#!/usr/local/bin/perl -w
###############################################################################
# Creates HTML chart of powers of two, intended to be my document
# http://eies.njit.edu/~walsh/powers/
#
# This is a brute-force solution, but it only took an hour to implement
# and it does the job.
#
# 04-Feb-1999 /KJW
#
# COPYRIGHT (c) 1999 Kevin J. Walsh
###############################################################################
require 5.002;
$max_power=2;
$max_power=100;
#$max_power=20;
$headerfile="header.html";
$trailerfile="trailer.html";

###############################################################################
#
###############################################################################
sub knuth
{
	my($iscalled)=$_[0];
	$iscalled=~s#/# / #g;
	$iscalled=~s/ / /g;
	return("<a href=knuth.html>$iscalled</a><br>\n");
}
###############################################################################
# Return string corresponding to arbitrarly long integer with 
# nicely spaced commas of a given base.
###############################################################################
sub nice_dec { return(&nice_notation($_[0], 10, 3, ""  )); }
sub nice_hex { return(&nice_notation($_[0], 16, 4, "x ")); }
sub nice_oct { return(&nice_notation($_[0],  8, 3, "o ")); }
sub nice_notation
{
	my($x, $base, $commas, $prefix) = @_;
	my($digit) = '';
	$_ = '';
	while ( $x > 0 )
	{
		$digit = `echo "$x % $base" | /usr/bin/bc`;
		$digit =~ s/\s+$//;
		$x = `echo "( $x - $digit ) / $base" | /usr/bin/bc`;
		$x =~ s/\s+$//;
		$_ = $hex[$digit] . $_;			# Hex good for decimal or oct!
	}

	1 while s/(\w)(\w{$commas,$commas})(?!\w)/$1, $2/g;	# Perl 5.02 or better 
	return("$prefix$_");
}
###############################################################################
#
###############################################################################
sub newstd
{
	my($iscalled)=$_[0];
	$iscalled=~s#/# / #g;
	$iscalled=~s/ /&nbsp;/g;
	return("<a href=newstd.html>$iscalled</a><br>\n");
}
###############################################################################
# Does babble section.
###############################################################################
sub notes
{
	if ( defined( $note[$POW] ) )
	{
		return("<a name=\"$ttt$POW\">$note[$POW]</a>");
	}
	return("&nbsp");
}

###############################################################################
# Write one table line.
###############################################################################
sub out
{
	#print join(' | ', @_) . "\n";
	print "<tr>
		<td align=center>2<sup>$_[0]</sup></td>
		<td align=left>$_[1]</td>
		<td align=left hspace=10>$_[2]</td>
		<td align=left>$_[3]</td>
		<td align=center>$_[4]</td></tr>\n";
}

###############################################################################
# Don't really wanna show every single value... just interesting ones.
###############################################################################
sub skip
{
	return(1) if $POW < 40;
}

###############################################################################
# Mainline starts
###############################################################################
$start_time = time();
$ttt='two_to_the_';

$bits="<br><font size=-1><i>(Only when counting "
	. "<a href=\"bits.vs.bytes.html\">bits</a>)</i></font>";

$note[0]="Bit$bits";
$note[2]="Nibble$bits";
$note[3]="Byte$bits";
$note[4]=&knuth("Wyde")
	."Halfword$bits";
$note[5]="Word$bits";
$note[6]="Double<br>Double-word$bits";
$note[7]="Quad<br>Quad-word$bits";
$note[10]=&newstd("Kilo-Binary-Byte/Kibibyte/KIb")
	.&knuth("Large Kilobyte/KKB")
	."K<br>Kilobyte<br>K-byte";
$jump{'10'}="K/KB/KIb/KKB";
$note[20]=&newstd("Mega-Binary-Byte/Mebibyte/MIb")
	.&knuth("Large Megabyte/MMB")
	.&knuth("Maybe-byte")
	."MB<br>Megabyte<br>Megs";
$jump{'20'}="M/MB/MIb/MMB";
$note[30]=&newstd("Giga-Binary-Byte/Gibibyte/GIb")
	.&knuth("Large Gigabyte/GGB")
	."GB<br>Gigabyte<br>Gigs<br><i>1,024 MB</i>";
$jump{'30'}="G/GB/GIb/GGB";
$note[40]=&newstd("Tera-Binary-Byte/Tebibyte/TIb")
	.&knuth("Large Terabyte/TTB")
	."TB<br>Terabyte"
	. "<br><i>1,048,576 MB</i>"
	. "<br><i>1,024 GB</i>";
$jump{'40'}="T/TB/TIb/TTB";
$note[50]=&newstd("Peta-Binary-Byte/Pebibyte/PIb")
	.&knuth("Large Petabyte/PPB")
	."PB<br>Petabyte<br><br><i>1,024 TB</i>"
	. "<br><i>1,048,576 GB</i>"
	. "<br><i>1,024 TB</i>";
$jump{'50'}="P/PB/PIb/PPB";
$note[60]=&newstd("Exa-Binary-Byte/Exbibyte/EIb")
	.&knuth("Large Exabyte/EEB")
	."EB<br>Exabyte<br><br><i>1,024 PB</i>"
	. "<br><i>1,048,576 TB</i>"
	. "<br><i>1,024 PB</i>";
$jump{'60'}="E/EB/EIb/EEB";
$note[70]=&newstd("Zetta-Binary-Byte/Zebibyte/ZIb")
	.&knuth("Large Zettabyte/ZZB")
	."<a href=\"more.info.html\">Zettabyte</a>";
$jump{'70'}="Z/ZB/ZIb/ZZB";
$note[80]=&newstd("Yotta-Binary-Byte/Yobibyte/YIb")
	.&knuth("Large Yottabyte/YYB")
	."<a href=\"more.info.html\">Yottabyte</a>";
$jump{'80'}="Y/YB/YIb/YYB";
$note[90]="<font size=+1>Way more than \"a lot\"</font>"
	. "<br><font size=-1>Please <a href=\"mailto:walsh\@njit.edu\">email</a>"
	. " if you know real term</font>";
$note[100]='<font size=+1>A <a href="censored.html">#!%$</a> load more '
	. 'than "a lot"</font>'
	. "<br><font size=-1>Please <a href=\"mailto:walsh\@njit.edu\">email</a>"
	. " if you know real term</font>";

