pickle.py

"""Create portable serialized representations of Python objects.

See module cPickle for a (much) faster implementation.
See module copy_reg for a mechanism for registering custom picklers.
See module pickletools source for extensive comments.

Classes:

 Pickler
 Unpickler

Functions:

 dump(object, file)
 dumps(object) -> string
 load(file) -> object
 loads(string) -> object

Misc variables:

 __version__
 format_version
 compatible_formats

"""

__version__ = "$Revision: 72223 $" # Code version

from types import *
from copy_reg import dispatch_table
from copy_reg import _extension_registry, _inverted_registry, _extension_cache
import marshal
import sys
import struct
import re

__all__ = ["PickleError", "PicklingError", "UnpicklingError", "Pickler",
 "Unpickler", "dump", "dumps", "load", "loads"]

# These are purely informational; no code uses these.
format_version = "2.0" # File format version we write
compatible_formats = ["1.0", # Original protocol 0
 "1.1", # Protocol 0 with INST added
 "1.2", # Original protocol 1
 "1.3", # Protocol 1 with BINFLOAT added
 "2.0", # Protocol 2
 ] # Old format versions we can read

# Keep in synch with cPickle. This is the highest protocol number we
# know how to read.
HIGHEST_PROTOCOL = 2

# Why use struct.pack() for pickling but marshal.loads() for
# unpickling? struct.pack() is 40% faster than marshal.dumps(), but
# marshal.loads() is twice as fast as struct.unpack()!
mloads = marshal.loads

class PickleError(Exception):
 """A common base class for the other pickling exceptions."""
 pass

class PicklingError(PickleError):
 """This exception is raised when an unpicklable object is passed to the
 dump() method.

 """
 pass

class UnpicklingError(PickleError):
 """This exception is raised when there is a problem unpickling an object,
 such as a security violation.

 Note that other exceptions may also be raised during unpickling, including
 (but not necessarily limited to) AttributeError, EOFError, ImportError,
 and IndexError.

 """
 pass

# An instance of _Stop is raised by Unpickler.load_stop() in response to
# the STOP opcode, passing the object that is the result of unpickling.
class _Stop(Exception):
 def __init__(self, value):
 self.value = value

# Jython has PyStringMap; it's a dict subclass with string keys
try:
 from org.python.core import PyStringMap
except ImportError:
 PyStringMap = None

# UnicodeType may or may not be exported (normally imported from types)
try:
 UnicodeType
except NameError:
 UnicodeType = None

# Pickle opcodes. See pickletools.py for extensive docs. The listing
# here is in kind-of alphabetical order of 1-character pickle code.
# pickletools groups them by purpose.

MARK = '(' # push special markobject on stack
STOP = '.' # every pickle ends with STOP
POP = '0' # discard topmost stack item
POP_MARK = '1' # discard stack top through topmost markobject
DUP = '2' # duplicate top stack item
FLOAT = 'F' # push float object; decimal string argument
INT = 'I' # push integer or bool; decimal string argument
BININT = 'J' # push four-byte signed int
BININT1 = 'K' # push 1-byte unsigned int
LONG = 'L' # push long; decimal string argument
BININT2 = 'M' # push 2-byte unsigned int
NONE = 'N' # push None
PERSID = 'P' # push persistent object; id is taken from string arg
BINPERSID = 'Q' # " " " ; " " " " stack
REDUCE = 'R' # apply callable to argtuple, both on stack
STRING = 'S' # push string; NL-terminated string argument
BINSTRING = 'T' # push string; counted binary string argument
SHORT_BINSTRING = 'U' # " " ; " " " " < 256 bytes
UNICODE = 'V' # push Unicode string; raw-unicode-escaped'd argument
BINUNICODE = 'X' # " " " ; counted UTF-8 string argument
APPEND = 'a' # append stack top to list below it
BUILD = 'b' # call __setstate__ or __dict__.update()
GLOBAL = 'c' # push self.find_class(modname, name); 2 string args
DICT = 'd' # build a dict from stack items
EMPTY_DICT = '}' # push empty dict
APPENDS = 'e' # extend list on stack by topmost stack slice
GET = 'g' # push item from memo on stack; index is string arg
BINGET = 'h' # " " " " " " ; " " 1-byte arg
INST = 'i' # build & push class instance
LONG_BINGET = 'j' # push item from memo on stack; index is 4-byte arg
LIST = 'l' # build list from topmost stack items
EMPTY_LIST = ']' # push empty list
OBJ = 'o' # build & push class instance
PUT = 'p' # store stack top in memo; index is string arg
BINPUT = 'q' # " " " " " ; " " 1-byte arg
LONG_BINPUT = 'r' # " " " " " ; " " 4-byte arg
SETITEM = 's' # add key+value pair to dict
TUPLE = 't' # build tuple from topmost stack items
EMPTY_TUPLE = ')' # push empty tuple
SETITEMS = 'u' # modify dict by adding topmost key+value pairs
BINFLOAT = 'G' # push float; arg is 8-byte float encoding

TRUE = 'I01\n' # not an opcode; see INT docs in pickletools.py
FALSE = 'I00\n' # not an opcode; see INT docs in pickletools.py

