Copy in the real code

src/Acquisition/Acquisition.h

+/*****************************************************************************
+
+  Copyright (c) 1996-2002 Zope Corporation and Contributors.
+  All Rights Reserved.
+
+  This software is subject to the provisions of the Zope Public License,
+  Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+  THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+  WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+  WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+  FOR A PARTICULAR PURPOSE
+
+ ****************************************************************************/
+
+#ifndef __ACQUISITION_H_
+#define __ACQUISITION_H_
+
+typedef struct {
+	PyObject *(*AQ_Acquire) (PyObject *obj, PyObject *name, PyObject *filter,
+		PyObject *extra, int explicit, PyObject *deflt,
+		int containment);
+	PyObject *(*AQ_Get) (PyObject *obj, PyObject *name, PyObject *deflt,
+		int containment);
+	int (*AQ_IsWrapper) (PyObject *obj);
+	PyObject *(*AQ_Base) (PyObject *obj);
+	PyObject *(*AQ_Parent) (PyObject *obj);
+	PyObject *(*AQ_Self) (PyObject *obj);
+	PyObject *(*AQ_Inner) (PyObject *obj);
+	PyObject *(*AQ_Chain) (PyObject *obj, int containment);
+} ACQUISITIONCAPI;
+
+#ifndef _IN_ACQUISITION_C
+
+#define aq_Acquire(obj, name, filter, extra, explicit, deflt, containment ) (AcquisitionCAPI == NULL ? NULL : (AcquisitionCAPI->AQ_Acquire(obj, name, filter, extra, explicit, deflt, containment)))
+#define aq_acquire(obj, name) (AcquisitionCAPI == NULL ? NULL : (AcquisitionCAPI->AQ_Acquire(obj, name, NULL, NULL, 1, NULL, 0)))
+#define aq_get(obj, name, deflt, containment) (AcquistionCAPI == NULL ? NULL : (AcquisitionCAPI->AQ_Get(obj, name, deflt, containment)))
+#define aq_isWrapper(obj)   (AcquisitionCAPI == NULL ? -1 : (AcquisitionCAPI->AQ_IsWrapper(obj)))
+#define aq_base(obj)   (AcquisitionCAPI == NULL ? NULL : (AcquisitionCAPI->AQ_Base(obj)))
+#define aq_parent(obj) (AcquisitionCAPI == NULL ? NULL : (AcquisitionCAPI->AQ_Parent(obj)))
+#define aq_self(obj)   (AcquisitionCAPI == NULL ? NULL : (AcquisitionCAPI->AQ_Self(obj)))
+#define aq_inner(obj)  (AcquisitionCAPI == NULL ? NULL : (AcquisitionCAPI->AQ_Inner(obj)))
+#define aq_chain(obj, containment) (AcquisitionCAPI == NULL ? NULL : (AcquisitionCAPI->AQ_CHain(obj, containment)))
+
+static ACQUISITIONCAPI *AcquisitionCAPI = NULL;
+
+#define aq_init() { \
+    PyObject *module; \
+    PyObject *api; \
+    if (! (module = PyImport_ImportModule("Acquisition"))) return; \
+    if (! (api = PyObject_GetAttrString(module,"AcquisitionCAPI"))) return; \
+    Py_DECREF(module); \
+    AcquisitionCAPI = PyCObject_AsVoidPtr(api); \
+    Py_DECREF(api); \
+}
+
+
+
+#endif
+
+#endif

src/Acquisition/README.txt

+.. contents::
+
+Introductory Example
+====================
+
+Zope implements acquisition with "Extension Class" mix-in classes. To
+use acquisition your classes must inherit from an acquisition base
+class. For example::
+
+  >>> import ExtensionClass, Acquisition
+
+  >>> class C(ExtensionClass.Base):
+  ...     color='red'
+
+  >>> class A(Acquisition.Implicit):
+  ...     def report(self):
+  ...         print self.color
+  ...
+  >>> a = A()
+  >>> c = C()
+  >>> c.a = a
+
+  >>> c.a.report()
+  red
+
+  >>> d = C()
+  >>> d.color = 'green'
+  >>> d.a = a
+
+  >>> d.a.report()
+  green
+
+  >>> a.report() # raises an attribute error
+  Traceback (most recent call last):
+    ...
+  AttributeError: color
+
+The class ``A`` inherits acquisition behavior from
+``Acquisition.Implicit``. The object, ``a``, "has" the color of
+objects ``c`` and d when it is accessed through them, but it has no
+color by itself. The object ``a`` obtains attributes from its
+environment, where its environment is defined by the access path used
+to reach ``a``.
+
+Acquisition Wrappers
+====================
+
+When an object that supports acquisition is accessed through an
+extension class instance, a special object, called an acquisition
+wrapper, is returned. In the example above, the expression ``c.a``
+returns an acquisition wrapper that contains references to both ``c``
+and ``a``. It is this wrapper that performs attribute lookup in ``c``
+when an attribute cannot be found in ``a``.
