use warnings FATAL => 'all';
no warnings 'recursion';
-# Never import symbols into our namespace. We are a class, not a library.
-# -RobK, 2008-05-27
-use Scalar::Util ();
-
-#use Data::Dumper ();
+use DBM::Deep::Iterator ();
# File-wide notes:
# * Every method in here assumes that the storage has been appropriately
# mutex. But, it's the caller's responsability to make sure that this has
# been done.
-# Setup file and tag signatures. These should never change.
-sub SIG_FILE () { 'DPDB' }
-sub SIG_HEADER () { 'h' }
-sub SIG_HASH () { 'H' }
-sub SIG_ARRAY () { 'A' }
-sub SIG_NULL () { 'N' }
-sub SIG_DATA () { 'D' }
-sub SIG_INDEX () { 'I' }
-sub SIG_BLIST () { 'B' }
-sub SIG_FREE () { 'F' }
-sub SIG_SIZE () { 1 }
-
-use DBM::Deep::Iterator ();
-use DBM::Deep::Engine::Sector::Data ();
-use DBM::Deep::Engine::Sector::BucketList ();
-use DBM::Deep::Engine::Sector::Index ();
-use DBM::Deep::Engine::Sector::Null ();
-use DBM::Deep::Engine::Sector::Reference ();
-use DBM::Deep::Engine::Sector::Scalar ();
-use DBM::Deep::Null ();
-
-my $STALE_SIZE = 2;
-
-# Please refer to the pack() documentation for further information
-my %StP = (
- 1 => 'C', # Unsigned char value (no order needed as it's just one byte)
- 2 => 'n', # Unsigned short in "network" (big-endian) order
- 4 => 'N', # Unsigned long in "network" (big-endian) order
- 8 => 'Q', # Usigned quad (no order specified, presumably machine-dependent)
-);
+sub SIG_HASH () { 'H' }
+sub SIG_ARRAY () { 'A' }
=head1 NAME
=head1 PURPOSE
-This is an internal-use-only object for L<DBM::Deep/>. It mediates the low-level
-mapping between the L<DBM::Deep/> objects and the storage medium.
+This is an internal-use-only object for L<DBM::Deep>. It mediates the low-level
+mapping between the L<DBM::Deep> objects and the storage medium.
The purpose of this documentation is to provide low-level documentation for
developers. It is B<not> intended to be used by the general public. This
=item * get_next_key
-=item * clear
+=item * setup
-=item * setup_fh
+=item * clear
=item * begin_work
=head2 STALENESS
-If another process uses a transaction slot and writes stuff to it, then terminates,
-the data that process wrote it still within the file. In order to address this,
-there is also a transaction staleness counter associated within every write.
-Each time a transaction is started, that process increments that transaction's
-staleness counter. If, when it reads a value, the staleness counters aren't
-identical, DBM::Deep will consider the value on disk to be stale and discard it.
+If another process uses a transaction slot and writes stuff to it, then
+terminates, the data that process wrote it still within the file. In order to
+address this, there is also a transaction staleness counter associated within
+every write. Each time a transaction is started, that process increments that
+transaction's staleness counter. If, when it reads a value, the staleness
+counters aren't identical, DBM::Deep will consider the value on disk to be stale
+and discard it.
=head2 DURABILITY
The fourth leg of ACID is Durability, the guarantee that when a commit returns,
the data will be there the next time you read from it. This should be regardless
-of any crashes or powerdowns in between the commit and subsequent read. DBM::Deep
-does provide that guarantee; once the commit returns, all of the data has been
-transferred from the transaction shadow to the HEAD. The issue arises with partial
-commits - a commit that is interrupted in some fashion. In keeping with DBM::Deep's
-"tradition" of very light error-checking and non-existent error-handling, there is
-no way to recover from a partial commit. (This is probably a failure in Consistency
-as well as Durability.)
-
-Other DBMSes use transaction logs (a separate file, generally) to achieve Durability.
-As DBM::Deep is a single-file, we would have to do something similar to what SQLite
-and BDB do in terms of committing using synchonized writes. To do this, we would have
-to use a much higher RAM footprint and some serious programming that make my head
-hurts just to think about it.
+of any crashes or powerdowns in between the commit and subsequent read.
+DBM::Deep does provide that guarantee; once the commit returns, all of the data
+has been transferred from the transaction shadow to the HEAD. The issue arises
+with partial commits - a commit that is interrupted in some fashion. In keeping
+with DBM::Deep's "tradition" of very light error-checking and non-existent
+error-handling, there is no way to recover from a partial commit. (This is
+probably a failure in Consistency as well as Durability.)
-=head1 EXTERNAL METHODS
-
-=head2 new()
-
-This takes a set of args. These args are described in the documentation for
-L<DBM::Deep/new>.
+Other DBMSes use transaction logs (a separate file, generally) to achieve
+Durability. As DBM::Deep is a single-file, we would have to do something
+similar to what SQLite and BDB do in terms of committing using synchonized
+writes. To do this, we would have to use a much higher RAM footprint and some
+serious programming that make my head hurts just to think about it.
=cut
-sub new {
- my $class = shift;
- my ($args) = @_;
-
- $args->{storage} = DBM::Deep::File->new( $args )
- unless exists $args->{storage};
-
- my $self = bless {
- byte_size => 4,
-
- digest => undef,
- hash_size => 16, # In bytes
- hash_chars => 256, # Number of chars the algorithm uses per byte
- max_buckets => 16,
- num_txns => 1, # The HEAD
- trans_id => 0, # Default to the HEAD
-
- data_sector_size => 64, # Size in bytes of each data sector
-
- entries => {}, # This is the list of entries for transactions
- storage => undef,
- }, $class;
-
- # Never allow byte_size to be set directly.
