From: rkinyon@cpan.org <rkinyon@cpan.org>
Date: Wed, 25 Jun 2008 14:59:31 +0000 (+0000)
Subject: Hash tests pass again with header being read and cached
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=badf847ca0fd2a37bf21caf92454a92d568e3ccf;hp=80656ce3c356053e563c882733b5bf66307c9c20;p=dbsrgits%2FDBM-Deep.git

Hash tests pass again with header being read and cached

git-svn-id: http://svn.ali.as/cpan/trunk/DBM-Deep@3637 88f4d9cd-8a04-0410-9d60-8f63309c3137
---

diff --git a/lib/DBM/Deep/Engine.pm b/lib/DBM/Deep/Engine.pm
index 7841b1e..9c41951 100644
--- a/lib/DBM/Deep/Engine.pm
+++ b/lib/DBM/Deep/Engine.pm
@@ -416,9 +416,7 @@ sub setup_fh {
 
     return 1 if $obj->_base_offset;
 
-    my $header = DBM::Deep::Engine::Sector::FileHeader->new({
-        engine => $self,
-    });
+    my $header = $self->_load_header;
 
     # Creating a new file
     if ( $header->is_new ) {
@@ -656,137 +654,99 @@ sub clear_entries {
 
 ################################################################################
 
-sub _load_sector {
-    my $self = shift;
-    my ($offset) = @_;
-
-    # Add a catch for offset of 0 or 1
-    return if !$offset || $offset <= 1;
-
-    unless ( exists $self->sector_cache->{ $offset } ) {
-        my $type = $self->storage->read_at( $offset, $self->SIG_SIZE );
-
-        # XXX Don't we want to do something more proactive here? -RobK, 2008-06-19
-        return if $type eq chr(0);
-
-        if ( $type eq $self->SIG_ARRAY || $type eq $self->SIG_HASH ) {
-            $self->sector_cache->{$offset} = 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 ) {
-            $self->sector_cache->{$offset} = DBM::Deep::Engine::Sector::BucketList->new({
-                engine => $self,
-                type   => $type,
-                offset => $offset,
-            });
-        }
-        elsif ( $type eq $self->SIG_INDEX ) {
-            $self->sector_cache->{$offset} = DBM::Deep::Engine::Sector::Index->new({
-                engine => $self,
-                type   => $type,
-                offset => $offset,
-            });
-        }
-        elsif ( $type eq $self->SIG_NULL ) {
-            $self->sector_cache->{$offset} = DBM::Deep::Engine::Sector::Null->new({
-                engine => $self,
-                type   => $type,
-                offset => $offset,
-            });
-        }
-        elsif ( $type eq $self->SIG_DATA ) {
-            $self->sector_cache->{$offset} = 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 $self->SIG_FREE ) {
-            return;
-        }
-        else {
-            DBM::Deep->_throw_error( "'$offset': Don't know what to do with type '$type'" );
-        }
-    }
-
-    return $self->sector_cache->{$offset};
-}
-
 sub _apply_digest {
     my $self = shift;
     return $self->{digest}->(@_);
 }
 
 sub _add_free_blist_sector { shift->_add_free_sector( 0, @_ ) }
-sub _add_free_data_sector { shift->_add_free_sector( 1, @_ ) }
+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 _add_free_sector {
-    my $self = shift;
-    my ($multiple, $offset, $size) = @_;
+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 $chains_offset = $multiple * $self->byte_size;
+################################################################################
 
-    my $storage = $self->storage;
+{
+    my %t = (
+        SIG_ARRAY => 'Reference',
+        SIG_HASH  => 'Reference',
+        SIG_BLIST => 'BucketList',
+        SIG_INDEX => 'Index',
+        SIG_NULL  => 'Null',
+        SIG_DATA  => 'Scalar',
+    );
 
-    # 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}, $staleness ) );
+    my %class_for;
+    while ( my ($k,$v) = each %t ) {
+        $class_for{ DBM::Deep::Engine->$k } = "DBM::Deep::Engine::Sector::$v";
+    }
 
