@@ -0,0 +1,311 @@
+# Copyright (C) 2010, 2011 Sebastian Thiel (byronimo@gmail.com) and contributors
+#
+# This module is part of GitDB and is released under
+# the New BSD License: http://www.opensource.org/licenses/bsd-license.php
+"""Module with basic data structures - they are designed to be lightweight and fast"""
+from util import (
+		bin_to_hex,
+		zlib
+	)
+
+from fun import (
+					type_id_to_type_map,
+					type_to_type_id_map
+				)
+
+__all__ = ('OInfo', 'OPackInfo', 'ODeltaPackInfo', 
+			'OStream', 'OPackStream', 'ODeltaPackStream',
+			'IStream', 'InvalidOInfo', 'InvalidOStream' )
+
+#{ ODB Bases
+
+class OInfo(tuple):
+	"""Carries information about an object in an ODB, provding information 
+	about the binary sha of the object, the type_string as well as the uncompressed size
+	in bytes.
+	
+	It can be accessed using tuple notation and using attribute access notation::
+	
+		assert dbi[0] == dbi.binsha
+		assert dbi[1] == dbi.type
+		assert dbi[2] == dbi.size
+	
+	The type is designed to be as lighteight as possible."""
+	__slots__ = tuple()
+	
+	def __new__(cls, sha, type, size):
+		return tuple.__new__(cls, (sha, type, size))
+	
+	def __init__(self, *args):
+		tuple.__init__(self)
+	
+	#{ Interface 
+	@property
+	def binsha(self):
+		""":return: our sha as binary, 20 bytes"""
+		return self[0]
+	
+	@property
+	def hexsha(self):
+		""":return: our sha, hex encoded, 40 bytes"""
+		return bin_to_hex(self[0])
+		
+	@property
+	def type(self):
+		return self[1]
+	
+	@property
+	def type_id(self):
+		return type_to_type_id_map[self[1]]
+		
+	@property
+	def size(self):
+		return self[2]
+	#} END interface
+	
+	
+class OPackInfo(tuple):
+	"""As OInfo, but provides a type_id property to retrieve the numerical type id, and 
+	does not include a sha.
+	
+	Additionally, the pack_offset is the absolute offset into the packfile at which 
+	all object information is located. The data_offset property points to the abosolute
+	location in the pack at which that actual data stream can be found."""
+	__slots__ = tuple()
+	
+	def __new__(cls, packoffset, type, size):
+		return tuple.__new__(cls, (packoffset,type, size))
+	
+	def __init__(self, *args):
+		tuple.__init__(self)
+		
+	#{ Interface 
+	
+	@property
+	def pack_offset(self):
+		return self[0]
+	
+	@property
+	def type(self):
+		return type_id_to_type_map[self[1]]
+	
+	@property
+	def type_id(self):
+		return self[1]
+		
+	@property
+	def size(self):
+		return self[2]
+		
+	#} END interface
+		
+		
+class ODeltaPackInfo(OPackInfo):
+	"""Adds delta specific information, 
+	Either the 20 byte sha which points to some object in the database, 
+	or the negative offset from the pack_offset, so that pack_offset - delta_info yields
+	the pack offset of the base object"""
+	__slots__ = tuple()
+	
+	def __new__(cls, packoffset, type, size, delta_info):
+		return tuple.__new__(cls, (packoffset, type, size, delta_info))
+		
+	#{ Interface 
+	@property
+	def delta_info(self):
+		return self[3]
+	#} END interface 
+	
+	
+class OStream(OInfo):
+	"""Base for object streams retrieved from the database, providing additional 
+	information about the stream.