- delete $args->{byte_size};
- if ( defined $args->{pack_size} ) {
- if ( lc $args->{pack_size} eq 'small' ) {
- $args->{byte_size} = 2;
- }
- elsif ( lc $args->{pack_size} eq 'medium' ) {
- $args->{byte_size} = 4;
- }
- elsif ( lc $args->{pack_size} eq 'large' ) {
- $args->{byte_size} = 8;
- }
- else {
- DBM::Deep->_throw_error( "Unknown pack_size value: '$args->{pack_size}'" );
- }
- }
-
- # Grab the parameters we want to use
- foreach my $param ( keys %$self ) {
- next unless exists $args->{$param};
- $self->{$param} = $args->{$param};
- }
-
- my %validations = (
- max_buckets => { floor => 16, ceil => 256 },
- num_txns => { floor => 1, ceil => 255 },
- data_sector_size => { floor => 32, ceil => 256 },
- );
-
- while ( my ($attr, $c) = each %validations ) {
- if ( !defined $self->{$attr}
- || !length $self->{$attr}
- || $self->{$attr} =~ /\D/
- || $self->{$attr} < $c->{floor}
- ) {
- $self->{$attr} = '(undef)' if !defined $self->{$attr};
- warn "Floor of $attr is $c->{floor}. Setting it to $c->{floor} from '$self->{$attr}'\n";
- $self->{$attr} = $c->{floor};
- }
- elsif ( $self->{$attr} > $c->{ceil} ) {
- warn "Ceiling of $attr is $c->{ceil}. Setting it to $c->{ceil} from '$self->{$attr}'\n";
- $self->{$attr} = $c->{ceil};
- }
- }
-
- if ( !$self->{digest} ) {
- require Digest::MD5;
- $self->{digest} = \&Digest::MD5::md5;
- }
-
- return $self;
-}
+=head1 METHODS
=head2 read_value( $obj, $key )
=cut
-sub read_value {
- my $self = shift;
- my ($obj, $key) = @_;
-
- # This will be a Reference sector
- my $sector = $self->_load_sector( $obj->_base_offset )
- or return;
-
- if ( $sector->staleness != $obj->_staleness ) {
- return;
- }
-
- my $key_md5 = $self->_apply_digest( $key );
-
- my $value_sector = $sector->get_data_for({
- key_md5 => $key_md5,
- allow_head => 1,
- });
-
- unless ( $value_sector ) {
- $value_sector = DBM::Deep::Engine::Sector::Null->new({
- engine => $self,
- data => undef,
- });
-
- $sector->write_data({
- key_md5 => $key_md5,
- key => $key,
- value => $value_sector,
- });
- }
-
- return $value_sector->data;
-}
+sub read_value { die "read_value must be implemented in a child class" }
=head2 get_classname( $obj )
-This takes an object that provides _base_offset() and returns the classname (if any)
-associated with it.
+This takes an object that provides _base_offset() and returns the classname (if
+any) associated with it.
It delegates to Sector::Reference::get_classname() for the heavy lifting.
=cut
-sub get_classname {
- my $self = shift;
- my ($obj) = @_;
-
- # This will be a Reference sector
- my $sector = $self->_load_sector( $obj->_base_offset )
- or DBM::Deep->_throw_error( "How did get_classname fail (no sector for '$obj')?!" );
-
- if ( $sector->staleness != $obj->_staleness ) {
- return;
- }
-
- return $sector->get_classname;
-}
+sub get_classname { die "get_classname must be implemented in a child class" }
=head2 make_reference( $obj, $old_key, $new_key )
This takes an object that provides _base_offset() and two strings. The
strings correspond to the old key and new key, respectively. This operation
-is equivalent to (given C<< $db->{foo} = []; >>) C<< $db->{bar} = $db->{foo}; >>.
+is equivalent to (given C<< $db->{foo} = []; >>) C<< $db->{bar} = $db->{foo} >>.
This returns nothing.
=cut
-sub make_reference {
- my $self = shift;
- my ($obj, $old_key, $new_key) = @_;
-
- # This will be a Reference sector
- my $sector = $self->_load_sector( $obj->_base_offset )
- or DBM::Deep->_throw_error( "How did make_reference fail (no sector for '$obj')?!" );
-
- if ( $sector->staleness != $obj->_staleness ) {
- return;
- }
-
- my $old_md5 = $self->_apply_digest( $old_key );
-
- my $value_sector = $sector->get_data_for({
- key_md5 => $old_md5,
- allow_head => 1,
- });
-
- unless ( $value_sector ) {
- $value_sector = DBM::Deep::Engine::Sector::Null->new({
- engine => $self,
- data => undef,
- });
-
- $sector->write_data({
- key_md5 => $old_md5,
- key => $old_key,
- value => $value_sector,
- });
- }
-
- if ( $value_sector->isa( 'DBM::Deep::Engine::Sector::Reference' ) ) {
- $sector->write_data({
- key => $new_key,
- key_md5 => $self->_apply_digest( $new_key ),
- value => $value_sector,
- });
- $value_sector->increment_refcount;
- }
- else {
- $sector->write_data({
- key => $new_key,
- key_md5 => $self->_apply_digest( $new_key ),
- value => $value_sector->clone,
- });
- }
-
- return;
-}
+sub make_reference { die "make_reference must be implemented in a child class" }
=head2 key_exists( $obj, $key )
=cut
-sub key_exists {
- my $self = shift;
- my ($obj, $key) = @_;
-
- # This will be a Reference sector
- my $sector = $self->_load_sector( $obj->_base_offset )
- or return '';
-
- if ( $sector->staleness != $obj->_staleness ) {
- return '';
- }
-
- my $data = $sector->get_data_for({
- key_md5 => $self->_apply_digest( $key ),
- allow_head => 1,
- });
-
- # exists() returns 1 or '' for true/false.
