X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBM%2FDeep%2FEngine.pm;h=0faa0d3d1c162fe4dc80c5067048d6e9456f497d;hb=97d40a0ac43400f8416c3e930c5626c5cb472a55;hp=19ac1fc1ba3c5070f3b1984820410a12e4270a8c;hpb=42f79e076d4d1843ff9bde87a7eceadf6f2a0720;p=dbsrgits%2FDBM-Deep.git

diff --git a/lib/DBM/Deep/Engine.pm b/lib/DBM/Deep/Engine.pm
index 19ac1fc..0faa0d3 100644
--- a/lib/DBM/Deep/Engine.pm
+++ b/lib/DBM/Deep/Engine.pm
@@ -1,14 +1,25 @@
 package DBM::Deep::Engine;
 
+use 5.006_000;
+
 use strict;
+use warnings FATAL => 'all';
+
+# Never import symbols into our namespace. We are a class, not a library.
+# -RobK, 2008-05-27
+use Scalar::Util ();
+
+#use Data::Dumper ();
 
-use Fcntl qw( :DEFAULT :flock :seek );
+# File-wide notes:
+# * Every method in here assumes that the storage has been appropriately
+#   safeguarded. This can be anything from flock() to some sort of manual
+#   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_INTERNAL () { 'i'    }
+sub SIG_HEADER   () { 'h'    }
 sub SIG_HASH     () { 'H'    }
 sub SIG_ARRAY    () { 'A'    }
 sub SIG_NULL     () { 'N'    }
@@ -18,1034 +29,879 @@ sub SIG_BLIST    () { 'B'    }
 sub SIG_FREE     () { 'F'    }
 sub SIG_SIZE     () {  1     }
 
-sub precalc_sizes {
-    ##
-    # Precalculate index, bucket and bucket list sizes
-    ##
-    my $self = shift;
-
-    $self->{index_size}       = (2**8) * $self->{long_size};
-    $self->{bucket_size}      = $self->{hash_size} + $self->{long_size} * 2;
-    $self->{bucket_list_size} = $self->{max_buckets} * $self->{bucket_size};
-
-    return 1;
-}
-
-sub set_pack {
-    ##
-    # Set pack/unpack modes (see file header for more)
-    ##
-    my $self = shift;
-    my ($long_s, $long_p, $data_s, $data_p) = @_;
-
-    ##
-    # Set to 4 and 'N' for 32-bit offset tags (default).  Theoretical limit of 4
-    # GB per file.
-    #    (Perl must be compiled with largefile support for files > 2 GB)
-    #
-    # Set to 8 and 'Q' for 64-bit offsets.  Theoretical limit of 16 XB per file.
-    #    (Perl must be compiled with largefile and 64-bit long support)
-    ##
-    $self->{long_size} = $long_s ? $long_s : 4;
-    $self->{long_pack} = $long_p ? $long_p : 'N';
-
-    ##
-    # Set to 4 and 'N' for 32-bit data length prefixes.  Limit of 4 GB for each
-    # key/value. Upgrading this is possible (see above) but probably not
-    # necessary. If you need more than 4 GB for a single key or value, this
-    # module is really not for you :-)
-    ##
-    $self->{data_size} = $data_s ? $data_s : 4;
-    $self->{data_pack} = $data_p ? $data_p : 'N';
-
-    return $self->precalc_sizes();
-}
-
-sub set_digest {
-    ##
-    # Set key digest function (default is MD5)
-    ##
-    my $self = shift;
-    my ($digest_func, $hash_size) = @_;
-
-    $self->{digest} = $digest_func ? $digest_func : \&Digest::MD5::md5;
-    $self->{hash_size} = $hash_size ? $hash_size : 16;
-
-    return $self->precalc_sizes();
-}
+our $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 StP { $StP{$_[1]} }
+
+# Import these after the SIG_* definitions because those definitions are used
+# in the headers of these classes. -RobK, 2008-06-20
+use DBM::Deep::Engine::Sector::BucketList;
+use DBM::Deep::Engine::Sector::FileHeader;
+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::Iterator;
+
+################################################################################
 
 sub new {
     my $class = shift;
     my ($args) = @_;
 
-    my $self = bless {
-        long_size   => 4,
-        long_pack   => 'N',
-        data_size   => 4,
-        data_pack   => 'N',
-
-        digest      => \&Digest::MD5::md5,
-        hash_size   => 16,
-
-        ##
-        # Maximum number of buckets per list before another level of indexing is
-        # done.
-        # Increase this value for slightly greater speed, but larger database
-        # files. DO NOT decrease this value below 16, due to risk of recursive
-        # reindex overrun.
-        ##
-        max_buckets => 16,
-    }, $class;
-
-    $self->precalc_sizes;
+    $args->{storage} = DBM::Deep::File->new( $args )
+        unless exists $args->{storage};
 
-    return $self;
-}
-
-sub write_file_signature {
-    my $self = shift;
-    my ($obj) = @_;
-
-    my $fh = $obj->_fh;
-
-    my $loc = $self->_request_space(
-        $obj, length( SIG_FILE ) + $self->{data_size},
-    );
-    seek($fh, $loc + $obj->_root->{file_offset}, SEEK_SET);
-    print( $fh SIG_FILE, pack($self->{data_pack}, 0) );
-
-    return;
-}
+    my $self = bless {
+        byte_size   => 4,
 
-sub read_file_signature {
-    my $self = shift;
-    my ($obj) = @_;
+        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
 
-    my $fh = $obj->_fh;
+        data_sector_size => 64, # Size in bytes of each data sector
 
-    seek($fh, 0 + $obj->_root->{file_offset}, SEEK_SET);
-    my $buffer;
-    my $bytes_read = read(
-        $fh, $buffer, length(SIG_FILE) + $self->{data_size},
-    );
+        entries => {}, # This is the list of entries for transactions
+        storage => undef,
+    }, $class;
 
-    if ( $bytes_read ) {
-        my ($signature, $version) = unpack( "A4 $self->{data_pack}", $buffer );
-        unless ($signature eq SIG_FILE) {
-            $self->close_fh( $obj );
-            $obj->_throw_error("Signature not found -- file is not a Deep DB");
+    # 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}'" );
         }
     }
 
