Use a Python __reduce__ method to make pickles match C.

On it's own, this breaks on protocols >= 2 (including Python 3 by
default) because the pickled object's class is required to match the
reduce output. One fix would be to change the pickle format to use a
custom constructor function, but then we'd have different pickle formats
in C and Python.

Rather than do that, we instead create a __class__ property for the
python implementation. This bypasses the protocol limitations. The
__class__ property wasn't assignable in the C implementation, so the
compatibility risk should be very small.

All the special pickle machinery is only defined in Python if needed.

BTrees/IFBTree.py

@@ -14,7 +14,7 @@
 
 __all__ = ('Bucket', 'Set', 'BTree', 'TreeSet',
            'IFBucket', 'IFSet', 'IFBTree', 'IFTreeSet',
-           'union', 'intersection', 'difference',  
+           'union', 'intersection', 'difference',
            'weightedUnion', 'weightedIntersection', 'multiunion',
           )
 
@@ -38,6 +38,7 @@
 from ._base import union as _union
 from ._base import weightedIntersection as _weightedIntersection
 from ._base import weightedUnion as _weightedUnion
+from ._base import _fix_pickle
 
 _BUCKET_SIZE = 120
 _TREE_SIZE = 500
@@ -134,4 +135,6 @@ class IFTreeIteratorPy(_TreeIterator):
 BTree = IFBTree
 TreeSet = IFTreeSet
 
+_fix_pickle(globals(), __name__)
+
 moduleProvides(IIntegerFloatBTreeModule)

BTrees/IIBTree.py

@@ -14,7 +14,7 @@
 
 __all__ = ('Bucket', 'Set', 'BTree', 'TreeSet',
            'IIBucket', 'IISet', 'IIBTree', 'IITreeSet',
-           'union', 'intersection', 'difference',  
+           'union', 'intersection', 'difference',
            'weightedUnion', 'weightedIntersection', 'multiunion',
           )
 
@@ -38,6 +38,7 @@
 from ._base import union as _union
 from ._base import weightedIntersection as _weightedIntersection
 from ._base import weightedUnion as _weightedUnion
+from ._base import _fix_pickle
 
 _BUCKET_SIZE = 120
 _TREE_SIZE = 500
@@ -135,4 +136,6 @@ class IITreeIteratorPy(_TreeIterator):
 BTree = IIBTree
 TreeSet = IITreeSet
 
+_fix_pickle(globals(), __name__)
+
 moduleProvides(IIntegerIntegerBTreeModule)

BTrees/IOBTree.py

@@ -33,6 +33,7 @@
 from ._base import to_int as _to_key
 from ._base import to_ob as _to_value
 from ._base import union as _union
+from ._base import _fix_pickle
 
 _BUCKET_SIZE = 60
 _TREE_SIZE = 500
@@ -113,4 +114,6 @@ class IOTreeIteratorPy(_TreeIterator):
 BTree = IOBTree
 TreeSet = IOTreeSet
 
+_fix_pickle(globals(), __name__)
+
 moduleProvides(IIntegerObjectBTreeModule)

BTrees/LFBTree.py

@@ -14,7 +14,7 @@
 
 __all__ = ('Bucket', 'Set', 'BTree', 'TreeSet',
            'LFBucket', 'LFSet', 'LFBTree', 'LFTreeSet',
-           'union', 'intersection', 'difference',  
+           'union', 'intersection', 'difference',
            'weightedUnion', 'weightedIntersection', 'multiunion',
           )
 
@@ -38,6 +38,7 @@
 from ._base import union as _union
 from ._base import weightedIntersection as _weightedIntersection
 from ._base import weightedUnion as _weightedUnion
+from ._base import _fix_pickle
 
 _BUCKET_SIZE = 120
 _TREE_SIZE = 500
@@ -135,4 +136,6 @@ class LFTreeIteratorPy(_TreeIterator):
 BTree = LFBTree
 TreeSet = LFTreeSet
 
+_fix_pickle(globals(), __name__)
+
 moduleProvides(IIntegerFloatBTreeModule)

BTrees/LLBTree.py

@@ -14,7 +14,7 @@
 
 __all__ = ('Bucket', 'Set', 'BTree', 'TreeSet',
            'LLBucket', 'LLSet', 'LLBTree', 'LLTreeSet',
-           'union', 'intersection', 'difference',  
+           'union', 'intersection', 'difference',
            'weightedUnion', 'weightedIntersection', 'multiunion',
           )
 