- return $data ? 1 : '';
-}
+sub key_exists { die "key_exists must be implemented in a child class" }
=head2 delete_key( $obj, $key )
=cut
-sub delete_key {
- my $self = shift;
- my ($obj, $key) = @_;
-
- my $sector = $self->_load_sector( $obj->_base_offset )
- or return;
-
- if ( $sector->staleness != $obj->_staleness ) {
- return;
- }
-
- return $sector->delete_key({
- key_md5 => $self->_apply_digest( $key ),
- allow_head => 0,
- });
-}
+sub delete_key { die "delete_key must be implemented in a child class" }
=head2 write_value( $obj, $key, $value )
This takes an object that provides _base_offset(), a string for the
-key, and a value. This value can be anything storable within L<DBM::Deep/>.
+key, and a value. This value can be anything storable within L<DBM::Deep>.
This returns 1 upon success.
=cut
-sub write_value {
- my $self = shift;
- my ($obj, $key, $value) = @_;
-
- my $r = Scalar::Util::reftype( $value ) || '';
- {
- last if $r eq '';
- last if $r eq 'HASH';
- last if $r eq 'ARRAY';
-
- DBM::Deep->_throw_error(
- "Storage of references of type '$r' is not supported."
- );
- }
-
- # This will be a Reference sector
- my $sector = $self->_load_sector( $obj->_base_offset )
- or DBM::Deep->_throw_error( "Cannot write to a deleted spot in DBM::Deep." );
-
- if ( $sector->staleness != $obj->_staleness ) {
- DBM::Deep->_throw_error( "Cannot write to a deleted spot in DBM::Deep." );
- }
-
- my ($class, $type);
- if ( !defined $value ) {
- $class = 'DBM::Deep::Engine::Sector::Null';
- }
- elsif ( $r eq 'ARRAY' || $r eq 'HASH' ) {
- my $tmpvar;
- if ( $r eq 'ARRAY' ) {
- $tmpvar = tied @$value;
- } elsif ( $r eq 'HASH' ) {
- $tmpvar = tied %$value;
- }
-
- if ( $tmpvar ) {
- my $is_dbm_deep = eval { local $SIG{'__DIE__'}; $tmpvar->isa( 'DBM::Deep' ); };
-
- unless ( $is_dbm_deep ) {
- DBM::Deep->_throw_error( "Cannot store something that is tied." );
- }
-
- unless ( $tmpvar->_engine->storage == $self->storage ) {
- DBM::Deep->_throw_error( "Cannot store values across DBM::Deep files. Please use export() instead." );
- }
-
- # First, verify if we're storing the same thing to this spot. If we are, then
- # this should be a no-op. -EJS, 2008-05-19
- my $loc = $sector->get_data_location_for({
- key_md5 => $self->_apply_digest( $key ),
- allow_head => 1,
- });
-
- if ( defined($loc) && $loc == $tmpvar->_base_offset ) {
- return 1;
- }
-
- #XXX Can this use $loc?
- my $value_sector = $self->_load_sector( $tmpvar->_base_offset );
- $sector->write_data({
- key => $key,
- key_md5 => $self->_apply_digest( $key ),
- value => $value_sector,
- });
- $value_sector->increment_refcount;
-
- return 1;
- }
-
- $class = 'DBM::Deep::Engine::Sector::Reference';
- $type = substr( $r, 0, 1 );
- }
- else {
- if ( tied($value) ) {
- DBM::Deep->_throw_error( "Cannot store something that is tied." );
- }
- $class = 'DBM::Deep::Engine::Sector::Scalar';
- }
-
- # Create this after loading the reference sector in case something bad happens.
- # This way, we won't allocate value sector(s) needlessly.
- my $value_sector = $class->new({
- engine => $self,
- data => $value,
- type => $type,
- });
-
- $sector->write_data({
- key => $key,
- key_md5 => $self->_apply_digest( $key ),
- value => $value_sector,
- });
-
- # This code is to make sure we write all the values in the $value to the disk
- # and to make sure all changes to $value after the assignment are reflected
- # on disk. This may be counter-intuitive at first, but it is correct dwimmery.
- # NOTE - simply tying $value won't perform a STORE on each value. Hence, the
- # copy to a temp value.
- if ( $r eq 'ARRAY' ) {
- my @temp = @$value;
- tie @$value, 'DBM::Deep', {
- base_offset => $value_sector->offset,
- staleness => $value_sector->staleness,
- storage => $self->storage,
- engine => $self,
- };
- @$value = @temp;
- bless $value, 'DBM::Deep::Array' unless Scalar::Util::blessed( $value );
- }
- elsif ( $r eq 'HASH' ) {
- my %temp = %$value;
- tie %$value, 'DBM::Deep', {
- base_offset => $value_sector->offset,
- staleness => $value_sector->staleness,
- storage => $self->storage,
- engine => $self,
- };
-
- %$value = %temp;
- bless $value, 'DBM::Deep::Hash' unless Scalar::Util::blessed( $value );
- }
-
- return 1;
-}
-
-=head2 get_next_key( $obj, $prev_key )
-
-This takes an object that provides _base_offset() and an optional string
-representing the prior key returned via a prior invocation of this method.
-
-This method delegates to C<< DBM::Deep::Iterator->get_next_key() >>.
-
-=cut
-
-# XXX Add staleness here
-sub get_next_key {
- my $self = shift;
- my ($obj, $prev_key) = @_;
-
- # XXX Need to add logic about resetting the iterator if any key in the reference has changed
- unless ( defined $prev_key ) {
- $obj->{iterator} = DBM::Deep::Iterator->new({
- base_offset => $obj->_base_offset,
- engine => $self,
- });
- }
-
- return $obj->{iterator}->get_next_key( $obj );
-}
-
-=head2 clear( $obj )
-
-This takes an object that provides _base_offset() and deletes all its
-elements, returning nothing.