-    return $bytes_read;
-}
-
-sub setup_fh {
-    my $self = shift;
-    my ($obj) = @_;
-
-    $self->open( $obj ) if !defined $obj->_fh;
-
-    my $fh = $obj->_fh;
-    flock $fh, LOCK_EX;
-
-    unless ( $obj->{base_offset} ) {
-        my $bytes_read = $self->read_file_signature( $obj );
-
-        ##
-        # File is empty -- write signature and master index
-        ##
-        if (!$bytes_read) {
-            $self->write_file_signature( $obj );
-
-            $obj->{base_offset} = $self->_request_space(
-                $obj, $self->tag_size( $self->{index_size} ),
-            );
+    # Grab the parameters we want to use
+    foreach my $param ( keys %$self ) {
+        next unless exists $args->{$param};
+        $self->{$param} = $args->{$param};
+    }
 
-            $self->write_tag(
-                $obj, $obj->_base_offset, $obj->_type,
-                chr(0)x$self->{index_size},
-            );
+    my %validations = (
+        max_buckets      => { floor => 16, ceil => 256 },
+        num_txns         => { floor => 1,  ceil => 255 },
+        data_sector_size => { floor => 32, ceil => 256 },
+    );
 
-            # Flush the filehandle
-            my $old_fh = select $fh;
-            my $old_af = $|; $| = 1; $| = $old_af;
-            select $old_fh;
+    while ( my ($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};
         }
-        else {
-            $obj->{base_offset} = $bytes_read;
-
-            ##
-            # Get our type from master index signature
-            ##
-            my $tag = $self->load_tag($obj, $obj->_base_offset)
-            or $obj->_throw_error("Corrupted file, no master index record");
-
-            unless ($obj->{type} eq $tag->{signature}) {
-                $obj->_throw_error("File type mismatch");
-            }
+        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};
         }
     }
 
-    #XXX We have to make sure we don't mess up when autoflush isn't turned on
-    unless ( $obj->_root->{inode} ) {
-        my @stats = stat($obj->_fh);
-        $obj->_root->{inode} = $stats[1];
-        $obj->_root->{end} = $stats[7];
+    if ( !$self->{digest} ) {
+        require Digest::MD5;
+        $self->{digest} = \&Digest::MD5::md5;
     }
 
-    flock $fh, LOCK_UN;
-
-    return 1;
+    return $self;
 }
 
-sub open {
-    ##
-    # Open a fh to the database, create if nonexistent.
-    # Make sure file signature matches DBM::Deep spec.
-    ##
-    my $self = shift;
-    my ($obj) = @_;
-
-    # Theoretically, adding O_BINARY should remove the need for the binmode
-    # Of course, testing it is going to be ... interesting.
-    my $flags = O_RDWR | O_CREAT | O_BINARY;
+################################################################################
 
-    my $fh;
-    my $filename = $obj->_root->{file};
-    sysopen( $fh, $filename, $flags )
-        or $obj->_throw_error("Cannot sysopen file '$filename': $!");
-    $obj->_root->{fh} = $fh;
+sub read_value {
+    my $self = shift;
+    my ($obj, $key) = @_;
 
-    # Even though we use O_BINARY, better be safe than sorry.
-    binmode $fh;
+    # This will be a Reference sector
+    my $sector = $self->_load_sector( $obj->_base_offset )
+        or return;
 
-    if ($obj->_root->{autoflush}) {
-        my $old = select $fh;
-        $|=1;
-        select $old;
+    if ( $sector->staleness != $obj->_staleness ) {
+        return;
     }
 
-    return 1;
-}
+    my $key_md5 = $self->_apply_digest( $key );
 
-sub close_fh {
-    my $self = shift;
-    my ($obj) = @_;
+    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,
+        });
 
-    if ( my $fh = $obj->_root->{fh} ) {
-        close $fh;
+        $sector->write_data({
+            key_md5 => $key_md5,
+            key     => $key,
+            value   => $value_sector,
+        });
     }
-    $obj->_root->{fh} = undef;
 
-    return 1;
+    return $value_sector->data;
 }
 
-sub tag_size {
+sub get_classname {
     my $self = shift;
-    my ($size) = @_;
-    return SIG_SIZE + $self->{data_size} + $size;
-}
-
-sub write_tag {
-    ##
-    # Given offset, signature and content, create tag and write to disk
-    ##
-    my $self = shift;
-    my ($obj, $offset, $sig, $content) = @_;
-    my $size = length( $content );
+    my ($obj) = @_;
 
-    my $fh = $obj->_fh;
+    # 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 ( defined $offset ) {
-        seek($fh, $offset + $obj->_root->{file_offset}, SEEK_SET);
+    if ( $sector->staleness != $obj->_staleness ) {
+        return;
     }
 
-    print( $fh $sig . pack($self->{data_pack}, $size) . $content );
-
-    return unless defined $offset;
-
-    return {
-        signature => $sig,
-        size => $size,
-        offset => $offset + SIG_SIZE + $self->{data_size},
-        content => $content
-    };
+    return $sector->get_classname;
 }
 
-sub load_tag {
-    ##
-    # Given offset, load single tag and return signature, size and data
-    ##
+sub make_reference {
     my $self = shift;
-    my ($obj, $offset) = @_;
+    my ($obj, $old_key, $new_key) = @_;
 
-#    print join(':',map{$_||''}caller(1)), $/;
+    # 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')?!" );
 
-    my $fh = $obj->_fh;
+    if ( $sector->staleness != $obj->_staleness ) {
+        return;
+    }
 
-    seek($fh, $offset + $obj->_root->{file_offset}, SEEK_SET);
+    my $old_md5 = $self->_apply_digest( $old_key );
 
-    #XXX I'm not sure this check will work if autoflush isn't enabled ...
-    return if eof $fh;
+    my $value_sector = $sector->get_data_for({
+        key_md5    => $old_md5,
+        allow_head => 1,
+    });
 
-    my $b;
-    read( $fh, $b, SIG_SIZE + $self->{data_size} );
-    my ($sig, $size) = unpack( "A $self->{data_pack}", $b );
+    unless ( $value_sector ) {
+        $value_sector = DBM::Deep::Engine::Sector::Null->new({
+            engine => $self,
+            data   => undef,
+        });
 