+
+Acquisition wrappers provide access to the wrapped objects through the
+attributes ``aq_parent``, ``aq_self``, ``aq_base``.  Continue the
+example from above::
+
+  >>> c.a.aq_parent is c
+  True
+  >>> c.a.aq_self is a
+  True
+
+Explicit and Implicit Acquisition
+=================================
+
+Two styles of acquisition are supported: implicit and explicit
+acquisition.
+
+Implicit acquisition
+--------------------
+
+Implicit acquisition is so named because it searches for attributes
+from the environment automatically whenever an attribute cannot be
+obtained directly from an object or through inheritance.
+
+An attribute can be implicitly acquired if its name does not begin
+with an underscore.
+
+To support implicit acquisition, your class should inherit from the
+mix-in class ``Acquisition.Implicit``.
+
+Explicit Acquisition
+--------------------
+
+When explicit acquisition is used, attributes are not automatically
+obtained from the environment. Instead, the method aq_acquire must be
+used. For example::
+
+  >>> print c.a.aq_acquire('color')
+  red
+
+To support explicit acquisition, your class should inherit from the
+mix-in class ``Acquisition.Explicit``.
+
+Controlling Acquisition
+-----------------------
+
+A class (or instance) can provide attribute by attribute control over
+acquisition. Your should subclass from ``Acquisition.Explicit``, and set
+all attributes that should be acquired to the special value
+``Acquisition.Acquired``. Setting an attribute to this value also allows
+inherited attributes to be overridden with acquired ones. For example::
+
+  >>> class C(Acquisition.Explicit):
+  ...     id=1
+  ...     secret=2
+  ...     color=Acquisition.Acquired
+  ...     __roles__=Acquisition.Acquired
+
+The only attributes that are automatically acquired from containing
+objects are color, and ``__roles__``. Note that the ``__roles__``
+attribute is acquired even though its name begins with an
+underscore. In fact, the special ``Acquisition.Acquired`` value can be
+used in ``Acquisition.Implicit`` objects to implicitly acquire
+selected objects that smell like private objects.
+
+Sometimes, you want to dynamically make an implicitly acquiring object
+acquire explicitly. You can do this by getting the object's
+aq_explicit attribute. This attribute provides the object with an
+explicit wrapper that places the original implicit wrapper.
+
+Filtered Acquisition
+====================
+
+The acquisition method, ``aq_acquire``, accepts two optional
+arguments. The first of the additional arguments is a "filtering"
+function that is used when considering whether to acquire an
+object. The second of the additional arguments is an object that is
+passed as extra data when calling the filtering function and which
+defaults to ``None``. The filter function is called with five
+arguments:
+
+* The object that the aq_acquire method was called on,
+
+* The object where an object was found,
+
+* The name of the object, as passed to aq_acquire,
+
+* The object found, and
+
+* The extra data passed to aq_acquire.
+
+If the filter returns a true object that the object found is returned,
+otherwise, the acquisition search continues.
+
+Here's an example::
+
+  >>> from Acquisition import Explicit
+
+  >>> class HandyForTesting:
+  ...     def __init__(self, name):
+  ...         self.name = name
+  ...     def __str__(self):
+  ...         return "%s(%s)" % (self.name, self.__class__.__name__)
+  ...     __repr__=__str__
+  ...
+  >>> class E(Explicit, HandyForTesting): pass
+  ...
+  >>> class Nice(HandyForTesting):
+  ...     isNice= 1 
+  ...     def __str__(self):
+  ...         return HandyForTesting.__str__(self)+' and I am nice!'
+  ...     __repr__=__str__
+  ...
+  >>> a = E('a')
+  >>> a.b = E('b')
+  >>> a.b.c = E('c')
+  >>> a.p = Nice('spam')
+  >>> a.b.p = E('p')
+
+  >>> def find_nice(self, ancestor, name, object, extra):
+  ...     return hasattr(object,'isNice') and object.isNice
+
+  >>> print a.b.c.aq_acquire('p', find_nice)
+  spam(Nice) and I am nice!
+
+The filtered acquisition in the last line skips over the first
+attribute it finds with the name ``p``, because the attribute doesn't
+satisfy the condition given in the filter.
+
+Filtered acquisition is rarely used in Zope.
+
+Acquiring from Context
+======================
+
+Normally acquisition allows objects to acquire data from their
+containers. However an object can acquire from objects that aren't its
+containers.
+
+Most of the examples we've seen so far show establishing of an
+acquisition context using getattr semantics. For example, ``a.b`` is a
+reference to ``b`` in the context of ``a``.
+
+You can also manually set acquisition context using the ``__of__``
+method. For example::
+
+  >>> from Acquisition import Implicit
+  >>> class C(Implicit): pass
+  ...
+  >>> a = C()
+  >>> b = C()
+  >>> a.color = "red"
+  >>> print b.__of__(a).color
+  red
+
+In this case, ``a`` does not contain ``b``, but it is put in ``b``'s
+context using the ``__of__`` method.