-
-=cut
-
-sub clear {
- my $self = shift;
- my $obj = shift;
-
- my $sector = $self->_load_sector( $obj->_base_offset )
- or return;
-
- if ( $sector->staleness != $obj->_staleness ) {
- return;
- }
-
- $sector->clear;
- return;
-}
+sub write_value { die "write_value must be implemented in a child class" }
-=head2 setup_fh( $obj )
+=head2 setup( $obj )
This takes an object that provides _base_offset(). It will do everything needed
in order to properly initialize all values for necessary functioning. If this is
=cut
-sub setup_fh {
- my $self = shift;
- my ($obj) = @_;
-
- # We're opening the file.
- unless ( $obj->_base_offset ) {
- my $bytes_read = $self->_read_file_header;
-
- # Creating a new file
- unless ( $bytes_read ) {
- $self->_write_file_header;
-
- # 1) Create Array/Hash entry
- my $initial_reference = DBM::Deep::Engine::Sector::Reference->new({
- engine => $self,
- type => $obj->_type,
- });
- $obj->{base_offset} = $initial_reference->offset;
- $obj->{staleness} = $initial_reference->staleness;
-
- $self->storage->flush;
- }
- # Reading from an existing file
- else {
- $obj->{base_offset} = $bytes_read;
- my $initial_reference = DBM::Deep::Engine::Sector::Reference->new({
- engine => $self,
- offset => $obj->_base_offset,
- });
- unless ( $initial_reference ) {
- DBM::Deep->_throw_error("Corrupted file, no master index record");
- }
-
- unless ($obj->_type eq $initial_reference->type) {
- DBM::Deep->_throw_error("File type mismatch");
- }
-
- $obj->{staleness} = $initial_reference->staleness;
- }
- }
-
- $self->storage->set_inode;
-
- return 1;
-}
+sub setup { die "setup must be implemented in a child class" }
=head2 begin_work( $obj )
=cut
-sub begin_work {
- my $self = shift;
- my ($obj) = @_;
-
- if ( $self->trans_id ) {
- DBM::Deep->_throw_error( "Cannot begin_work within an active transaction" );
- }
-
- my @slots = $self->read_txn_slots;
- my $found;
- for my $i ( 0 .. $#slots ) {
- next if $slots[$i];
-
- $slots[$i] = 1;
- $self->set_trans_id( $i + 1 );
- $found = 1;
- last;
- }
- unless ( $found ) {
- DBM::Deep->_throw_error( "Cannot allocate transaction ID" );
- }
- $self->write_txn_slots( @slots );
-
- if ( !$self->trans_id ) {
- DBM::Deep->_throw_error( "Cannot begin_work - no available transactions" );
- }
-
- return;
-}
+sub begin_work { die "begin_work must be implemented in a child class" }
=head2 rollback( $obj )
=cut
-sub rollback {
- my $self = shift;
- my ($obj) = @_;
-
- if ( !$self->trans_id ) {
- DBM::Deep->_throw_error( "Cannot rollback without an active transaction" );
- }
-
- # Each entry is the file location for a bucket that has a modification for
- # this transaction. The entries need to be expunged.
- foreach my $entry (@{ $self->get_entries } ) {
- # Remove the entry here
- my $read_loc = $entry
- + $self->hash_size
- + $self->byte_size
- + $self->byte_size
- + ($self->trans_id - 1) * ( $self->byte_size + $STALE_SIZE );
-
- my $data_loc = $self->storage->read_at( $read_loc, $self->byte_size );
- $data_loc = unpack( $StP{$self->byte_size}, $data_loc );
- $self->storage->print_at( $read_loc, pack( $StP{$self->byte_size}, 0 ) );
-
- if ( $data_loc > 1 ) {
- $self->_load_sector( $data_loc )->free;
- }
- }
-
- $self->clear_entries;
-
- my @slots = $self->read_txn_slots;
- $slots[$self->trans_id-1] = 0;
- $self->write_txn_slots( @slots );
- $self->inc_txn_staleness_counter( $self->trans_id );
- $self->set_trans_id( 0 );
-
- return 1;
-}
+sub rollback { die "rollback must be implemented in a child class" }
=head2 commit( $obj )
=cut
-sub commit {
- my $self = shift;
- my ($obj) = @_;
+sub commit { die "commit must be implemented in a child class" }
- if ( !$self->trans_id ) {
- DBM::Deep->_throw_error( "Cannot commit without an active transaction" );
- }
+=head2 get_next_key( $obj, $prev_key )
- foreach my $entry (@{ $self->get_entries } ) {
- # Overwrite the entry in head with the entry in trans_id
- my $base = $entry
- + $self->hash_size
- + $self->byte_size;
-
- my $head_loc = $self->storage->read_at( $base, $self->byte_size );
- $head_loc = unpack( $StP{$self->byte_size}, $head_loc );
-
- my $spot = $base + $self->byte_size + ($self->trans_id - 1) * ( $self->byte_size + $STALE_SIZE );
- my $trans_loc = $self->storage->read_at(
- $spot, $self->byte_size,
- );
-
- $self->storage->print_at( $base, $trans_loc );
- $self->storage->print_at(
- $spot,
- pack( $StP{$self->byte_size} . ' ' . $StP{$STALE_SIZE}, (0) x 2 ),
- );
-
- if ( $head_loc > 1 ) {
- $self->_load_sector( $head_loc )->free;
- }
- }
+This takes an object that provides _base_offset() and an optional string
+representing the prior key returned via a prior invocation of this method.
- $self->clear_entries;
+This method delegates to C<< DBM::Deep::Iterator->get_next_key() >>.
- my @slots = $self->read_txn_slots;
- $slots[$self->trans_id-1] = 0;
- $self->write_txn_slots( @slots );
- $self->inc_txn_staleness_counter( $self->trans_id );
- $self->set_trans_id( 0 );
+=cut
- return 1;
+# XXX Add staleness here
+sub get_next_key {
+ my $self = shift;
+ my ($obj, $prev_key) = @_;
+
+ # XXX Need to add logic about resetting the iterator if any key in the
+ # reference has changed
+ unless ( defined $prev_key ) {
+ eval "use " . $self->iterator_class; die $@ if $@;
+ $obj->{iterator} = $self->iterator_class->new({
+ base_offset => $obj->_base_offset,
+ engine => $self,
+ });
+ }
+
+ return $obj->{iterator}->get_next_key( $obj );
}
=head2 lock_exclusive()
=head2 unlock()
This takes an object that provides _base_offset(). It will guarantee that
-the storage has released all locks taken.
