SWE/DB/Lock.pm

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

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.
  ##
  ## In addition, if you are locking for an ID, then you can't lock
  ## for another ID.
  ##
  ## XXX Maybe we should get rid of IDs and Name locks because they
  ## conflict with ID and Names locks respectively.  Additionally,
  ## maybe we should remove Global lock as well.

  ## idgen is currently controled by Names lock.

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 ($CurrentlyLocking->{$lt}) {
      die qq[$0: It is currently locking for "$lt" so that it cannot be locked for the "$self_lt"];
    } elsif ($self_lt eq $lt) {
      last;
    }
  }

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

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

warn "XXX @{[$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	wakaba	1.1	package SWE::DB::Lock;
2			use strict;
3	wakaba	1.2
4			my $CurrentlyLocking = {};
5			my $LockTypes = [qw/
6			ID Name Index IDs Names Graph Weight Global
7			/];
8	wakaba	1.4	## If you are locking for Graph, then you cannot lock for Global, but
9			## still you can lock for ID.
10	wakaba	1.5	##
11			## In addition, if you are locking for an ID, then you can't lock
12			## for another ID.
13			##
14			## XXX Maybe we should get rid of IDs and Name locks because they
15			## conflict with ID and Names locks respectively. Additionally,
16			## maybe we should remove Global lock as well.
17	wakaba	1.4
18			## idgen is currently controled by Names lock.
19	wakaba	1.1
20			use Fcntl ':flock';
21
22			sub new ($) {
23			my $self = bless {
24			'file_name' => 'lock',
25	wakaba	1.2	lock_type => 'Global',
26	wakaba	1.1	}, shift;
27			return $self;
28			} # new
29
30	wakaba	1.2	sub lock_type ($;$) {
31			my $self = shift;
32			if (@_) {
33			$self->{lock_type} = shift;
34			}
35			return $self->{lock_type};
36			} # lock_type
37
38			sub check_lockability ($) {
39			my $self = shift;
40
41			my $self_lt = $self->lock_type;
42			for my $lt (@$LockTypes) {
43	wakaba	1.5	if ($CurrentlyLocking->{$lt}) {
44			die qq[$0: It is currently locking for "$lt" so that it cannot be locked for the "$self_lt"];
45			} elsif ($self_lt eq $lt) {
46	wakaba	1.2	last;
47			}
48			}
49
50			return 1;
51			} # check_lockability
52
53	wakaba	1.1	sub lock ($) {
54			my $self = shift;
55	wakaba	1.2
56			$self->check_lockability;
57			$CurrentlyLocking->{$self->lock_type}++;
58	wakaba	1.5
59			warn "XXX @{[$self->lock_type]} $CurrentlyLocking->{$self->lock_type} $self->{file_name}";
60	wakaba	1.1
61			open my $file, '>', $self->{file_name} or die "$0: $self->{file_name}: $!";
62			flock $file, LOCK_EX;
63			$self->{lock} = $file;
64			} # lock
65
66			sub unlock ($) {
67	wakaba	1.2	my $self = shift;
68
69			$CurrentlyLocking->{$self->lock_type}--;
70
71			close $self->{lock};
72	wakaba	1.1	} # unlock
73
74			sub DESTROY ($) {
75			$_[0]->unlock;
76			} # DESTROY
77
78			1;