+
+Here's another subtler example that shows how you can construct an
+acquisition context that includes non-container objects::
+
+  >>> from Acquisition import Implicit
+
+  >>> class C(Implicit):
+  ...     def __init__(self, name):
+  ...         self.name = name
+
+  >>> a = C("a")
+  >>> a.b = C("b")
+  >>> a.b.color = "red"
+  >>> a.x = C("x")
+
+  >>> print a.b.x.color
+  red
+
+Even though ``b`` does not contain ``x``, ``x`` can acquire the color
+attribute from ``b``. This works because in this case, ``x`` is accessed
+in the context of ``b`` even though it is not contained by ``b``.
+
+Here acquisition context is defined by the objects used to access
+another object.
+
+Containment Before Context
+==========================
+
+If in the example above suppose both a and b have an color attribute::
+
+  >>> a = C("a")
+  >>> a.color = "green"
+  >>> a.b = C("b")
+  >>> a.b.color = "red"
+  >>> a.x = C("x")
+
+  >>> print a.b.x.color
+  green
+
+Why does ``a.b.x.color`` acquire color from ``a`` and not from ``b``?
+The answer is that an object acquires from its containers before
+non-containers in its context.
+
+To see why consider this example in terms of expressions using the
+``__of__`` method::
+
+  a.x -> x.__of__(a)
+
+  a.b -> b.__of__(a)
+
+  a.b.x -> x.__of__(a).__of__(b.__of__(a))
+
+Keep in mind that attribute lookup in a wrapper is done by trying to
+look up the attribute in the wrapped object first and then in the
+parent object. So in the expressions above proceeds from left to
+right.
+
+The upshot of these rules is that attributes are looked up by
+containment before context.
+
+This rule holds true also for more complex examples. For example,
+``a.b.c.d.e.f.g.attribute`` would search for attribute in ``g`` and
+all its containers first. (Containers are searched in order from the
+innermost parent to the outermost container.) If the attribute is not
+found in ``g`` or any of its containers, then the search moves to
+``f`` and all its containers, and so on.
+
+Additional Attributes and Methods
+=================================
+
+You can use the special method ``aq_inner`` to access an object
+wrapped only by containment. So in the example above,
+``a.b.x.aq_inner`` is equivalent to ``a.x``.
+
+You can find out the acquisition context of an object using the
+aq_chain method like so:
+
+  >>> [obj.name for obj in a.b.x.aq_chain]
+  ['x', 'b', 'a']
+
+You can find out if an object is in the containment context of another
+object using the ``aq_inContextOf`` method. For example:
+
+  >>> a.b.aq_inContextOf(a)
+  1
+
+.. Note: as of this writing the aq_inContextOf examples don't work the
+   way they should be working. According to Jim, this is because
+   aq_inContextOf works by comparing object pointer addresses, which
+   (because they are actually different wrapper objects) doesn't give
+   you the expected results. He acknowledges that this behavior is
+   controversial, and says that there is a collector entry to change
+   it so that you would get the answer you expect in the above. (We
+   just need to get to it).
+
+Acquisition Module Functions
+============================
+
+In addition to using acquisition attributes and methods directly on
+objects you can use similar functions defined in the ``Acquisition``
+module. These functions have the advantage that you don't need to
+check to make sure that the object has the method or attribute before
+calling it.
+
+``aq_acquire(object, name [, filter, extra, explicit, default, containment])``
+    Acquires an object with the given name.
+
+    This function can be used to explictly acquire when using explicit
+    acquisition and to acquire names that wouldn't normally be
+    acquired.
+
+    The function accepts a number of optional arguments:
+
+    ``filter``
+        A callable filter object that is used to decide if an object
+        should be acquired.
+
+        The filter is called with five arguments:
+
+        * The object that the aq_acquire method was called on,
+
+        * The object where an object was found,
+
+        * The name of the object, as passed to aq_acquire,
+
+        * The object found, and
+
+        * The extra argument passed to aq_acquire.
+
+        If the filter returns a true object that the object found is
+        returned, otherwise, the acquisition search continues.
+
+    ``extra``
+        Extra data to be passed as the last argument to the filter.
+
+    ``explicit``
+        A flag (boolean value) indicating whether explicit acquisition
+        should be used. The default value is true. If the flag is
+        true, then acquisition will proceed regardless of whether
+        wrappers encountered in the search of the acquisition
+        hierarchy are explicit or implicit wrappers. If the flag is
+        false, then parents of explicit wrappers are not searched.
+
+        This argument is useful if you want to apply a filter without
+        overriding explicit wrappers.
+
+    ``default``
+        A default value to return if no value can be acquired.
+
+    ``containment``
+        A flag indicating whether the search should be limited to the
+        containment hierarchy.
+
+    In addition, arguments can be provided as keywords.
+
+``aq_base(object)``
+    Return the object with all wrapping removed.
+
+``aq_chain(object [, containment])``
+    Return a list containing the object and it's acquisition
+    parents. The optional argument, containment, controls whether the
+    containment or access hierarchy is used.
