summaryrefslogtreecommitdiffstats
path: root/Lib/pickle.py
blob: 45bc38c6256d591fbdd682dfd8661f98ea1151a7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
"""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__ = "$Revision$"       # Code version

from types import *
from copy_reg import dispatch_table, _reconstructor
from copy_reg import extension_registry, inverted_registry, extension_cache
import marshal
import sys
import struct
import re
import warnings

__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

# 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, proto=0):
        """This takes a file-like object for writing a pickle data stream.

        The optional proto 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.)

        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 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 proto < 0:
            proto = 2
        elif proto not in (0, 1, 2):
            raise ValueError, "pickle protocol must be 0, 1 or 2"
        self.write = file.write
        self.memo = {}
        self.proto = int(proto)
        self.bin = proto >= 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.

        Either the binary or ASCII format will be used, depending on the
        value of the bin flag passed to the constructor.

        """
        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 + `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 + `i` + '\n'

    def save(self, obj):
        # Check for persistent id (defined by a subclass)
        pid = self.persistent_id(obj)
        if pid:
            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 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 copy_reg.dispatch_table
        reduce = dispatch_table.get(t)
        if not reduce:
            # Check for a __reduce__ method.
            # Subtle: get the unbound method from the class, so that
            # protocol 2 can override the default __reduce__ that all
            # classes inherit from object.  This has the added
            # advantage that the call always has the form reduce(obj)
            reduce = getattr(t, "__reduce__", None)
            if self.proto >= 2:
                # Protocol 2 can do better than the default __reduce__
                if reduce is object.__reduce__:
                    reduce = None
                if not reduce:
                    self.save_newobj(obj)
                    return
            if not reduce:
                raise PicklingError("Can't pickle %r object: %r" %
                                    (t.__name__, obj))
        rv = reduce(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 be called by some subclasses

        # Assert that args is a tuple or None
        if not isinstance(args, TupleType):
            if args is None:
                # A hack for Jim Fulton's ExtensionClass, now deprecated.
                # See load_reduce()
                warnings.warn("__basicnew__ special case is deprecated",
                              DeprecationWarning)
            else:
                raise PicklingError(
                    "args from reduce() should be a tuple")

        # Assert that func is callable
        if not callable(func):
            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:
            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)

    def save_newobj(self, obj):
        # Save a new-style class instance, using protocol 2.
        assert self.proto >= 2          # This only works for protocol 2
        t = type(obj)
        getnewargs = getattr(obj, "__getnewargs__", None)
        if getnewargs:
            args = getnewargs()         # This better not reference obj
        else:
            args = ()

        save = self.save
        write = self.write

        self.save(t)
        save(args)
        write(NEWOBJ)
        self.memoize(obj)

        if isinstance(obj, list):
            self._batch_appends(iter(obj))
        elif isinstance(obj, dict):
            self._batch_setitems(obj.iteritems())

        getstate = getattr(obj, "__getstate__", None)

        if getstate:
            # A class may define both __getstate__ and __getnewargs__.
            # If they are the same function, we ignore __getstate__.
            # This is for the benefit of protocols 0 and 1, which don't
            # use __getnewargs__.  Note that the only way to make them
            # the same function is something like this:
            #
            #   class C(object):
            #       def __getstate__(self):
            #           return ...
            #       __getnewargs__ = __getstate__
            #
            # No tricks are needed to ignore __setstate__; it simply
            # won't be called when we don't generate BUILD.
            # Also note that when __getnewargs__ and __getstate__ are
            # the same function, we don't do the default thing of
            # looking for __dict__ and slots either -- it is assumed
            # that __getnewargs__ returns all the state there is
            # (which should be a safe assumption since __getstate__
            # returns the *same* state).
            if getstate == getnewargs:
                return

            try:
                state = getstate()
            except TypeError, err:
                # XXX Catch generic exception caused by __slots__
                if str(err) != ("a class that defines __slots__ "
                                "without defining __getstate__ "
                                "cannot be pickled"):
                    print repr(str(err))
                    raise # Not that specific exception
                getstate = None

        if not getstate:
            state = getattr(obj, "__dict__", None)
            if not state:
                state = None
            # If there are slots, the state becomes a tuple of two
            # items: the first item the regular __dict__ or None, and
            # the second a dict mapping slot names to slot values
            names = _slotnames(t)
            if names:
                slots = {}
                nil = []
                for name in names:
                    value = getattr(obj, name, nil)
                    if value is not nil:
                        slots[name] = value
                if slots:
                    state = (state, slots)

        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 + `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)
        self.write(LONG + `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 + `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 + `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 == 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 + `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 and proto:
            write(EMPTY_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 n and 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 (including the empty-tuple case for protocol 0).
        self.write(TUPLE)
        if obj:                      # No need to memoize empty 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

    _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:
                    tmp.append(items.next())
                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 _slotnames(cls):
    """Return a list of slot names for a given class.

    This needs to find slots defined by the class and its bases, so we
    can't simply return the __slots__ attribute.  We must walk down
    the Method Resolution Order and concatenate the __slots__ of each
    class found there.  (This assumes classes don't modify their
    __slots__ attribute to misrepresent their slots after the class is
    defined.)
    """
    if not hasattr(cls, "__slots__"):
        return []
    names = []
    for c in cls.__mro__:
        if "__slots__" in c.__dict__:
            names += list(c.__dict__["__slots__"])
    return names

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 \
            hasattr(module, funcname) and \
            getattr(module, funcname) 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.

        This class automatically determines whether the data stream was
        written in binary mode or not, so it does not need a flag as in
        the Pickler class factory.

        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)
        return decode_long(bytes)
    dispatch[LONG1] = load_long1

    def load_long4(self):
        n = mloads('i' + self.read(4))
        bytes = self.read(n)
        return 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 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]
        if args is None:
            # A hack for Jim Fulton's ExtensionClass, now deprecated
            warnings.warn("__basicnew__ special case is deprecated",
                          DeprecationWarning)
            value = func.__basicnew__()
        else:
            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[`i`])
    dispatch[BINGET] = load_binget

    def load_long_binget(self):
        i = mloads('i' + self.read(4))
        self.append(self.memo[`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[`i`] = self.stack[-1]
    dispatch[BINPUT] = load_binput

    def load_long_binput(self):
        i = mloads('i' + self.read(4))
        self.memo[`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:
                inst.__dict__.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.
                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:
            # need an even # of nibbles for unhexlify
            nibbles += 1
        nbits = nibbles * 4
        x += 1L << nbits
        assert x > 0
        ashex = hex(x)
        if x >> (nbits - 1) == 0:
            # "looks positive", so need a byte of sign bits
            ashex = "0xff" + x[2:]

    if ashex.endswith('L'):
        ashex = ashex[2:-1]
    else:
        ashex = ashex[2:]
    assert len(ashex) & 1 == 0
    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)
    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, proto=0):
    Pickler(file, proto).dump(obj)

def dumps(obj, proto=0):
    file = StringIO()
    Pickler(file, proto).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()