package DBM::Deep::File;
-use 5.6.0;
+use 5.006_000;
use strict;
-use warnings;
+use warnings FATAL => 'all';
use Fcntl qw( :DEFAULT :flock :seek );
-our $VERSION = '0.01';
+use constant DEBUG => 0;
+
+=head1 NAME
+
+DBM::Deep::File
+
+=head1 PURPOSE
+
+This is an internal-use-only object for L<DBM::Deep/>. It mediates the low-level
+interaction with the storage mechanism.
+
+Currently, the only storage mechanism supported is the file system.
+
+=head1 OVERVIEW
+
+This class provides an abstraction to the storage mechanism so that the Engine (the
+only class that uses this class) doesn't have to worry about that.
+
+=head1 METHODS
+
+=head2 new( \%args )
+
+=cut
sub new {
my $class = shift;
my ($args) = @_;
my $self = bless {
- autobless => undef,
- autoflush => undef,
+ autobless => 1,
+ autoflush => 1,
end => 0,
fh => undef,
file => undef,
file_offset => 0,
- locking => undef,
+ locking => 1,
locked => 0,
+#XXX Migrate this to the engine, where it really belongs.
filter_store_key => undef,
filter_store_value => undef,
filter_fetch_key => undef,
filter_fetch_value => undef,
-
- transaction_id => 0,
- transaction_offset => 0,
}, $class;
# Grab the parameters we want to use
return $self;
}
+=head2 open()
+
+This method opens the filehandle for the filename in C< file >.
+
+There is no return value.
+
+=cut
+
sub open {
my $self = shift;
- # Adding O_BINARY does remove the need for the binmode below. However,
+ # Adding O_BINARY should remove the need for the binmode below. However,
# I'm not going to remove it because I don't have the Win32 chops to be
# absolutely certain everything will be ok.
- my $flags = O_RDWR | O_CREAT | O_BINARY;
+ my $flags = O_CREAT | O_BINARY;
+
+ if ( !-e $self->{file} || -w _ ) {
+ $flags |= O_RDWR;
+ }
+ else {
+ $flags |= O_RDONLY;
+ }
my $fh;
sysopen( $fh, $self->{file}, $flags )
return 1;
}
+=head2 close()
+
+If the filehandle is opened, this will close it.
+
+There is no return value.
+
+=cut
+
sub close {
my $self = shift;
return 1;
}
-sub DESTROY {
- my $self = shift;
- return unless $self;
+=head2 size()
- $self->close;
+This will return the size of the DB. If file_offset is set, this will take that into account.
- return;
-}
+=cut
-##
-# If db locking is set, flock() the db file. If called multiple
-# times before unlock(), then the same number of unlocks() must
-# be called before the lock is released.
-##
-sub lock {
+sub size {
my $self = shift;
- my ($obj, $type) = @_;
- $type = LOCK_EX unless defined $type;
- if (!defined($self->{fh})) { return; }
+ return 0 unless $self->{fh};
+ return( (-s $self->{fh}) - $self->{file_offset} );
+}
- if ($self->{locking}) {
- if (!$self->{locked}) {
- flock($self->{fh}, $type);
+=head2 set_inode()
- # refresh end counter in case file has changed size
- my @stats = stat($self->{fh});
- $self->{end} = $stats[7];
+This will set the inode value of the underlying file object.
- # double-check file inode, in case another process
- # has optimize()d our file while we were waiting.
- if ($stats[1] != $self->{inode}) {
- $self->close;
- $self->open;
+This is only needed to handle some obscure Win32 bugs. It reqlly shouldn't be needed outside
+this object.
- #XXX This needs work
- $obj->{engine}->setup_fh( $obj );
+There is no return value.
- flock($self->{fh}, $type); # re-lock
+=cut
- # This may not be necessary after re-opening
- $self->{end} = (stat($self->{fh}))[7]; # re-end
- }
- }
- $self->{locked}++;
+sub set_inode {
+ my $self = shift;
- return 1;
+ unless ( defined $self->{inode} ) {
+ my @stats = stat($self->{fh});
+ $self->{inode} = $stats[1];
+ $self->{end} = $stats[7];
}
- return;
+ return 1;
}
-##
-# If db locking is set, unlock the db file. See note in lock()
-# regarding calling lock() multiple times.
-##
-sub unlock {
+=head2 print_at( $offset, @data )
+
+This takes an optional offset and some data to print.