-    my $buffer;
-    read( $fh, $buffer, $size);
+        $sector->write_data({
+            key_md5 => $old_md5,
+            key     => $old_key,
+            value   => $value_sector,
+        });
+    }
 
-    return {
-        signature => $sig,
-        size => $size,
-        offset => $offset + SIG_SIZE + $self->{data_size},
-        content => $buffer
-    };
+    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,
+        });
+    }
 }
 
-sub _length_needed {
+sub key_exists {
     my $self = shift;
-    my ($obj, $value, $key) = @_;
+    my ($obj, $key) = @_;
 
-    my $is_dbm_deep = eval {
-        local $SIG{'__DIE__'};
-        $value->isa( 'DBM::Deep' );
-    };
+    # This will be a Reference sector
+    my $sector = $self->_load_sector( $obj->_base_offset )
+        or return '';
 
-    my $len = SIG_SIZE + $self->{data_size}
-            + $self->{data_size} + length( $key );
-
-    if ( $is_dbm_deep && $value->_root eq $obj->_root ) {
-        return $len + $self->{long_size};
+    if ( $sector->staleness != $obj->_staleness ) {
+        return '';
     }
 
-    my $r = Scalar::Util::reftype( $value ) || '';
-    if ( $obj->_root->{autobless} ) {
-        # This is for the bit saying whether or not this thing is blessed.
-        $len += 1;
-    }
+    my $data = $sector->get_data_for({
+        key_md5    => $self->_apply_digest( $key ),
+        allow_head => 1,
+    });
 
-    unless ( $r eq 'HASH' || $r eq 'ARRAY' ) {
-        if ( defined $value ) {
-            $len += length( $value );
-        }
-        return $len;
-    }
+    # exists() returns 1 or '' for true/false.
+    return $data ? 1 : '';
+}
 
-    $len += $self->{index_size};
+sub delete_key {
+    my $self = shift;
+    my ($obj, $key) = @_;
 
-    # if autobless is enabled, must also take into consideration
-    # the class name as it is stored after the key.
-    if ( $obj->_root->{autobless} ) {
-        my $value_class = Scalar::Util::blessed($value);
-        if ( defined $value_class && !$is_dbm_deep ) {
-            $len += $self->{data_size} + length($value_class);
-        }
+    my $sector = $self->_load_sector( $obj->_base_offset )
+        or return;
+
+    if ( $sector->staleness != $obj->_staleness ) {
+        return;
     }
 
-    return $len;
+    return $sector->delete_key({
+        key_md5    => $self->_apply_digest( $key ),
+        allow_head => 0,
+    });
 }
 
-sub add_bucket {
-    ##
-    # Adds one key/value pair to bucket list, given offset, MD5 digest of key,
-    # plain (undigested) key and value.
-    ##
+sub write_value {
     my $self = shift;
-    my ($obj, $tag, $md5, $plain_key, $value) = @_;
+    my ($obj, $key, $value) = @_;
 
-    # This verifies that only supported values will be stored.
+    my $r = Scalar::Util::reftype( $value ) || '';
     {
-        my $r = Scalar::Util::reftype( $value );
-        last if !defined $r;
-
+        last if $r eq '';
         last if $r eq 'HASH';
         last if $r eq 'ARRAY';
 
-        $obj->_throw_error(
-            "Storage of variables of type '$r' is not supported."
+        DBM::Deep->_throw_error(
+            "Storage of references of type '$r' is not supported."
         );
     }
 
-    my $location = 0;
-    my $result = 2;
+    # This will be a Reference sector
+    my $sector = $self->_load_sector( $obj->_base_offset )
+        or DBM::Deep->_throw_error( "1: Cannot write to a deleted spot in DBM::Deep." );
 
-    my $root = $obj->_root;
-    my $fh   = $obj->_fh;
+    if ( $sector->staleness != $obj->_staleness ) {
+        DBM::Deep->_throw_error( "2: Cannot write to a deleted spot in DBM::Deep." );
+    }
 
-    my $actual_length = $self->_length_needed( $obj, $value, $plain_key );
+    my ($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;
+        }
 
-    my ($subloc, $offset, $size) = $self->_find_in_buckets( $tag, $md5 );
+        if ( $tmpvar ) {
+            my $is_dbm_deep = eval { local $SIG{'__DIE__'}; $tmpvar->isa( 'DBM::Deep' ); };
 
-#    $self->_release_space( $obj, $size, $subloc );
-    # Updating a known md5
-#XXX This needs updating to use _release_space
-    if ( $subloc ) {
-        $result = 1;
+            unless ( $is_dbm_deep ) {
+                DBM::Deep->_throw_error( "Cannot store something that is tied." );
+            }
 
-        if ($actual_length <= $size) {
-            $location = $subloc;
-        }
-        else {
-            $location = $self->_request_space( $obj, $actual_length );
-            seek(
-                $fh,
-                $tag->{offset} + $offset
-              + $self->{hash_size} + $root->{file_offset},
-                SEEK_SET,
-            );
-            print( $fh pack($self->{long_pack}, $location ) );
-            print( $fh pack($self->{long_pack}, $actual_length ) );
-        }
-    }
-    # Adding a new md5
-    elsif ( defined $offset ) {
-        $location = $self->_request_space( $obj, $actual_length );
+            unless ( $tmpvar->_engine->storage == $self->storage ) {
+                DBM::Deep->_throw_error( "Cannot store values across DBM::Deep files. Please use export() instead." );
+            }
 
-        seek( $fh, $tag->{offset} + $offset + $root->{file_offset}, SEEK_SET );
-        print( $fh $md5 . pack($self->{long_pack}, $location ) );
-        print( $fh pack($self->{long_pack}, $actual_length ) );
-    }
-    # If bucket didn't fit into list, split into a new index level
-    # split_index() will do the _request_space() call
-    else {
-        $location = $self->split_index( $obj, $md5, $tag );
-    }
+            # 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,
+            });
 
-    $self->write_value( $obj, $location, $plain_key, $value );
+            if ( defined($loc) && $loc == $tmpvar->_base_offset ) {
+                return 1;
+            }
 
