Lib/pickle.py

   1 """Create portable serialized representations of Python objects.
   2
   3 See module cPickle for a (much) faster implementation.
   4 See module copy_reg for a mechanism for registering custom picklers.
   5 See module pickletools source for extensive comments.
   6
   7 Classes:
   8
   9     Pickler
  10     Unpickler
  11
  12 Functions:
  13
  14     dump(object, file)
  15     dumps(object) -> string
  16     load(file) -> object
  17     loads(string) -> object
  18
  19 Misc variables:
  20
  21     __version__
  22     format_version
  23     compatible_formats
  24
  25 """
  26
  27 __version__ = "$Revision$"       # Code version
  28
  29 from types import *
  30 from copy_reg import dispatch_table
  31 from copy_reg import _extension_registry, _inverted_registry, _extension_cache
  32 import marshal
  33 import sys
  34 import struct
  35 import re
  36
  37 __all__ = ["PickleError", "PicklingError", "UnpicklingError", "Pickler",
  38            "Unpickler", "dump", "dumps", "load", "loads"]
  39
  40 # These are purely informational; no code uses these.
  41 format_version = "2.0"                  # File format version we write
  42 compatible_formats = ["1.0",            # Original protocol 0
  43                       "1.1",            # Protocol 0 with INST added
  44                       "1.2",            # Original protocol 1
  45                       "1.3",            # Protocol 1 with BINFLOAT added
  46                       "2.0",            # Protocol 2
  47                       ]                 # Old format versions we can read
  48
  49 # Keep in synch with cPickle.  This is the highest protocol number we
  50 # know how to read.
  51 HIGHEST_PROTOCOL = 2
  52
  53 # Why use struct.pack() for pickling but marshal.loads() for
  54 # unpickling?  struct.pack() is 40% faster than marshal.dumps(), but
  55 # marshal.loads() is twice as fast as struct.unpack()!
  56 mloads = marshal.loads
  57
  58 class PickleError(Exception):
  59     """A common base class for the other pickling exceptions."""
  60     pass
  61
  62 class PicklingError(PickleError):
  63     """This exception is raised when an unpicklable object is passed to the
  64     dump() method.
  65
  66     """
  67     pass
  68
  69 class UnpicklingError(PickleError):
  70     """This exception is raised when there is a problem unpickling an object,
  71     such as a security violation.
  72
  73     Note that other exceptions may also be raised during unpickling, including
  74     (but not necessarily limited to) AttributeError, EOFError, ImportError,
  75     and IndexError.
  76
  77     """
  78     pass
  79
  80 # An instance of _Stop is raised by Unpickler.load_stop() in response to
  81 # the STOP opcode, passing the object that is the result of unpickling.
  82 class _Stop(Exception):
  83     def __init__(self, value):
  84         self.value = value
  85
  86 # Jython has PyStringMap; it's a dict subclass with string keys
  87 try:
  88     from org.python.core import PyStringMap
  89 except ImportError:
  90     PyStringMap = None
  91
  92 # UnicodeType may or may not be exported (normally imported from types)
  93 try:
  94     UnicodeType
  95 except NameError:
  96     UnicodeType = None
  97
  98 # Pickle opcodes.  See pickletools.py for extensive docs.  The listing
  99 # here is in kind-of alphabetical order of 1-character pickle code.
 100 # pickletools groups them by purpose.
 101
 102 MARK            = '('   # push special markobject on stack
 103 STOP            = '.'   # every pickle ends with STOP
 104 POP             = '0'   # discard topmost stack item
 105 POP_MARK        = '1'   # discard stack top through topmost markobject
 106 DUP             = '2'   # duplicate top stack item
 107 FLOAT           = 'F'   # push float object; decimal string argument
 108 INT             = 'I'   # push integer or bool; decimal string argument
 109 BININT          = 'J'   # push four-byte signed int
 110 BININT1         = 'K'   # push 1-byte unsigned int
 111 LONG            = 'L'   # push long; decimal string argument
 112 BININT2         = 'M'   # push 2-byte unsigned int
 113 NONE            = 'N'   # push None
 114 PERSID          = 'P'   # push persistent object; id is taken from string arg
 115 BINPERSID       = 'Q'   #  "       "         "  ;  "  "   "     "  stack
 116 REDUCE          = 'R'   # apply callable to argtuple, both on stack
 117 STRING          = 'S'   # push string; NL-terminated string argument
 118 BINSTRING       = 'T'   # push string; counted binary string argument
 119 SHORT_BINSTRING = 'U'   #  "     "   ;    "      "       "      " < 256 bytes
 120 UNICODE         = 'V'   # push Unicode string; raw-unicode-escaped'd argument
 121 BINUNICODE      = 'X'   #   "     "       "  ; counted UTF-8 string argument
 122 APPEND          = 'a'   # append stack top to list below it
 123 BUILD           = 'b'   # call __setstate__ or __dict__.update()
 124 GLOBAL          = 'c'   # push self.find_class(modname, name); 2 string args
 125 DICT            = 'd'   # build a dict from stack items
 126 EMPTY_DICT      = '}'   # push empty dict
 127 APPENDS         = 'e'   # extend list on stack by topmost stack slice
 128 GET             = 'g'   # push item from memo on stack; index is string arg
 129 BINGET          = 'h'   #   "    "    "    "   "   "  ;   "    " 1-byte arg
 130 INST            = 'i'   # build & push class instance
 131 LONG_BINGET     = 'j'   # push item from memo on stack; index is 4-byte arg
 132 LIST            = 'l'   # build list from topmost stack items
 133 EMPTY_LIST      = ']'   # push empty list
 134 OBJ             = 'o'   # build & push class instance
 135 PUT             = 'p'   # store stack top in memo; index is string arg
 136 BINPUT          = 'q'   #   "     "    "   "   " ;   "    " 1-byte arg
 137 LONG_BINPUT     = 'r'   #   "     "    "   "   " ;   "    " 4-byte arg
 138 SETITEM         = 's'   # add key+value pair to dict
 139 TUPLE           = 't'   # build tuple from topmost stack items
 140 EMPTY_TUPLE     = ')'   # push empty tuple
 141 SETITEMS        = 'u'   # modify dict by adding topmost key+value pairs
 142 BINFLOAT        = 'G'   # push float; arg is 8-byte float encoding
 143
 144 TRUE            = 'I01\n'  # not an opcode; see INT docs in pickletools.py
 145 FALSE           = 'I00\n'  # not an opcode; see INT docs in pickletools.py
 146
 147 # Protocol 2
 148
 149 PROTO           = '\x80'  # identify pickle protocol
 150 NEWOBJ          = '\x81'  # build object by applying cls.__new__ to argtuple
 151 EXT1            = '\x82'  # push object from extension registry; 1-byte index
 152 EXT2            = '\x83'  # ditto, but 2-byte index
 153 EXT4            = '\x84'  # ditto, but 4-byte index
 154 TUPLE1          = '\x85'  # build 1-tuple from stack top
 155 TUPLE2          = '\x86'  # build 2-tuple from two topmost stack items
 156 TUPLE3          = '\x87'  # build 3-tuple from three topmost stack items
 157 NEWTRUE         = '\x88'  # push True
 158 NEWFALSE        = '\x89'  # push False
 159 LONG1           = '\x8a'  # push long from < 256 bytes
 160 LONG4           = '\x8b'  # push really big long
 161
 162 _tuplesize2code = [EMPTY_TUPLE, TUPLE1, TUPLE2, TUPLE3]
 163
 164
 165 __all__.extend([x for x in dir() if re.match("[A-Z][A-Z0-9_]+$",x)])
 166 del x
 167
 168
 169 # Pickling machinery
 170
 171 class Pickler:
 172
 173     def __init__(self, file, protocol=None):
 174         """This takes a file-like object for writing a pickle data stream.
