<div style="background: lime; bottom: 17.5%; left: 10%; position: absolute; right: 41.66666667%; top: 80%"></div>
<div style="background: lime; bottom: 5%; left: 33.33333333%; position: absolute; right: 50%; top: 92.5%"></div>
<div style="background: lime; bottom: 5%; left: 51.66666667%; position: absolute; right: 11.66666667%; top: 92.5%"></div>
</div>
</div>
</div>
<div class="legend"><ul>
<li>black: tracking</li>
<li>silver: width and height</li>
<li>blue: data</li>
<li>red: clock</li>
<li>lime: hash</li>
</ul></div>
</div>
<div class="separator"></div>
<div class="content">
<h2 id="speed-up">Speed up</h2>
<p>With some fiddling Thufir can reach not completely useless speeds.</p>
<ul>
<li>High brightness and contrast of the display separate black and
white more and may also make transitions faster.</li>
<li>Manual threshold mode and brightness scheme process images
faster.</li>
<li>Higher parallelism can speed up image processing, but too high
values may even slow it down.</li>
<li>The delay between barcodes should be at least twice as much as the
times between captured frames, sometimes much higher, especially in
preview mode.</li>
<li>Larger tracking cells provide more precision.</li>
<li>Distortions can be decreased by centering and aligning the barcode
in the image.</li>
<li>Holding the camera too close to the display increases the
distortions.</li>
<li>Anything longer than tiny files require some contraption to hold
the phone in place.</li>
</ul>
</div>
<div class="separator"></div>
<div class="content">
<h2 id="examples">Examples</h2>
<h3 id="examples-correct">Correctly typed in program</h3>
<table>
<thead>
<tr><th>CRC32</th><th>Line</th><th></th></tr>
</thead>
<tbody>
<tr><td>a8c83ed3</td><td class="line-number">1</td><td class="source">import java.io.*;</td></tr>
<tr><td>dddb3930</td><td class="line-number">2</td><td class="source">public class Crc {</td></tr>
<tr><td>9751e7ad</td><td class="line-number">3</td><td class="source">static int[] t=new int[256];</td></tr>
<tr><td>740694de</td><td class="line-number">4</td><td class="source">static int c(int c, byte[] b) {</td></tr>
<tr><td>0124674f</td><td class="line-number">5</td><td class="source"> c=~c;</td></tr>
<tr><td>c3df6896</td><td class="line-number">6</td><td class="source"> for (int i=0; b.length>i; ++i)</td></tr>
<tr><td>08f11529</td><td class="line-number">7</td><td class="source"> c​=t[(c^b[i])​&0xff]​^((c>>8)​&0xffffff);</td></tr>
<tr><td>48188b89</td><td class="line-number">8</td><td class="source"> return ~c;</td></tr>
<tr><td>abb6cde8</td><td class="line-number">9</td><td class="source">}</td></tr>
<tr><td>ce6e9f77</td><td class="line-number">10</td><td class="source">static String h(int c) {</td></tr>
<tr><td>264eccfe</td><td class="line-number">11</td><td class="source"> String s​=Integer​.toHexString(c);</td></tr>
<tr><td>b1e67caf</td><td class="line-number">12</td><td class="source"> while (8>s.length()) s='0'+s;</td></tr>
<tr><td>56fb8a46</td><td class="line-number">13</td><td class="source"> return s;</td></tr>
<tr><td>90d3281c</td><td class="line-number">14</td><td class="source">}</td></tr>
<tr><td>9aaf0931</td><td class="line-number">15</td><td class="source">public static void main(String[] a) throws Throwable {</td></tr>
<tr><td>7567ecd8</td><td class="line-number">16</td><td class="source"> for (int n=0; 256>n; ++n) {</td></tr>
<tr><td>e080902d</td><td class="line-number">17</td><td class="source"> int c=n;</td></tr>
<tr><td>0c9667f6</td><td class="line-number">18</td><td class="source"> for (int k=0; 8>k; ++k)</td></tr>
<tr><td>5c782d22</td><td class="line-number">19</td><td class="source"> c​=(0!=(c&1)​?0xedb88320:0)​^((c>>1)​&0x7fffffff);</td></tr>
<tr><td>058b5b2c</td><td class="line-number">20</td><td class="source"> t[n]=c;</td></tr>
<tr><td>fe151a03</td><td class="line-number">21</td><td class="source"> }</td></tr>
<tr><td>8167e01d</td><td class="line-number">22</td><td class="source"> BufferedReader r=new BufferedReader(new FileReader(a[0]));</td></tr>