+the storage has released the most recently-taken lock.
This returns nothing.
=head1 INTERNAL METHODS
-The following methods are internal-use-only to DBM::Deep::Engine.
-
-=cut
-
-=head2 read_txn_slots()
-
-This takes no arguments.
-
-This will return an array with a 1 or 0 in each slot. Each spot represents one
-available transaction. If the slot is 1, that transaction is taken. If it is 0,
-the transaction is available.
+The following methods are internal-use-only to DBM::Deep::Engine and its
+child classes.
=cut
-sub read_txn_slots {
- my $self = shift;
- my $bl = $self->txn_bitfield_len;
- my $num_bits = $bl * 8;
- return split '', unpack( 'b'.$num_bits,
- $self->storage->read_at(
- $self->trans_loc, $bl,
- )
- );
-}
-
-=head2 write_txn_slots( @slots )
-
-This takes an array of 1's and 0's. This array represents the transaction slots
-returned by L</read_txn_slots()>. In other words, the following is true:
-
- @x = read_txn_slots( write_txn_slots( @x ) );
-
-(With the obviously missing object referents added back in.)
-
-=cut
-
-sub write_txn_slots {
- my $self = shift;
- my $num_bits = $self->txn_bitfield_len * 8;
- $self->storage->print_at( $self->trans_loc,
- pack( 'b'.$num_bits, join('', @_) ),
- );
-}
-
-=head2 get_running_txn_ids()
-
-This takes no arguments.
-
-This will return an array of taken transaction IDs. This wraps L</read_txn_slots()>.
-
-=cut
-
-sub get_running_txn_ids {
- my $self = shift;
- my @transactions = $self->read_txn_slots;
- my @trans_ids = map { $_+1 } grep { $transactions[$_] } 0 .. $#transactions;
-}
-
-=head2 get_txn_staleness_counter( $trans_id )
-
-This will return the staleness counter for the given transaction ID. Please see
-L</TRANSACTION STALENESS> for more information.
-
-=cut
-
-sub get_txn_staleness_counter {
- my $self = shift;
- my ($trans_id) = @_;
-
- # Hardcode staleness of 0 for the HEAD
- return 0 unless $trans_id;
-
- return unpack( $StP{$STALE_SIZE},
- $self->storage->read_at(
- $self->trans_loc + $self->txn_bitfield_len + $STALE_SIZE * ($trans_id - 1),
- $STALE_SIZE,
- )
- );
-}
-
-=head2 inc_txn_staleness_counter( $trans_id )
-
-This will increment the staleness counter for the given transaction ID. Please see
-L</TRANSACTION STALENESS> for more information.
-
-=cut
-
-sub inc_txn_staleness_counter {
- my $self = shift;
- my ($trans_id) = @_;
-
- # Hardcode staleness of 0 for the HEAD
- return 0 unless $trans_id;
-
- $self->storage->print_at(
- $self->trans_loc + $self->txn_bitfield_len + $STALE_SIZE * ($trans_id - 1),
- pack( $StP{$STALE_SIZE}, $self->get_txn_staleness_counter( $trans_id ) + 1 ),
- );
-}
-
-=head2 get_entries()
-
-This takes no arguments.
-
-This returns a list of all the sectors that have been modified by this transaction.
-
-=cut
-
-sub get_entries {
- my $self = shift;
- return [ keys %{ $self->{entries}{$self->trans_id} ||= {} } ];
-}
-
-=head2 add_entry( $trans_id, $location )
-
-This takes a transaction ID and a file location and marks the sector at that location
-as having been modified by the transaction identified by $trans_id.
-
-This returns nothing.
-
-B<NOTE>: Unlike all the other _entries() methods, there are several cases where
-C<< $trans_id != $self->trans_id >> for this method.
-
-=cut
-
-sub add_entry {
- my $self = shift;
- my ($trans_id, $loc) = @_;
-
- $self->{entries}{$trans_id} ||= {};
- $self->{entries}{$trans_id}{$loc} = undef;
-}
-
-=head2 reindex_entry( $old_loc, $new_loc )
-
-This takes two locations (old and new, respectively). If a location that has been
-modified by this transaction is subsequently reindexed due to a bucketlist
-overflowing, then the entries hash needs to be made aware of this change.
-
-This returns nothing.
-
-=cut
-
-sub reindex_entry {
- my $self = shift;
- my ($old_loc, $new_loc) = @_;
-
- TRANS:
- while ( my ($trans_id, $locs) = each %{ $self->{entries} } ) {
- if ( exists $locs->{$old_loc} ) {
- delete $locs->{$old_loc};
- $locs->{$new_loc} = undef;
- next TRANS;
- }
- }
-}
-
-=head2 clear_entries()
+=head2 flush()
-This takes no arguments. It will clear the entries list for the running transaction.
+This takes no arguments. It will do everything necessary to flush all things to
+disk. This is usually called during unlock() and setup().
This returns nothing.
=cut
-sub clear_entries {
- my $self = shift;
- delete $self->{entries}{$self->trans_id};
-}
-
-=head2 _write_file_header()
-
-This writes the file header for a new file. This will write the various settings
-that set how the file is interpreted.
-
-=head2 _read_file_header()
-
-This reads the file header from an existing file. This will read the various
-settings that set how the file is interpreted.
