diff --git a/lib/sbdb.rb b/lib/sbdb.rb
index 9b68299..cc59366 100644
--- a/lib/sbdb.rb
+++ b/lib/sbdb.rb
@@ -1,269 +1,16 @@
 require 'bdb'
+require 'sbdb/environment'
+require 'sbdb/db'
+require 'sbdb/cursor'
 
 module SBDB
-	CREATE = Bdb::DB_CREATE
+	CREATE      = Bdb::DB_CREATE
 	AUTO_COMMIT = Bdb::DB_AUTO_COMMIT
-	INIT_TXN = Bdb::DB_INIT_TXN
-	INIT_LOCK = Bdb::DB_INIT_LOCK
-	INIT_LOG = Bdb::DB_INIT_LOG
-	INIT_MPOOL = Bdb::DB_INIT_MPOOL
 
-	# Environments are for storing one or more databases and are important
-	# if you want to work with more than one process on one database.
-	# You needn't use Environment,  but it's usefull.
-	class Environment
-		# returns the Bdb-object.
-		def bdb_object
-			@env
-		end
-
-		def initialize dir = nil, flags = nil, mode = nil
-			dif ||= '.'
-			flags ||= INIT_TXN | INIT_LOCK | INIT_LOG | INIT_MPOOL | CREATE
-			mode ||= 0
-			@env = Bdb::Env.new 0
-			begin @env.open dir, flags, mode
-			rescue Object
-				close
-				raise
-			end
-
-			return self  unless block_given?
-
-			begin yield self
-			ensure close
-			end
-			nil
-		end
-
-		# Close the Environment.
-		# First you should close all databases!
-		def close
-			@env.close
-		end
-
-		class << self
-			alias open new
-		end
-
-		# Opens a Database.
-		# see SBDB::DB, SBDB::Btree, SBDB::Hash, SBDB::Recno, SBDB::Queue
-		def open type, *p, &e
-			p[5] = self
-			type ||= SBDB::Unkown
-			type.new *p, &e
-		end
-		alias db open
-		alias open_db open
-
-		def [] file, name = nil, &e
-			open nil, file, name, CREATE | AUTO_COMMIT, &e
-		end
-	end
-	Env = Environment
-
-	class DB
-		UNKNOWN = Bdb::Db::UNKNOWN
-		BTREE = Bdb::Db::BTREE
-		HASH = Bdb::Db::HASH
-		QUEUE = Bdb::Db::QUEUE
-		ARRAY = RECNO = Bdb::Db::RECNO
-
-		attr_reader :home
-
-		include Enumerable
-		def bdb_object
-			@db
-		end
-
-		class << self
-			def new *p, &e
-				x = super *p
-				return x  unless e
-				begin e.call x
-				ensure
-					x.sync
-					x.close
-				end
-			end
-			alias open new
-		end
-
-		def initialize file, name = nil, type = nil, flags = nil, mode = nil, txn = nil, env = nil
-			flags ||= 0
-			type ||= UNKNOWN
-			type = BTREE  if type == UNKNOWN and (flags & CREATE) == CREATE
-			mode ||= 0
-			@home = env
-			@db = env ? env.bdb_object.db : Bdb::Db.new
-			begin @db.open txn, file, name, type, flags, mode
-			rescue Object
-				close
-				raise $!
-			end
-		end
-
-		def sync
-			@db.sync
-		end
-
-		def close f = nil
-			@db.close f || 0
-		end
-
-		def [] k
-			@db.get nil, k, nil, 0
-		end
-
-		def []= k, v
-			@db.put nil, k, v, 0
-		end
-
-		def cursor &e
-			Cursor.new self, &e
-		end
-
-		def each k = nil, v = nil, &e
-			cursor{|c|c.each k, v, &e}
-		end
-
-		def reverse k = nil, v = nil, &e
-			cursor{|c|c.reverse k, v, &e}
-		end
-
-		def to_hash k = nil, v = nil
-			h = {}
-			each( k, v) {|k, v| h[ k] = v }
-			h
-		end
-	end
-
-	class Cursor
-		NEXT = Bdb::DB_NEXT
-		FIRST = Bdb::DB_FIRST
-		LAST = Bdb::DB_LAST
-		PREV = Bdb::DB_PREV
-		SET = Bdb::DB_SET
-
-		attr_reader :db
-
-		include Enumerable
-		def bdb_object
-			@cursor
-		end
-
-		def self.new *p
-			x = super *p
-			return x  unless block_given?