# Protocol 2

PROTO = '\x80' # identify pickle protocol
NEWOBJ = '\x81' # build object by applying cls.__new__ to argtuple
EXT1 = '\x82' # push object from extension registry; 1-byte index
EXT2 = '\x83' # ditto, but 2-byte index
EXT4 = '\x84' # ditto, but 4-byte index
TUPLE1 = '\x85' # build 1-tuple from stack top
TUPLE2 = '\x86' # build 2-tuple from two topmost stack items
TUPLE3 = '\x87' # build 3-tuple from three topmost stack items
NEWTRUE = '\x88' # push True
NEWFALSE = '\x89' # push False
LONG1 = '\x8a' # push long from < 256 bytes
LONG4 = '\x8b' # push really big long

_tuplesize2code = [EMPTY_TUPLE, TUPLE1, TUPLE2, TUPLE3]


__all__.extend([x for x in dir() if re.match("[A-Z][A-Z0-9_]+$",x)])
del x


# Pickling machinery

class Pickler:

 def __init__(self, file, protocol=None):
 """This takes a file-like object for writing a pickle data stream.

 The optional protocol argument tells the pickler to use the
 given protocol; supported protocols are 0, 1, 2. The default
 protocol is 0, to be backwards compatible. (Protocol 0 is the
 only protocol that can be written to a file opened in text
 mode and read back successfully. When using a protocol higher
 than 0, make sure the file is opened in binary mode, both when
 pickling and unpickling.)

 Protocol 1 is more efficient than protocol 0; protocol 2 is
 more efficient than protocol 1.

 Specifying a negative protocol version selects the highest
 protocol version supported. The higher the protocol used, the
 more recent the version of Python needed to read the pickle
 produced.

 The file parameter must have a write() method that accepts a single
 string argument. It can thus be an open file object, a StringIO
 object, or any other custom object that meets this interface.

 """
 if protocol is None:
 protocol = 0
 if protocol < 0:
 protocol = HIGHEST_PROTOCOL
 elif not 0 <= protocol <= HIGHEST_PROTOCOL:
 raise ValueError("pickle protocol must be <= %d" % HIGHEST_PROTOCOL)
 self.write = file.write
 self.memo = {}
 self.proto = int(protocol)
 self.bin = protocol >= 1
 self.fast = 0

 def clear_memo(self):
 """Clears the pickler's "memo".

 The memo is the data structure that remembers which objects the
 pickler has already seen, so that shared or recursive objects are
 pickled by reference and not by value. This method is useful when
 re-using picklers.

 """
 self.memo.clear()

 def dump(self, obj):
 """Write a pickled representation of obj to the open file."""
 if self.proto >= 2:
 self.write(PROTO + chr(self.proto))
 self.save(obj)
 self.write(STOP)

 def memoize(self, obj):
 """Store an object in the memo."""

 # The Pickler memo is a dictionary mapping object ids to 2-tuples
 # that contain the Unpickler memo key and the object being memoized.
 # The memo key is written to the pickle and will become
 # the key in the Unpickler's memo. The object is stored in the
 # Pickler memo so that transient objects are kept alive during
 # pickling.

 # The use of the Unpickler memo length as the memo key is just a
 # convention. The only requirement is that the memo values be unique.
 # But there appears no advantage to any other scheme, and this
 # scheme allows the Unpickler memo to be implemented as a plain (but
 # growable) array, indexed by memo key.
 if self.fast:
 return
 assert id(obj) not in self.memo
 memo_len = len(self.memo)
 self.write(self.put(memo_len))
 self.memo[id(obj)] = memo_len, obj

 # Return a PUT (BINPUT, LONG_BINPUT) opcode string, with argument i.
 def put(self, i, pack=struct.pack):
 if self.bin:
 if i < 256:
 return BINPUT + chr(i)
 else:
 return LONG_BINPUT + pack("<i", i)

 return PUT + repr(i) + '\n'

 # Return a GET (BINGET, LONG_BINGET) opcode string, with argument i.
 def get(self, i, pack=struct.pack):
 if self.bin:
 if i < 256:
 return BINGET + chr(i)
 else:
 return LONG_BINGET + pack("<i", i)

 return GET + repr(i) + '\n'

 def save(self, obj):
 # Check for persistent id (defined by a subclass)
 pid = self.persistent_id(obj)
 if pid is not None:
 self.save_pers(pid)
 return

 # Check the memo
 x = self.memo.get(id(obj))
 if x:
 self.write(self.get(x[0]))
 return

 # Check the type dispatch table
 t = type(obj)
 f = self.dispatch.get(t)
 if f:
 f(self, obj) # Call unbound method with explicit self
 return

 # Check copy_reg.dispatch_table
 reduce = dispatch_table.get(t)
 if reduce:
 rv = reduce(obj)
 else:
 # Check for a class with a custom metaclass; treat as regular class
 try:
 issc = issubclass(t, TypeType)
 except TypeError: # t is not a class (old Boost; see SF #502085)
 issc = 0
 if issc:
 self.save_global(obj)
 return

 # Check for a __reduce_ex__ method, fall back to __reduce__
 reduce = getattr(obj, "__reduce_ex__", None)
 if reduce:
 rv = reduce(self.proto)
 else:
 reduce = getattr(obj, "__reduce__", None)
 if reduce:
 rv = reduce()
 else:
 raise PicklingError("Can't pickle %r object: %r" %
 (t.__name__, obj))