-    return $result;
-}
+            #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;
 
-sub _get_tied {
-    my $item = shift;
-    my $r = Scalar::Util::reftype( $item ) || return;
-    if ( $r eq 'HASH' ) {
-        return tied(%$item);
-    }
-    elsif ( $r eq 'ARRAY' ) {
-        return tied(@$item);
+            return 1;
+        }
+
+        $class = 'DBM::Deep::Engine::Sector::Reference';
+        $type = substr( $r, 0, 1 );
     }
     else {
-        return;
-    };
-}
-
-sub _get_dbm_object {
-    my $item = shift;
-
-    my $obj = eval {
-        local $SIG{__DIE__};
-        if ($item->isa( 'DBM::Deep' )) {
-            return $item;
+        if ( tied($value) ) {
+            DBM::Deep->_throw_error( "Cannot store something that is tied." );
         }
-        return;
-    };
-    return $obj if $obj;
-
-    my $r = Scalar::Util::reftype( $item ) || '';
-    if ( $r eq 'HASH' ) {
-        my $obj = eval {
-            local $SIG{__DIE__};
-            my $obj = tied(%$item);
-            if ($obj->isa( 'DBM::Deep' )) {
-                return $obj;
-            }
-            return;
+        $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,
         };
-        return $obj if $obj;
+        @$value = @temp;
+        bless $value, 'DBM::Deep::Array' unless Scalar::Util::blessed( $value );
     }
-    elsif ( $r eq 'ARRAY' ) {
-        my $obj = eval {
-            local $SIG{__DIE__};
-            my $obj = tied(@$item);
-            if ($obj->isa( 'DBM::Deep' )) {
-                return $obj;
-            }
-            return;
+    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,
         };
-        return $obj if $obj;
+
+        %$value = %temp;
+        bless $value, 'DBM::Deep::Hash' unless Scalar::Util::blessed( $value );
     }
 
-    return;
+    return 1;
 }
 
-sub write_value {
+# XXX Add staleness here
+sub get_next_key {
     my $self = shift;
-    my ($obj, $location, $key, $value) = @_;
+    my ($obj, $prev_key) = @_;
 
-    my $fh = $obj->_fh;
-    my $root = $obj->_root;
-
-    my $dbm_deep_obj = _get_dbm_object( $value );
-    if ( $dbm_deep_obj && $dbm_deep_obj->_root ne $obj->_root ) {
-        $obj->_throw_error( "Cannot cross-reference. Use export() instead" );
+    # XXX Need to add logic about resetting the iterator if any key in the reference has changed
+    unless ( $prev_key ) {
+        $obj->{iterator} = DBM::Deep::Iterator->new({
+            base_offset => $obj->_base_offset,
+            engine      => $self,
+        });
     }
 
-    seek($fh, $location + $root->{file_offset}, SEEK_SET);
+    return $obj->{iterator}->get_next_key( $obj );
+}
 
-    ##
-    # Write signature based on content type, set content length and write
-    # actual value.
-    ##
-    my $r = Scalar::Util::reftype( $value ) || '';
-    if ( $dbm_deep_obj ) {
-        $self->write_tag( $obj, undef, SIG_INTERNAL,pack($self->{long_pack}, $dbm_deep_obj->_base_offset) );
-    }
-    elsif ($r eq 'HASH') {
-        if ( !$dbm_deep_obj && tied %{$value} ) {
-            $obj->_throw_error( "Cannot store something that is tied" );
-        }
-        $self->write_tag( $obj, undef, SIG_HASH, chr(0)x$self->{index_size} );
-    }
-    elsif ($r eq 'ARRAY') {
-        if ( !$dbm_deep_obj && tied @{$value} ) {
-            $obj->_throw_error( "Cannot store something that is tied" );
-        }
-        $self->write_tag( $obj, undef, SIG_ARRAY, chr(0)x$self->{index_size} );
-    }
-    elsif (!defined($value)) {
-        $self->write_tag( $obj, undef, SIG_NULL, '' );
+################################################################################
+
+sub setup_fh {
+    my $self = shift;
+    my ($obj) = @_;
+
+    return 1 if $obj->_base_offset;
+
+    my $header = $self->_load_header;
+
+    # Creating a new file
+    if ( $header->is_new ) {
+        # 1) Create Array/Hash entry
+        my $sector = DBM::Deep::Engine::Sector::Reference->new({
+            engine => $self,
+            type   => $obj->_type,
+        });
+        $obj->{base_offset} = $sector->offset;
+        $obj->{staleness} = $sector->staleness;
+
+        $self->flush;
     }
+    # Reading from an existing file
     else {
-        $self->write_tag( $obj, undef, SIG_DATA, $value );
-    }
-
-    ##
-    # Plain key is stored AFTER value, as keys are typically fetched less often.
-    ##
-    print( $fh pack($self->{data_pack}, length($key)) . $key );
-
-    # Internal references don't care about autobless
-    return 1 if $dbm_deep_obj;
-
-    ##
-    # If value is blessed, preserve class name
-    ##
-    if ( $root->{autobless} ) {
-        my $value_class = Scalar::Util::blessed($value);
-        if ( defined $value_class && !$dbm_deep_obj ) {
-            print( $fh chr(1) );
-            print( $fh pack($self->{data_pack}, length($value_class)) . $value_class );
+        $obj->{base_offset} = $header->size;
+        my $sector = DBM::Deep::Engine::Sector::Reference->new({
+            engine => $self,
+            offset => $obj->_base_offset,
+        });
+        unless ( $sector ) {
+            DBM::Deep->_throw_error("Corrupted file, no master index record");
         }
-        else {
-            print( $fh chr(0) );
+
+        unless ($obj->_type eq $sector->type) {
+            DBM::Deep->_throw_error("File type mismatch");
         }
-    }
 
-    ##
-    # If content is a hash or array, create new child DBM::Deep object and
-    # pass each key or element to it.
-    ##
-    if ($r eq 'HASH') {
-        my %x = %$value;
-        tie %$value, 'DBM::Deep', {
-            base_offset => $location,
-            root => $root,
-        };
-        %$value = %x;
-    }
-    elsif ($r eq 'ARRAY') {
-        my @x = @$value;
-        tie @$value, 'DBM::Deep', {
-            base_offset => $location,
-            root => $root,
-        };
-        @$value = @x;
+        $obj->{staleness} = $sector->staleness;
     }
 