+
+``aq_get(object, name [, default, containment])``
+    Acquire an attribute, name. A default value can be provided, as
+    can a flag that limits search to the containment hierarchy.
+
+``aq_inner(object)``
+    Return the object with all but the innermost layer of wrapping
+    removed.
+
+``aq_parent(object)``
+    Return the acquisition parent of the object or None if the object
+    is unwrapped.
+
+``aq_self(object)``
+    Return the object with one layer of wrapping removed, unless the
+    object is unwrapped, in which case the object is returned.
+
+In most cases it is more convenient to use these module functions
+instead of the acquisition attributes and methods directly.
+
+Acquisition and Methods
+=======================
+
+Python methods of objects that support acquisition can use acquired
+attributes. When a Python method is called on an object that is
+wrapped by an acquisition wrapper, the wrapper is passed to the method
+as the first argument. This rule also applies to user-defined method
+types and to C methods defined in pure mix-in classes.
+
+Unfortunately, C methods defined in extension base classes that define
+their own data structures, cannot use aquired attributes at this
+time. This is because wrapper objects do not conform to the data
+structures expected by these methods. In practice, you will seldom
+find this a problem.
+
+Conclusion
+==========
+
+Acquisition provides a powerful way to dynamically share information
+between objects. Zope 2 uses acquisition for a number of its key
+features including security, object publishing, and DTML variable
+lookup. Acquisition also provides an elegant solution to the problem
+of circular references for many classes of problems. While acquisition
+is powerful, you should take care when using acquisition in your
+applications. The details can get complex, especially with the
+differences between acquiring from context and acquiring from
+containment.

src/Acquisition/_Acquisition.c

+/*****************************************************************************
+
+  Copyright (c) 1996-2003 Zope Corporation and Contributors.
+  All Rights Reserved.
+
+  This software is subject to the provisions of the Zope Public License,
+  Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+  THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+  WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+  WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+  FOR A PARTICULAR PURPOSE
+
+ ****************************************************************************/
+
+#include "ExtensionClass/ExtensionClass.h"
+
+#define _IN_ACQUISITION_C
+#include "Acquisition/Acquisition.h"
+
+static ACQUISITIONCAPI AcquisitionCAPI;
+
+static void
+PyVar_Assign(PyObject **v,  PyObject *e)
+{
+  Py_XDECREF(*v);
+  *v=e;
+}
+
+#define ASSIGN(V,E) PyVar_Assign(&(V),(E))
+#define UNLESS(E) if (!(E))
+#define UNLESS_ASSIGN(V,E) ASSIGN(V,E); UNLESS(V)
+#define OBJECT(O) ((PyObject*)(O))
+
+static PyObject *py__add__, *py__sub__, *py__mul__, *py__div__,
+  *py__mod__, *py__pow__, *py__divmod__, *py__lshift__, *py__rshift__,
+  *py__and__, *py__or__, *py__xor__, *py__coerce__, *py__neg__,
+  *py__pos__, *py__abs__, *py__nonzero__, *py__invert__, *py__int__,
+  *py__long__, *py__float__, *py__oct__, *py__hex__,
+  *py__getitem__, *py__setitem__, *py__delitem__,
+  *py__getslice__, *py__setslice__, *py__delslice__,  *py__contains__,
+  *py__len__, *py__of__, *py__call__, *py__repr__, *py__str__, *py__cmp__,
+  *py__iter__;
+
+static PyObject *Acquired=0;
+
+static void
+init_py_names(void)
+{
+#define INIT_PY_NAME(N) py ## N = PyString_FromString(#N)
+  INIT_PY_NAME(__add__);