 # Check for string returned by reduce(), meaning "save as global"
 if type(rv) is StringType:
 self.save_global(obj, rv)
 return

 # Assert that reduce() returned a tuple
 if type(rv) is not TupleType:
 raise PicklingError("%s must return string or tuple" % reduce)

 # Assert that it returned an appropriately sized tuple
 l = len(rv)
 if not (2 <= l <= 5):
 raise PicklingError("Tuple returned by %s must have "
 "two to five elements" % reduce)

 # Save the reduce() output and finally memoize the object
 self.save_reduce(obj=obj, *rv)

 def persistent_id(self, obj):
 # This exists so a subclass can override it
 return None

 def save_pers(self, pid):
 # Save a persistent id reference
 if self.bin:
 self.save(pid)
 self.write(BINPERSID)
 else:
 self.write(PERSID + str(pid) + '\n')

 def save_reduce(self, func, args, state=None,
 listitems=None, dictitems=None, obj=None):
 # This API is called by some subclasses

 # Assert that args is a tuple or None
 if not isinstance(args, TupleType):
 raise PicklingError("args from reduce() should be a tuple")

 # Assert that func is callable
 if not hasattr(func, '__call__'):
 raise PicklingError("func from reduce should be callable")

 save = self.save
 write = self.write

 # Protocol 2 special case: if func's name is __newobj__, use NEWOBJ
 if self.proto >= 2 and getattr(func, "__name__", "") == "__newobj__":
 # A __reduce__ implementation can direct protocol 2 to
 # use the more efficient NEWOBJ opcode, while still
 # allowing protocol 0 and 1 to work normally. For this to
 # work, the function returned by __reduce__ should be
 # called __newobj__, and its first argument should be a
 # new-style class. The implementation for __newobj__
 # should be as follows, although pickle has no way to
 # verify this:
 #
 # def __newobj__(cls, *args):
 # return cls.__new__(cls, *args)
 #
 # Protocols 0 and 1 will pickle a reference to __newobj__,
 # while protocol 2 (and above) will pickle a reference to
 # cls, the remaining args tuple, and the NEWOBJ code,
 # which calls cls.__new__(cls, *args) at unpickling time
 # (see load_newobj below). If __reduce__ returns a
 # three-tuple, the state from the third tuple item will be
 # pickled regardless of the protocol, calling __setstate__
 # at unpickling time (see load_build below).
 #
 # Note that no standard __newobj__ implementation exists;
 # you have to provide your own. This is to enforce
 # compatibility with Python 2.2 (pickles written using
 # protocol 0 or 1 in Python 2.3 should be unpicklable by
 # Python 2.2).
 cls = args[0]
 if not hasattr(cls, "__new__"):
 raise PicklingError(
 "args[0] from __newobj__ args has no __new__")
 if obj is not None and cls is not obj.__class__:
 raise PicklingError(
 "args[0] from __newobj__ args has the wrong class")
 args = args[1:]
 save(cls)
 save(args)
 write(NEWOBJ)
 else:
 save(func)
 save(args)
 write(REDUCE)

 if obj is not None:
 # If the object is already in the memo, this means it is
 # recursive. In this case, throw away everything we put on the
 # stack, and fetch the object back from the memo.
 if id(obj) in self.memo:
 write(POP + self.get(self.memo[id(obj)][0]))
 else:
 self.memoize(obj)

 # More new special cases (that work with older protocols as
 # well): when __reduce__ returns a tuple with 4 or 5 items,
 # the 4th and 5th item should be iterators that provide list
 # items and dict items (as (key, value) tuples), or None.

 if listitems is not None:
 self._batch_appends(listitems)

 if dictitems is not None:
 self._batch_setitems(dictitems)

 if state is not None:
 save(state)
 write(BUILD)

 # Methods below this point are dispatched through the dispatch table

 dispatch = {}

 def save_none(self, obj):
 self.write(NONE)
 dispatch[NoneType] = save_none

 def save_bool(self, obj):
 if self.proto >= 2:
 self.write(obj and NEWTRUE or NEWFALSE)
 else:
 self.write(obj and TRUE or FALSE)
 dispatch[bool] = save_bool

 def save_int(self, obj, pack=struct.pack):
 if self.bin:
 # If the int is small enough to fit in a signed 4-byte 2's-comp
 # format, we can store it more efficiently than the general
 # case.
 # First one- and two-byte unsigned ints:
 if obj >= 0:
 if obj <= 0xff:
 self.write(BININT1 + chr(obj))
 return
 if obj <= 0xffff:
 self.write("%c%c%c" % (BININT2, obj&0xff, obj>>8))
 return
 # Next check for 4-byte signed ints:
 high_bits = obj >> 31 # note that Python shift sign-extends
 if high_bits == 0 or high_bits == -1:
 # All high bits are copies of bit 2**31, so the value
 # fits in a 4-byte signed int.
 self.write(BININT + pack("<i", obj))
 return
 # Text pickle, or int too big to fit in signed 4-byte format.
 self.write(INT + repr(obj) + '\n')
 dispatch[IntType] = save_int