@@ -38,6 +38,7 @@
 from ._base import union as _union
 from ._base import weightedIntersection as _weightedIntersection
 from ._base import weightedUnion as _weightedUnion
+from ._base import _fix_pickle
 
 _BUCKET_SIZE = 120
 _TREE_SIZE = 500
@@ -135,4 +136,6 @@ class LLTreeIteratorPy(_TreeIterator):
 BTree = LLBTree
 TreeSet = LLTreeSet
 
+_fix_pickle(globals(), __name__)
+
 moduleProvides(IIntegerIntegerBTreeModule)

BTrees/LOBTree.py

@@ -33,6 +33,7 @@
 from ._base import to_long as _to_key
 from ._base import to_ob as _to_value
 from ._base import union as _union
+from ._base import _fix_pickle
 
 _BUCKET_SIZE = 60
 _TREE_SIZE = 500
@@ -114,4 +115,6 @@ class LOTreeIteratorPy(_TreeIterator):
 BTree = LOBTree
 TreeSet = LOTreeSet
 
+_fix_pickle(globals(), __name__)
+
 moduleProvides(IIntegerObjectBTreeModule)

BTrees/OIBTree.py

@@ -14,7 +14,7 @@
 
 __all__ = ('Bucket', 'Set', 'BTree', 'TreeSet',
            'OIBucket', 'OISet', 'OIBTree', 'OITreeSet',
-           'union', 'intersection', 'difference',  
+           'union', 'intersection', 'difference',
            'weightedUnion', 'weightedIntersection',
           )
 
@@ -37,6 +37,7 @@
 from ._base import union as _union
 from ._base import weightedIntersection as _weightedIntersection
 from ._base import weightedUnion as _weightedUnion
+from ._base import _fix_pickle
 
 _BUCKET_SIZE = 60
 _TREE_SIZE = 250
@@ -131,4 +132,6 @@ class OITreeIteratorPy(_TreeIterator):
 BTree = OIBTree
 TreeSet = OITreeSet
 
+_fix_pickle(globals(), __name__)
+
 moduleProvides(IObjectIntegerBTreeModule)

BTrees/OLBTree.py

@@ -14,7 +14,7 @@
 
 __all__ = ('Bucket', 'Set', 'BTree', 'TreeSet',
            'OLBucket', 'OLSet', 'OLBTree', 'OLTreeSet',
-           'union', 'intersection', 'difference',  
+           'union', 'intersection', 'difference',
            'weightedUnion', 'weightedIntersection',
           )
 
@@ -37,6 +37,7 @@
 from ._base import union as _union
 from ._base import weightedIntersection as _weightedIntersection
 from ._base import weightedUnion as _weightedUnion
+from ._base import _fix_pickle
 
 _BUCKET_SIZE = 60
 _TREE_SIZE = 250
@@ -131,4 +132,6 @@ class OLTreeIteratorPy(_TreeIterator):
 BTree = OLBTree
 TreeSet = OLTreeSet
 
+_fix_pickle(globals(), __name__)
+
 moduleProvides(IObjectIntegerBTreeModule)

BTrees/OOBTree.py

@@ -14,7 +14,7 @@
 
 __all__ = ('Bucket', 'Set', 'BTree', 'TreeSet',
            'OOBucket', 'OOSet', 'OOBTree', 'OOTreeSet',
-           'union', 'intersection','difference',  
+           'union', 'intersection','difference',
           )
 
 from zope.interface import moduleProvides
@@ -31,6 +31,7 @@
 from ._base import to_ob as _to_key
 from ._base import to_ob as _to_value
 from ._base import union as _union
+from ._base import _fix_pickle
 
 _BUCKET_SIZE = 30
 _TREE_SIZE = 250
@@ -102,9 +103,13 @@ class OOTreeIteratorPy(_TreeIterator):
     from ._OOBTree import union
     from ._OOBTree import intersection
 
+
+
 Bucket = OOBucket
 Set = OOSet
 BTree = OOBTree
 TreeSet = OOTreeSet
 
+_fix_pickle(globals(), __name__)
+
 moduleProvides(IObjectObjectBTreeModule)