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|
#!/usr/bin/perl -w
### see titlecompression.txt to understand how this works!
$datasize = 0x1700;
use bytes;
# skip xex header
#read(STDIN, our $junk, 6); # no longer need
read(STDIN, $data, $datasize);
for(split //, $data) {
$got{ord($_)}++;
}
$firstcode = shift || 128; # must be >=128
if($firstcode eq '-l') {
$list_codes = 1;
$firstcode = 128;
$tabsize = shift || 25;
}
for($firstcode..255) {
push @available_codes, $_ unless $got{$_};
}
print scalar keys %got, " unique byte values\n";
print scalar @available_codes . " available run codes >= $firstcode\n";
if($list_codes) {
$lowest = 256;
$best = 0;
# print join("\t", @available_codes) . "\n";
for($i = 0; $i < @available_codes - $tabsize - 1; $i++) {
$used = $available_codes[$i + $tabsize - 1] - $available_codes[$i] + 1;
if($used < $lowest) {
$lowest = $used, $best = $available_codes[$i];
}
print $available_codes[$i] . " " . $used . "\n";
}
print "== optimum firstcode value is $best\n";
exit(0);
}
sub allocate_code {
if(!@available_codes) {
die "out of run codes!\n";
}
return shift @available_codes;
}
# add a $ff to the end, to force the last run to be written
# if the file ends in a run. Remove it afterwards.
$run = 0;
$output = "";
for(split //, $data . chr(0xff)) {
if($_ eq "\0") {
if($run) {
$run++;
if($run == 256) {
die "can't handle runs >= 256, sorry\n";
}
} else {
$run = 1;
}
} else {
if($run > 1) {
if($runlengths{$run}) {
$output .= chr($runlengths{$run});
} else {
my $code = allocate_code();
$runlengths{$run} = $code;
$used_codes{$code} = $run;
$output .= chr($code);
$lastcode = $code;
}
} elsif($run == 1) {
$output .= "\0";
}
$run = 0;
$output .= $_;
}
}
# remove the $ff we added above.
substr($output, -1) = "";
open $out, ">comptitle.dat";
print $out $output;
close $out;
$pct = int(length($output) * 1000 / length($data))/ 10;
print "1st code $firstcode, last $lastcode, table size " . ($lastcode - $firstcode + 1) . "\n";
print length($output) . " bytes compressed data, $pct% ratio\n";
print "used " . keys(%runlengths) . " codes\n";
for($firstcode..$lastcode) {
$table .= " .byte ";
if(exists($used_codes{$_})) {
$table .= '$' . sprintf("%02x", $used_codes{$_}) . " ; " . sprintf("%02x", $_);
} else {
$table .= "\$00 ; SELF";
}
$table .= "\n";
}
open $in, "<comptitle.s.in" or die $!;
open $out, ">comptitle.s" or die $!;
while(<$in>) {
s/__TABLE__/$table/;
s/__FIRSTCODE__/$firstcode/g;
s/__LASTCODE__/$lastcode/g;
print $out $_;
}
close $in;
close $out;
|