 def save_long(self, obj, pack=struct.pack):
 if self.proto >= 2:
 bytes = encode_long(obj)
 n = len(bytes)
 if n < 256:
 self.write(LONG1 + chr(n) + bytes)
 else:
 self.write(LONG4 + pack("<i", n) + bytes)
 return
 self.write(LONG + repr(obj) + '\n')
 dispatch[LongType] = save_long

 def save_float(self, obj, pack=struct.pack):
 if self.bin:
 self.write(BINFLOAT + pack('>d', obj))
 else:
 self.write(FLOAT + repr(obj) + '\n')
 dispatch[FloatType] = save_float

 def save_string(self, obj, pack=struct.pack):
 if self.bin:
 n = len(obj)
 if n < 256:
 self.write(SHORT_BINSTRING + chr(n) + obj)
 else:
 self.write(BINSTRING + pack("<i", n) + obj)
 else:
 self.write(STRING + repr(obj) + '\n')
 self.memoize(obj)
 dispatch[StringType] = save_string

 def save_unicode(self, obj, pack=struct.pack):
 if self.bin:
 encoding = obj.encode('utf-8')
 n = len(encoding)
 self.write(BINUNICODE + pack("<i", n) + encoding)
 else:
 obj = obj.replace("\\", "\\u005c")
 obj = obj.replace("\n", "\\u000a")
 self.write(UNICODE + obj.encode('raw-unicode-escape') + '\n')
 self.memoize(obj)
 dispatch[UnicodeType] = save_unicode

 if StringType is UnicodeType:
 # This is true for Jython
 def save_string(self, obj, pack=struct.pack):
 unicode = obj.isunicode()

 if self.bin:
 if unicode:
 obj = obj.encode("utf-8")
 l = len(obj)
 if l < 256 and not unicode:
 self.write(SHORT_BINSTRING + chr(l) + obj)
 else:
 s = pack("<i", l)
 if unicode:
 self.write(BINUNICODE + s + obj)
 else:
 self.write(BINSTRING + s + obj)
 else:
 if unicode:
 obj = obj.replace("\\", "\\u005c")
 obj = obj.replace("\n", "\\u000a")
 obj = obj.encode('raw-unicode-escape')
 self.write(UNICODE + obj + '\n')
 else:
 self.write(STRING + repr(obj) + '\n')
 self.memoize(obj)
 dispatch[StringType] = save_string

 def save_tuple(self, obj):
 write = self.write
 proto = self.proto

 n = len(obj)
 if n == 0:
 if proto:
 write(EMPTY_TUPLE)
 else:
 write(MARK + TUPLE)
 return

 save = self.save
 memo = self.memo
 if n <= 3 and proto >= 2:
 for element in obj:
 save(element)
 # Subtle. Same as in the big comment below.
 if id(obj) in memo:
 get = self.get(memo[id(obj)][0])
 write(POP * n + get)
 else:
 write(_tuplesize2code[n])
 self.memoize(obj)
 return

 # proto 0 or proto 1 and tuple isn't empty, or proto > 1 and tuple
 # has more than 3 elements.
 write(MARK)
 for element in obj:
 save(element)

 if id(obj) in memo:
 # Subtle. d was not in memo when we entered save_tuple(), so
 # the process of saving the tuple's elements must have saved
 # the tuple itself: the tuple is recursive. The proper action
 # now is to throw away everything we put on the stack, and
 # simply GET the tuple (it's already constructed). This check
 # could have been done in the "for element" loop instead, but
 # recursive tuples are a rare thing.
 get = self.get(memo[id(obj)][0])
 if proto:
 write(POP_MARK + get)
 else: # proto 0 -- POP_MARK not available
 write(POP * (n+1) + get)
 return

 # No recursion.
 self.write(TUPLE)
 self.memoize(obj)

 dispatch[TupleType] = save_tuple

 # save_empty_tuple() isn't used by anything in Python 2.3. However, I
 # found a Pickler subclass in Zope3 that calls it, so it's not harmless
 # to remove it.
 def save_empty_tuple(self, obj):
 self.write(EMPTY_TUPLE)

 def save_list(self, obj):
 write = self.write

 if self.bin:
 write(EMPTY_LIST)
 else: # proto 0 -- can't use EMPTY_LIST
 write(MARK + LIST)

 self.memoize(obj)
 self._batch_appends(iter(obj))

 dispatch[ListType] = save_list

 # Keep in synch with cPickle's BATCHSIZE. Nothing will break if it gets
 # out of synch, though.
 _BATCHSIZE = 1000

 def _batch_appends(self, items):
 # Helper to batch up APPENDS sequences
 save = self.save
 write = self.write

 if not self.bin:
 for x in items:
 save(x)
 write(APPEND)
 return

 r = xrange(self._BATCHSIZE)
 while items is not None:
 tmp = []
 for i in r:
 try:
 x = items.next()
 tmp.append(x)
 except StopIteration:
 items = None
 break
 n = len(tmp)
 if n > 1:
 write(MARK)
 for x in tmp:
 save(x)
 write(APPENDS)
 elif n:
 save(tmp[0])
 write(APPEND)
 # else tmp is empty, and we're done