+  INIT_PY_NAME(__sub__);
+  INIT_PY_NAME(__mul__);
+  INIT_PY_NAME(__div__);
+  INIT_PY_NAME(__mod__);
+  INIT_PY_NAME(__pow__);
+  INIT_PY_NAME(__divmod__);
+  INIT_PY_NAME(__lshift__);
+  INIT_PY_NAME(__rshift__);
+  INIT_PY_NAME(__and__);
+  INIT_PY_NAME(__or__);
+  INIT_PY_NAME(__xor__);
+  INIT_PY_NAME(__coerce__);
+  INIT_PY_NAME(__neg__);
+  INIT_PY_NAME(__pos__);
+  INIT_PY_NAME(__abs__);
+  INIT_PY_NAME(__nonzero__);
+  INIT_PY_NAME(__invert__);
+  INIT_PY_NAME(__int__);
+  INIT_PY_NAME(__long__);
+  INIT_PY_NAME(__float__);
+  INIT_PY_NAME(__oct__);
+  INIT_PY_NAME(__hex__);
+  INIT_PY_NAME(__getitem__);
+  INIT_PY_NAME(__setitem__);
+  INIT_PY_NAME(__delitem__);
+  INIT_PY_NAME(__getslice__);
+  INIT_PY_NAME(__setslice__);
+  INIT_PY_NAME(__delslice__);
+  INIT_PY_NAME(__contains__);
+  INIT_PY_NAME(__len__);
+  INIT_PY_NAME(__of__);
+  INIT_PY_NAME(__call__);
+  INIT_PY_NAME(__repr__);
+  INIT_PY_NAME(__str__);
+  INIT_PY_NAME(__cmp__);
+  INIT_PY_NAME(__iter__);
+  
+#undef INIT_PY_NAME
+}
+
+static PyObject *
+CallMethodO(PyObject *self, PyObject *name,
+            PyObject *args, PyObject *kw)
+{
+  if (! args && PyErr_Occurred()) return NULL;
+  UNLESS(name=PyObject_GetAttr(self,name)) {
+    if (args) { Py_DECREF(args); }
+    return NULL;
+  }
+  ASSIGN(name,PyEval_CallObjectWithKeywords(name,args,kw));
+  if (args) { Py_DECREF(args); }
+  return name;
+}
+
+#define Build Py_BuildValue
+
+/* Declarations for objects of type Wrapper */
+
+typedef struct {
+  PyObject_HEAD
+  PyObject *obj;
+  PyObject *container;
+} Wrapper;
+
+staticforward PyExtensionClass Wrappertype, XaqWrappertype;
+
+#define isWrapper(O) ((O)->ob_type==(PyTypeObject*)&Wrappertype || \
+		      (O)->ob_type==(PyTypeObject*)&XaqWrappertype)
+#define WRAPPER(O) ((Wrapper*)(O))
+
+static int
+Wrapper__init__(Wrapper *self, PyObject *args, PyObject *kwargs)
+{
+  PyObject *obj, *container;
+
+  if (kwargs && PyDict_Size(kwargs) != 0)
+    {
+      PyErr_SetString(PyExc_TypeError,
+                      "kwyword arguments not allowed");
+      return -1;
+    }
+
+  UNLESS(PyArg_ParseTuple(args, "OO:__init__", &obj, &container)) return -1;
+
+  if (self == WRAPPER(obj)) {
+  	PyErr_SetString(PyExc_ValueError,
+		"Cannot wrap acquisition wrapper in itself (Wrapper__init__)");
+  	return -1;
+  }
+
+  Py_INCREF(obj);
+  self->obj=obj;
+
+  if (container != Py_None)
+    {
+      Py_INCREF(container);
+      self->container=container;
+    }
+  return 0;
+}
+
+/* ---------------------------------------------------------------- */
+
+static PyObject *
+__of__(PyObject *inst, PyObject *parent)
+{
+  PyObject *r, *t;
+
+  UNLESS(r=PyObject_GetAttr(inst, py__of__)) return NULL;
+  UNLESS(t=PyTuple_New(1)) goto err;
+  Py_INCREF(parent);
+  PyTuple_SET_ITEM(t,0,parent);
+  ASSIGN(r,PyObject_CallObject(r,t));
+  Py_DECREF(t);
+
+  if (r != NULL
+      && isWrapper(r) 
+      && WRAPPER(r)->container && isWrapper(WRAPPER(r)->container)
+      )
+    while (WRAPPER(r)->obj && isWrapper(WRAPPER(r)->obj)
+	   && (WRAPPER(WRAPPER(r)->obj)->container == 
+	       WRAPPER(WRAPPER(r)->container)->obj)
+	   )
+      {
+        if (r->ob_refcnt !=1 )
+          {
+            t = PyObject_CallFunctionObjArgs((PyObject *)(r->ob_type), 
+                                             WRAPPER(r)->obj, 
+                                             WRAPPER(r)->container,
+                                             NULL);
+            Py_DECREF(r);
+            if (t==NULL)
+              return NULL;
+            r = t;
+          }
+
+        /* Simplify wrapper */
+        Py_XINCREF(WRAPPER(WRAPPER(r)->obj)->obj);