-    my $old_head = $storage->read_at( $self->chains_loc + $chains_offset, $self->byte_size );
+    sub load_sector {
+        my $self = shift;
+        my ($offset) = @_;
 
-    $storage->print_at( $self->chains_loc + $chains_offset,
-        pack( $StP{$self->byte_size}, $offset ),
-    );
+        #warn join(':',(caller)[0,2]) . " -> $offset\n";
+        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;
 
-    # Record the old head in the new sector after the signature and staleness counter
-    $storage->print_at( $offset + SIG_SIZE + $STALE_SIZE, $old_head );
-}
+    sub load_header {
+        my $self = shift;
 
-sub _request_blist_sector { shift->_request_sector( 0, @_ ) }
-sub _request_data_sector { shift->_request_sector( 1, @_ ) }
-sub _request_index_sector { shift->_request_sector( 2, @_ ) }
+        #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;
 
-sub _request_sector {
-    my $self = shift;
-    my ($multiple, $size) = @_;
+    sub get_data {
+        my $self = shift;
+        my ($offset, $size) = @_;
+        return unless defined $offset;
 
-    my $chains_offset = $multiple * $self->byte_size;
+        unless ( exists $self->sector_cache->{$offset} ) {
+            # Don't worry about the header sector. It will manage itself.
+            return unless $offset;
 
-    my $old_head = $self->storage->read_at( $self->chains_loc + $chains_offset, $self->byte_size );
-    my $loc = unpack( $StP{$self->byte_size}, $old_head );
+            if ( !defined $size ) {
+                my $type = $self->storage->read_at( $offset, 1 )
+                    or die "($offset): Cannot read from '$offset' to find the type\n";
 
-    # 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 );
+                if ( $type eq $self->SIG_FREE ) {
+                    return;
+                }
 
-        # Zero out the new sector. This also guarantees correct increases
-        # in the filesize.
-        $self->storage->print_at( $offset, chr(0) x $size );
+                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;
+            }
+        }
 
-        return $offset;
+        return \$self->sector_cache->{$offset};
     }
-
-    # 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 ),
-    );
-
-    return $loc;
 }
 
-################################################################################
-
 sub sector_cache {
     my $self = shift;
     return $self->{sector_cache} ||= {};
@@ -809,13 +769,9 @@ sub clear_dirty_sectors {
 
 sub add_dirty_sector {
     my $self = shift;
-    my ($sector) = @_;
-
-#    if ( exists $self->dirty_sectors->{ $sector->offset } ) {
-#        DBM::Deep->_throw_error( "We have a duplicate sector!! " . $sector->offset );
-#    }
+    my ($offset) = @_;
 
-    $self->dirty_sectors->{ $sector->offset } = $sector;
+    $self->dirty_sectors->{ $offset } = undef;
 }
 
 sub flush {
@@ -823,7 +779,7 @@ sub flush {
 
     my $sectors = $self->dirty_sectors;
     for my $offset (sort { $a <=> $b } keys %{ $sectors }) {
-        $sectors->{$offset}->flush;
+        $self->storage->print_at( $offset, $self->sector_cache->{$offset} );
     }
 
     $self->clear_dirty_sectors;
diff --git a/lib/DBM/Deep/Engine/Sector.pm b/lib/DBM/Deep/Engine/Sector.pm
index 1438b5c..c997ec7 100644
--- a/lib/DBM/Deep/Engine/Sector.pm
+++ b/lib/DBM/Deep/Engine/Sector.pm
@@ -11,20 +11,8 @@ sub new {
     my $self = bless $_[1], $_[0];
     Scalar::Util::weaken( $self->{engine} );
 
-    if ( $self->offset ) {
-        $self->{string} = $self->engine->storage->read_at(
-            $self->offset, $self->size,
-        );
-    }
-    else {
-        $self->{string} = chr(0) x $self->size;
-    }
-
     $self->_init;
 