-
-=cut
-
-{
- my $header_fixed = length( SIG_FILE ) + 1 + 4 + 4;
- my $this_file_version = 3;
-
- sub _write_file_header {
- my $self = shift;
-
- my $nt = $self->num_txns;
- my $bl = $self->txn_bitfield_len;
-
- my $header_var = 1 + 1 + 1 + 1 + $bl + $STALE_SIZE * ($nt - 1) + 3 * $self->byte_size;
-
- my $loc = $self->storage->request_space( $header_fixed + $header_var );
-
- $self->storage->print_at( $loc,
- SIG_FILE,
- SIG_HEADER,
- pack('N', $this_file_version), # At this point, we're at 9 bytes
- pack('N', $header_var), # header size
- # --- Above is $header_fixed. Below is $header_var
- pack('C', $self->byte_size),
-
- # These shenanigans are to allow a 256 within a C
- pack('C', $self->max_buckets - 1),
- pack('C', $self->data_sector_size - 1),
-
- pack('C', $nt),
- pack('C' . $bl, 0 ), # Transaction activeness bitfield
- pack($StP{$STALE_SIZE}.($nt-1), 0 x ($nt-1) ), # Transaction staleness counters
- pack($StP{$self->byte_size}, 0), # Start of free chain (blist size)
- pack($StP{$self->byte_size}, 0), # Start of free chain (data size)
- pack($StP{$self->byte_size}, 0), # Start of free chain (index size)
- );
-
- #XXX Set these less fragilely
- $self->set_trans_loc( $header_fixed + 4 );
- $self->set_chains_loc( $header_fixed + 4 + $bl + $STALE_SIZE * ($nt-1) );
-
- return;
- }
-
- sub _read_file_header {
- my $self = shift;
-
- my $buffer = $self->storage->read_at( 0, $header_fixed );
- return unless length($buffer);
-
- my ($file_signature, $sig_header, $file_version, $size) = unpack(
- 'A4 A N N', $buffer
- );
-
- unless ( $file_signature eq SIG_FILE ) {
- $self->storage->close;
- DBM::Deep->_throw_error( "Signature not found -- file is not a Deep DB" );
- }
-
- unless ( $sig_header eq SIG_HEADER ) {
- $self->storage->close;
- DBM::Deep->_throw_error( "Pre-1.00 file version found" );
- }
-
- unless ( $file_version == $this_file_version ) {
- $self->storage->close;
- DBM::Deep->_throw_error(
- "Wrong file version found - " . $file_version .
- " - expected " . $this_file_version
- );
- }
-
- my $buffer2 = $self->storage->read_at( undef, $size );
- my @values = unpack( 'C C C C', $buffer2 );
-
- if ( @values != 4 || grep { !defined } @values ) {
- $self->storage->close;
- DBM::Deep->_throw_error("Corrupted file - bad header");
- }
-
- #XXX Add warnings if values weren't set right
- @{$self}{qw(byte_size max_buckets data_sector_size num_txns)} = @values;
-
- # These shenangians are to allow a 256 within a C
- $self->{max_buckets} += 1;
- $self->{data_sector_size} += 1;
-
- my $bl = $self->txn_bitfield_len;
-
- my $header_var = scalar(@values) + $bl + $STALE_SIZE * ($self->num_txns - 1) + 3 * $self->byte_size;
- unless ( $size == $header_var ) {
- $self->storage->close;
- DBM::Deep->_throw_error( "Unexpected size found ($size <-> $header_var)." );
- }
-
- $self->set_trans_loc( $header_fixed + scalar(@values) );
- $self->set_chains_loc( $header_fixed + scalar(@values) + $bl + $STALE_SIZE * ($self->num_txns - 1) );
-
- return length($buffer) + length($buffer2);
- }
-}
-
-=head2 _load_sector( $offset )
-
-This will instantiate and return the sector object that represents the data found
-at $offset.
-
-=cut
-
-sub _load_sector {
+sub flush {
my $self = shift;
- my ($offset) = @_;
-
- # Add a catch for offset of 0 or 1
- return if !$offset || $offset <= 1;
- my $type = $self->storage->read_at( $offset, 1 );
- return if $type eq chr(0);
-
- if ( $type eq $self->SIG_ARRAY || $type eq $self->SIG_HASH ) {
- return DBM::Deep::Engine::Sector::Reference->new({
- engine => $self,
- type => $type,
- offset => $offset,
- });
- }
- # XXX Don't we need key_md5 here?
- elsif ( $type eq $self->SIG_BLIST ) {
- return DBM::Deep::Engine::Sector::BucketList->new({
- engine => $self,
- type => $type,
- offset => $offset,
- });
- }
- elsif ( $type eq $self->SIG_INDEX ) {
- return DBM::Deep::Engine::Sector::Index->new({
- engine => $self,
- type => $type,
- offset => $offset,
- });
- }
- elsif ( $type eq $self->SIG_NULL ) {
- return DBM::Deep::Engine::Sector::Null->new({
- engine => $self,
- type => $type,
- offset => $offset,
- });
- }
- elsif ( $type eq $self->SIG_DATA ) {
- return DBM::Deep::Engine::Sector::Scalar->new({
- engine => $self,
- type => $type,
- offset => $offset,
- });
- }
- # This was deleted from under us, so just return and let the caller figure it out.
- elsif ( $type eq $self->SIG_FREE ) {
- return;
- }
-
- DBM::Deep->_throw_error( "'$offset': Don't know what to do with type '$type'" );
-}
-
-=head2 _apply_digest( @stuff )
-
-This will apply the digest methd (default to Digest::MD5::md5) to the arguments
-passed in and return the result.
-
-=cut
+ # Why do we need to have the storage flush? Shouldn't autoflush take care of
+ # things? -RobK, 2008-06-26
+ $self->storage->flush;
-sub _apply_digest {
- my $self = shift;
- return $self->{digest}->(@_);
+ return;
}
-=head2 _add_free_blist_sector( $offset, $size )
-
-=head2 _add_free_data_sector( $offset, $size )
-
-=head2 _add_free_index_sector( $offset, $size )
+=head2 load_sector( $loc )
-These methods are all wrappers around _add_free_sector(), providing the proper
-chain offset ($multiple) for the sector type.