+    $self->storage->set_inode;
+
     return 1;
 }
 
-sub split_index {
+sub begin_work {
     my $self = shift;
-    my ($obj, $md5, $tag) = @_;
-
-    my $fh = $obj->_fh;
-    my $root = $obj->_root;
+    my ($obj) = @_;
 
-    my $loc = $self->_request_space(
-        $obj, $self->tag_size( $self->{index_size} ),
-    );
+    if ( $self->trans_id ) {
+        DBM::Deep->_throw_error( "Cannot begin_work within an active transaction" );
+    }
 
-    seek($fh, $tag->{ref_loc} + $root->{file_offset}, SEEK_SET);
-    print( $fh pack($self->{long_pack}, $loc) );
+    my @slots = $self->read_txn_slots;
+    my $found;
+    for my $i ( 0 .. $#slots ) {
+        next if $slots[$i];
 
-    my $index_tag = $self->write_tag(
-        $obj, $loc, SIG_INDEX,
-        chr(0)x$self->{index_size},
-    );
+        $slots[$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 );
 
-    my $newtag_loc = $self->_request_space(
-        $obj, $self->tag_size( $self->{bucket_list_size} ),
-    );
+    if ( !$self->trans_id ) {
+        DBM::Deep->_throw_error( "Cannot begin_work - no available transactions" );
+    }
 
-    my $keys = $tag->{content}
-             . $md5 . pack($self->{long_pack}, $newtag_loc)
-                    . pack($self->{long_pack}, 0);
+    return;
+}
 
-    my @newloc = ();
-    BUCKET:
-    for (my $i = 0; $i <= $self->{max_buckets}; $i++) {
-        my ($key, $old_subloc, $size) = $self->_get_key_subloc( $keys, $i );
+sub rollback {
+    my $self = shift;
+    my ($obj) = @_;
 
-        die "[INTERNAL ERROR]: No key in split_index()\n" unless $key;
-        die "[INTERNAL ERROR]: No subloc in split_index()\n" unless $old_subloc;
+    if ( !$self->trans_id ) {
+        DBM::Deep->_throw_error( "Cannot rollback without an active transaction" );
+    }
 
-        my $num = ord(substr($key, $tag->{ch} + 1, 1));
+    foreach my $entry ( @{ $self->get_entries } ) {
+        my ($sector, $idx) = split ':', $entry;
+        $self->_load_sector( $sector )->rollback( $idx );
+    }
 
-        if ($newloc[$num]) {
-            seek($fh, $newloc[$num] + $root->{file_offset}, SEEK_SET);
-            my $subkeys;
-            read( $fh, $subkeys, $self->{bucket_list_size});
+    $self->clear_entries;
 
-            # This is looking for the first empty spot
-            my ($subloc, $offset, $size) = $self->_find_in_buckets(
-                { content => $subkeys }, '',
-            );
+    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 );
 
-            seek($fh, $newloc[$num] + $offset + $root->{file_offset}, SEEK_SET);
-            print( $fh $key . pack($self->{long_pack}, $old_subloc) );
+    return 1;
+}
 
-            next;
-        }
+sub commit {
+    my $self = shift;
+    my ($obj) = @_;
 
-        seek($fh, $index_tag->{offset} + ($num * $self->{long_size}) + $root->{file_offset}, SEEK_SET);
+    if ( !$self->trans_id ) {
+        DBM::Deep->_throw_error( "Cannot commit without an active transaction" );
+    }
 
-        my $loc = $self->_request_space(
-            $obj, $self->tag_size( $self->{bucket_list_size} ),
-        );
+    foreach my $entry ( @{ $self->get_entries } ) {
+        my ($sector, $idx) = split ':', $entry;
+        $self->_load_sector( $sector )->commit( $idx );
+    }
 
-        print( $fh pack($self->{long_pack}, $loc) );
+    $self->clear_entries;
 
-        my $blist_tag = $self->write_tag(
-            $obj, $loc, SIG_BLIST,
-            chr(0)x$self->{bucket_list_size},
-        );
+    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 );
 
-        seek($fh, $blist_tag->{offset} + $root->{file_offset}, SEEK_SET);
-        print( $fh $key . pack($self->{long_pack}, $old_subloc) );
+    return 1;
+}
 
-        $newloc[$num] = $blist_tag->{offset};
-    }
+sub read_txn_slots {
+    my $self = shift;
+    return $self->_load_header->read_txn_slots(@_);
+}
 
-    $self->_release_space(
-        $obj, $self->tag_size( $self->{bucket_list_size} ),
-        $tag->{offset} - SIG_SIZE - $self->{data_size},
-    );
+sub write_txn_slots {
+    my $self = shift;
+    return $self->_load_header->write_txn_slots(@_);
+}
 
-    return $newtag_loc;
+sub get_running_txn_ids {
+    my $self = shift;
+    my @transactions = $self->read_txn_slots;
+    my @trans_ids = map { $_+1} grep { $transactions[$_] } 0 .. $#transactions;
 }
 
-sub read_from_loc {
+sub get_txn_staleness_counter {
     my $self = shift;
-    my ($obj, $subloc) = @_;
-
-    my $fh = $obj->_fh;
-
-    ##
-    # Found match -- seek to offset and read signature
-    ##
-    my $signature;
-    seek($fh, $subloc + $obj->_root->{file_offset}, SEEK_SET);
-    read( $fh, $signature, SIG_SIZE);
-
-    ##
-    # If value is a hash or array, return new DBM::Deep object with correct offset
-    ##
-    if (($signature eq SIG_HASH) || ($signature eq SIG_ARRAY)) {
-        my $new_obj = DBM::Deep->new({
-            type => $signature,
-            base_offset => $subloc,
-            root => $obj->_root,
-        });
+    return $self->_load_header->get_txn_staleness_counter(@_);
+}
 