-    # Add new sectors to the sector cache.
-    $self->engine->sector_cache->{$self->offset} = $self;
-
     return $self;
 }
 
@@ -36,9 +24,13 @@ sub offset { $_[0]{offset} }
 sub type   { $_[0]{type}   }
 
 sub base_size {
-   my $self = shift;
-   no warnings 'once';
-   return $self->engine->SIG_SIZE + $DBM::Deep::Engine::STALE_SIZE;
+    my $self = shift;
+    if ( ref($self) ) {
+        return $self->engine->SIG_SIZE + $DBM::Deep::Engine::STALE_SIZE;
+    }
+    else {
+        return $_[0]->SIG_SIZE + $DBM::Deep::Engine::STALE_SIZE;
+    }
 }
 
 sub free {
@@ -49,33 +41,26 @@ sub free {
     $self->write( 0, $e->SIG_FREE );
     $self->write( $self->base_size, chr(0) x ($self->size - $self->base_size) );
 
-    $e->flush;
-
-#    $e->storage->print_at( $self->offset, $e->SIG_FREE );
-#    # Skip staleness counter
-#    $e->storage->print_at( $self->offset + $self->base_size,
-#        chr(0) x ($self->size - $self->base_size),
-#    );
-
-    #TODO When freeing two sectors, we cannot flush them right away! This means the following:
-    # 1) The header has to understand about unflushed items.
-    # 2) Loading a sector has to go through a cache to make sure we see what's already been loaded.
-    # 3) The header should be cached.
-
     my $free_meth = $self->free_meth;
-    $e->$free_meth( $self->offset, $self->size );
+    $e->$free_meth( $self );
 
     return;
 }
 
 sub read {
     my $self = shift;
-    my ($start, $length) = @_;
-    if ( $length ) {
-        return substr( $self->{string}, $start, $length );
+
+    if ( @_ == 1 ) {
+        return substr( ${$self->engine->get_data( $self->offset, $self->size )}, $_[0] );
+    }
+    elsif ( @_ == 2 ) {
+        return substr( ${$self->engine->get_data( $self->offset, $self->size )}, $_[0], $_[1] );
+    }
+    elsif ( @_ < 1 ) {
+        die "read( start [, length ]): No parameters found.";
     }
     else {
-        return substr( $self->{string}, $start );
+        die "read( start [, length ]): Too many parameters found (@_).";
     }
 }
 
@@ -83,19 +68,14 @@ sub write {
     my $self = shift;
     my ($start, $text) = @_;
 
-    substr( $self->{string}, $start, length($text) ) = $text;
+    substr( ${$self->engine->get_data( $self->offset, $self->size )}, $start, length($text) ) = $text;
 
     $self->mark_dirty;
 }
 
 sub mark_dirty {
     my $self = shift;
-    $self->engine->add_dirty_sector( $self );
-}
-
-sub flush {
-    my $self = shift;
-    $self->engine->storage->print_at( $self->offset, $self->{string} );
+    $self->engine->add_dirty_sector( $self->offset );
 }
 
 1;
diff --git a/lib/DBM/Deep/Engine/Sector/BucketList.pm b/lib/DBM/Deep/Engine/Sector/BucketList.pm
index b3bd6b2..36537aa 100644
--- a/lib/DBM/Deep/Engine/Sector/BucketList.pm
+++ b/lib/DBM/Deep/Engine/Sector/BucketList.pm
@@ -35,11 +35,17 @@ sub clear {
 
 sub size {
     my $self = shift;
-    unless ( $self->{size} ) {
-        # Base + numbuckets * bucketsize
-        $self->{size} = $self->base_size + $self->engine->max_buckets * $self->bucket_size;
+    if ( ref($self) ) {
+        unless ( $self->{size} ) {
+            # Base + numbuckets * bucketsize
+            $self->{size} = $self->base_size + $self->engine->max_buckets * $self->bucket_size;
+        }
+        return $self->{size};
+    }
+    else {
+        my $e = shift;
+        return $self->base_size($e) + $e->max_buckets * $self->bucket_size($e);
     }
-    return $self->{size};
 }
 