<tr><td>4050ec3f</td><td class="line-number">23</td><td class="source"> int c=0, ln=1;</td></tr>
<tr><td>028c6158</td><td class="line-number">24</td><td class="source"> for (String l; null!=(l=r.readLine()); ++ln) {</td></tr>
<tr><td>f42a8be3</td><td class="line-number">25</td><td class="source"> c=c(c, (l.trim()+'\n')​.getBytes());</td></tr>
<tr><td>00ff8af9</td><td class="line-number">26</td><td class="source"> System.out.println(​h(c)+'|'+ln+'|'+l);</td></tr>
<tr><td>f38ecc6f</td><td class="line-number">27</td><td class="source"> }</td></tr>
<tr><td>4b2af627</td><td class="line-number">28</td><td class="source">}</td></tr>
<tr><td>b586523c</td><td class="line-number">29</td><td class="source">}</td></tr>
</tbody>
</table>
<h3 id="examples-typo">Program with 2 typos checked by a correct program</h3>
<table>
<thead>
<tr><th>CRC32</th><th>Line</th><th></th></tr>
</thead>
<tbody>
<tr><td>a8c83ed3</td><td class="line-number">1</td><td class="source">import java.io.*;</td></tr>
<tr><td>dddb3930</td><td class="line-number">2</td><td class="source">public class Crc {</td></tr>
<tr><td>9751e7ad</td><td class="line-number">3</td><td class="source">static int[] t=new int[256];</td></tr>
<tr><td>740694de</td><td class="line-number">4</td><td class="source">static int c(int c, byte[] b) {</td></tr>
<tr><td>0124674f</td><td class="line-number">5</td><td class="source"> c=~c;</td></tr>
<tr><td>c3df6896</td><td class="line-number">6</td><td class="source"> for (int i=0; b.length>i; ++i)</td></tr>
<tr><td>08f11529</td><td class="line-number">7</td><td class="source"> c​=t[(c^b[i])​&0xff]​^((c>>8)​&0xffffff);</td></tr>
<tr><td>48188b89</td><td class="line-number">8</td><td class="source"> return ~c;</td></tr>
<tr><td>abb6cde8</td><td class="line-number">9</td><td class="source">}</td></tr>
<tr><td>ce6e9f77</td><td class="line-number">10</td><td class="source">static String h(int c) {</td></tr>
<tr><td>264eccfe</td><td class="line-number">11</td><td class="source"> String s​=Integer​.toHexString(c);</td></tr>
<tr><td>b1e67caf</td><td class="line-number">12</td><td class="source"> while (8>s.length()) s='0'+s;</td></tr>
<tr><td>56fb8a46</td><td class="line-number">13</td><td class="source"> return s;</td></tr>
<tr><td>90d3281c</td><td class="line-number">14</td><td class="source">}</td></tr>
<tr><td>9aaf0931</td><td class="line-number">15</td><td class="source">public static void main(String[] a) throws Throwable {</td></tr>
<tr><td>7567ecd8</td><td class="line-number">16</td><td class="source"> for (int n=0; 256>n; ++n) {</td></tr>
<tr><td>e080902d</td><td class="line-number">17</td><td class="source"> int c=n;</td></tr>
<tr><td>0c9667f6</td><td class="line-number">18</td><td class="source"> for (int k=0; 8>k; ++k)</td></tr>
<tr><td class="error">57ac83ec</td><td class="line-number">19</td><td class="source"> c​=(0!=(c&1)​?0xedb8<span class="error">3</span>320:0)​^((c>>1)​&0x7fffffff);</td></tr>
<tr><td class="error">834cc932</td><td class="line-number">20</td><td class="source"> t[n]=c;</td></tr>
<tr><td class="error">34555173</td><td class="line-number">21</td><td class="source"> }</td></tr>
<tr><td class="error">dee7f9de</td><td class="line-number">22</td><td class="source"> BufferedReader r=new BufferedReader(new FileReader(a[0]));</td></tr>
<tr><td class="error">48e88cde</td><td class="line-number">23</td><td class="source"> int c=<span class="error">8</span>, ln=1;</td></tr>
<tr><td class="error">67cc7385</td><td class="line-number">24</td><td class="source"> for (String l; null!=(l=r.readLine()); ++ln) {</td></tr>
<tr><td class="error">55bd81c3</td><td class="line-number">25</td><td class="source"> c=c(c, (l.trim()+'\n')​.getBytes());</td></tr>
<tr><td class="error">0ad11246</td><td class="line-number">26</td><td class="source"> System.out.println(​h(c)+'|'+ln+'|'+l);</td></tr>
<tr><td class="error">6e076f40</td><td class="line-number">27</td><td class="source"> }</td></tr>
<tr><td class="error">16e9a191</td><td class="line-number">28</td><td class="source">}</td></tr>
<tr><td class="error">f216c296</td><td class="line-number">29</td><td class="source">}</td></tr>
