Current File : //usr/share/perl5/vendor_perl/Munin/Common/SyncDictFile.pm
package Munin::Common::SyncDictFile;
require Tie::Hash;
our @ISA = qw(Tie::Hash);
our $DEBUG_ENABLED;
use IO::File;
# The method invoked by the command tie %hash, classname.
# Associates a new hash instance with the specified class.
# LIST would represent additional arguments (along the lines
# of AnyDBM_File and compatriots) needed to complete the association.
sub TIEHASH {
my $classname = shift;
my ($filename) = @_;
my $self = {
filename => $filename,
};
new IO::File($filename, O_CREAT) unless (-f $filename);
return bless($self, $classname);
}
# Store datum value into key for the tied hash this.
sub STORE {
my ($self, $key, $value) = @_;
DEBUG("STORE($key, $value)");
$key = escape_key($key);
use IO::File;
my $fh = _lock_write($self->{filename}, "r");
my $fh_tmp = _lock_write($self->{filename} . ".tmp");
# Read the whole file, writing it to $fh_tmp
while(my $line = <$fh>) {
chomp($line);
DEBUG("read line $line");
# Print the read line, but ignore the key we are currently storing
print $fh_tmp "$line\n" unless $line =~ m/^$key:/;
}
# Print the stored key at the end
DEBUG("Print the stored $key:$value");
print $fh_tmp "$key:$value\n";
# close (therefore flush data) before rename
$fh_tmp = undef;
# overwrite atomically
# XXX - any locked process will have an old version
rename $self->{filename} . ".tmp", $self->{filename};
}
# Retrieve the datum in key for the tied hash this.
sub FETCH {
my ($self, $key) = @_;
DEBUG("FETCH($key)");
$key = escape_key($key);
my $fh = _lock_read($self->{filename});
# Read the whole file
while(my $line = <$fh>) {
chomp($line);
next unless $line =~ m/^$key:(.*)/;
# Found
return $1;
}
}
# Return the first key in the hash.
sub FIRSTKEY {
my ($self) = @_;
DEBUG("FIRSTKEY()");
my $fh = _lock_read($self->{filename});
# Read the file to find a key
while(my $line = <$fh>) {
chomp($line);
next unless $line =~ m/^(\w+):/;
# Found
return $1;
}
}
# Return the next key in the hash.
sub NEXTKEY {
my ($self, $lastkey) = @_;
DEBUG("NEXTKEY($lastkey)");
$key = escape_key($key);
my $fh = _lock_read($self->{filename});
# Read the file to find a key
while(my $line = <$fh>) {
chomp($line);
next unless $line =~ m/^$key:(.*)/;
# Found, read another line
my $new_line = <$fh>;
chomp($new_line);
if ($new_line =~ m/^(\w+):/) {
return $1;
} else {
# EOF
return undef;
}
}
}
# Verify that key exists with the tied hash this.
sub EXISTS {
my ($self, $key) = @_;
DEBUG("EXISTS($key)");
$key = escape_key($key);
my $fh = _lock_read($self->{filename});
# Read the whole file
while(my $line = <$fh>) {
chomp($line);
next unless $line =~ m/^$key:(.*)/;
# Found
return 1;
}
# Not found
return 0;
}
# Delete the key key from the tied hash this.
sub DELETE {
my ($self, $key) = @_;
DEBUG("DELETE($key)");
$key = escape_key($key);
$self->_lock_write();
}
# Clear all values from the tied hash this.
sub CLEAR {
my ($self) = @_;
DEBUG("CLEAR()");
my $fh = $self->_lock_write();
}
sub SCALAR {
my ($self) = @_;
DEBUG("SCALAR()");
my $fh = _lock_read($self->{filename});
# Read the file to read the number of lines
my $nb_lines = 0;
while(my $line = <$fh>) {
$nb_lines ++;
}
return $nb_lines;
}
sub _lock_read {
my ($filename) = @_;
use Fcntl qw(:flock);
use IO::File;
my $fh = IO::File->new($filename, "r")
or die "Cannot open tied file '$filename' - $!";
flock($fh, LOCK_SH) or die "Cannot lock tied file '$filename' - $!";
return $fh;
}
sub _lock_write {
my ($filename, $mode) = @_;
$mode ||= "a+";
use Fcntl qw(:flock);
use IO::File;
my $fh = IO::File->new($filename, $mode)
or die "Cannot open tied file '$filename' - $!";
flock($fh, LOCK_EX) or die "Cannot lock tied file '$filename' - $!";
return $fh;
}
sub DEBUG {
print STDOUT "[DEBUG] @_" . "\n" if $DEBUG_ENABLED;
}
# XXX - collision if there is a ____
# But should not happen often anyway
sub escape_key {
my $key = shift;
$key =~ s/:/____/g;
return $key;
}
1;
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