 175
 176         The optional protocol argument tells the pickler to use the
 177         given protocol; supported protocols are 0, 1, 2.  The default
 178         protocol is 0, to be backwards compatible.  (Protocol 0 is the
 179         only protocol that can be written to a file opened in text
 180         mode and read back successfully.  When using a protocol higher
 181         than 0, make sure the file is opened in binary mode, both when
 182         pickling and unpickling.)
 183
 184         Protocol 1 is more efficient than protocol 0; protocol 2 is
 185         more efficient than protocol 1.
 186
 187         Specifying a negative protocol version selects the highest
 188         protocol version supported.  The higher the protocol used, the
 189         more recent the version of Python needed to read the pickle
 190         produced.
 191
 192         The file parameter must have a write() method that accepts a single
 193         string argument.  It can thus be an open file object, a StringIO
 194         object, or any other custom object that meets this interface.
 195
 196         """
 197         if protocol is None:
 198             protocol = 0
 199         if protocol < 0:
 200             protocol = HIGHEST_PROTOCOL
 201         elif not 0 <= protocol <= HIGHEST_PROTOCOL:
 202             raise ValueError("pickle protocol must be <= %d" % HIGHEST_PROTOCOL)
 203         self.write = file.write
 204         self.memo = {}
 205         self.proto = int(protocol)
 206         self.bin = protocol >= 1
 207         self.fast = 0
 208
 209     def clear_memo(self):
 210         """Clears the pickler's "memo".
 211
 212         The memo is the data structure that remembers which objects the
 213         pickler has already seen, so that shared or recursive objects are
 214         pickled by reference and not by value.  This method is useful when
 215         re-using picklers.
 216
 217         """
 218         self.memo.clear()
 219
 220     def dump(self, obj):
 221         """Write a pickled representation of obj to the open file."""
 222         if self.proto >= 2:
 223             self.write(PROTO + chr(self.proto))
 224         self.save(obj)
 225         self.write(STOP)
 226
 227     def memoize(self, obj):
 228         """Store an object in the memo."""
 229
 230         # The Pickler memo is a dictionary mapping object ids to 2-tuples
 231         # that contain the Unpickler memo key and the object being memoized.
 232         # The memo key is written to the pickle and will become
 233         # the key in the Unpickler's memo.  The object is stored in the
 234         # Pickler memo so that transient objects are kept alive during
 235         # pickling.
 236
 237         # The use of the Unpickler memo length as the memo key is just a
 238         # convention.  The only requirement is that the memo values be unique.
 239         # But there appears no advantage to any other scheme, and this
 240         # scheme allows the Unpickler memo to be implemented as a plain (but
 241         # growable) array, indexed by memo key.
 242         if self.fast:
 243             return
 244         assert id(obj) not in self.memo
 245         memo_len = len(self.memo)
 246         self.write(self.put(memo_len))
 247         self.memo[id(obj)] = memo_len, obj
 248
 249     # Return a PUT (BINPUT, LONG_BINPUT) opcode string, with argument i.
 250     def put(self, i, pack=struct.pack):
 251         if self.bin:
 252             if i < 256:
 253                 return BINPUT + chr(i)
 254             else:
 255                 return LONG_BINPUT + pack("<i", i)
 256
 257         return PUT + repr(i) + '\n'
 258
 259     # Return a GET (BINGET, LONG_BINGET) opcode string, with argument i.