 def save_dict(self, obj):
 write = self.write

 if self.bin:
 write(EMPTY_DICT)
 else: # proto 0 -- can't use EMPTY_DICT
 write(MARK + DICT)

 self.memoize(obj)
 self._batch_setitems(obj.iteritems())

 dispatch[DictionaryType] = save_dict
 if not PyStringMap is None:
 dispatch[PyStringMap] = save_dict

 def _batch_setitems(self, items):
 # Helper to batch up SETITEMS sequences; proto >= 1 only
 save = self.save
 write = self.write

 if not self.bin:
 for k, v in items:
 save(k)
 save(v)
 write(SETITEM)
 return

 r = xrange(self._BATCHSIZE)
 while items is not None:
 tmp = []
 for i in r:
 try:
 tmp.append(items.next())
 except StopIteration:
 items = None
 break
 n = len(tmp)
 if n > 1:
 write(MARK)
 for k, v in tmp:
 save(k)
 save(v)
 write(SETITEMS)
 elif n:
 k, v = tmp[0]
 save(k)
 save(v)
 write(SETITEM)
 # else tmp is empty, and we're done

 def save_inst(self, obj):
 cls = obj.__class__

 memo = self.memo
 write = self.write
 save = self.save

 if hasattr(obj, '__getinitargs__'):
 args = obj.__getinitargs__()
 len(args) # XXX Assert it's a sequence
 _keep_alive(args, memo)
 else:
 args = ()

 write(MARK)

 if self.bin:
 save(cls)
 for arg in args:
 save(arg)
 write(OBJ)
 else:
 for arg in args:
 save(arg)
 write(INST + cls.__module__ + '\n' + cls.__name__ + '\n')

 self.memoize(obj)

 try:
 getstate = obj.__getstate__
 except AttributeError:
 stuff = obj.__dict__
 else:
 stuff = getstate()
 _keep_alive(stuff, memo)
 save(stuff)
 write(BUILD)

 dispatch[InstanceType] = save_inst

 def save_global(self, obj, name=None, pack=struct.pack):
 write = self.write
 memo = self.memo

 if name is None:
 name = obj.__name__

 module = getattr(obj, "__module__", None)
 if module is None:
 module = whichmodule(obj, name)

 try:
 __import__(module)
 mod = sys.modules[module]
 klass = getattr(mod, name)
 except (ImportError, KeyError, AttributeError):
 raise PicklingError(
 "Can't pickle %r: it's not found as %s.%s" %
 (obj, module, name))
 else:
 if klass is not obj:
 raise PicklingError(
 "Can't pickle %r: it's not the same object as %s.%s" %
 (obj, module, name))

 if self.proto >= 2:
 code = _extension_registry.get((module, name))
 if code:
 assert code > 0
 if code <= 0xff:
 write(EXT1 + chr(code))
 elif code <= 0xffff:
 write("%c%c%c" % (EXT2, code&0xff, code>>8))
 else:
 write(EXT4 + pack("<i", code))
 return

 write(GLOBAL + module + '\n' + name + '\n')
 self.memoize(obj)

 dispatch[ClassType] = save_global
 dispatch[FunctionType] = save_global
 dispatch[BuiltinFunctionType] = save_global
 dispatch[TypeType] = save_global

# Pickling helpers

def _keep_alive(x, memo):
 """Keeps a reference to the object x in the memo.

 Because we remember objects by their id, we have
 to assure that possibly temporary objects are kept
 alive by referencing them.
 We store a reference at the id of the memo, which should
 normally not be used unless someone tries to deepcopy
 the memo itself...
 """
 try:
 memo[id(memo)].append(x)
 except KeyError:
 # aha, this is the first one :-)
 memo[id(memo)]=[x]


# A cache for whichmodule(), mapping a function object to the name of
# the module in which the function was found.

classmap = {} # called classmap for backwards compatibility

def whichmodule(func, funcname):
 """Figure out the module in which a function occurs.

 Search sys.modules for the module.
 Cache in classmap.
 Return a module name.
 If the function cannot be found, return "__main__".
 """
 # Python functions should always get an __module__ from their globals.
 mod = getattr(func, "__module__", None)
 if mod is not None:
 return mod
 if func in classmap:
 return classmap[func]

 for name, module in sys.modules.items():
 if module is None:
 continue # skip dummy package entries
 if name != '__main__' and getattr(module, funcname, None) is func:
 break
 else:
 name = '__main__'
 classmap[func] = name
 return name


# Unpickling machinery

class Unpickler:

 def __init__(self, file):
 """This takes a file-like object for reading a pickle data stream.

 The protocol version of the pickle is detected automatically, so no
 proto argument is needed.

 The file-like object must have two methods, a read() method that
 takes an integer argument, and a readline() method that requires no
 arguments. Both methods should return a string. Thus file-like
 object can be a file object opened for reading, a StringIO object,
 or any other custom object that meets this interface.
 """
 self.readline = file.readline
 self.read = file.read
 self.memo = {}

 def load(self):
 """Read a pickled object representation from the open file.