@hex = split(//,'0123456789ABCDEF');

#print "<html><head><title>Powers of Two</title></head>\n";
#print "<body background=mybg.gif>\n";
#print "<h1>Powers of Two</h1>";
#print "<img src=http://counter.njit.edu/Count.cgi?df=kevin.powers|sh=N>\n";
#print "<br><A href=\"more.info.html\">More info</a>\n";
#print "<br><a href=\"thanks.html\">Credits</a><p>\n";
if ( -f $headerfile )
{
	@header = `cat $headerfile`;
	foreach $x ( @header )
	{
		print $x;
	}
}
else
{
	print STDERR "Missing \"$headerfile\"\n";
	exit(1);
}
@jumps=();
foreach $POW ( keys(%jump) )
{
	$_ = $jump{$POW};
	s#/#<br>#g;
	@jumps=(@jumps, "\t\t<td align=center><a href=#$ttt$POW>$_</a></td>\n");
}
$jumpcount = $#jumps+1;
print "<table border rows=5 cellspacing=0 cellpadding=5 \"width=100%\">\n";
print "\t<tr><td colspan=$jumpcount>Jump to</td></tr>\n\t<tr>\n";
foreach $jump ( @jumps ) { print $jump; }
print "\t</tr></table>\n";

print "<table border cellspacing=0 cellpadding=5 \"width=100%\">\n";
print "<tr>
	<th>Power<br>of Two</th>
	<th>Decimal<br>Value</th>
	<th>Hexidecimal<br>Value</th>
	<th>Octal<br>Value</th>
	<th>Technobabble<br>Jargon</th></tr>\n";

$known_power[0] = 1;		# That's 2^0
$known_power[1] = 2;		# That's 2^1
for($POW=0; $POW <= $max_power; $POW++ )
{
	$pPOW=$POW - 1;
	if ( defined( $known_power[$POW] ) )
	{
		$val = $known_power[$POW];
	}
	elsif ( defined( $known_power[$pPOW] ) )
	{
#print STDERR "\$known_power[$pPOW] = {$known_power[$pPOW]}\n";
		$val = $known_power[$POW-1];
		$val = `echo "$val * 2" | /usr/bin/bc`;
	}
	else		# We'll probably never get here.
	{
		$val = `echo "2 ^ $POW" | /usr/bin/bc`;
		print STDERR "Forgot 2^\$POW-1??\n"; exit(1);
	}
	$val =~ s/\s+$//;
	$known_power[$POW] = $val;
#print STDERR "\$known_power[$POW] = {$known_power[$POW]} (NEW)\n";
	if ( $val eq '' ) { print STDERR "Error in bc?\n"; exit(1); }
	&out($POW, &nice_dec($val), &nice_hex($val), &nice_oct($val), &notes());
	if ( $POW == 19 )
	{
		$val=1000000;
		out("19.93...", &nice_dec($val), &nice_hex($val), &nice_oct($val),
			"<a href=\"mungedabyte.html\">Mungedabyte</a>");
	
		$val=1024000;
		out("19.96...", &nice_dec($val), &nice_hex($val), &nice_oct($val),
			"<a href=\"newstd.html\">Moronabyte</a>");
	}
}

$run_time = time() - $start_time;
$run_time = &nice_dec($run_time);

print "</table><p>
	This document was generated in $run_time real-time seconds with
	<a href=\"powers.pl\">powers.pl</a>.\n<br>";

if ( -f $trailerfile )
{
	@trailer = `cat $trailerfile`;
	foreach $x ( @trailer )
	{
		print $x;
	}
}
else
{
	print STDERR "Missing \"$trailerfile\"\n";
	exit(1);
}