 260     def get(self, i, pack=struct.pack):
 261         if self.bin:
 262             if i < 256:
 263                 return BINGET + chr(i)
 264             else:
 265                 return LONG_BINGET + pack("<i", i)
 266
 267         return GET + repr(i) + '\n'
 268
 269     def save(self, obj):
 270         # Check for persistent id (defined by a subclass)
 271         pid = self.persistent_id(obj)
 272         if pid:
 273             self.save_pers(pid)
 274             return
 275
 276         # Check the memo
 277         x = self.memo.get(id(obj))
 278         if x:
 279             self.write(self.get(x[0]))
 280             return
 281
 282         # Check the type dispatch table
 283         t = type(obj)
 284         f = self.dispatch.get(t)
 285         if f:
 286             f(self, obj) # Call unbound method with explicit self
 287             return
 288
 289         # Check for a class with a custom metaclass; treat as regular class
 290         try:
 291             issc = issubclass(t, TypeType)
 292         except TypeError: # t is not a class (old Boost; see SF #502085)
 293             issc = 0
 294         if issc:
 295             self.save_global(obj)
 296             return
 297
 298         # Check copy_reg.dispatch_table
 299         reduce = dispatch_table.get(t)
 300         if reduce:
 301             rv = reduce(obj)
 302         else:
 303             # Check for a __reduce_ex__ method, fall back to __reduce__
 304             reduce = getattr(obj, "__reduce_ex__", None)
 305             if reduce:
 306                 rv = reduce(self.proto)
 307             else:
 308                 reduce = getattr(obj, "__reduce__", None)
 309                 if reduce:
 310                     rv = reduce()
 311                 else:
 312                     raise PicklingError("Can't pickle %r object: %r" %
 313                                         (t.__name__, obj))
 314
 315         # Check for string returned by reduce(), meaning "save as global"
 316         if type(rv) is StringType:
 317             self.save_global(obj, rv)
 318             return
 319
 320         # Assert that reduce() returned a tuple
 321         if type(rv) is not TupleType:
 322             raise PicklingError("%s must return string or tuple" % reduce)
 323
 324         # Assert that it returned an appropriately sized tuple
 325         l = len(rv)
 326         if not (2 <= l <= 5):
 327             raise PicklingError("Tuple returned by %s must have "
 328                                 "two to five elements" % reduce)
 329
 330         # Save the reduce() output and finally memoize the object
 331         self.save_reduce(obj=obj, *rv)
 332
 333     def persistent_id(self, obj):
 334         # This exists so a subclass can override it
 335         return None
 336
 337     def save_pers(self, pid):
 338         # Save a persistent id reference
 339         if self.bin:
 340             self.save(pid)
 341             self.write(BINPERSID)
 342         else:
 343             self.write(PERSID + str(pid) + '\n')
 344
 345     def save_reduce(self, func, args, state=None,
 346                     listitems=None, dictitems=None, obj=None):
 347         # This API is called by some subclasses
 348
 349         # Assert that args is a tuple or None
 350         if not isinstance(args, TupleType):
 351             raise PicklingError("args from reduce() should be a tuple")
 352
 353         # Assert that func is callable
 354         if not hasattr(func, '__call__'):
 355             raise PicklingError("func from reduce should be callable")
 356
 357         save = self.save
 358         write = self.write
 359
 360         # Protocol 2 special case: if func's name is __newobj__, use NEWOBJ
 361         if self.proto >= 2 and getattr(func, "__name__", "") == "__newobj__":
 362             # A __reduce__ implementation can direct protocol 2 to
 363             # use the more efficient NEWOBJ opcode, while still
 364             # allowing protocol 0 and 1 to work normally.  For this to
 365             # work, the function returned by __reduce__ should be
 366             # called __newobj__, and its first argument should be a
 367             # new-style class.  The implementation for __newobj__
 368             # should be as follows, although pickle has no way to
 369             # verify this:
 370             #
 371             # def __newobj__(cls, *args):
 372             #     return cls.__new__(cls, *args)
 373             #
 374             # Protocols 0 and 1 will pickle a reference to __newobj__,
 375             # while protocol 2 (and above) will pickle a reference to
 376             # cls, the remaining args tuple, and the NEWOBJ code,
 377             # which calls cls.__new__(cls, *args) at unpickling time
 378             # (see load_newobj below).  If __reduce__ returns a
 379             # three-tuple, the state from the third tuple item will be
 380             # pickled regardless of the protocol, calling __setstate__
 381             # at unpickling time (see load_build below).
 382             #
 383             # Note that no standard __newobj__ implementation exists;
 384             # you have to provide your own.  This is to enforce
 385             # compatibility with Python 2.2 (pickles written using
 386             # protocol 0 or 1 in Python 2.3 should be unpicklable by
 387             # Python 2.2).
 388             cls = args[0]
 389             if not hasattr(cls, "__new__"):
 390                 raise PicklingError(
 391                     "args[0] from __newobj__ args has no __new__")
 392             if obj is not None and cls is not obj.__class__:
 393                 raise PicklingError(
 394                     "args[0] from __newobj__ args has the wrong class")
 395             args = args[1:]
 396             save(cls)
 397             save(args)
 398             write(NEWOBJ)
 399         else:
 400             save(func)
 401             save(args)
 402             write(REDUCE)
 403
 404         if obj is not None:
 405             self.memoize(obj)
 406
 407         # More new special cases (that work with older protocols as
 408         # well): when __reduce__ returns a tuple with 4 or 5 items,
 409         # the 4th and 5th item should be iterators that provide list
 410         # items and dict items (as (key, value) tuples), or None.
 411
 412         if listitems is not None:
 413             self._batch_appends(listitems)
 414
 415         if dictitems is not None:
 416             self._batch_setitems(dictitems)
 417
 418         if state is not None:
 419             save(state)
 420             write(BUILD)
 421
 422     # Methods below this point are dispatched through the dispatch table
 423
 424     dispatch = {}
 425
 426     def save_none(self, obj):
 427         self.write(NONE)
 428     dispatch[NoneType] = save_none
 429
 430     def save_bool(self, obj):
 431         if self.proto >= 2:
 432             self.write(obj and NEWTRUE or NEWFALSE)
 433         else:
 434             self.write(obj and TRUE or FALSE)
 435     dispatch[bool] = save_bool
 436
 437     def save_int(self, obj, pack=struct.pack):
 438         if self.bin:
 439             # If the int is small enough to fit in a signed 4-byte 2's-comp
 440             # format, we can store it more efficiently than the general
 441             # case.
 442             # First one- and two-byte unsigned ints:
 443             if obj >= 0:
 444                 if obj <= 0xff:
 445                     self.write(BININT1 + chr(obj))
 446                     return
 447                 if obj <= 0xffff:
 448                     self.write("%c%c%c" % (BININT2, obj&0xff, obj>>8))
 449                     return
 450             # Next check for 4-byte signed ints:
 451             high_bits = obj >> 31  # note that Python shift sign-extends
 452             if high_bits == 0 or high_bits == -1:
 453                 # All high bits are copies of bit 2**31, so the value
 454                 # fits in a 4-byte signed int.
 455                 self.write(BININT + pack("<i", obj))
 456                 return
 457         # Text pickle, or int too big to fit in signed 4-byte format.