+This takes an id/location/offset and loads the sector based on the engine's
+defined sector type.
=cut
-sub _add_free_blist_sector { shift->_add_free_sector( 0, @_ ) }
-sub _add_free_data_sector { shift->_add_free_sector( 1, @_ ) }
-sub _add_free_index_sector { shift->_add_free_sector( 2, @_ ) }
-
-=head2 _add_free_sector( $multiple, $offset, $size )
-
-_add_free_sector() takes the offset into the chains location, the offset of the
-sector, and the size of that sector. It will mark the sector as a free sector
-and put it into the list of sectors that are free of this type for use later.
-
-This returns nothing.
-
-B<NOTE>: $size is unused?
-
-=cut
-
-sub _add_free_sector {
- my $self = shift;
- my ($multiple, $offset, $size) = @_;
-
- my $chains_offset = $multiple * $self->byte_size;
-
- my $storage = $self->storage;
-
- # Increment staleness.
- # XXX Can this increment+modulo be done by "&= 0x1" ?
- my $staleness = unpack( $StP{$STALE_SIZE}, $storage->read_at( $offset + SIG_SIZE, $STALE_SIZE ) );
- $staleness = ($staleness + 1 ) % ( 2 ** ( 8 * $STALE_SIZE ) );
- $storage->print_at( $offset + SIG_SIZE, pack( $StP{$STALE_SIZE}, $staleness ) );
-
- my $old_head = $storage->read_at( $self->chains_loc + $chains_offset, $self->byte_size );
+sub load_sector { $_[0]->sector_type->load( @_ ) }
- $storage->print_at( $self->chains_loc + $chains_offset,
- pack( $StP{$self->byte_size}, $offset ),
- );
-
- # Record the old head in the new sector after the signature and staleness counter
- $storage->print_at( $offset + SIG_SIZE + $STALE_SIZE, $old_head );
-}
-
-=head2 _request_blist_sector( $size )
-
-=head2 _request_data_sector( $size )
-
-=head2 _request_index_sector( $size )
+=head2 clear( $obj )
-These methods are all wrappers around _request_sector(), providing the proper
-chain offset ($multiple) for the sector type.
+This takes an object that provides _base_offset() and deletes all its
+elements, returning nothing.
=cut
-sub _request_blist_sector { shift->_request_sector( 0, @_ ) }
-sub _request_data_sector { shift->_request_sector( 1, @_ ) }
-sub _request_index_sector { shift->_request_sector( 2, @_ ) }
-
-=head2 _request_sector( $multiple $size )
+sub clear { die "clear must be implemented in a child class" }
-This takes the offset into the chains location and the size of that sector.
+=head2 cache / clear_cache
-This returns the object with the sector. If there is an available free sector of
-that type, then it will be reused. If there isn't one, then a new one will be
-allocated.
+This is the cache of loaded Reference sectors.
=cut
-sub _request_sector {
- my $self = shift;
- my ($multiple, $size) = @_;
-
- my $chains_offset = $multiple * $self->byte_size;
-
- my $old_head = $self->storage->read_at( $self->chains_loc + $chains_offset, $self->byte_size );
- my $loc = unpack( $StP{$self->byte_size}, $old_head );
-
- # We don't have any free sectors of the right size, so allocate a new one.
- unless ( $loc ) {
- my $offset = $self->storage->request_space( $size );
+sub cache { $_[0]{cache} ||= {} }
+sub clear_cache { %{$_[0]->cache} = () }
- # Zero out the new sector. This also guarantees correct increases
- # in the filesize.
- $self->storage->print_at( $offset, chr(0) x $size );
+=head2 supports( $option )
- return $offset;
- }
+This returns a boolean depending on if this instance of DBM::Dep supports
+that feature. C<$option> can be one of:
- # Read the new head after the signature and the staleness counter
- my $new_head = $self->storage->read_at( $loc + SIG_SIZE + $STALE_SIZE, $self->byte_size );
- $self->storage->print_at( $self->chains_loc + $chains_offset, $new_head );
- $self->storage->print_at(
- $loc + SIG_SIZE + $STALE_SIZE,
- pack( $StP{$self->byte_size}, 0 ),
- );
+=over 4
- return $loc;
-}
+=item * transactions
-=head2 flush()
+=item * singletons
-This takes no arguments. It will do everything necessary to flush all things to
-disk. This is usually called during unlock() and setup_fh().
+=back
-This returns nothing.
+Any other value will return false.
=cut
-sub flush {
- my $self = shift;
-
- # Why do we need to have the storage flush? Shouldn't autoflush take care of things?
- # -RobK, 2008-06-26
- $self->storage->flush;
-}
+sub supports { die "supports must be implemented in a child class" }
-=head2 ACCESSORS
+=head1 ACCESSORS
The following are readonly attributes.
=item * storage
-=item * byte_size
-
-=item * hash_size
-
-=item * hash_chars
-
-=item * num_txns
-
-=item * max_buckets
-
-=item * blank_md5
-
-=item * data_sector_size
+=item * sector_type
-=item * txn_bitfield_len
+=item * iterator_class
=back
=cut
-sub storage { $_[0]{storage} }
-sub byte_size { $_[0]{byte_size} }
-sub hash_size { $_[0]{hash_size} }
-sub hash_chars { $_[0]{hash_chars} }
-sub num_txns { $_[0]{num_txns} }
-sub max_buckets { $_[0]{max_buckets} }
-sub blank_md5 { chr(0) x $_[0]->hash_size }
-sub data_sector_size { $_[0]{data_sector_size} }
-
-# This is a calculated value
-sub txn_bitfield_len {
- my $self = shift;
- unless ( exists $self->{txn_bitfield_len} ) {
- my $temp = ($self->num_txns) / 8;
- if ( $temp > int( $temp ) ) {
- $temp = int( $temp ) + 1;
- }
- $self->{txn_bitfield_len} = $temp;
- }
- return $self->{txn_bitfield_len};
-}
-
-=pod
-
-The following are read/write attributes.
