Merge remote branch 'grml-scripts/master'

[grml-scripts-core.git] / usr_bin / bincompare.pl

diff --git a/usr_bin/bincompare.pl b/usr_bin/bincompare.pl
new file mode 100755 (executable)
index 0000000..767b8a3
--- /dev/null
+++ b/usr_bin/bincompare.pl
@@ -0,0 +1,68 @@
+#!/usr/bin/perl
+# Filename:      bincompare.pl
+# Purpose:       Binary File Similarity Checking
+# Authors:       (C) Copyright 2004 Diomidis Spinellis
+# Bug-Reports:   see http://grml.org/bugs/
+# License:       See notes by author (Diomidis Spinellis).
+################################################################################
+# See http://www.dmst.aueb.gr/dds/blog/20040319/index.html
+#
+# Original notes:
+# 
+# (C) Copyright 2004 Diomidis Spinellis
+#
+# Permission to use, copy, and distribute this software and its
+# documentation for any purpose and without fee is hereby granted,
+# provided that the above copyright notice appear in all copies and that
+# both that copyright notice and this permission notice appear in
+# supporting documentation.
+#
+# THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
+# WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+# MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+
+# Return the entropy of the file passed as the argument
+sub
+entropy
+{
+        my($file) = @_;
+        my($i, $l);
+
+        # File length
+        $l = `wc -c $file`;
+        # File information (approximation)
+        $i = `bzip2 -c $file | wc -c`;
+        print STDERR "$0: warning file size exceeds bzip2 block size\n" if ($l > 900 * 1024);
+        return ($i / $l);
+}
+
+
+# Return the entropy of the two files passed as arguments
+sub
+entropy2
+{
+        my($file1, $file2) = @_;
+        my($oldrs) = ($/);
+        my($tmp) = ("/tmp/entropy.$$");
+
+        undef($/);
+        open(IN, $file1) || die "read from $file1: $!\n";
+        binmode(IN);
+        open(OUT, ">$tmp") || die "write to $tmp: $!\n";
+        print OUT <IN>;
+        open(IN, $file2) || die "read from $file2: $!\n";
+        binmode(IN);
+        print OUT <IN>;
+        close(IN);
+        close(OUT);
+        my($e) = (entropy($tmp));
+        unlink($tmp);
+        return ($e);
+}
+
+$#ARGV == 1 || die "Usage $0: file1 file2\n";
+
+printf("%.3g - Entropy of $ARGV[0]\n", $e0 = entropy($ARGV[0]));
+printf("%.3g - Entropy of $ARGV[1]\n", $e1 = entropy($ARGV[1]));
+printf("%.3g - Combined predicted entropy\n", ($e0 + $e1) / 2);
+printf("%.3g - Combined actual entropy\n", entropy2($ARGV[0], $ARGV[1]));