sub verify_torrent {
	my($filename, $basepath) = @_;
	
	my $ref   = _slurp($filename);
	my $plen  = $ref->{info}->{'piece length'};
	my $sha   = $ref->{info}->{pieces};
	my $files = [];
	
	if(ref($ref->{info}->{files}) eq 'ARRAY') {
		foreach my $fref (@{$ref->{info}->{files}}) {
			push(@$files, {path=>join("/", @{$fref->{path}}), length=>$fref->{length}});
		}
	}
	else {
		push(@$files, {path=>$ref->{info}->{name}, length=>$ref->{info}->{length}});
	}
	
	
	my $file_index = 0;
	my $this_path  = undef;
	my $cnt_good   = 0;
	my $cnt_bad    = 0;
	my $badfiles   = {};
	
	for(my $i=0; $i<length($sha); $i+=SHASIZE) {
		my $this_sha   = substr($sha,$i,SHASIZE);
		my $this_piece = $i / SHASIZE;
		my $need_bytes = $plen;
		my $pbuffer    = '';
		
		while($need_bytes > 0) {
			my $src_ref = $files->[$file_index] or last; # got all pieces
			if($src_ref->{path} ne $this_path) { # new file -> must update FH
				close(FH);
				$this_path  = $src_ref->{path};
				my $vfs     = join("/",$basepath, $this_path);
				open(FH, "<", join("/",$vfs)) or warn "Could not open: $vfs\n";
			}
			my $buff        = '';
			my $got_bytes   = sysread(FH,$buff,$need_bytes);
			   $pbuffer    .= $buff;
			   $need_bytes -= $got_bytes;
			$file_index++ if $got_bytes < 1;
		}
		
		if( unpack("H*",$this_sha) eq sha1_hex($pbuffer) ) {
			$cnt_good++;
		}
		else {
			$cnt_bad++;
			$badfiles->{$this_path}++;
		}
		
		print "\rpiece=$this_piece, ok=$cnt_good, bad=$cnt_bad" if $this_piece % 4 == 0;
	}
	
	print "\r".(" " x 32 );
	print "\rfound $cnt_bad bad piece(s)\n";
	foreach my $this_bad (keys(%$badfiles)) {
		printf("%-64s : %d bad bytes (%d pieces)\n", $this_bad, $badfiles->{$this_bad}*$plen, $badfiles->{$this_bad});
	}
	
	
}