 458         self.write(INT + repr(obj) + '\n')
 459     dispatch[IntType] = save_int
 460
 461     def save_long(self, obj, pack=struct.pack):
 462         if self.proto >= 2:
 463             bytes = encode_long(obj)
 464             n = len(bytes)
 465             if n < 256:
 466                 self.write(LONG1 + chr(n) + bytes)
 467             else:
 468                 self.write(LONG4 + pack("<i", n) + bytes)
 469             return
 470         self.write(LONG + repr(obj) + '\n')
 471     dispatch[LongType] = save_long
 472
 473     def save_float(self, obj, pack=struct.pack):
 474         if self.bin:
 475             self.write(BINFLOAT + pack('>d', obj))
 476         else:
 477             self.write(FLOAT + repr(obj) + '\n')
 478     dispatch[FloatType] = save_float
 479
 480     def save_string(self, obj, pack=struct.pack):
 481         if self.bin:
 482             n = len(obj)
 483             if n < 256:
 484                 self.write(SHORT_BINSTRING + chr(n) + obj)
 485             else:
 486                 self.write(BINSTRING + pack("<i", n) + obj)
 487         else:
 488             self.write(STRING + repr(obj) + '\n')
 489         self.memoize(obj)
 490     dispatch[StringType] = save_string
 491
 492     def save_unicode(self, obj, pack=struct.pack):
 493         if self.bin:
 494             encoding = obj.encode('utf-8')
 495             n = len(encoding)
 496             self.write(BINUNICODE + pack("<i", n) + encoding)
 497         else:
 498             obj = obj.replace("\\", "\\u005c")
 499             obj = obj.replace("\n", "\\u000a")
 500             self.write(UNICODE + obj.encode('raw-unicode-escape') + '\n')
 501         self.memoize(obj)
 502     dispatch[UnicodeType] = save_unicode
 503
 504     if StringType is UnicodeType:
 505         # This is true for Jython
 506         def save_string(self, obj, pack=struct.pack):
 507             unicode = obj.isunicode()
 508
 509             if self.bin:
 510                 if unicode:
 511                     obj = obj.encode("utf-8")
 512                 l = len(obj)
 513                 if l < 256 and not unicode:
 514                     self.write(SHORT_BINSTRING + chr(l) + obj)
 515                 else:
 516                     s = pack("<i", l)
 517                     if unicode:
 518                         self.write(BINUNICODE + s + obj)
 519                     else:
 520                         self.write(BINSTRING + s + obj)
 521             else:
 522                 if unicode:
 523                     obj = obj.replace("\\", "\\u005c")
 524                     obj = obj.replace("\n", "\\u000a")
 525                     obj = obj.encode('raw-unicode-escape')
 526                     self.write(UNICODE + obj + '\n')
 527                 else:
 528                     self.write(STRING + repr(obj) + '\n')
 529             self.memoize(obj)
 530         dispatch[StringType] = save_string
 531
 532     def save_tuple(self, obj):
 533         write = self.write
 534         proto = self.proto
 535
 536         n = len(obj)
 537         if n == 0:
 538             if proto:
 539                 write(EMPTY_TUPLE)
 540             else:
 541                 write(MARK + TUPLE)
 542             return
 543
 544         save = self.save
 545         memo = self.memo
 546         if n <= 3 and proto >= 2:
 547             for element in obj:
 548                 save(element)
 549             # Subtle.  Same as in the big comment below.
 550             if id(obj) in memo:
 551                 get = self.get(memo[id(obj)][0])
 552                 write(POP * n + get)
 553             else:
 554                 write(_tuplesize2code[n])
 555                 self.memoize(obj)
 556             return
 557
 558         # proto 0 or proto 1 and tuple isn't empty, or proto > 1 and tuple
 559         # has more than 3 elements.
 560         write(MARK)
 561         for element in obj:
 562             save(element)
 563
 564         if id(obj) in memo:
 565             # Subtle.  d was not in memo when we entered save_tuple(), so
 566             # the process of saving the tuple's elements must have saved
 567             # the tuple itself:  the tuple is recursive.  The proper action
 568             # now is to throw away everything we put on the stack, and
 569             # simply GET the tuple (it's already constructed).  This check
 570             # could have been done in the "for element" loop instead, but
 571             # recursive tuples are a rare thing.
 572             get = self.get(memo[id(obj)][0])
 573             if proto:
 574                 write(POP_MARK + get)
 575             else:   # proto 0 -- POP_MARK not available
 576                 write(POP * (n+1) + get)
 577             return
 578
 579         # No recursion.
 580         self.write(TUPLE)
 581         self.memoize(obj)
 582
 583     dispatch[TupleType] = save_tuple
 584
 585     # save_empty_tuple() isn't used by anything in Python 2.3.  However, I
 586     # found a Pickler subclass in Zope3 that calls it, so it's not harmless
 587     # to remove it.
 588     def save_empty_tuple(self, obj):
 589         self.write(EMPTY_TUPLE)
 590
 591     def save_list(self, obj):
 592         write = self.write
 593
 594         if self.bin:
 595             write(EMPTY_LIST)
 596         else:   # proto 0 -- can't use EMPTY_LIST
 597             write(MARK + LIST)
 598
 599         self.memoize(obj)
 600         self._batch_appends(iter(obj))
 601
 602     dispatch[ListType] = save_list
 603
 604     # Keep in synch with cPickle's BATCHSIZE.  Nothing will break if it gets
 605     # out of synch, though.
