#! /usr/bin/perl

use strict;
use warnings;

use BerkeleyDB;
use DBI;
use Data::Dumper;
use Digest::SHA1;
use Fcntl;

$| = 1;

my $env = new BerkeleyDB::Env({
										 -Home => $ENV{'HOME'} . "/work/bulk",
										});

my @blocksizes = (qw/16384 8192 4096 1024 512/);
#my @blocksizes = (qw/16384/);

while (my $device = shift) {
  my $device_size = `env POSIXLY_CORRECT=1 df $device | tail -1 | awk '{printf "%d", \$1}'`;
  if ($device_size <= 0) {
	 die "Unable to find device block count through df, make sure you pass /dev/mapper/devicename for logical volumes.\n";
  }

  foreach my $blocksize (sort {$a <=> $b} @blocksizes) {
	 my $device_blocks = ($device_size * 512) / $blocksize;

	 print "Testing \`$device': $blocksize bytes, $device_blocks blocks\n";

	 my $device_sanitized = $device;
	 $device_sanitized =~ s@/@_@g;
	 $device_sanitized =~ s/[^-a-zA-Z0-9_]//g;

	 my $data;
	 my $percent_done = 0;
	 my $blocks = 0;

	 my %hashes;
	 unlink("$device_sanitized.db");
	 my $db = tie %hashes, 'BerkeleyDB::Hash',
		-Filename => "$device_sanitized.db",
		  -Cachesize => 2**26,
			 -Flags    => DB_CREATE;
			 

	 my $time_start = time();
	 sysopen(DEVICE, $device, O_RDONLY) or die;
	 while ((my $bytes_read = sysread(DEVICE, $data, 2**20)) >= $blocksize) {
		# Read 1M at a time
		for (my $i = 0; $i < $bytes_read / $blocksize; $i++) {
		  my $substr = substr($data, $i * $blocksize, $blocksize);
		  #printf("Block %d, i = %d, offset = %d\n",
			#		$blocks, $i, $i * $blocksize);
		  my $digest = Digest::SHA1->sha1($substr);
		  $hashes{$digest}++;
		  $blocks++;
		  my $pdone = int(100 * ($blocks / $device_blocks));
		  if ($pdone != $percent_done) {
			 printf STDERR ("Done: %d%% %d/%d, %d seconds\n",
								$pdone, $blocks, $device_blocks,
								time() - $time_start);
			 $percent_done = $pdone;
			 $time_start = time();
		  }
		}
	 }
	 close(DEVICE);

	 my $blocks_saved = 0.0;
	 while (my ($key, $value) = each(%hashes)) {
		if ($value > 1) {
		  $blocks_saved += $value;
		}
	 }
	 my $saved = $blocks_saved * $blocksize;
	 my $total_size = $blocks * $blocksize;

	 printf("%s: %5d byte blocks, %d blocks\n",
			  $device, $blocksize);
	 printf("\t%d duplicate blocks, %.0f duplicate bytes.\n",
			  $blocks, $blocks_saved, $saved);
	 printf("\t%.2f%% overhead, %.2f%% duplicate.\n",
			  (20.0 / $blocksize) * 100, ($saved / ($total_size + $saved)) * 100);
  }
}