 Return the reconstituted object hierarchy specified in the file.
 """
 self.mark = object() # any new unique object
 self.stack = []
 self.append = self.stack.append
 read = self.read
 dispatch = self.dispatch
 try:
 while 1:
 key = read(1)
 dispatch[key](self)
 except _Stop, stopinst:
 return stopinst.value

 # Return largest index k such that self.stack[k] is self.mark.
 # If the stack doesn't contain a mark, eventually raises IndexError.
 # This could be sped by maintaining another stack, of indices at which
 # the mark appears. For that matter, the latter stack would suffice,
 # and we wouldn't need to push mark objects on self.stack at all.
 # Doing so is probably a good thing, though, since if the pickle is
 # corrupt (or hostile) we may get a clue from finding self.mark embedded
 # in unpickled objects.
 def marker(self):
 stack = self.stack
 mark = self.mark
 k = len(stack)-1
 while stack[k] is not mark: k = k-1
 return k

 dispatch = {}

 def load_eof(self):
 raise EOFError
 dispatch[''] = load_eof

 def load_proto(self):
 proto = ord(self.read(1))
 if not 0 <= proto <= 2:
 raise ValueError, "unsupported pickle protocol: %d" % proto
 dispatch[PROTO] = load_proto

 def load_persid(self):
 pid = self.readline()[:-1]
 self.append(self.persistent_load(pid))
 dispatch[PERSID] = load_persid

 def load_binpersid(self):
 pid = self.stack.pop()
 self.append(self.persistent_load(pid))
 dispatch[BINPERSID] = load_binpersid

 def load_none(self):
 self.append(None)
 dispatch[NONE] = load_none

 def load_false(self):
 self.append(False)
 dispatch[NEWFALSE] = load_false

 def load_true(self):
 self.append(True)
 dispatch[NEWTRUE] = load_true

 def load_int(self):
 data = self.readline()
 if data == FALSE[1:]:
 val = False
 elif data == TRUE[1:]:
 val = True
 else:
 try:
 val = int(data)
 except ValueError:
 val = long(data)
 self.append(val)
 dispatch[INT] = load_int

 def load_binint(self):
 self.append(mloads('i' + self.read(4)))
 dispatch[BININT] = load_binint

 def load_binint1(self):
 self.append(ord(self.read(1)))
 dispatch[BININT1] = load_binint1

 def load_binint2(self):
 self.append(mloads('i' + self.read(2) + '\000\000'))
 dispatch[BININT2] = load_binint2

 def load_long(self):
 self.append(long(self.readline()[:-1], 0))
 dispatch[LONG] = load_long

 def load_long1(self):
 n = ord(self.read(1))
 bytes = self.read(n)
 self.append(decode_long(bytes))
 dispatch[LONG1] = load_long1

 def load_long4(self):
 n = mloads('i' + self.read(4))
 bytes = self.read(n)
 self.append(decode_long(bytes))
 dispatch[LONG4] = load_long4

 def load_float(self):
 self.append(float(self.readline()[:-1]))
 dispatch[FLOAT] = load_float

 def load_binfloat(self, unpack=struct.unpack):
 self.append(unpack('>d', self.read(8))[0])
 dispatch[BINFLOAT] = load_binfloat

 def load_string(self):
 rep = self.readline()[:-1]
 for q in "\"'": # double or single quote
 if rep.startswith(q):
 if len(rep) < 2 or not rep.endswith(q):
 raise ValueError, "insecure string pickle"
 rep = rep[len(q):-len(q)]
 break
 else:
 raise ValueError, "insecure string pickle"
 self.append(rep.decode("string-escape"))
 dispatch[STRING] = load_string

 def load_binstring(self):
 len = mloads('i' + self.read(4))
 self.append(self.read(len))
 dispatch[BINSTRING] = load_binstring

 def load_unicode(self):
 self.append(unicode(self.readline()[:-1],'raw-unicode-escape'))
 dispatch[UNICODE] = load_unicode

 def load_binunicode(self):
 len = mloads('i' + self.read(4))
 self.append(unicode(self.read(len),'utf-8'))
 dispatch[BINUNICODE] = load_binunicode

 def load_short_binstring(self):
 len = ord(self.read(1))
 self.append(self.read(len))
 dispatch[SHORT_BINSTRING] = load_short_binstring

 def load_tuple(self):
 k = self.marker()
 self.stack[k:] = [tuple(self.stack[k+1:])]
 dispatch[TUPLE] = load_tuple

 def load_empty_tuple(self):
 self.stack.append(())
 dispatch[EMPTY_TUPLE] = load_empty_tuple

 def load_tuple1(self):
 self.stack[-1] = (self.stack[-1],)
 dispatch[TUPLE1] = load_tuple1

 def load_tuple2(self):
 self.stack[-2:] = [(self.stack[-2], self.stack[-1])]
 dispatch[TUPLE2] = load_tuple2

 def load_tuple3(self):
 self.stack[-3:] = [(self.stack[-3], self.stack[-2], self.stack[-1])]
 dispatch[TUPLE3] = load_tuple3

 def load_empty_list(self):
 self.stack.append([])
 dispatch[EMPTY_LIST] = load_empty_list

 def load_empty_dictionary(self):
 self.stack.append({})
 dispatch[EMPTY_DICT] = load_empty_dictionary

 def load_list(self):
 k = self.marker()
 self.stack[k:] = [self.stack[k+1:]]
 dispatch[LIST] = load_list

 def load_dict(self):
 k = self.marker()
 d = {}
 items = self.stack[k+1:]
 for i in range(0, len(items), 2):
 key = items[i]
 value = items[i+1]
 d[key] = value
 self.stack[k:] = [d]
 dispatch[DICT] = load_dict

