#!/usr/bin/perl

sub usage
{
	print STDERR "usage: $0 [-s] [log_file]\n";
	exit(1);
}


if ($ARGV[0] eq "-s") {
	shift @ARGV;
	$sim = 1;
}
&usage if $ARGV[0] =~ /^-/;

$n = 1;
while (<>) {
	next unless /^=== (\d+) ===/;
	while ($1 != $n) {
		push(@f, $n);
		$n++;
	}
	$n++;
}

$n--;
$t = int($n/@f+0.5);

$last = 0;
for (@f) {
	push(@d, $_-$last);
	$last = $_;
}

if ($sim) {
	# y = 1-exp(-x/T)
	# 1-y = exp(-x/T)
	# ln(1-y) = -x/T
	# -T*ln(1-y) = x

	$type = " (SIMULATED)";
	@d = ();
	for ($i = 0; $i != @f; $i++) {
		push(@d, -$t*log(1-rand));
	}
}

for (@d) {
	$max = $_ if $_ > $max;
}

$cmd = "|gnuplot -e '".
    'set term postscript color eps enhanced solid lw 2 20;'.
    'set output "out.eps";'.
    'set xrange [0:'.$max*1.05.'];'.
    'set yrange [0:'.$max*1.05.'];'.
    'set title "Correlation of time to adjacent corruptions'.$type.'";'.
    'set xlabel "Cycles since previous event";'.
    'set ylabel "Cycles until next event";'.
    'plot "-" with points pt 7 notitle'.
    "'";

open(PIPE, $cmd) || die "open: $!";
undef $last;
for (@d) {
	print PIPE "$last $_\n" if defined $last;
	$last = $_;
}
close(PIPE) || die "close: $!";

system("cat out.eps | ".
    "gs -sDEVICE=ppmraw -r100 -sOutputFile=- ".
    "-dTextAlphaBits=4 -dGraphicsAlphaBits=4 -sPAPERSIZE=a4 -q - | ".
    "convert -trim - out.png");
unlink("out.eps");