 sub free_meth { return '_add_free_blist_sector' }
@@ -80,13 +86,20 @@ sub free {
 
 sub bucket_size {
     my $self = shift;
-    unless ( $self->{bucket_size} ) {
-        my $e = $self->engine;
-        # Key + head (location) + transactions (location + staleness-counter)
+    if ( ref($self) ) {
+        unless ( $self->{bucket_size} ) {
+            my $e = $self->engine;
+            # Key + head (location) + transactions (location + staleness-counter)
+            my $location_size = $e->byte_size + $e->byte_size + ($e->num_txns - 1) * ($e->byte_size + $DBM::Deep::Engine::STALE_SIZE);
+            $self->{bucket_size} = $e->hash_size + $location_size;
+        }
+        return $self->{bucket_size};
+    }
+    else {
+        my $e = shift;
         my $location_size = $e->byte_size + $e->byte_size + ($e->num_txns - 1) * ($e->byte_size + $DBM::Deep::Engine::STALE_SIZE);
-        $self->{bucket_size} = $e->hash_size + $location_size;
+        return $e->hash_size + $location_size;
     }
-    return $self->{bucket_size};
 }
 
 # XXX This is such a poor hack. I need to rethink this code.
diff --git a/lib/DBM/Deep/Engine/Sector/Data.pm b/lib/DBM/Deep/Engine/Sector/Data.pm
index c9695ee..e12e942 100644
--- a/lib/DBM/Deep/Engine/Sector/Data.pm
+++ b/lib/DBM/Deep/Engine/Sector/Data.pm
@@ -9,7 +9,10 @@ use DBM::Deep::Engine::Sector;
 our @ISA = qw( DBM::Deep::Engine::Sector );
 
 # This is in bytes
-sub size { $_[0]{engine}->data_sector_size }
+sub size {
+    my $e = ref($_[0]) ? $_[0]{engine} : $_[1];
+    return $e->data_sector_size;
+}
 sub free_meth { return '_add_free_data_sector' }
 
 sub clone {
diff --git a/lib/DBM/Deep/Engine/Sector/FileHeader.pm b/lib/DBM/Deep/Engine/Sector/FileHeader.pm
index b069065..ae56c0f 100644
--- a/lib/DBM/Deep/Engine/Sector/FileHeader.pm
+++ b/lib/DBM/Deep/Engine/Sector/FileHeader.pm
@@ -17,8 +17,7 @@ sub _init {
     my $e = $self->engine;
 
     # This means the file is being created.
-    # Use defined() here because the offset should always be 0. -RobK. 2008-06-20
-    unless ( $e->storage->size ) {
+    unless ( exists $self->engine->sector_cache->{0} || $self->engine->storage->size ) {
         my $nt = $e->num_txns;
         my $bl = $e->txn_bitfield_len;
 
@@ -27,7 +26,10 @@ sub _init {
         $self->{offset} = $e->storage->request_space( $header_fixed + $header_var );
         DBM::Deep::_throw_error( "Offset wasn't 0, it's '$self->{offset}'" ) unless $self->offset == 0;
 
-        $self->write( $self->offset,
+        # Make sure we set up sector caching so that get_data() works. -RobK, 2008-06-24
+        $self->engine->sector_cache->{$self->offset} = chr(0) x ($header_fixed + $header_var);
+
+        $self->write( 0,
             $e->SIG_FILE
           . $e->SIG_HEADER
           . pack('N', $this_file_version) # At this point, we're at 9 bytes
@@ -54,6 +56,9 @@ sub _init {
     }
     else {
         $self->{offset} = 0;
+        $self->{is_new} = 0;
+
+        return if exists $self->engine->sector_cache->{0};
 
         my $s = $e->storage;
 
@@ -108,24 +113,85 @@ sub _init {
         my $bl = $e->txn_bitfield_len;
         $e->set_chains_loc( $header_fixed + scalar(@values) + $bl + $DBM::Deep::Engine::STALE_SIZE * ($e->num_txns - 1) );
 