 # INST and OBJ differ only in how they get a class object. It's not
 # only sensible to do the rest in a common routine, the two routines
 # previously diverged and grew different bugs.
 # klass is the class to instantiate, and k points to the topmost mark
 # object, following which are the arguments for klass.__init__.
 def _instantiate(self, klass, k):
 args = tuple(self.stack[k+1:])
 del self.stack[k:]
 instantiated = 0
 if (not args and
 type(klass) is ClassType and
 not hasattr(klass, "__getinitargs__")):
 try:
 value = _EmptyClass()
 value.__class__ = klass
 instantiated = 1
 except RuntimeError:
 # In restricted execution, assignment to inst.__class__ is
 # prohibited
 pass
 if not instantiated:
 try:
 value = klass(*args)
 except TypeError, err:
 raise TypeError, "in constructor for %s: %s" % (
 klass.__name__, str(err)), sys.exc_info()[2]
 self.append(value)

 def load_inst(self):
 module = self.readline()[:-1]
 name = self.readline()[:-1]
 klass = self.find_class(module, name)
 self._instantiate(klass, self.marker())
 dispatch[INST] = load_inst

 def load_obj(self):
 # Stack is ... markobject classobject arg1 arg2 ...
 k = self.marker()
 klass = self.stack.pop(k+1)
 self._instantiate(klass, k)
 dispatch[OBJ] = load_obj

 def load_newobj(self):
 args = self.stack.pop()
 cls = self.stack[-1]
 obj = cls.__new__(cls, *args)
 self.stack[-1] = obj
 dispatch[NEWOBJ] = load_newobj

 def load_global(self):
 module = self.readline()[:-1]
 name = self.readline()[:-1]
 klass = self.find_class(module, name)
 self.append(klass)
 dispatch[GLOBAL] = load_global

 def load_ext1(self):
 code = ord(self.read(1))
 self.get_extension(code)
 dispatch[EXT1] = load_ext1

 def load_ext2(self):
 code = mloads('i' + self.read(2) + '\000\000')
 self.get_extension(code)
 dispatch[EXT2] = load_ext2

 def load_ext4(self):
 code = mloads('i' + self.read(4))
 self.get_extension(code)
 dispatch[EXT4] = load_ext4

 def get_extension(self, code):
 nil = []
 obj = _extension_cache.get(code, nil)
 if obj is not nil:
 self.append(obj)
 return
 key = _inverted_registry.get(code)
 if not key:
 raise ValueError("unregistered extension code %d" % code)
 obj = self.find_class(*key)
 _extension_cache[code] = obj
 self.append(obj)

 def find_class(self, module, name):
 # Subclasses may override this
 __import__(module)
 mod = sys.modules[module]
 klass = getattr(mod, name)
 return klass

 def load_reduce(self):
 stack = self.stack
 args = stack.pop()
 func = stack[-1]
 value = func(*args)
 stack[-1] = value
 dispatch[REDUCE] = load_reduce

 def load_pop(self):
 del self.stack[-1]
 dispatch[POP] = load_pop

 def load_pop_mark(self):
 k = self.marker()
 del self.stack[k:]
 dispatch[POP_MARK] = load_pop_mark

 def load_dup(self):
 self.append(self.stack[-1])
 dispatch[DUP] = load_dup

 def load_get(self):
 self.append(self.memo[self.readline()[:-1]])
 dispatch[GET] = load_get

 def load_binget(self):
 i = ord(self.read(1))
 self.append(self.memo[repr(i)])
 dispatch[BINGET] = load_binget

 def load_long_binget(self):
 i = mloads('i' + self.read(4))
 self.append(self.memo[repr(i)])
 dispatch[LONG_BINGET] = load_long_binget

 def load_put(self):
 self.memo[self.readline()[:-1]] = self.stack[-1]
 dispatch[PUT] = load_put

 def load_binput(self):
 i = ord(self.read(1))
 self.memo[repr(i)] = self.stack[-1]
 dispatch[BINPUT] = load_binput

 def load_long_binput(self):
 i = mloads('i' + self.read(4))
 self.memo[repr(i)] = self.stack[-1]
 dispatch[LONG_BINPUT] = load_long_binput

 def load_append(self):
 stack = self.stack
 value = stack.pop()
 list = stack[-1]
 list.append(value)
 dispatch[APPEND] = load_append

 def load_appends(self):
 stack = self.stack
 mark = self.marker()
 list = stack[mark - 1]
 list.extend(stack[mark + 1:])
 del stack[mark:]
 dispatch[APPENDS] = load_appends

 def load_setitem(self):
 stack = self.stack
 value = stack.pop()
 key = stack.pop()
 dict = stack[-1]
 dict[key] = value
 dispatch[SETITEM] = load_setitem

