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|
package NDB::Util::Lock;
use strict;
use Carp;
use Symbol;
use Fcntl qw(:flock);
use Errno;
use File::Basename;
require NDB::Util::File;
use vars qw(@ISA);
@ISA = qw(NDB::Util::File);
# constructors
my $log;
sub initmodule {
$log = NDB::Util::Log->instance;
}
NDB::Util::Lock->attributes(
pid => sub { $_ != 0 },
);
sub new {
my $class = shift;
@_ % 2 == 0 or confess 0+@_;
my(%attr) = @_;
my $lock = $class->SUPER::new(%attr);
return $lock;
}
sub desc {
my $lock = shift;
return $lock->getpath;
}
# test / set
sub test {
my $lock = shift;
@_ == 0 or confess 0+@_;
my $fh = gensym();
if (! open($fh, "+<$lock->{path}")) {
if ($! != Errno::ENOENT) {
$log->put("$lock->{path}: open failed: $!");
return undef;
}
return 0; # file does not exist
}
if (flock($fh, LOCK_EX|LOCK_NB)) {
close($fh);
return 0; # file was not locked
}
if ($^O eq 'MSWin32') {
close($fh);
if (! open($fh, "<$lock->{path}x")) {
$log->put("$lock->{path}x: open failed: $!");
return undef;
}
}
my $pid = <$fh>;
close($fh);
($pid) = split(' ', $pid);
if ($pid+0 == 0) {
$log->put("$lock->{path}: locked but pid='$pid' is zero");
return undef;
}
$lock->{pid} = $pid;
return 1; # file was locked
}
sub set {
my $lock = shift;
@_ == 0 or confess 0+@_;
my $fh = gensym();
if (! open($fh, "+<$lock->{path}")) {
if ($! != Errno::ENOENT) {
$log->put("$lock->{path}: open failed: $!");
return undef;
}
close($fh);
if (! open($fh, ">$lock->{path}")) {
$log->put("$lock->{path}: create failed: $!");
return undef;
}
}
if (! flock($fh, LOCK_EX|LOCK_NB)) {
$log->put("$lock->{path}: flock failed: $!");
close($fh);
return 0; # file was probably locked
}
my $line = "$$\n";
if ($^O eq 'MSWin32') {
my $gh = gensym();
if (! open($gh, ">$lock->{path}x")) {
$log->put("$lock->{path}x: open for write failed: $!");
close($fh);
return undef;
}
if (! syswrite($gh, $line)) {
close($fh);
close($gh);
$log->put("$lock->{path}x: write failed: $!");
return undef;
}
close($gh);
} else {
if (! truncate($fh, 0)) {
close($fh);
$log->put("$lock->{path}: truncate failed: $!");
return undef;
}
if (! syswrite($fh, $line)) {
close($fh);
$log->put("$lock->{path}: write failed: $!");
return undef;
}
}
$lock->{fh} = $fh;
return 1; # file is now locked by us
}
sub close {
my $lock = shift;
@_ == 0 or confess 0+@_;
my $fh = delete $lock->{fh};
if ($fh) {
close($fh);
}
}
1;
# vim:set sw=4:
|