+        ASSIGN(WRAPPER(r)->obj, WRAPPER(WRAPPER(r)->obj)->obj);
+      }
+
+  return r;
+err:
+  Py_DECREF(r);
+  return NULL;
+}
+
+static PyObject *
+Wrapper_descrget(Wrapper *self, PyObject *inst, PyObject *cls)
+{
+
+  if (inst == NULL)
+    {
+      Py_INCREF(self);
+      return (PyObject *)self;
+    }
+  
+  return __of__((PyObject *)self, inst);
+}
+
+
+#define newWrapper(obj, container, Wrappertype) \
+    PyObject_CallFunctionObjArgs(OBJECT(Wrappertype), obj, container, NULL)
+
+
+static int
+Wrapper_traverse(Wrapper *self, visitproc visit, void *arg)
+{
+    int vret;
+
+    if (self->obj) {
+        vret = visit(self->obj, arg);
+        if (vret != 0)
+            return vret;
+    }
+    if (self->container) {
+        vret = visit(self->container, arg);
+        if (vret != 0)
+            return vret;
+    }
+
+    return 0;
+}
+
+static int 
+Wrapper_clear(Wrapper *self)
+{
+    PyObject *tmp;
+
+    tmp = self->obj;
+    self->obj = NULL;
+    Py_XDECREF(tmp);
+
+    tmp = self->container;
+    self->container = NULL;
+    Py_XDECREF(tmp);
+
+    return 0;
+}
+
+static void
+Wrapper_dealloc(Wrapper *self)     
+{
+  Wrapper_clear(self);
+  self->ob_type->tp_free((PyObject*)self);
+}
+
+static PyObject *
+Wrapper_special(Wrapper *self, char *name, PyObject *oname)
+{
+  PyObject *r=0;
+
+  switch(*name)
+    {
+    case 'b':
+      if (strcmp(name,"base")==0)
+	{
+	  if (self->obj)
+	    {
+	      r=self->obj;
+	      while (isWrapper(r) && WRAPPER(r)->obj) r=WRAPPER(r)->obj;
+	    }
+	  else r=Py_None;
+	  Py_INCREF(r);
+	  return r;
+	}
+      break;
+    case 'p':
+      if (strcmp(name,"parent")==0)
+	{
+	  if (self->container) r=self->container;
+	  else r=Py_None;
+	  Py_INCREF(r);
+	  return r;
+	}
+      break;
+    case 's':
+      if (strcmp(name,"self")==0)
+	{
+	  if (self->obj) r=self->obj;
+	  else r=Py_None;
+	  Py_INCREF(r);
+	  return r;
+	}
+      break;
+    case 'e':
+      if (strcmp(name,"explicit")==0)
+	{
+	  if (self->ob_type != (PyTypeObject *)&XaqWrappertype)
+	    return newWrapper(self->obj, self->container, 
+			      (PyTypeObject *)&XaqWrappertype);
+	  Py_INCREF(self);
+	  return OBJECT(self);
+	}
+      break;
+    case 'a':
+      if (strcmp(name,"acquire")==0)
+	{
+	  return Py_FindAttr(OBJECT(self),oname);
+	}
+      break;
+    case 'c':
+      if (strcmp(name,"chain")==0)
+	{
+	  if ((r = PyList_New(0)))
+	    while (1)
+	      {
+		if (PyList_Append(r,OBJECT(self)) >= 0)
+		  {
+		    if (isWrapper(self) && self->container) 
+		      {
+			self=WRAPPER(self->container);
+			continue;
+		      }
+		  }
+		else
+		  {
+		    Py_DECREF(r);
+		  }
+		break;
+	      }
+	  return r;
+	}
+      break;
+    case 'i':
+      if (strcmp(name,"inContextOf")==0)
+	{
+	  return Py_FindAttr(OBJECT(self),oname);
+	}
+      if (strcmp(name,"inner")==0)
+	{
+	  if (self->obj)
+	    {
+	      r=self->obj;
+	      while (isWrapper(r) && WRAPPER(r)->obj) 
+		{
+		  self=WRAPPER(r);
+		  r=WRAPPER(r)->obj;
+		}
+	      r=OBJECT(self);
+	    }
+	  else r=Py_None;
+
+	  Py_INCREF(r);
+	  return r;
+	}
+      break;
+
+    case 'u':
+      if (strcmp(name,"uncle")==0)
+	{
+	  return PyString_FromString("Bob");
+	}
+      break;
+      
+    }
+
+  return NULL;
+}
+
+static int
+apply_filter(PyObject *filter, PyObject *inst, PyObject *oname, PyObject *r,
+	     PyObject *extra, PyObject *orig)
+{
+  /* Calls the filter, passing arguments.
+
+  Returns 1 if the filter accepts the value, 0 if not, -1 if an
+  exception occurred.
+
+  Note the special reference counting rule: This function decrements
+  the refcount of 'r' when it returns 0 or -1.  When it returns 1, it
+  leaves the refcount unchanged.