 606     _BATCHSIZE = 1000
 607
 608     def _batch_appends(self, items):
 609         # Helper to batch up APPENDS sequences
 610         save = self.save
 611         write = self.write
 612
 613         if not self.bin:
 614             for x in items:
 615                 save(x)
 616                 write(APPEND)
 617             return
 618
 619         r = xrange(self._BATCHSIZE)
 620         while items is not None:
 621             tmp = []
 622             for i in r:
 623                 try:
 624                     x = items.next()
 625                     tmp.append(x)
 626                 except StopIteration:
 627                     items = None
 628                     break
 629             n = len(tmp)
 630             if n > 1:
 631                 write(MARK)
 632                 for x in tmp:
 633                     save(x)
 634                 write(APPENDS)
 635             elif n:
 636                 save(tmp[0])
 637                 write(APPEND)
 638             # else tmp is empty, and we're done
 639
 640     def save_dict(self, obj):
 641         write = self.write
 642
 643         if self.bin:
 644             write(EMPTY_DICT)
 645         else:   # proto 0 -- can't use EMPTY_DICT
 646             write(MARK + DICT)
 647
 648         self.memoize(obj)
 649         self._batch_setitems(obj.iteritems())
 650
 651     dispatch[DictionaryType] = save_dict
 652     if not PyStringMap is None:
 653         dispatch[PyStringMap] = save_dict
 654
 655     def _batch_setitems(self, items):
 656         # Helper to batch up SETITEMS sequences; proto >= 1 only
 657         save = self.save
 658         write = self.write
 659
 660         if not self.bin:
 661             for k, v in items:
 662                 save(k)
 663                 save(v)
 664                 write(SETITEM)
 665             return
 666
 667         r = xrange(self._BATCHSIZE)
 668         while items is not None:
 669             tmp = []
 670             for i in r:
 671                 try:
 672                     tmp.append(items.next())
 673                 except StopIteration:
 674                     items = None
 675                     break
 676             n = len(tmp)
 677             if n > 1:
 678                 write(MARK)
 679                 for k, v in tmp:
 680                     save(k)
 681                     save(v)
 682                 write(SETITEMS)
 683             elif n:
 684                 k, v = tmp[0]
 685                 save(k)
 686                 save(v)
 687                 write(SETITEM)
 688             # else tmp is empty, and we're done
 689
 690     def save_inst(self, obj):
 691         cls = obj.__class__
 692
 693         memo  = self.memo
 694         write = self.write
 695         save  = self.save
 696
 697         if hasattr(obj, '__getinitargs__'):
 698             args = obj.__getinitargs__()
 699             len(args) # XXX Assert it's a sequence
 700             _keep_alive(args, memo)
 701         else:
 702             args = ()
 703
 704         write(MARK)
 705
 706         if self.bin:
 707             save(cls)
 708             for arg in args:
 709                 save(arg)
 710             write(OBJ)
 711         else:
 712             for arg in args:
 713                 save(arg)
 714             write(INST + cls.__module__ + '\n' + cls.__name__ + '\n')
 715
 716         self.memoize(obj)
 717
 718         try:
 719             getstate = obj.__getstate__
 720         except AttributeError:
 721             stuff = obj.__dict__
 722         else:
 723             stuff = getstate()
 724             _keep_alive(stuff, memo)
 725         save(stuff)
 726         write(BUILD)
 727
 728     dispatch[InstanceType] = save_inst
 729
 730     def save_global(self, obj, name=None, pack=struct.pack):
 731         write = self.write
 732         memo = self.memo
 733
 734         if name is None:
 735             name = obj.__name__
 736
 737         module = getattr(obj, "__module__", None)
 738         if module is None:
 739             module = whichmodule(obj, name)
 740
 741         try:
 742             __import__(module)
 743             mod = sys.modules[module]
 744             klass = getattr(mod, name)
 745         except (ImportError, KeyError, AttributeError):
 746             raise PicklingError(
 747                 "Can't pickle %r: it's not found as %s.%s" %
 748                 (obj, module, name))
 749         else:
 750             if klass is not obj:
 751                 raise PicklingError(
 752                     "Can't pickle %r: it's not the same object as %s.%s" %
 753                     (obj, module, name))
 754
 755         if self.proto >= 2:
 756             code = _extension_registry.get((module, name))
 757             if code:
 758                 assert code > 0
 759                 if code <= 0xff:
 760                     write(EXT1 + chr(code))
 761                 elif code <= 0xffff:
 762                     write("%c%c%c" % (EXT2, code&0xff, code>>8))
 763                 else:
 764                     write(EXT4 + pack("<i", code))
 765                 return
 766
 767         write(GLOBAL + module + '\n' + name + '\n')
 768         self.memoize(obj)
 769
 770     dispatch[ClassType] = save_global
 771     dispatch[FunctionType] = save_global
 772     dispatch[BuiltinFunctionType] = save_global
 773     dispatch[TypeType] = save_global
 774
 775 # Pickling helpers
 776
 777 def _keep_alive(x, memo):
 778     """Keeps a reference to the object x in the memo.
 779
 780     Because we remember objects by their id, we have
 781     to assure that possibly temporary objects are kept
 782     alive by referencing them.
 783     We store a reference at the id of the memo, which should
 784     normally not be used unless someone tries to deepcopy
 785     the memo itself...
 786     """
 787     try:
 788         memo[id(memo)].append(x)
 789     except KeyError:
 790         # aha, this is the first one :-)
 791         memo[id(memo)]=[x]
 792
 793
 794 # A cache for whichmodule(), mapping a function object to the name of
 795 # the module in which the function was found.
 796
 797 classmap = {} # called classmap for backwards compatibility
 798
 799 def whichmodule(func, funcname):
 800     """Figure out the module in which a function occurs.
 801
 802     Search sys.modules for the module.
 803     Cache in classmap.
 804     Return a module name.
 805     If the function cannot be found, return "__main__".
 806     """
 807     # Python functions should always get an __module__ from their globals.
 808     mod = getattr(func, "__module__", None)
 809     if mod is not None:
 810         return mod
 811     if func in classmap:
 812         return classmap[func]
 813
 814     for name, module in sys.modules.items():
 815         if module is None:
 816             continue # skip dummy package entries
 817         if name != '__main__' and getattr(module, funcname, None) is func:
 818             break
 819     else:
 820         name = '__main__'
 821     classmap[func] = name
 822     return name
 823
 824
 825 # Unpickling machinery
 826
 827 class Unpickler:
 828
 829     def __init__(self, file):
 830         """This takes a file-like object for reading a pickle data stream.
 831
 832         The protocol version of the pickle is detected automatically, so no
 833         proto argument is needed.
 834
 835         The file-like object must have two methods, a read() method that
 836         takes an integer argument, and a readline() method that requires no
 837         arguments.  Both methods should return a string.  Thus file-like
 838         object can be a file object opened for reading, a StringIO object,
 839         or any other custom object that meets this interface.
 840         """
 841         self.readline = file.readline
 842         self.read = file.read
 843         self.memo = {}
 844
 845     def load(self):
 846         """Read a pickled object representation from the open file.