-        if ($new_obj->_root->{autobless}) {
-            ##
-            # Skip over value and plain key to see if object needs
-            # to be re-blessed
-            ##
-            seek($fh, $self->{data_size} + $self->{index_size}, SEEK_CUR);
-
-            my $size;
-            read( $fh, $size, $self->{data_size});
-            $size = unpack($self->{data_pack}, $size);
-            if ($size) { seek($fh, $size, SEEK_CUR); }
-
-            my $bless_bit;
-            read( $fh, $bless_bit, 1);
-            if (ord($bless_bit)) {
-                ##
-                # Yes, object needs to be re-blessed
-                ##
-                my $class_name;
-                read( $fh, $size, $self->{data_size});
-                $size = unpack($self->{data_pack}, $size);
-                if ($size) { read( $fh, $class_name, $size); }
-                if ($class_name) { $new_obj = bless( $new_obj, $class_name ); }
-            }
-        }
+sub inc_txn_staleness_counter {
+    my $self = shift;
+    return $self->_load_header->inc_txn_staleness_counter(@_);
+}
 
-        return $new_obj;
-    }
-    elsif ( $signature eq SIG_INTERNAL ) {
-        my $size;
-        read( $fh, $size, $self->{data_size});
-        $size = unpack($self->{data_pack}, $size);
+sub get_entries {
+    my $self = shift;
+    return [ keys %{ $self->{entries}{$self->trans_id} ||= {} } ];
+}
 
-        if ( $size ) {
-            my $new_loc;
-            read( $fh, $new_loc, $size );
-            $new_loc = unpack( $self->{long_pack}, $new_loc );
+sub add_entry {
+    my $self = shift;
+    my ($trans_id, $loc, $idx) = @_;
 
-            return $self->read_from_loc( $obj, $new_loc );
-        }
-        else {
-            return;
-        }
-    }
-    ##
-    # Otherwise return actual value
-    ##
-    elsif ($signature eq SIG_DATA) {
-        my $size;
-        read( $fh, $size, $self->{data_size});
-        $size = unpack($self->{data_pack}, $size);
-
-        my $value = '';
-        if ($size) { read( $fh, $value, $size); }
-        return $value;
-    }
+    return unless $trans_id;
 
-    ##
-    # Key exists, but content is null
-    ##
-    return;
+    $self->{entries}{$trans_id} ||= {};
+    $self->{entries}{$trans_id}{"$loc:$idx"} = undef;
 }
 
-sub get_bucket_value {
-    ##
-    # Fetch single value given tag and MD5 digested key.
-    ##
+# If the buckets are being relocated because of a reindexing, the entries
+# mechanism needs to be made aware of it.
+sub reindex_entry {
     my $self = shift;
-    my ($obj, $tag, $md5) = @_;
-
-    my ($subloc, $offset, $size) = $self->_find_in_buckets( $tag, $md5 );
-    if ( $subloc ) {
-        return $self->read_from_loc( $obj, $subloc );
+    my ($old_loc, $old_idx, $new_loc, $new_idx) = @_;
+
+    TRANS:
+    while ( my ($trans_id, $locs) = each %{ $self->{entries} } ) {
+        if ( exists $locs->{"$old_loc:$old_idx"} ) {
+            delete $locs->{"$old_loc:$old_idx"};
+            $locs->{"$new_loc:$new_idx"} = undef;
+            next TRANS;
+        }
     }
-    return;
 }
 
-sub delete_bucket {
-    ##
-    # Delete single key/value pair given tag and MD5 digested key.
-    ##
+sub clear_entries {
     my $self = shift;
-    my ($obj, $tag, $md5) = @_;
-
-    my ($subloc, $offset, $size) = $self->_find_in_buckets( $tag, $md5 );
-#XXX This needs _release_space()
-    if ( $subloc ) {
-        my $fh = $obj->_fh;
-        seek($fh, $tag->{offset} + $offset + $obj->_root->{file_offset}, SEEK_SET);
-        print( $fh substr($tag->{content}, $offset + $self->{bucket_size} ) );
-        print( $fh chr(0) x $self->{bucket_size} );
-
-        return 1;
-    }
-    return;
+    delete $self->{entries}{$self->trans_id};
 }
 
-sub bucket_exists {
-    ##
-    # Check existence of single key given tag and MD5 digested key.
-    ##
-    my $self = shift;
-    my ($obj, $tag, $md5) = @_;
+################################################################################
 
-    my ($subloc, $offset, $size) = $self->_find_in_buckets( $tag, $md5 );
-    return $subloc && 1;
+sub _apply_digest {
+    my $self = shift;
+    return $self->{digest}->(@_);
 }
 
-sub find_bucket_list {
-    ##
-    # Locate offset for bucket list, given digested key
-    ##
-    my $self = shift;
-    my ($obj, $md5, $args) = @_;
-    $args = {} unless $args;
+sub _add_free_blist_sector { shift->_add_free_sector( 0, @_ ) }
+sub _add_free_data_sector  { shift->_add_free_sector( 1, @_ ) }
+sub _add_free_index_sector { shift->_add_free_sector( 2, @_ ) }
+sub _add_free_sector       { shift->_load_header->add_free_sector( @_ ) }
+
+sub _request_blist_sector { shift->_request_sector( 0, @_ ) }
+sub _request_data_sector  { shift->_request_sector( 1, @_ ) }
+sub _request_index_sector { shift->_request_sector( 2, @_ ) }
+sub _request_sector       { shift->_load_header->request_sector( @_ ) }
+
+################################################################################
+
+{
+    my %t = (
+        SIG_ARRAY => 'Reference',
+        SIG_HASH  => 'Reference',
+        SIG_BLIST => 'BucketList',
+        SIG_INDEX => 'Index',
+        SIG_NULL  => 'Null',
+        SIG_DATA  => 'Scalar',
+    );
+
+    my %class_for;
+    while ( my ($k,$v) = each %t ) {
+        $class_for{ DBM::Deep::Engine->$k } = "DBM::Deep::Engine::Sector::$v";
+    }
 
-    ##
-    # Locate offset for bucket list using digest index system
-    ##
-    my $tag = $self->load_tag($obj, $obj->_base_offset)
-        or $obj->_throw_error( "INTERNAL ERROR - Cannot find tag" );
+    sub load_sector {
+        my $self = shift;
+        my ($offset) = @_;
 