+  */
+
+  PyObject *fr;
+  int ir;
+
+  UNLESS(fr=PyTuple_New(5)) goto err;
+  PyTuple_SET_ITEM(fr,0,orig);
+  Py_INCREF(orig);
+  PyTuple_SET_ITEM(fr,1,inst);
+  Py_INCREF(inst);
+  PyTuple_SET_ITEM(fr,2,oname);
+  Py_INCREF(oname);
+  PyTuple_SET_ITEM(fr,3,r);
+  Py_INCREF(r);
+  PyTuple_SET_ITEM(fr,4,extra);
+  Py_INCREF(extra);
+  UNLESS_ASSIGN(fr,PyObject_CallObject(filter, fr)) goto err;
+  ir=PyObject_IsTrue(fr);
+  Py_DECREF(fr);
+  if (ir) return 1;
+  Py_DECREF(r);
+  return 0;
+err:
+  Py_DECREF(r);
+  return -1;
+}
+
+static PyObject *
+Wrapper_acquire(Wrapper *self, PyObject *oname, 
+		PyObject *filter, PyObject *extra, PyObject *orig,
+		int explicit, int containment);
+
+static PyObject *
+Wrapper_findattr(Wrapper *self, PyObject *oname,
+		PyObject *filter, PyObject *extra, PyObject *orig,
+		int sob, int sco, int explicit, int containment)
+{
+  PyObject *r, *v, *tb;
+  char *name="";
+
+  if (PyString_Check(oname)) name=PyString_AS_STRING(oname);
+  if (*name=='a' && name[1]=='q' && name[2]=='_')
+    if ((r=Wrapper_special(self, name+3, oname)))
+      {
+	if (filter)
+	  switch(apply_filter(filter,OBJECT(self),oname,r,extra,orig))
+	    {
+	    case -1: return NULL;
+	    case 1: return r;
+	    }
+	else return r;
+      }
+    else PyErr_Clear();
+  else if (*name=='_' && name[1]=='_' && 
+           (strcmp(name+2,"reduce__")==0 ||
+            strcmp(name+2,"reduce_ex__")==0 ||
+            strcmp(name+2,"getstate__")==0
+            ))
+    return PyObject_GenericGetAttr(((PyObject*)self), oname);
+
+  /* If we are doing a containment search, then replace self with aq_inner */
+  if (containment)
+    while (self->obj && isWrapper(self->obj))
+      self=WRAPPER(self->obj);
+
+  if (sob && self->obj)
+    {
+      if (isWrapper(self->obj))
+	{
+	  if (self == WRAPPER(self->obj)) {
+	  	PyErr_SetString(PyExc_RuntimeError,
+			"Recursion detected in acquisition wrapper");
+		return NULL;
+	  }
+	  if ((r=Wrapper_findattr(WRAPPER(self->obj),
+				 oname, filter, extra, orig, 1, 
+
+				 /* Search object container if explicit,
+				    or object is implicit acquirer */
+				 explicit ||
+				 self->obj->ob_type == 
+				 (PyTypeObject*)&Wrappertype,
+				  explicit, containment)))
+	    {
+	      if (PyECMethod_Check(r) && PyECMethod_Self(r)==self->obj)
+		ASSIGN(r,PyECMethod_New(r,OBJECT(self)));
+	      else if (has__of__(r)) ASSIGN(r,__of__(r,OBJECT(self)));
+	      return r;
+	    }
+
+	  PyErr_Fetch(&r,&v,&tb);
+	  if (r && (r != PyExc_AttributeError))
+	    {
+	      PyErr_Restore(r,v,tb);
+	      return NULL;
+	    }
+	  Py_XDECREF(r); Py_XDECREF(v); Py_XDECREF(tb);
+	  r=NULL;
+	}
+      else if ((r=PyObject_GetAttr(self->obj,oname)))
+	{
+	  if (r==Acquired)
+	    {
+	      Py_DECREF(r);
+	      return Wrapper_acquire(self, oname, filter, extra, orig, 1, 
+				     containment);
+	    }
+
+	  if (PyECMethod_Check(r) && PyECMethod_Self(r)==self->obj)
+	    ASSIGN(r,PyECMethod_New(r,OBJECT(self)));
+	  else if (has__of__(r)) ASSIGN(r,__of__(r,OBJECT(self)));
+
+	  if (r && filter)
+	    switch(apply_filter(filter,OBJECT(self),oname,r,extra,orig))
+	      {
+	      case -1: return NULL;
+	      case 1: return r;
+	      }
+	  else return r;
+	}
+      else {
+	PyErr_Fetch(&r,&v,&tb);
+	if (r != PyExc_AttributeError)
+	  {
+	    PyErr_Restore(r,v,tb);
+	    return NULL;
+	  }
+	Py_XDECREF(r); Py_XDECREF(v); Py_XDECREF(tb);
+	r=NULL;
+      }
+      PyErr_Clear();
+    }
+
+  if (sco && (*name != '_' || explicit)) 
+    return Wrapper_acquire(self, oname, filter, extra, orig, explicit, 
+			   containment);
+
+  PyErr_SetObject(PyExc_AttributeError,oname);
+  return NULL;
+}
+
+static PyObject *
+Wrapper_acquire(Wrapper *self, PyObject *oname, 
+		PyObject *filter, PyObject *extra, PyObject *orig,
+		int explicit, int containment)
+{
+  PyObject *r;
+  int sob=1, sco=1;
+
+  if (self->container)
+    {
+      if (isWrapper(self->container))
+	{
+	  if (self->obj && isWrapper(self->obj))
+	    {
+	      /* Try to optimize search by recognizing repeated obs in path */
+	      if (WRAPPER(self->obj)->container==
+		  WRAPPER(self->container)->container) 