 847
 848         Return the reconstituted object hierarchy specified in the file.
 849         """
 850         self.mark = object() # any new unique object
 851         self.stack = []
 852         self.append = self.stack.append
 853         read = self.read
 854         dispatch = self.dispatch
 855         try:
 856             while 1:
 857                 key = read(1)
 858                 dispatch[key](self)
 859         except _Stop, stopinst:
 860             return stopinst.value
 861
 862     # Return largest index k such that self.stack[k] is self.mark.
 863     # If the stack doesn't contain a mark, eventually raises IndexError.
 864     # This could be sped by maintaining another stack, of indices at which
 865     # the mark appears.  For that matter, the latter stack would suffice,
 866     # and we wouldn't need to push mark objects on self.stack at all.
 867     # Doing so is probably a good thing, though, since if the pickle is
 868     # corrupt (or hostile) we may get a clue from finding self.mark embedded
 869     # in unpickled objects.
 870     def marker(self):
 871         stack = self.stack
 872         mark = self.mark
 873         k = len(stack)-1
 874         while stack[k] is not mark: k = k-1
 875         return k
 876
 877     dispatch = {}
 878
 879     def load_eof(self):
 880         raise EOFError
 881     dispatch[''] = load_eof
 882
 883     def load_proto(self):
 884         proto = ord(self.read(1))
 885         if not 0 <= proto <= 2:
 886             raise ValueError, "unsupported pickle protocol: %d" % proto
 887     dispatch[PROTO] = load_proto
 888
 889     def load_persid(self):
 890         pid = self.readline()[:-1]
 891         self.append(self.persistent_load(pid))
 892     dispatch[PERSID] = load_persid
 893
 894     def load_binpersid(self):
 895         pid = self.stack.pop()
 896         self.append(self.persistent_load(pid))
 897     dispatch[BINPERSID] = load_binpersid
 898
 899     def load_none(self):
 900         self.append(None)
 901     dispatch[NONE] = load_none
 902
 903     def load_false(self):
 904         self.append(False)
 905     dispatch[NEWFALSE] = load_false
 906
 907     def load_true(self):
 908         self.append(True)
 909     dispatch[NEWTRUE] = load_true
 910
 911     def load_int(self):
 912         data = self.readline()
 913         if data == FALSE[1:]:
 914             val = False
 915         elif data == TRUE[1:]:
 916             val = True
 917         else:
 918             try:
 919                 val = int(data)
 920             except ValueError:
 921                 val = long(data)
 922         self.append(val)
 923     dispatch[INT] = load_int
 924
 925     def load_binint(self):
 926         self.append(mloads('i' + self.read(4)))
 927     dispatch[BININT] = load_binint
 928
 929     def load_binint1(self):
 930         self.append(ord(self.read(1)))
 931     dispatch[BININT1] = load_binint1
 932
 933     def load_binint2(self):
 934         self.append(mloads('i' + self.read(2) + '\000\000'))
 935     dispatch[BININT2] = load_binint2
 936
 937     def load_long(self):
 938         self.append(long(self.readline()[:-1], 0))
 939     dispatch[LONG] = load_long
 940
 941     def load_long1(self):
 942         n = ord(self.read(1))
 943         bytes = self.read(n)
 944         self.append(decode_long(bytes))
 945     dispatch[LONG1] = load_long1
 946
 947     def load_long4(self):
 948         n = mloads('i' + self.read(4))
 949         bytes = self.read(n)
 950         self.append(decode_long(bytes))
 951     dispatch[LONG4] = load_long4
 952
 953     def load_float(self):
 954         self.append(float(self.readline()[:-1]))
 955     dispatch[FLOAT] = load_float
 956
 957     def load_binfloat(self, unpack=struct.unpack):
 958         self.append(unpack('>d', self.read(8))[0])
 959     dispatch[BINFLOAT] = load_binfloat
 960
 961     def load_string(self):
 962         rep = self.readline()[:-1]
 963         for q in "\"'": # double or single quote
 964             if rep.startswith(q):
 965                 if not rep.endswith(q):
 966                     raise ValueError, "insecure string pickle"
 967                 rep = rep[len(q):-len(q)]
 968                 break
 969         else:
 970             raise ValueError, "insecure string pickle"
 971         self.append(rep.decode("string-escape"))
 972     dispatch[STRING] = load_string
 973
 974     def load_binstring(self):
 975         len = mloads('i' + self.read(4))
 976         self.append(self.read(len))
 977     dispatch[BINSTRING] = load_binstring
 978
 979     def load_unicode(self):
 980         self.append(unicode(self.readline()[:-1],'raw-unicode-escape'))
 981     dispatch[UNICODE] = load_unicode
 982
 983     def load_binunicode(self):
 984         len = mloads('i' + self.read(4))
 985         self.append(unicode(self.read(len),'utf-8'))
 986     dispatch[BINUNICODE] = load_binunicode
 987
 988     def load_short_binstring(self):
 989         len = ord(self.read(1))
 990         self.append(self.read(len))
 991     dispatch[SHORT_BINSTRING] = load_short_binstring
 992
 993     def load_tuple(self):
 994         k = self.marker()
 995         self.stack[k:] = [tuple(self.stack[k+1:])]
 996     dispatch[TUPLE] = load_tuple
 997
 998     def load_empty_tuple(self):
 999         self.stack.append(())
1000     dispatch[EMPTY_TUPLE] = load_empty_tuple
1001
1002     def load_tuple1(self):
1003         self.stack[-1] = (self.stack[-1],)
1004     dispatch[TUPLE1] = load_tuple1
1005
1006     def load_tuple2(self):
1007         self.stack[-2:] = [(self.stack[-2], self.stack[-1])]
1008     dispatch[TUPLE2] = load_tuple2
1009
1010     def load_tuple3(self):
1011         self.stack[-3:] = [(self.stack[-3], self.stack[-2], self.stack[-1])]
1012     dispatch[TUPLE3] = load_tuple3
1013
1014     def load_empty_list(self):
1015         self.stack.append([])
1016     dispatch[EMPTY_LIST] = load_empty_list
1017
1018     def load_empty_dictionary(self):
1019         self.stack.append({})
1020     dispatch[EMPTY_DICT] = load_empty_dictionary
1021
1022     def load_list(self):
1023         k = self.marker()
1024         self.stack[k:] = [self.stack[k+1:]]
1025     dispatch[LIST] = load_list
1026
1027     def load_dict(self):
1028         k = self.marker()
1029         d = {}
1030         items = self.stack[k+1:]
1031         for i in range(0, len(items), 2):
1032             key = items[i]
1033             value = items[i+1]
1034             d[key] = value
1035         self.stack[k:] = [d]
1036     dispatch[DICT] = load_dict
1037
1038     # INST and OBJ differ only in how they get a class object.  It's not
1039     # only sensible to do the rest in a common routine, the two routines
1040     # previously diverged and grew different bugs.