</tbody>
</table>
<h3 id="examples-incorrect">Program with 2 typos checked by itself</h3>
<table>
<thead>
<tr><th>CRC32</th><th>Line</th><th></th></tr>
</thead>
<tbody>
<tr><td class="error">1e71963d</td><td class="line-number">1</td><td class="source">import java.io.*;</td></tr>
<tr><td class="error">30b00b37</td><td class="line-number">2</td><td class="source">public class Crc {</td></tr>
<tr><td class="error">4303654c</td><td class="line-number">3</td><td class="source">static int[] t=new int[256];</td></tr>
<tr><td class="error">8ef4bc58</td><td class="line-number">4</td><td class="source">static int c(int c, byte[] b) {</td></tr>
<tr><td class="error">6ee7a927</td><td class="line-number">5</td><td class="source"> c=~c;</td></tr>
<tr><td class="error">e8d6e6b5</td><td class="line-number">6</td><td class="source"> for (int i=0; b.length>i; ++i)</td></tr>
<tr><td class="error">58067491</td><td class="line-number">7</td><td class="source"> c​=t[(c^b[i])​&0xff]​^((c>>8)​&0xffffff);</td></tr>
<tr><td class="error">4f0b41b2</td><td class="line-number">8</td><td class="source"> return ~c;</td></tr>
<tr><td class="error">ecb51357</td><td class="line-number">9</td><td class="source">}</td></tr>
<tr><td class="error">acc6c613</td><td class="line-number">10</td><td class="source">static String h(int c) {</td></tr>
<tr><td class="error">cd94a962</td><td class="line-number">11</td><td class="source"> String s​=Integer​.toHexString(c);</td></tr>
<tr><td class="error">4ece8b08</td><td class="line-number">12</td><td class="source"> while (8>s.length()) s='0'+s;</td></tr>
<tr><td class="error">01aaf4d5</td><td class="line-number">13</td><td class="source"> return s;</td></tr>
<tr><td class="error">466c0f87</td><td class="line-number">14</td><td class="source">}</td></tr>
<tr><td class="error">8dc43e22</td><td class="line-number">15</td><td class="source">public static void main(String[] a) throws Throwable {</td></tr>
<tr><td class="error">8bdc1685</td><td class="line-number">16</td><td class="source"> for (int n=0; 256>n; ++n) {</td></tr>
<tr><td class="error">04762cea</td><td class="line-number">17</td><td class="source"> int c=n;</td></tr>
<tr><td class="error">d395c5d9</td><td class="line-number">18</td><td class="source"> for (int k=0; 8>k; ++k)</td></tr>
<tr><td class="error">99aac77b</td><td class="line-number">19</td><td class="source"> c​=(0!=(c&1)​?0xedb8<span class="error">3</span>320:0)​^((c>>1)​&0x7fffffff);</td></tr>
<tr><td class="error">e0c5fb4b</td><td class="line-number">20</td><td class="source"> t[n]=c;</td></tr>
<tr><td class="error">4fcd1be7</td><td class="line-number">21</td><td class="source"> }</td></tr>
<tr><td class="error">433055b6</td><td class="line-number">22</td><td class="source"> BufferedReader r=new BufferedReader(new FileReader(a[0]));</td></tr>
<tr><td class="error">4ec127a2</td><td class="line-number">23</td><td class="source"> int c=<span class="error">8</span>, ln=1;</td></tr>
<tr><td class="error">6c8ab352</td><td class="line-number">24</td><td class="source"> for (String l; null!=(l=r.readLine()); ++ln) {</td></tr>
<tr><td class="error">abce9318</td><td class="line-number">25</td><td class="source"> c=c(c, (l.trim()+'\n')​.getBytes());</td></tr>
<tr><td class="error">3f8279e3</td><td class="line-number">26</td><td class="source"> System.out.println(​h(c)+'|'+ln+'|'+l);</td></tr>
<tr><td class="error">2aa555da</td><td class="line-number">27</td><td class="source"> }</td></tr>
<tr><td class="error">5b4b9d14</td><td class="line-number">28</td><td class="source">}</td></tr>
<tr><td class="error">ed51c25c</td><td class="line-number">29</td><td class="source">}</td></tr>
</tbody>
</table>
</div>
<p></p>
<div class="separator"></div>
<div class="content">
<h2 id="license">License</h2>
<p>Thufir the Confessor is licensed under the GPLv3. Source code can be
acquired <a href="source.tar.gz">here</a>.</p>
<br>
<br>
<pre style="white-space: pre-wrap">
GNU GENERAL PUBLIC LICENSE
Version 3, 29 June 2007
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