-
-=over 4
-
-=item * trans_id / set_trans_id( $new_id )
-
-=item * trans_loc / set_trans_loc( $new_loc )
-
-=item * chains_loc / set_chains_loc( $new_loc )
-
-=back
-
-=cut
-
-sub trans_id { $_[0]{trans_id} }
-sub set_trans_id { $_[0]{trans_id} = $_[1] }
-
-sub trans_loc { $_[0]{trans_loc} }
-sub set_trans_loc { $_[0]{trans_loc} = $_[1] }
-
-sub chains_loc { $_[0]{chains_loc} }
-sub set_chains_loc { $_[0]{chains_loc} = $_[1] }
-
-sub cache { $_[0]{cache} ||= {} }
-sub clear_cache { %{$_[0]->cache} = () }
+sub storage { $_[0]{storage} }
-=head2 _dump_file()
+sub sector_type { die "sector_type must be implemented in a child class" }
+sub iterator_class { die "iterator_class must be implemented in a child class" }
-This method takes no arguments. It's used to print out a textual representation of the DBM::Deep
-DB file. It assumes the file is not-corrupted.
-
-=cut
-
-sub _dump_file {
+# This code is to make sure we write all the values in the $value to the
+# disk and to make sure all changes to $value after the assignment are
+# reflected on disk. This may be counter-intuitive at first, but it is
+# correct dwimmery.
+# NOTE - simply tying $value won't perform a STORE on each value. Hence,
+# the copy to a temp value.
+sub _descend {
my $self = shift;
+ my ($value, $value_sector) = @_;
+ my $r = Scalar::Util::reftype( $value ) || '';
- # Read the header
- my $spot = $self->_read_file_header();
-
- my %types = (
- 0 => 'B',
- 1 => 'D',
- 2 => 'I',
- );
-
- my %sizes = (
- 'D' => $self->data_sector_size,
- 'B' => DBM::Deep::Engine::Sector::BucketList->new({engine=>$self,offset=>1})->size,
- 'I' => DBM::Deep::Engine::Sector::Index->new({engine=>$self,offset=>1})->size,
- );
-
- my $return = "";
-
- # Header values
- $return .= "NumTxns: " . $self->num_txns . $/;
-
- # Read the free sector chains
- my %sectors;
- foreach my $multiple ( 0 .. 2 ) {
- $return .= "Chains($types{$multiple}):";
- my $old_loc = $self->chains_loc + $multiple * $self->byte_size;
- while ( 1 ) {
- my $loc = unpack(
- $StP{$self->byte_size},
- $self->storage->read_at( $old_loc, $self->byte_size ),
- );
-
- # We're now out of free sectors of this kind.
- unless ( $loc ) {
- last;
- }
-
- $sectors{ $types{$multiple} }{ $loc } = undef;
- $old_loc = $loc + SIG_SIZE + $STALE_SIZE;
- $return .= " $loc";
- }
- $return .= $/;
+ if ( $r eq 'ARRAY' ) {
+ my @temp = @$value;
+ tie @$value, 'DBM::Deep', {
+ base_offset => $value_sector->offset,
+ staleness => $value_sector->staleness,
+ storage => $self->storage,
+ engine => $self,
+ };
+ @$value = @temp;
+ bless $value, 'DBM::Deep::Array' unless Scalar::Util::blessed( $value );
}
-
- SECTOR:
- while ( $spot < $self->storage->{end} ) {
- # Read each sector in order.
- my $sector = $self->_load_sector( $spot );
- if ( !$sector ) {
- # Find it in the free-sectors that were found already
- foreach my $type ( keys %sectors ) {
- if ( exists $sectors{$type}{$spot} ) {
- my $size = $sizes{$type};
- $return .= sprintf "%08d: %s %04d\n", $spot, 'F' . $type, $size;
- $spot += $size;
- next SECTOR;
- }
- }
-
- die "********\n$return\nDidn't find free sector for $spot in chains\n********\n";
- }
- else {
- $return .= sprintf "%08d: %s %04d", $spot, $sector->type, $sector->size;
- if ( $sector->type eq 'D' ) {
- $return .= ' ' . $sector->data;
- }
- elsif ( $sector->type eq 'A' || $sector->type eq 'H' ) {
- $return .= ' REF: ' . $sector->get_refcount;
- }
- elsif ( $sector->type eq 'B' ) {
- foreach my $bucket ( $sector->chopped_up ) {
- $return .= "\n ";
- $return .= sprintf "%08d", unpack($StP{$self->byte_size},
- substr( $bucket->[-1], $self->hash_size, $self->byte_size),
- );
- my $l = unpack( $StP{$self->byte_size},
- substr( $bucket->[-1],
- $self->hash_size + $self->byte_size,
- $self->byte_size,
- ),
- );
- $return .= sprintf " %08d", $l;
- foreach my $txn ( 0 .. $self->num_txns - 2 ) {
- my $l = unpack( $StP{$self->byte_size},
- substr( $bucket->[-1],
- $self->hash_size + 2 * $self->byte_size + $txn * ($self->byte_size + $STALE_SIZE),
- $self->byte_size,
- ),
- );
- $return .= sprintf " %08d", $l;
- }
- }
- }
- $return .= $/;
-
- $spot += $sector->size;
- }
+ elsif ( $r eq 'HASH' ) {
+ my %temp = %$value;
+ tie %$value, 'DBM::Deep', {
+ base_offset => $value_sector->offset,
+ staleness => $value_sector->staleness,
+ storage => $self->storage,
+ engine => $self,
+ };
+ %$value = %temp;
+ bless $value, 'DBM::Deep::Hash' unless Scalar::Util::blessed( $value );
}
- return $return;
+ return;
}
1;
projects / dbsrgits/DBM-Deep.git / blobdiff