+	Generally, ODB streams are read-only as objects are immutable"""
+	__slots__ = tuple()
+	
+	def __new__(cls, sha, type, size, stream, *args, **kwargs):
+		"""Helps with the initialization of subclasses"""
+		return tuple.__new__(cls, (sha, type, size, stream))
+	
+	
+	def __init__(self, *args, **kwargs):
+		tuple.__init__(self)
+	
+	#{ Stream Reader Interface 
+	
+	def read(self, size=-1):
+		return self[3].read(size)
+		
+	@property
+	def stream(self):
+		return self[3]
+		
+	#} END stream reader interface
+	
+	
+class ODeltaStream(OStream):
+	"""Uses size info of its stream, delaying reads"""
+	
+	def __new__(cls, sha, type, size, stream, *args, **kwargs):
+		"""Helps with the initialization of subclasses"""
+		return tuple.__new__(cls, (sha, type, size, stream))
+	
+	#{ Stream Reader Interface
+	
+	@property
+	def size(self):
+		return self[3].size
+		
+	#} END stream reader interface
+	
+	
+class OPackStream(OPackInfo):
+	"""Next to pack object information, a stream outputting an undeltified base object
+	is provided"""
+	__slots__ = tuple()
+	
+	def __new__(cls, packoffset, type, size, stream, *args):
+		"""Helps with the initialization of subclasses"""
+		return tuple.__new__(cls, (packoffset, type, size, stream))
+		
+	#{ Stream Reader Interface 
+	def read(self, size=-1):
+		return self[3].read(size)
+		
+	@property
+	def stream(self):
+		return self[3]
+	#} END stream reader interface
+
+	
+class ODeltaPackStream(ODeltaPackInfo):
+	"""Provides a stream outputting the uncompressed offset delta information"""
+	__slots__ = tuple()
+	
+	def __new__(cls, packoffset, type, size, delta_info, stream):
+		return tuple.__new__(cls, (packoffset, type, size, delta_info, stream))
+
+
+	#{ Stream Reader Interface 
+	def read(self, size=-1):
+		return self[4].read(size)
+		
+	@property
+	def stream(self):
+		return self[4]
+	#} END stream reader interface
+
+
+class IStream(list):
+	"""Represents an input content stream to be fed into the ODB. It is mutable to allow 
+	the ODB to record information about the operations outcome right in this instance.
+	
+	It provides interfaces for the OStream and a StreamReader to allow the instance
+	to blend in without prior conversion.
+	
+	The only method your content stream must support is 'read'"""
+	__slots__ = tuple()
+	
+	def __new__(cls, type, size, stream, sha=None):
+		return list.__new__(cls, (sha, type, size, stream, None))
+		
+	def __init__(self, type, size, stream, sha=None):
+		list.__init__(self, (sha, type, size, stream, None))
+	
+	#{ Interface 
+	@property
+	def hexsha(self):
+		""":return: our sha, hex encoded, 40 bytes"""
+		return bin_to_hex(self[0])
+		
+	def _error(self):
+		""":return: the error that occurred when processing the stream, or None"""
+		return self[4]
+		
+	def _set_error(self, exc):
+		"""Set this input stream to the given exc, may be None to reset the error"""
+		self[4] = exc
+			
+	error = property(_error, _set_error)
+	
+	#} END interface
+	
+	#{ Stream Reader Interface
+	
+	def read(self, size=-1):
+		"""Implements a simple stream reader interface, passing the read call on 
+			to our internal stream"""
+		return self[3].read(size)
+		
+	#} END stream reader interface 
+	
+	#{  interface
+	
+	def _set_binsha(self, binsha):
+		self[0] = binsha
+		
+	def _binsha(self):
+		return self[0]
+		
+	binsha = property(_binsha, _set_binsha)
+	
+	
+	def _type(self):
+		return self[1]
+	
+	def _set_type(self, type):
+		self[1] = type
+		
+	type = property(_type, _set_type)
+	
+	def _size(self):
+		return self[2]
+		
+	def _set_size(self, size):
+		self[2] = size
+	
+	size = property(_size, _set_size)
+	
+	def _stream(self):
+		return self[3]
+		
+	def _set_stream(self, stream):
+		self[3] = stream
+	
+	stream = property(_stream, _set_stream)
+	
+	#} END odb info interface 
+		
+
+class InvalidOInfo(tuple):
+	"""Carries information about a sha identifying an object which is invalid in 
+	the queried database. The exception attribute provides more information about
+	the cause of the issue"""
+	__slots__ = tuple()
+	
+	def __new__(cls, sha, exc):
+		return tuple.__new__(cls, (sha, exc))
+		
+	def __init__(self, sha, exc):
+		tuple.__init__(self, (sha, exc))
+	
+	@property
+	def binsha(self):
+		return self[0]
+		
+	@property
+	def hexsha(self):
+		return bin_to_hex(self[0])
+		
+	@property
+	def error(self):
+		""":return: exception instance explaining the failure"""
+		return self[1]
+
+
+class InvalidOStream(InvalidOInfo):
+	"""Carries information about an invalid ODB stream"""
+	__slots__ = tuple()
+	
+#} END ODB Bases
+