 def load_setitems(self):
 stack = self.stack
 mark = self.marker()
 dict = stack[mark - 1]
 for i in range(mark + 1, len(stack), 2):
 dict[stack[i]] = stack[i + 1]

 del stack[mark:]
 dispatch[SETITEMS] = load_setitems

 def load_build(self):
 stack = self.stack
 state = stack.pop()
 inst = stack[-1]
 setstate = getattr(inst, "__setstate__", None)
 if setstate:
 setstate(state)
 return
 slotstate = None
 if isinstance(state, tuple) and len(state) == 2:
 state, slotstate = state
 if state:
 try:
 d = inst.__dict__
 try:
 for k, v in state.iteritems():
 d[intern(k)] = v
 # keys in state don't have to be strings
 # don't blow up, but don't go out of our way
 except TypeError:
 d.update(state)

 except RuntimeError:
 # XXX In restricted execution, the instance's __dict__
 # is not accessible. Use the old way of unpickling
 # the instance variables. This is a semantic
 # difference when unpickling in restricted
 # vs. unrestricted modes.
 # Note, however, that cPickle has never tried to do the
 # .update() business, and always uses
 # PyObject_SetItem(inst.__dict__, key, value) in a
 # loop over state.items().
 for k, v in state.items():
 setattr(inst, k, v)
 if slotstate:
 for k, v in slotstate.items():
 setattr(inst, k, v)
 dispatch[BUILD] = load_build

 def load_mark(self):
 self.append(self.mark)
 dispatch[MARK] = load_mark

 def load_stop(self):
 value = self.stack.pop()
 raise _Stop(value)
 dispatch[STOP] = load_stop

# Helper class for load_inst/load_obj

class _EmptyClass:
 pass

# Encode/decode longs in linear time.

import binascii as _binascii

def encode_long(x):
 r"""Encode a long to a two's complement little-endian binary string.
 Note that 0L is a special case, returning an empty string, to save a
 byte in the LONG1 pickling context.

 >>> encode_long(0L)
 ''
 >>> encode_long(255L)
 '\xff\x00'
 >>> encode_long(32767L)
 '\xff\x7f'
 >>> encode_long(-256L)
 '\x00\xff'
 >>> encode_long(-32768L)
 '\x00\x80'
 >>> encode_long(-128L)
 '\x80'
 >>> encode_long(127L)
 '\x7f'
 >>>
 """

 if x == 0:
 return ''
 if x > 0:
 ashex = hex(x)
 assert ashex.startswith("0x")
 njunkchars = 2 + ashex.endswith('L')
 nibbles = len(ashex) - njunkchars
 if nibbles & 1:
 # need an even # of nibbles for unhexlify
 ashex = "0x0" + ashex[2:]
 elif int(ashex[2], 16) >= 8:
 # "looks negative", so need a byte of sign bits
 ashex = "0x00" + ashex[2:]
 else:
 # Build the 256's-complement: (1L << nbytes) + x. The trick is
 # to find the number of bytes in linear time (although that should
 # really be a constant-time task).
 ashex = hex(-x)
 assert ashex.startswith("0x")
 njunkchars = 2 + ashex.endswith('L')
 nibbles = len(ashex) - njunkchars
 if nibbles & 1:
 # Extend to a full byte.
 nibbles += 1
 nbits = nibbles * 4
 x += 1L << nbits
 assert x > 0
 ashex = hex(x)
 njunkchars = 2 + ashex.endswith('L')
 newnibbles = len(ashex) - njunkchars
 if newnibbles < nibbles:
 ashex = "0x" + "0" * (nibbles - newnibbles) + ashex[2:]
 if int(ashex[2], 16) < 8:
 # "looks positive", so need a byte of sign bits
 ashex = "0xff" + ashex[2:]

 if ashex.endswith('L'):
 ashex = ashex[2:-1]
 else:
 ashex = ashex[2:]
 assert len(ashex) & 1 == 0, (x, ashex)
 binary = _binascii.unhexlify(ashex)
 return binary[::-1]

def decode_long(data):
 r"""Decode a long from a two's complement little-endian binary string.

 >>> decode_long('')
 0L
 >>> decode_long("\xff\x00")
 255L
 >>> decode_long("\xff\x7f")
 32767L
 >>> decode_long("\x00\xff")
 -256L
 >>> decode_long("\x00\x80")
 -32768L
 >>> decode_long("\x80")
 -128L
 >>> decode_long("\x7f")
 127L
 """

 nbytes = len(data)
 if nbytes == 0:
 return 0L
 ashex = _binascii.hexlify(data[::-1])
 n = long(ashex, 16) # quadratic time before Python 2.3; linear now
 if data[-1] >= '\x80':
 n -= 1L << (nbytes * 8)
 return n

# Shorthands

try:
 from cStringIO import StringIO
except ImportError:
 from StringIO import StringIO

def dump(obj, file, protocol=None):
 Pickler(file, protocol).dump(obj)

def dumps(obj, protocol=None):
 file = StringIO()
 Pickler(file, protocol).dump(obj)
 return file.getvalue()

def load(file):
 return Unpickler(file).load()

def loads(str):
 file = StringIO(str)
 return Unpickler(file).load()

# Doctest

def _test():
 import doctest
 return doctest.testmod()

if __name__ == "__main__":
 _test()