-			begin yield x
-			ensure x.close
-			end
-		end
-
-		def initialize ref
-			obj = ref.bdb_object
-			@cursor, @db = *if Cursor === ref
-					[obj.dup, ref.db]
-				else [obj.cursor( nil, 0), ref]
-				end
-		end
-
-		def close
-			@cursor.close
-		end
-
-		def get k, v, f
-			@cursor.get k, v, f
-		end
-
-		def count
-			@cursor.count
-		end
-
-		def reverse k = nil, v = nil, &e
-			each k, v, LAST, PREV, &e
-		end
-
-		def each k = nil, v = nil, f = nil, n = nil
-			return Enumerator.new( self, :each, k, v, f, n)  unless block_given?
-			n ||= NEXT
-			e = @cursor.get k, v, f || FIRST
-			return  unless e
-			yield *e
-			yield *e  while e = @cursor.get( k, v, n)
-			nil
-		end
-
-		def first k = nil, v = nil
-			@cursor.get k, v, FIRST
-		end
-
-		def last k = nil, v = nil
-			@cursor.get k, v, LAST
-		end
-
-		def next k = nil, v = nil
-			@cursor.get k, v, NEXT
-		end
-
-		def prev k = nil, v = nil
-			@cursor.get k, v, PREV
-		end
-	end
-
-	class Unknown < DB
-		def self.new *p, &e
-			db = super *p[0...2], UNKNOWN, *p[2..-1], &e
-			case db.bdb_object.get_type
-			when BTREE  then Btree.new *p
-			when HASH   then Hash.new *p
-			when RECNO  then Recno.new *p
-			when QUEUE  then Queue.new *p
-			else super *p[0...2], UNKNOWN, *p[2..-1], &e
-			end
-		ensure
-			db.close
-		end
-	end
-
-	class Btree < DB
-		def self.new *p, &e
-			super *p[0...2], BTREE, *p[2..-1], &e
-		end
-	end
-
-	class Hash < DB
-		def self.new *p, &e
-			super *p[0...2], HASH, *p[2..-1], &e
-		end
-	end
-
-	class Recno < DB
-		def self.new *p, &e
-			super *p[0...2], RECNO, *p[2..-1], &e
-		end
-
-		def [] k
-			super k.to_s
-		end
-
-		def []= k, v
-			super k.to_s
-		end
-	end
-	Array = Recno
-
-	class Queue < DB
-		def self.new *p, &e
-			super *p[0...2], QUEUE, *p[2..-1], &e
-		end
-
-		def [] k
-			super k.to_s
-		end
-
-		def []= k, v
-			super k.to_s
-		end
-	end
+	def btree( *p)   Btree.new *p   end
+	def hash( *p)    Hash.new *p    end
+	def recno( *p)   Recno.new *p   end
+	def queue( *p)   Queue.new *p   end 
+	def unknown( *p) Unknown.new *p end
+	alias open_db unknown
 end
diff --git a/lib/sbdb/cursor.rb b/lib/sbdb/cursor.rb
new file mode 100644
index 0000000..50454a7
--- /dev/null
+++ b/lib/sbdb/cursor.rb
@@ -0,0 +1,52 @@
+
+module SBDB
+	class Cursor
+		NEXT  = Bdb::DB_NEXT
+		FIRST = Bdb::DB_FIRST
+		LAST  = Bdb::DB_LAST
+		PREV  = Bdb::DB_PREV
+		SET   = Bdb::DB_SET
+
+		attr_reader :db
+
+		include Enumerable
+		def bdb_object()  @cursor  end
+		def close()  @cursor.close  end
+		def get( k, v, f)  @cursor.get k, v, f  end
+		def count()  @cursor.count  end
+		def first( k = nil, v = nil)  @cursor.get k, v, FIRST  end
+		def last(  k = nil, v = nil)  @cursor.get k, v, LAST   end 
+		def next(  k = nil, v = nil)  @cursor.get k, v, NEXT   end 
+		def prev(  k = nil, v = nil)  @cursor.get k, v, PREV   end
+
+		def self.new *p
+			x = super *p
+			return x  unless block_given?