-    my $ch = 0;
-    while ($tag->{signature} ne SIG_BLIST) {
-        my $num = ord substr($md5, $ch, 1);
+        my $data = $self->get_data( $offset )
+            or return;#die "Cannot read from '$offset'\n";
+        my $type = substr( $$data, 0, 1 );
+        my $class = $class_for{ $type };
+        return $class->new({
+            engine => $self,
+            type   => $type,
+            offset => $offset,
+        });
+    }
+    *_load_sector = \&load_sector;
 
-        my $ref_loc = $tag->{offset} + ($num * $self->{long_size});
-        $tag = $self->index_lookup( $obj, $tag, $num );
+    sub load_header {
+        my $self = shift;
 
-        if (!$tag) {
-            return if !$args->{create};
+        #XXX Does this mean we make too many objects? -RobK, 2008-06-23
+        return DBM::Deep::Engine::Sector::FileHeader->new({
+            engine => $self,
+            offset => 0,
+        });
+    }
+    *_load_header = \&load_header;
 
-            my $loc = $self->_request_space(
-                $obj, $self->tag_size( $self->{bucket_list_size} ),
-            );
+    sub get_data {
+        my $self = shift;
+        my ($offset, $size) = @_;
+        return unless defined $offset;
 
-            my $fh = $obj->_fh;
-            seek($fh, $ref_loc + $obj->_root->{file_offset}, SEEK_SET);
-            print( $fh pack($self->{long_pack}, $loc) );
+        unless ( exists $self->sector_cache->{$offset} ) {
+            # Don't worry about the header sector. It will manage itself.
+            return unless $offset;
 
-            $tag = $self->write_tag(
-                $obj, $loc, SIG_BLIST,
-                chr(0)x$self->{bucket_list_size},
-            );
+            if ( !defined $size ) {
+                my $type = $self->storage->read_at( $offset, 1 )
+                    or die "($offset): Cannot read from '$offset' to find the type\n";
 
-            $tag->{ref_loc} = $ref_loc;
-            $tag->{ch} = $ch;
+                if ( $type eq $self->SIG_FREE ) {
+                    return;
+                }
 
-            last;
+                my $class = $class_for{$type}
+                    or die "($offset): Cannot find class for '$type'\n";
+                $size = $class->size( $self )
+                    or die "($offset): '$class' doesn't return a size\n";
+                $self->sector_cache->{$offset} = $type . $self->storage->read_at( undef, $size - 1 );
+            }
+            else {
+                $self->sector_cache->{$offset} = $self->storage->read_at( $offset, $size )
+                    or return;
+            }
         }
 
-        $tag->{ch} = $ch++;
-        $tag->{ref_loc} = $ref_loc;
+        return \$self->sector_cache->{$offset};
     }
-
-    return $tag;
 }
 
-sub index_lookup {
-    ##
-    # Given index tag, lookup single entry in index and return .
-    ##
+sub sector_cache {
     my $self = shift;
-    my ($obj, $tag, $index) = @_;
-
-    my $location = unpack(
-        $self->{long_pack},
-        substr(
-            $tag->{content},
-            $index * $self->{long_size},
-            $self->{long_size},
-        ),
-    );
+    return $self->{sector_cache} ||= {};
+}
 
-    if (!$location) { return; }
+sub clear_sector_cache {
+    my $self = shift;
+    $self->{sector_cache} = {};
+}
 
-    return $self->load_tag( $obj, $location );
+sub dirty_sectors {
+    my $self = shift;
+    return $self->{dirty_sectors} ||= {};
 }
 
-sub traverse_index {
-    ##
-    # Scan index and recursively step into deeper levels, looking for next key.
-    ##
+sub clear_dirty_sectors {
     my $self = shift;
-    my ($obj, $offset, $ch, $force_return_next) = @_;
+    $self->{dirty_sectors} = {};
+}
 
-    my $tag = $self->load_tag($obj, $offset );
+sub add_dirty_sector {
+    my $self = shift;
+    my ($offset) = @_;
 
-    my $fh = $obj->_fh;
+    $self->dirty_sectors->{ $offset } = undef;
+}
 
-    if ($tag->{signature} ne SIG_BLIST) {
-        my $content = $tag->{content};
-        my $start = $obj->{return_next} ? 0 : ord(substr($obj->{prev_md5}, $ch, 1));
+sub flush {
+    my $self = shift;
 
-        for (my $idx = $start; $idx < (2**8); $idx++) {
-            my $subloc = unpack(
-                $self->{long_pack},
-                substr(
-                    $content,
-                    $idx * $self->{long_size},
-                    $self->{long_size},
-                ),
-            );
+    my $sectors = $self->dirty_sectors;
+    for my $offset (sort { $a <=> $b } keys %{ $sectors }) {
+        $self->storage->print_at( $offset, $self->sector_cache->{$offset} );
+    }
 
-            if ($subloc) {
-                my $result = $self->traverse_index(
-                    $obj, $subloc, $ch + 1, $force_return_next,
-                );
+    # Why do we need to have the storage flush? Shouldn't autoflush take care of things?
+    # -RobK, 2008-06-26
+    $self->storage->flush;
 
-                if (defined($result)) { return $result; }
-            }
-        } # index loop
+    $self->clear_dirty_sectors;
 
-        $obj->{return_next} = 1;
-    } # tag is an index
+    $self->clear_sector_cache;
+}
 
-    else {
-        my $keys = $tag->{content};
-        if ($force_return_next) { $obj->{return_next} = 1; }
-
-        ##
-        # Iterate through buckets, looking for a key match
-        ##
-        for (my $i = 0; $i < $self->{max_buckets}; $i++) {
-            my ($key, $subloc) = $self->_get_key_subloc( $keys, $i );
-
-            # End of bucket list -- return to outer loop
-            if (!$subloc) {
-                $obj->{return_next} = 1;
-                last;
-            }
-            # Located previous key -- return next one found
-            elsif ($key eq $obj->{prev_md5}) {
-                $obj->{return_next} = 1;
-                next;
-            }
-            # Seek to bucket location and skip over signature
-            elsif ($obj->{return_next}) {
-                seek($fh, $subloc + $obj->_root->{file_offset}, SEEK_SET);
-
-                # Skip over value to get to plain key
-                my $sig;
-                read( $fh, $sig, SIG_SIZE );
-
-                my $size;
-                read( $fh, $size, $self->{data_size});
-                $size = unpack($self->{data_pack}, $size);
-                if ($size) { seek($fh, $size, SEEK_CUR); }
-
-                # Read in plain key and return as scalar
-                my $plain_key;
-                read( $fh, $size, $self->{data_size});
-                $size = unpack($self->{data_pack}, $size);
-                if ($size) { read( $fh, $plain_key, $size); }
-
-                return $plain_key;
-            }
-        }
+################################################################################
 