-        # Make sure we set up the string so that the caching works. -RobK, 2008-06-20
-        $self->{string} = $buffer . $buffer2;
-
-        $self->{is_new} = 0;
+        # Make sure we set up sector caching so that get_data() works. -RobK, 2008-06-24
+        $self->engine->sector_cache->{$self->offset} = $buffer . $buffer2;
     }
 }
 
 sub header_var_size {
     my $self = shift;
-    my $e = $self->engine;
+    my $e = shift || $self->engine;
     return 1 + 1 + 1 + 1 + $e->txn_bitfield_len + $DBM::Deep::Engine::STALE_SIZE * ($e->num_txns - 1) + 3 * $e->byte_size;
 }
 
-sub size   {
+sub size {
     my $self = shift;
-    $self->{size} ||= $header_fixed + $self->header_var_size;
+    if ( ref($self) ) {
+        $self->{size} ||= $header_fixed + $self->header_var_size;
+    }
+    else {
+        return $header_fixed + $self->header_var_size( @_ );
+    }
 }
+
 sub is_new { $_[0]{is_new} }
 
+sub add_free_sector {
+    my $self = shift;
+    my ($multiple, $sector) = @_;
+
+    my $e = $self->engine;
+
+    my $chains_offset = $multiple * $e->byte_size;
+
+    # Increment staleness.
+    # XXX Can this increment+modulo be done by "&= 0x1" ?
+    my $staleness = unpack( $e->StP($DBM::Deep::Engine::STALE_SIZE), $sector->read( $e->SIG_SIZE, $DBM::Deep::Engine::STALE_SIZE ) );
+    $staleness = ($staleness + 1 ) % ( 2 ** ( 8 * $DBM::Deep::Engine::STALE_SIZE ) );
+    $sector->write( $e->SIG_SIZE, pack( $e->StP($DBM::Deep::Engine::STALE_SIZE), $staleness ) );
+
+    my $old_head = $self->read( $e->chains_loc + $chains_offset, $e->byte_size );
+
+    $self->write( $e->chains_loc + $chains_offset,
+        pack( $e->StP($e->byte_size), $sector->offset ),
+    );
+
+    # Record the old head in the new sector after the signature and staleness counter
+    $sector->write( $e->SIG_SIZE + $DBM::Deep::Engine::STALE_SIZE, $old_head );
+}
+
+sub request_sector {
+    my $self = shift;
+    my ($multiple, $size) = @_;
+
+    my $e = $self->engine;
+
+    my $chains_offset = $multiple * $e->byte_size;
+
+    my $old_head = $self->read( $e->chains_loc + $chains_offset, $e->byte_size );
+    my $loc = unpack( $e->StP($e->byte_size), $old_head );
+
+    # We don't have any free sectors of the right size, so allocate a new one.
+    unless ( $loc ) {
+        my $offset = $e->storage->request_space( $size );
+
+        # Zero out the new sector. This also guarantees correct increases
+        # in the filesize.
+        $self->engine->sector_cache->{$offset} = chr(0) x $size;
+
+        return $offset;
+    }
+
+    # Need to load the new sector so we can read from it.
+    my $new_sector = $self->engine->storage->read_at( $loc, $size );
+
+    # Read the new head after the signature and the staleness counter
+    my $new_head = substr( $new_sector, $e->SIG_SIZE + $DBM::Deep::Engine::STALE_SIZE, $e->byte_size );
+
+    $self->write( $e->chains_loc + $chains_offset, $new_head );
+
+    return $loc;
+}
+
 1;
 __END__
diff --git a/lib/DBM/Deep/Engine/Sector/Index.pm b/lib/DBM/Deep/Engine/Sector/Index.pm
index e937233..a7c9334 100644
--- a/lib/DBM/Deep/Engine/Sector/Index.pm
+++ b/lib/DBM/Deep/Engine/Sector/Index.pm
@@ -26,11 +26,17 @@ sub _init {
 #XXX Why? -RobK, 2008-06-18
 sub size {
     my $self = shift;
-    unless ( $self->{size} ) {
-        my $e = $self->engine;
-        $self->{size} = $self->base_size + $e->byte_size * $e->hash_chars;
+    if ( ref($self) ) {
+        unless ( $self->{size} ) {
+            my $e = $self->engine;
+            $self->{size} = $self->base_size + $e->byte_size * $e->hash_chars;
+        }
+        return $self->{size};
+    }
+    else {
+        my $e = shift;
+        return $self->base_size($e) + $e->byte_size * $e->hash_chars;
     }
-    return $self->{size};
 }
 