+
+C< $offset >, if defined, will be used to seek into the file. If file_offset is set, it will be used
+as the zero location. If it is undefined, no seeking will occur. Then, C< @data > will be printed to
+the current location.
+
+There is no return value.
+
+=cut
+
+sub print_at {
my $self = shift;
+ my $loc = shift;
- if (!defined($self->{fh})) { return; }
+ local ($,,$\);
- if ($self->{locking} && $self->{locked} > 0) {
- $self->{locked}--;
- if (!$self->{locked}) { flock($self->{fh}, LOCK_UN); }
+ my $fh = $self->{fh};
+ if ( defined $loc ) {
+ seek( $fh, $loc + $self->{file_offset}, SEEK_SET );
+ }
- return 1;
+ if ( DEBUG ) {
+ my $caller = join ':', (caller)[0,2];
+ my $len = length( join '', @_ );
+ warn "($caller) print_at( " . (defined $loc ? $loc : '<undef>') . ", $len )\n";
}
- return;
-}
+ print( $fh @_ ) or die "Internal Error (print_at($loc)): $!\n";
-sub set_transaction_offset {
- my $self = shift;
- $self->{transaction_offset} = shift;
+ return 1;
}
-sub begin_transaction {
+=head2 read_at( $offset, $length )
+
+This takes an optional offset and a length.
+
+C< $offset >, if defined, will be used to seek into the file. If file_offset is set, it will be used
+as the zero location. If it is undefined, no seeking will occur. Then, C< $length > bytes will be
+read from the current location.
+
+The data read will be returned.
+
+=cut
+
+sub read_at {
my $self = shift;
+ my ($loc, $size) = @_;
my $fh = $self->{fh};
+ if ( defined $loc ) {
+ seek( $fh, $loc + $self->{file_offset}, SEEK_SET );
+ }
- $self->lock;
+ if ( DEBUG ) {
+ my $caller = join ':', (caller)[0,2];
+ warn "($caller) read_at( " . (defined $loc ? $loc : '<undef>') . ", $size )\n";
+ }
- seek( $fh, $self->{transaction_offset}, SEEK_SET );
my $buffer;
- read( $fh, $buffer, 4 );
- $buffer = unpack( 'N', $buffer );
-
- for ( 1 .. 32 ) {
- next if $buffer & (1 << ($_ - 1));
- $self->{transaction_id} = $_;
- $buffer &= (1 << $_);
- last;
- }
+ read( $fh, $buffer, $size);
+
+ return $buffer;
+}
+
+=head2 DESTROY
+
+When the ::File object goes out of scope, it will be closed.
+
+=cut
+
+sub DESTROY {
+ my $self = shift;
+ return unless $self;
+
+ $self->close;
+
+ return;
+}
+
+=head2 request_space( $size )
+
+This takes a size and adds that much space to the DBM.
+
+This returns the offset for the new location.
+
+=cut
- seek( $fh, $self->{transaction_offset}, SEEK_SET );
- print( $fh pack( 'N', $buffer ) );
+sub request_space {
+ my $self = shift;
+ my ($size) = @_;
- $self->unlock;
+ #XXX Do I need to reset $self->{end} here? I need a testcase
+ my $loc = $self->{end};
+ $self->{end} += $size;
- return $self->{transaction_id};
+ return $loc;
}
-sub end_transaction {
+=head2 flush()
+
+This flushes the filehandle. This takes no parameters and returns nothing.
+
+=cut
+
+sub flush {
+ my $self = shift;
+
+ # Flush the filehandle
+ my $old_fh = select $self->{fh};
+ my $old_af = $|; $| = 1; $| = $old_af;
+ select $old_fh;
+
+ return 1;
+}
+
+=head2 is_writable()
+
+This takes no parameters. It returns a boolean saying if this filehandle is
+writable.
+
+Taken from L<http://www.perlmonks.org/?node_id=691054/>.
