SWE/DB/Lock.pm

package SWE::DB::Lock;
use strict;
use warnings;

my $CurrentlyLocking = {};
my $LockTypes = [qw/
  ID Name Index IDs Names Graph Weight Global
/];
  # If you are locking for Graph, then you cannot lock for Global, but
  # still you can lock for ID.

use Fcntl ':flock';

sub new ($) {
  my $self = bless {
    'file_name' => 'lock',
    lock_type => 'Global',
  }, shift;
  return $self;
} # new

sub lock_type ($;$) {
  my $self = shift;
  if (@_) {
    $self->{lock_type} = shift;
  }
  return $self->{lock_type};
} # lock_type

sub check_lockability ($) {
  my $self = shift;
  
  my $self_lt = $self->lock_type;
  for my $lt (@$LockTypes) {
    if ($self_lt eq $lt) {
      last;
    } elsif ($CurrentlyLocking->{$lt}) {
      die qq[$0: It is currently locking for "$lt" so that it cannot be locked for the "$self_lt"];
    }
  }

  return 1;
} # check_lockability
                       
sub lock ($) {
  my $self = shift;

  $self->check_lockability;
  $CurrentlyLocking->{$self->lock_type}++;
warn "@{[$self->lock_type]} $CurrentlyLocking->{$self->lock_type} $self->{file_name}";
  
  open my $file, '>', $self->{file_name} or die "$0: $self->{file_name}: $!";
  flock $file, LOCK_EX;
  $self->{lock} = $file;
} # lock

sub unlock ($) {
  my $self = shift;

  $CurrentlyLocking->{$self->lock_type}--;

  close $self->{lock};
} # unlock

sub DESTROY ($) {
  $_[0]->unlock;
} # DESTROY

1;
1	package SWE::DB::Lock;
2	use strict;
3	use warnings;
4
5	my $CurrentlyLocking = {};
6	my $LockTypes = [qw/
7	ID Name Index IDs Names Graph Weight Global
8	/];
9	# If you are locking for Graph, then you cannot lock for Global, but
10	# still you can lock for ID.
11
12	use Fcntl ':flock';
13
14	sub new ($) {
15	my $self = bless {
16	'file_name' => 'lock',
17	lock_type => 'Global',
18	}, shift;
19	return $self;
20	} # new
21
22	sub lock_type ($;$) {
23	my $self = shift;
24	if (@_) {
25	$self->{lock_type} = shift;
26	}
27	return $self->{lock_type};
28	} # lock_type
29
30	sub check_lockability ($) {
31	my $self = shift;
32
33	my $self_lt = $self->lock_type;
34	for my $lt (@$LockTypes) {
35	if ($self_lt eq $lt) {
36	last;
37	} elsif ($CurrentlyLocking->{$lt}) {
38	die qq[$0: It is currently locking for "$lt" so that it cannot be locked for the "$self_lt"];
39	}
40	}
41
42	return 1;
43	} # check_lockability
44
45	sub lock ($) {
46	my $self = shift;
47
48	$self->check_lockability;
49	$CurrentlyLocking->{$self->lock_type}++;
50	warn "@{[$self->lock_type]} $CurrentlyLocking->{$self->lock_type} $self->{file_name}";
51
52	open my $file, '>', $self->{file_name} or die "$0: $self->{file_name}: $!";
53	flock $file, LOCK_EX;
54	$self->{lock} = $file;
55	} # lock
56
57	sub unlock ($) {
58	my $self = shift;
59
60	$CurrentlyLocking->{$self->lock_type}--;
61
62	close $self->{lock};
63	} # unlock
64
65	sub DESTROY ($) {
66	$_[0]->unlock;
67	} # DESTROY
68
69	1;