1041     # klass is the class to instantiate, and k points to the topmost mark
1042     # object, following which are the arguments for klass.__init__.
1043     def _instantiate(self, klass, k):
1044         args = tuple(self.stack[k+1:])
1045         del self.stack[k:]
1046         instantiated = 0
1047         if (not args and
1048                 type(klass) is ClassType and
1049                 not hasattr(klass, "__getinitargs__")):
1050             try:
1051                 value = _EmptyClass()
1052                 value.__class__ = klass
1053                 instantiated = 1
1054             except RuntimeError:
1055                 # In restricted execution, assignment to inst.__class__ is
1056                 # prohibited
1057                 pass
1058         if not instantiated:
1059             try:
1060                 value = klass(*args)
1061             except TypeError, err:
1062                 raise TypeError, "in constructor for %s: %s" % (
1063                     klass.__name__, str(err)), sys.exc_info()[2]
1064         self.append(value)
1065
1066     def load_inst(self):
1067         module = self.readline()[:-1]
1068         name = self.readline()[:-1]
1069         klass = self.find_class(module, name)
1070         self._instantiate(klass, self.marker())
1071     dispatch[INST] = load_inst
1072
1073     def load_obj(self):
1074         # Stack is ... markobject classobject arg1 arg2 ...
1075         k = self.marker()
1076         klass = self.stack.pop(k+1)
1077         self._instantiate(klass, k)
1078     dispatch[OBJ] = load_obj
1079
1080     def load_newobj(self):
1081         args = self.stack.pop()
1082         cls = self.stack[-1]
1083         obj = cls.__new__(cls, *args)
1084         self.stack[-1] = obj
1085     dispatch[NEWOBJ] = load_newobj
1086
1087     def load_global(self):
1088         module = self.readline()[:-1]
1089         name = self.readline()[:-1]
1090         klass = self.find_class(module, name)
1091         self.append(klass)
1092     dispatch[GLOBAL] = load_global
1093
1094     def load_ext1(self):
1095         code = ord(self.read(1))
1096         self.get_extension(code)
1097     dispatch[EXT1] = load_ext1
1098
1099     def load_ext2(self):
1100         code = mloads('i' + self.read(2) + '\000\000')
1101         self.get_extension(code)
1102     dispatch[EXT2] = load_ext2
1103
1104     def load_ext4(self):
1105         code = mloads('i' + self.read(4))
1106         self.get_extension(code)
1107     dispatch[EXT4] = load_ext4
1108
1109     def get_extension(self, code):
1110         nil = []
1111         obj = _extension_cache.get(code, nil)
1112         if obj is not nil:
1113             self.append(obj)
1114             return
1115         key = _inverted_registry.get(code)
1116         if not key:
1117             raise ValueError("unregistered extension code %d" % code)
1118         obj = self.find_class(*key)
1119         _extension_cache[code] = obj
1120         self.append(obj)
1121
1122     def find_class(self, module, name):
1123         # Subclasses may override this
1124         __import__(module)
1125         mod = sys.modules[module]
1126         klass = getattr(mod, name)
1127         return klass
1128
1129     def load_reduce(self):
1130         stack = self.stack
1131         args = stack.pop()
1132         func = stack[-1]
1133         value = func(*args)
1134         stack[-1] = value
1135     dispatch[REDUCE] = load_reduce
1136
1137     def load_pop(self):
1138         del self.stack[-1]
1139     dispatch[POP] = load_pop
1140
1141     def load_pop_mark(self):
1142         k = self.marker()
1143         del self.stack[k:]
1144     dispatch[POP_MARK] = load_pop_mark
1145
1146     def load_dup(self):
1147         self.append(self.stack[-1])
1148     dispatch[DUP] = load_dup
1149
1150     def load_get(self):
1151         self.append(self.memo[self.readline()[:-1]])
1152     dispatch[GET] = load_get
1153
1154     def load_binget(self):
1155         i = ord(self.read(1))
1156         self.append(self.memo[repr(i)])
1157     dispatch[BINGET] = load_binget
1158
1159     def load_long_binget(self):
1160         i = mloads('i' + self.read(4))
1161         self.append(self.memo[repr(i)])
1162     dispatch[LONG_BINGET] = load_long_binget
1163
1164     def load_put(self):
1165         self.memo[self.readline()[:-1]] = self.stack[-1]
1166     dispatch[PUT] = load_put
1167
1168     def load_binput(self):
1169         i = ord(self.read(1))
1170         self.memo[repr(i)] = self.stack[-1]
1171     dispatch[BINPUT] = load_binput
1172
1173     def load_long_binput(self):
1174         i = mloads('i' + self.read(4))
1175         self.memo[repr(i)] = self.stack[-1]
1176     dispatch[LONG_BINPUT] = load_long_binput
1177
1178     def load_append(self):
1179         stack = self.stack
1180         value = stack.pop()
1181         list = stack[-1]
1182         list.append(value)
1183     dispatch[APPEND] = load_append
1184
1185     def load_appends(self):
1186         stack = self.stack
1187         mark = self.marker()
1188         list = stack[mark - 1]
1189         list.extend(stack[mark + 1:])
1190         del stack[mark:]
1191     dispatch[APPENDS] = load_appends
1192
1193     def load_setitem(self):
1194         stack = self.stack
1195         value = stack.pop()
1196         key = stack.pop()
1197         dict = stack[-1]
1198         dict[key] = value
1199     dispatch[SETITEM] = load_setitem
1200
1201     def load_setitems(self):
1202         stack = self.stack
1203         mark = self.marker()
1204         dict = stack[mark - 1]
1205         for i in range(mark + 1, len(stack), 2):
1206             dict[stack[i]] = stack[i + 1]
1207
1208         del stack[mark:]
1209     dispatch[SETITEMS] = load_setitems
1210
1211     def load_build(self):
1212         stack = self.stack
1213         state = stack.pop()
1214         inst = stack[-1]
1215         setstate = getattr(inst, "__setstate__", None)
1216         if setstate:
1217             setstate(state)
1218             return
1219         slotstate = None
1220         if isinstance(state, tuple) and len(state) == 2:
1221             state, slotstate = state
1222         if state:
1223             try:
1224                 inst.__dict__.update(state)
1225             except RuntimeError:
1226                 # XXX In restricted execution, the instance's __dict__
1227                 # is not accessible.  Use the old way of unpickling
1228                 # the instance variables.  This is a semantic
1229                 # difference when unpickling in restricted
1230                 # vs. unrestricted modes.