+			begin yield x
+			ensure x.close
+			end
+		end
+
+		def initialize ref
+			@cursor, @db = *case ref
+				when Cursor  then [ref.bdb_object.dup, ref.db]
+				when Bd::Db::Cursor  then [ref]
+				else [ref.bdb_object.cursor( nil, 0), ref]
+				end
+		end
+
+		def reverse k = nil, v = nil, &e
+			each k, v, LAST, PREV, &e
+		end
+
+		def each k = nil, v = nil, f = nil, n = nil
+			return Enumerator.new( self, :each, k, v, f, n)  unless block_given?
+			n ||= NEXT
+			e = @cursor.get k, v, f || FIRST
+			return  unless e
+			yield *e
+			yield *e  while e = @cursor.get( k, v, n)
+			nil
+		end
+	end
+end
diff --git a/lib/sbdb/db.rb b/lib/sbdb/db.rb
new file mode 100644
index 0000000..0d44f27
--- /dev/null
+++ b/lib/sbdb/db.rb
@@ -0,0 +1,105 @@
+require 'bdb'
+require 'sbdb/cursor'
+
+module SBDB
+	class DB
+		UNKNOWN = Bdb::Db::UNKNOWN
+		BTREE = Bdb::Db::BTREE
+		HASH = Bdb::Db::HASH
+		QUEUE = Bdb::Db::QUEUE
+		ARRAY = RECNO = Bdb::Db::RECNO
+
+		attr_reader :home
+		include Enumerable
+		def bdb_object()  @db  end
+		def sync()  @db.sync  end
+		def close( f = nil)  @db.close f || 0  end
+		def []( k)  @db.get nil, k, nil, 0  end
+		def []=( k, v)  @db.put nil, k, v, 0  end
+		def cursor( &e)  Cursor.new self, &e  end
+
+		class << self
+			def new *p, &e
+				x = super *p
+				return x  unless e
+				begin e.call x
+				ensure
+					x.sync
+					x.close
+				end
+			end
+			alias open new
+		end
+
+		def initialize file, name = nil, type = nil, flags = nil, mode = nil, txn = nil, env = nil
+			flags ||= 0
+			type ||= UNKNOWN
+			type = BTREE  if type == UNKNOWN and (flags & CREATE) == CREATE
+			@home, @db = env, env ? env.bdb_object.db : Bdb::Db.new
+			begin @db.open txn, file, name, type, flags, mode || 0
+			rescue Object
+				close
+				raise $!