 sub free_meth { return '_add_free_index_sector' }
diff --git a/t/02_hash.t b/t/02_hash.t
index 4ad5d92..ab428e5 100644
--- a/t/02_hash.t
+++ b/t/02_hash.t
@@ -181,4 +181,3 @@ throws_ok {
 throws_ok {
     $db->exists(undef);
 } qr/Cannot use an undefined hash key/, "EXISTS fails on an undefined key";
-
diff --git a/t/04_array.t b/t/04_array.t
index 3bfc933..f746f4e 100644
--- a/t/04_array.t
+++ b/t/04_array.t
@@ -19,13 +19,13 @@ my $db = DBM::Deep->new(
 # basic put/get/push
 ##
 $db->[0] = "elem1";
-#$db->push( "elem2" );
-#$db->put(2, "elem3");
-#$db->store(3, "elem4");
-warn $db->_engine->_dump_file;
+$db->push( "elem2" );
+$db->put(2, "elem3");
+$db->store(3, "elem4");
+#warn $db->_engine->_dump_file;
 $db->unshift("elem0");
-warn $db->_engine->_dump_file;
-__END__
+#warn $db->_engine->_dump_file;
+#__END__
 
 is( $db->[0], 'elem0', "Array get for shift works" );
 is( $db->[1], 'elem1', "Array get for array set works" );
@@ -68,14 +68,23 @@ throws_ok {
     $db->[-6] = 'whoops!';
 } qr/Modification of non-creatable array value attempted, subscript -6/, "Correct error thrown";
 
+warn "1: \n" . $db->_engine->_dump_file;
 my $popped = $db->pop;
+warn "2: \n" . $db->_engine->_dump_file;
 is( $db->length, 4, "... and we have four after popping" );
+warn "3: \n" . $db->_engine->_dump_file;
 is( $db->[0], 'elem0', "0th element still there after popping" );
+warn "4: \n" . $db->_engine->_dump_file;
 is( $db->[1], 'elem1', "1st element still there after popping" );
+warn "5: \n" . $db->_engine->_dump_file;
 is( $db->[2], 'elem2', "2nd element still there after popping" );
+warn "6: \n" . $db->_engine->_dump_file;
 is( $db->[3], 'elem3', "3rd element still there after popping" );
+warn "7: \n" . $db->_engine->_dump_file;
 is( $popped, 'elem4.1', "Popped value is correct" );
 
+die $db->_engine->_dump_file;
+
 my $shifted = $db->shift;
 is( $db->length, 3, "... and we have three after shifting" );
 is( $db->[0], 'elem1', "0th element still there after shifting" );
@@ -136,6 +145,8 @@ is( $db->length(), 0, "After pop() on empty array, length is still 0" );
 is( $db->shift, undef, "shift on an empty array returns undef" );
 is( $db->length(), 0, "After shift() on empty array, length is still 0" );
 
+warn "BEFORE: " . $db->_engine->_dump_file;
+__END__
 is( $db->unshift( 1, 2, 3 ), 3, "unshift returns the number of elements in the array" );
 is( $db->unshift( 1, 2, 3 ), 6, "unshift returns the number of elements in the array" );
 is( $db->push( 1, 2, 3 ), 9, "push returns the number of elements in the array" );