1231                 # Note, however, that cPickle has never tried to do the
1232                 # .update() business, and always uses
1233                 #     PyObject_SetItem(inst.__dict__, key, value) in a
1234                 # loop over state.items().
1235                 for k, v in state.items():
1236                     setattr(inst, k, v)
1237         if slotstate:
1238             for k, v in slotstate.items():
1239                 setattr(inst, k, v)
1240     dispatch[BUILD] = load_build
1241
1242     def load_mark(self):
1243         self.append(self.mark)
1244     dispatch[MARK] = load_mark
1245
1246     def load_stop(self):
1247         value = self.stack.pop()
1248         raise _Stop(value)
1249     dispatch[STOP] = load_stop
1250
1251 # Helper class for load_inst/load_obj
1252
1253 class _EmptyClass:
1254     pass
1255
1256 # Encode/decode longs in linear time.
1257
1258 import binascii as _binascii
1259
1260 def encode_long(x):
1261     r"""Encode a long to a two's complement little-endian binary string.
1262     Note that 0L is a special case, returning an empty string, to save a
1263     byte in the LONG1 pickling context.
1264
1265     >>> encode_long(0L)
1266     ''
1267     >>> encode_long(255L)
1268     '\xff\x00'
1269     >>> encode_long(32767L)
1270     '\xff\x7f'
1271     >>> encode_long(-256L)
1272     '\x00\xff'
1273     >>> encode_long(-32768L)
1274     '\x00\x80'
1275     >>> encode_long(-128L)
1276     '\x80'
1277     >>> encode_long(127L)
1278     '\x7f'
1279     >>>
1280     """
1281
1282     if x == 0:
1283         return ''
1284     if x > 0:
1285         ashex = hex(x)
1286         assert ashex.startswith("0x")
1287         njunkchars = 2 + ashex.endswith('L')
1288         nibbles = len(ashex) - njunkchars
1289         if nibbles & 1:
1290             # need an even # of nibbles for unhexlify
1291             ashex = "0x0" + ashex[2:]
1292         elif int(ashex[2], 16) >= 8:
1293             # "looks negative", so need a byte of sign bits
1294             ashex = "0x00" + ashex[2:]
1295     else:
1296         # Build the 256's-complement:  (1L << nbytes) + x.  The trick is
1297         # to find the number of bytes in linear time (although that should
1298         # really be a constant-time task).
1299         ashex = hex(-x)
1300         assert ashex.startswith("0x")
1301         njunkchars = 2 + ashex.endswith('L')
1302         nibbles = len(ashex) - njunkchars
1303         if nibbles & 1:
1304             # Extend to a full byte.
1305             nibbles += 1
1306         nbits = nibbles * 4
1307         x += 1L << nbits
1308         assert x > 0
1309         ashex = hex(x)
1310         njunkchars = 2 + ashex.endswith('L')
1311         newnibbles = len(ashex) - njunkchars
1312         if newnibbles < nibbles:
1313             ashex = "0x" + "0" * (nibbles - newnibbles) + ashex[2:]
1314         if int(ashex[2], 16) < 8:
1315             # "looks positive", so need a byte of sign bits
1316             ashex = "0xff" + ashex[2:]
1317
1318     if ashex.endswith('L'):
1319         ashex = ashex[2:-1]
1320     else:
1321         ashex = ashex[2:]
1322     assert len(ashex) & 1 == 0, (x, ashex)
1323     binary = _binascii.unhexlify(ashex)
1324     return binary[::-1]
1325
1326 def decode_long(data):
1327     r"""Decode a long from a two's complement little-endian binary string.
1328
1329     >>> decode_long('')
1330     0L
1331     >>> decode_long("\xff\x00")
1332     255L
1333     >>> decode_long("\xff\x7f")
1334     32767L
1335     >>> decode_long("\x00\xff")
1336     -256L
1337     >>> decode_long("\x00\x80")
1338     -32768L
1339     >>> decode_long("\x80")
1340     -128L
1341     >>> decode_long("\x7f")
1342     127L
1343     """
1344
1345     nbytes = len(data)
1346     if nbytes == 0:
1347         return 0L
1348     ashex = _binascii.hexlify(data[::-1])
1349     n = long(ashex, 16) # quadratic time before Python 2.3; linear now
1350     if data[-1] >= '\x80':
1351         n -= 1L << (nbytes * 8)
1352     return n
1353
1354 # Shorthands
1355
1356 try:
1357     from cStringIO import StringIO
1358 except ImportError:
1359     from StringIO import StringIO
1360
1361 def dump(obj, file, protocol=None):
1362     Pickler(file, protocol).dump(obj)
1363
1364 def dumps(obj, protocol=None):
1365     file = StringIO()
1366     Pickler(file, protocol).dump(obj)
1367     return file.getvalue()
1368
1369 def load(file):
1370     return Unpickler(file).load()
1371
1372 def loads(str):
1373     file = StringIO(str)
1374     return Unpickler(file).load()
1375
1376 # Doctest
1377
1378 def _test():
1379     import doctest
1380     return doctest.testmod()
1381
1382 if __name__ == "__main__":
1383     _test()