+			end
+		end
+
+		def each k = nil, v = nil, &e
+			cursor{|c|c.each k, v, &e}
+		end
+
+		def reverse k = nil, v = nil, &e
+			cursor{|c|c.reverse k, v, &e}
+		end
+
+		def to_hash k = nil, v = nil
+			h = {}
+			each( k, v) {|k, v| h[ k] = v }
+			h
+		end
+	end
+
+	class Unknown < DB
+		def self.new *p, &e
+			db = super *p[0...2], UNKNOWN, *p[2..-1], &e
+			case db.bdb_object.get_type
+			when BTREE  then Btree.new *p
+			when HASH   then Hash.new  *p
+			when RECNO  then Recno.new *p
+			when QUEUE  then Queue.new *p
+			else super *p[0...2], UNKNOWN, *p[2..-1], &e
+			end
+		ensure db.close
+		end
+	end
+
+	class Btree < DB
+		def self.new *p, &e
+			super *p[0...2], BTREE, *p[2..-1], &e
+		end
+	end
+
+	class Hash < DB
+		def self.new *p, &e
+			super *p[0...2], HASH, *p[2..-1], &e
+		end
+	end
+
+	class Recno < DB
+		def self.new *p, &e
+			super *p[0...2], RECNO, *p[2..-1], &e
+		end
+
+		def []( k)     super k.to_s  end
+		def []=( k, v) super k.to_s  end
+	end
+	Array = Recno
+
+	class Queue < DB
+		def self.new *p, &e
+			super *p[0...2], QUEUE, *p[2..-1], &e
+		end
+
+		def []( k)     super k.to_s  end 
+		def []=( k, v) super k.to_s  end
+	end
+end
diff --git a/lib/sbdb/environment.rb b/lib/sbdb/environment.rb
new file mode 100644
index 0000000..fe6ddcb
--- /dev/null
+++ b/lib/sbdb/environment.rb
@@ -0,0 +1,77 @@
+require 'bdb'
+require 'sbdb/weakhash'
+require 'sbdb/db'
+
+module SBDB
+	# Environments are for storing one or more databases and are important
+	# if you want to work with more than one process on one database.
+	# You needn't use Environment,  but it's usefull.
+	class Environment
+		INIT_TXN   = Bdb::DB_INIT_TXN
+		INIT_LOCK  = Bdb::DB_INIT_LOCK
+		INIT_LOG   = Bdb::DB_INIT_LOG
+		INIT_MPOOL = Bdb::DB_INIT_MPOOL
+		INIT_TRANSACTION = INIT_TXN | INIT_LOCK | INIT_LOG | INIT_MPOOL
+		LOCKDOWN   = Bdb::DB_LOCKDOWN
+		NOMMAP     = Bdb::DB_NOMMAP
+		PRIVATE    = Bdb::DB_PRIVATE
+		SYSTEM_MEM = Bdb::DB_SYSTEM_MEM
+		TXN_NOSYNC = Bdb::DB_TXN_NOSYNC
+
+		# returns the Bdb-object.
+		def bdb_object()  @env  end
+		# Opens a Btree in this Environment
+		def btree( *p, &e)   Btree.new   *p[0...5], self, p[5..-1], &e end 
+		# Opens a Hash in this Environment
+		def hash( *p, &e)    Hash.new    *p[0...5], self, p[5..-1], &e end 
+		# Opens a Recno in this Environment
+		def recno( *p, &e)   Recno.new   *p[0...5], self, p[5..-1], &e end 
+		# Opens a Queue in this Environment
+		def queue( *p, &e)   Queue.new   *p[0...5], self, p[5..-1], &e end 
+		# Opens a DB of unknown type in this Environment
+		def unknown( *p, &e) Unknown.new *p[0...5], self, p[5..-1], &e end 
+
+		def initialize dir = nil, flags = nil, mode = nil
+			@env = Bdb::Env.new 0
+			begin @env.open dir || '.', flags || INIT_TRANSACTION | CREATE, mode || 0
+			rescue Object
+				close
+				raise
+			end
+
+			return self  unless block_given?
+
+			begin yield self
+			ensure close
+			end
+			nil
+		end
+
+		# Close the Environment.
+		# First you should close all databases!
+		def close
+			@dbs.each{|db|db.close}
+			@env.close
+		end
+
+		class << self
+			alias open new
+		end
+
+		# Opens a Database.