+
+=cut
+
+sub is_writable {
my $self = shift;
my $fh = $self->{fh};
+ return unless defined $fh;
+ return unless defined fileno $fh;
+ local $\ = ''; # just in case
+ no warnings; # temporarily disable warnings
+ local $^W; # temporarily disable warnings
+ return print $fh '';
+}
- $self->lock;
+=head2 copy_stats( $target_filename )
- seek( $fh, $self->{transaction_offset}, SEEK_SET );
- my $buffer;
- read( $fh, $buffer, 4 );
- $buffer = unpack( 'N', $buffer );
+This will take the stats for the current filehandle and apply them to
+C< $target_filename >. The stats copied are:
+
+=over 4
- # Unset $self->{transaction_id} bit
+=item * Onwer UID and GID
- seek( $fh, $self->{transaction_offset}, SEEK_SET );
- print( $fh pack( 'N', $buffer ) );
+=item * Permissions
- $self->unlock;
+=back
- $self->{transaction_id} = 0;
+=cut
+
+sub copy_stats {
+ my $self = shift;
+ my ($temp_filename) = @_;
+
+ my @stats = stat( $self->{fh} );
+ my $perms = $stats[2] & 07777;
+ my $uid = $stats[4];
+ my $gid = $stats[5];
+ chown( $uid, $gid, $temp_filename );
+ chmod( $perms, $temp_filename );
+}
+
+=head1 LOCKING
+
+This is where the actual locking of the storage medium is performed.
+Nested locking is supported.
+
+B<NOTE>: It is unclear what will happen if a read lock is taken, then
+a write lock is taken as a nested lock, then the write lock is released.
+
+Currently, the only locking method supported is flock(1). This is a
+whole-file lock. In the future, more granular locking may be supported.
+The API for that is unclear right now.
+
+The following methods manage the locking status. In all cases, they take
+a L<DBM::Deep/> object and returns nothing.
+
+=over 4
+
+=item * lock_exclusive( $obj )
+
+Take a lock usable for writing.
+
+=item * lock_shared( $obj )
+
+Take a lock usable for reading.
+
+=item * unlock( $obj )
+
+Releases the last lock taken. If this is the outermost lock, then the
+object is actually unlocked.
+
+=back
+
+=cut
+
+sub lock_exclusive {
+ my $self = shift;
+ my ($obj) = @_;
+ return $self->_lock( $obj, LOCK_EX );
}
-sub current_transactions {
+sub lock_shared {
my $self = shift;
+ my ($obj) = @_;
+ return $self->_lock( $obj, LOCK_SH );
+}
- my $fh = $self->{fh};
+sub _lock {
+ my $self = shift;
+ my ($obj, $type) = @_;
- $self->lock;
+ $type = LOCK_EX unless defined $type;
- seek( $fh, $self->{transaction_offset}, SEEK_SET );
- my $buffer;
- read( $fh, $buffer, 4 );
- $buffer = unpack( 'N', $buffer );
+ #XXX This is a temporary fix for Win32 and autovivification. It
+ # needs to improve somehow. -RobK, 2008-03-09
+ if ( $^O eq 'MSWin32' || $^O eq 'cygwin' ) {
+ $type = LOCK_EX;
+ }
+
+ if (!defined($self->{fh})) { return; }
- $self->unlock;
+ #XXX This either needs to allow for upgrading a shared lock to an
+ # exclusive lock or something else with autovivification.
+ # -RobK, 2008-03-09
+ if ($self->{locking}) {
+ if (!$self->{locked}) {
+ flock($self->{fh}, $type);
+
+ # refresh end counter in case file has changed size
+ my @stats = stat($self->{fh});
+ $self->{end} = $stats[7];
+
+ # double-check file inode, in case another process
+ # has optimize()d our file while we were waiting.
+ if (defined($self->{inode}) && $stats[1] != $self->{inode}) {
+ $self->close;
+ $self->open;
+
+ #XXX This needs work
+ $obj->{engine}->setup_fh( $obj );
+
+ flock($self->{fh}, $type); # re-lock
- my @transactions;
- for ( 1 .. 32 ) {
- if ( $buffer & (1 << ($_ - 1)) ) {
- push @transactions, $_;
+ # This may not be necessary after re-opening
+ $self->{end} = (stat($self->{fh}))[7]; # re-end
+ }
}
+ $self->{locked}++;
+
+ return 1;
}
- return @transactions;
+ return;
}
-sub transaction_id { return $_[0]->{transaction_id} }
+sub unlock {
+ my $self = shift;
+
+ if (!defined($self->{fh})) { return; }
+
+ if ($self->{locking} && $self->{locked} > 0) {
+ $self->{locked}--;
-#sub commit {
-#}
+ if (!$self->{locked}) {
+ flock($self->{fh}, LOCK_UN);
+ return 1;
+ }
+
+ return;
+ }
+
+ return;
+}
1;
__END__
-
projects / dbsrgits/DBM-Deep.git / blobdiff