-        $obj->{return_next} = 1;
-    } # tag is a bucket list
+sub lock_exclusive {
+    my $self = shift;
+    my ($obj) = @_;
+    return $self->storage->lock_exclusive( $obj );
+}
 
-    return;
+sub lock_shared {
+    my $self = shift;
+    my ($obj) = @_;
+    return $self->storage->lock_shared( $obj );
 }
 
-sub get_next_key {
-    ##
-    # Locate next key, given digested previous one
-    ##
+sub unlock {
     my $self = shift;
     my ($obj) = @_;
 
-    $obj->{prev_md5} = $_[1] ? $_[1] : undef;
-    $obj->{return_next} = 0;
+    my $rv = $self->storage->unlock( $obj );
 
-    ##
-    # If the previous key was not specifed, start at the top and
-    # return the first one found.
-    ##
-    if (!$obj->{prev_md5}) {
-        $obj->{prev_md5} = chr(0) x $self->{hash_size};
-        $obj->{return_next} = 1;
-    }
+    $self->flush if $rv;
 
-    return $self->traverse_index( $obj, $obj->_base_offset, 0 );
+    return $rv;
 }
 
-# Utilities
-
-sub _get_key_subloc {
-    my $self = shift;
-    my ($keys, $idx) = @_;
-
-    my ($key, $subloc, $size) = unpack(
-        "a$self->{hash_size} $self->{long_pack} $self->{long_pack}",
-        substr(
-            $keys,
-            ($idx * $self->{bucket_size}),
-            $self->{bucket_size},
-        ),
-    );
+################################################################################
 
-    return ($key, $subloc, $size);
-}
+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} }
 
-sub _find_in_buckets {
+# This is a calculated value
+sub txn_bitfield_len {
     my $self = shift;
-    my ($tag, $md5) = @_;
+    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};
+}
 
-    BUCKET:
-    for ( my $i = 0; $i < $self->{max_buckets}; $i++ ) {
-        my ($key, $subloc, $size) = $self->_get_key_subloc(
-            $tag->{content}, $i,
-        );
+sub trans_id     { $_[0]{trans_id} }
+sub set_trans_id { $_[0]{trans_id} = $_[1] }
 
-        return ($subloc, $i * $self->{bucket_size}, $size) unless $subloc;
+sub trans_loc     { $_[0]{trans_loc} }
+sub set_trans_loc { $_[0]{trans_loc} = $_[1] }
 
-        next BUCKET if $key ne $md5;
+sub chains_loc     { $_[0]{chains_loc} }
+sub set_chains_loc { $_[0]{chains_loc} = $_[1] }
 
-        return ($subloc, $i * $self->{bucket_size}, $size);
-    }
+sub cache       { $_[0]{cache} ||= {} }
+sub clear_cache { %{$_[0]->cache} = () }
 
-    return;
-}
-
-#sub _print_at {
-#    my $self = shift;
-#    my ($obj, $spot, $data) = @_;
-#
-#    my $fh = $obj->_fh;
-#    seek( $fh, $spot, SEEK_SET );
-#    print( $fh $data );
-#
-#    return;
-#}
-
-sub _request_space {
+sub _dump_file {
     my $self = shift;
-    my ($obj, $size) = @_;
+    $self->flush;
 
-    my $loc = $obj->_root->{end};
-    $obj->_root->{end} += $size;
+    # Read the header
+    my $header_sector = DBM::Deep::Engine::Sector::FileHeader->new({
+        engine => $self,
+    });
 
-    return $loc;
-}
+    my %types = (
+        0 => 'B',
+        1 => 'D',
+        2 => 'I',
+    );
 
-sub _release_space {
-    my $self = shift;
-    my ($obj, $size, $loc) = @_;
+    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 $next_loc = 0;
+    my $return = "";
 
-    my $fh = $obj->_fh;
-    seek( $fh, $loc + $obj->_root->{file_offset}, SEEK_SET );
-    print( $fh SIG_FREE
-        . pack($self->{long_pack}, $size )
-        . pack($self->{long_pack}, $next_loc )
-    );
+    # Filesize
+    $return .= "Size: " . (-s $self->storage->{fh}) . $/;
 
-    return;
-}
+    # Header values
+    $return .= "NumTxns: " . $self->num_txns . $/;
 
-1;
-__END__
+    # 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 ),
+            );
 
-# This will be added in later, after more refactoring is done. This is an early
-# attempt at refactoring on the physical level instead of the virtual level.
-sub _read_at {
-    my $self = shift;
-    my ($obj, $spot, $amount, $unpack) = @_;
+            # We're now out of free sectors of this kind.
+            unless ( $loc ) {
+                last;
+            }
 
-    my $fh = $obj->_fh;
-    seek( $fh, $spot + $obj->_root->{file_offset}, SEEK_SET );
+            $sectors{ $types{$multiple} }{ $loc } = undef;
+            $old_loc = $loc + SIG_SIZE + $STALE_SIZE;
+            $return .= " $loc";
+        }
+        $return .= $/;
+    }
+
+    my $spot = $header_sector->size;
+    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;
+                }
+            }
 
-    my $buffer;
-    my $bytes_read = read( $fh, $buffer, $amount );
+            die "********\n$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 .= $/;
 
-    if ( $unpack ) {
-        $buffer = unpack( $unpack, $buffer );
+            $spot += $sector->size;
+        }
     }
 
-    if ( wantarray ) {
-        return ($buffer, $bytes_read);
-    }
-    else {
-        return $buffer;
-    }
+    return $return;
 }
+
+1;
+__END__