+		# see SBDB::DB, SBDB::Btree, SBDB::Hash, SBDB::Recno, SBDB::Queue
+		def open type, *p, &e
+			(type || SBDB::Unkown).new *p[0...5], self, p[5..-1], &e
+		end
+		alias db open
+		alias open_db open
+
+		# Returns the DB like open,  but if it's already opened,
+		# it returns the old instance.
+		# If you use this,  never use close. It's possible somebody else use it.
+		def [] file, name = nil, type = nil, &e
+			@dbs[ [file, name]] ||= (type || SBDB::Unkown).new file, name, nil, nil, self, &e
+		end
+	end
+	Env = Environment
+end
diff --git a/lib/sbdb/weakhash.rb b/lib/sbdb/weakhash.rb
new file mode 100644
index 0000000..3bd0248
--- /dev/null
+++ b/lib/sbdb/weakhash.rb
@@ -0,0 +1,48 @@
+module SBDB
+
+# See http://eigenclass.org/hiki/deferred-finalizers-in-Ruby
+
+class WeakHash
+	attr_reader :cache
+	def initialize( cache = Hash.new )
+		@cache = cache
+		@key_map = {}
+		@rev_cache = Hash.new{|h,k| h[k] = {}}
+		@reclaim_value = lambda do |value_id| 
+			if @rev_cache.has_key? value_id
+				@rev_cache[value_id].each_key{|key| @cache.delete key}
+				@rev_cache.delete value_id
+			end
+		end
+		@reclaim_key = lambda do |key_id|
+			if @key_map.has_key? key_id
+				@cache.delete @key_map[key_id]
+			end
+		end
+	end
+
+	 def []( key )
+		 value_id = @cache[key]
+		 return ObjectSpace._id2ref(value_id) unless value_id.nil?
+		 nil
+	 rescue RangeError
+		 nil
+	 end
+
+	 def []=( key, value )
+		 case key
+		 when Fixnum, Symbol, true, false
+			 key2 = key
+		 else
+			 key2 = key.dup
+		 end
+		 @rev_cache[value.object_id][key2] = true
+		 @cache[key2] = value.object_id
+		 @key_map[key.object_id] = key2
+
+		 ObjectSpace.define_finalizer(value, @reclaim_value)
+		 ObjectSpace.define_finalizer(key, @reclaim_key)
+	 end
+end
+
+end
diff --git a/sbdb.gemspec b/sbdb.gemspec
index 9df2741..43fa861 100644
--- a/sbdb.gemspec
+++ b/sbdb.gemspec
@@ -9,16 +9,21 @@ Gem::Specification.new do |s|
 
   s.required_rubygems_version = Gem::Requirement.new(">= 0") if s.respond_to? :required_rubygems_version=
   s.authors = ["Denis Knauf"]
-  s.date = %q{2010-01-29}
+  s.date = %q{2010-02-02}
   s.description = %q{Simple Ruby Berkeley DB wrapper library for bdb.}
   s.email = %q{Denis.Knauf@gmail.com}
   s.extra_rdoc_files = [
-    "README"
+    "LICENSE",
+     "README"
   ]
   s.files = [
     "README",
      "VERSION",
-     "lib/sbdb.rb"
+     "lib/sbdb.rb",
+     "lib/sbdb/cursor.rb",
+     "lib/sbdb/db.rb",
+     "lib/sbdb/environment.rb",
+     "lib/sbdb/weakhash.rb"
   ]
   s.homepage = %q{http://github.com/DenisKnauf/bdb}
   s.rdoc_options = ["--charset=UTF-8"]
@@ -31,9 +36,12 @@ Gem::Specification.new do |s|
     s.specification_version = 3
 
     if Gem::Version.new(Gem::RubyGemsVersion) >= Gem::Version.new('1.2.0') then
+      s.add_runtime_dependency(%q<bdb>, [">= 0"])
     else
+      s.add_dependency(%q<bdb>, [">= 0"])
     end
   else
+    s.add_dependency(%q<bdb>, [">= 0"])
   end
 end