+		sco=0;
+	      else if (WRAPPER(self->obj)->container==
+		      WRAPPER(self->container)->obj)  
+		sob=0;
+	   }
+
+	  r=Wrapper_findattr((Wrapper*)self->container,
+			     oname, filter, extra, orig, sob, sco, explicit, 
+			     containment);
+	  
+	  if (r && has__of__(r)) ASSIGN(r,__of__(r,OBJECT(self)));
+	  return r;
+	}
+      else
+	{
+	  if ((r=PyObject_GetAttr(self->container,oname))) {
+	    if (r == Acquired) {
+	      Py_DECREF(r);
+	    }
+	    else {
+	      if (filter) {
+		switch(apply_filter(filter,self->container,oname,r,
+				    extra,orig))
+		  {
+		  case -1: 
+		    return NULL;
+		  case 1: 
+		    if (has__of__(r)) ASSIGN(r,__of__(r,OBJECT(self)));
+		    return r;
+		  }
+	      }
+	      else {
+		if (has__of__(r)) ASSIGN(r,__of__(r,OBJECT(self)));
+		return r;
+	      }
+	    }
+	  }
+	  else {
+	    /* May be AttributeError or some other kind of error */
+	    return NULL;
+	  }
+	}
+    }
+  
+  PyErr_SetObject(PyExc_AttributeError, oname);
+  return NULL;
+}
+
+static PyObject *
+Wrapper_getattro(Wrapper *self, PyObject *oname)
+{
+  if (self->obj || self->container)
+    return Wrapper_findattr(self, oname, NULL, NULL, NULL, 1, 1, 0, 0);
+
+  /* Maybe we are getting initialized? */
+  return Py_FindAttr(OBJECT(self),oname);
+}
+
+static PyObject *
+Xaq_getattro(Wrapper *self, PyObject *oname)
+{
+  char *name="";
+
+  /* Special case backward-compatible acquire method. */
+  if (PyString_Check(oname)) name=PyString_AS_STRING(oname);
+  if (*name=='a' && name[1]=='c' && strcmp(name+2,"quire")==0)
+    return Py_FindAttr(OBJECT(self),oname);
+
+  if (self->obj || self->container)
+    return Wrapper_findattr(self, oname, NULL, NULL, NULL, 1, 0, 0, 0);
+
+  /* Maybe we are getting initialized? */
+  return Py_FindAttr(OBJECT(self),oname);
+}
+
+static int
+Wrapper_setattro(Wrapper *self, PyObject *oname, PyObject *v)
+{
+  char *name="";
+
+  /* Allow assignment to parent, to change context. */
+  if (PyString_Check(oname)) name=PyString_AS_STRING(oname);
+  if (*name=='a' && name[1]=='q' && name[2]=='_' 
+      && strcmp(name+3,"parent")==0)
+    {
+      Py_XINCREF(v);
+      ASSIGN(self->container, v);
+      return 0;
+    }
+
+  if (self->obj)
+    {
+      /* Unwrap passed in wrappers! */
+      while (v && isWrapper(v))
+	v=WRAPPER(v)->obj;
+
+      if (v) return PyObject_SetAttr(self->obj, oname, v);
+      else   return PyObject_DelAttr(self->obj, oname);
+    }
+
+  PyErr_SetString(PyExc_AttributeError, 
+		  "Attempt to set attribute on empty acquisition wrapper");
+  return -1;
+}
+
+static int
+Wrapper_compare(Wrapper *self, PyObject *w)
+{
+  PyObject *obj, *wobj;
+  PyObject *m;
+  int r;
+
+  if (OBJECT(self) == w) return 0;
+
+  UNLESS (m=PyObject_GetAttr(OBJECT(self), py__cmp__))
+    {
+      /* Unwrap self completely -> obj. */
+      while (self->obj && isWrapper(self->obj))
+        self=WRAPPER(self->obj);
+      obj = self->obj;
+      /* Unwrap w completely -> wobj. */
+      if (isWrapper(w))
+        {
+          while (WRAPPER(w)->obj && isWrapper(WRAPPER(w)->obj))
+            w=WRAPPER(w)->obj;
+          wobj = WRAPPER(w)->obj;
+        }
+      else wobj = w;
+
+      PyErr_Clear();
+      if (obj == wobj) return 0;
+      return (obj < w) ? -1 : 1;
+    }
+
+  ASSIGN(m, PyObject_CallFunction(m, "O", w));
+  UNLESS (m) return -1;
+  
+  r=PyInt_AsLong(m);
+
+  Py_DECREF(m);
+
+  return r;  
+}
+
+static PyObject *
+Wrapper_repr(Wrapper *self)
+{
+  PyObject *r;
+
+  if ((r=PyObject_GetAttr(OBJECT(self),py__repr__)))
+    {
+      ASSIGN(r,PyObject_CallFunction(r,NULL,NULL));
+      return r;
+    }
+  else
+    {
+      PyErr_Clear();
+      return PyObject_Repr(self->obj);
+    }
+}
+
+static PyObject *
+Wrapper_str(Wrapper *self)
+{
+  PyObject *r;
+
+  if ((r=PyObject_GetAttr(OBJECT(self),py__str__)))
+    {
+      ASSIGN(r,PyObject_CallFunction(r,NULL,NULL));
+      return r;
+    }
+  else
+    {
+      PyErr_Clear();
+      return PyObject_Str(self->obj);
+    }
+}
+
+static long
+Wrapper_hash(Wrapper *self)
+{
+  return PyObject_Hash(self->obj);
+}
+
+static PyObject *
+Wrapper_call(Wrapper *self, PyObject *args, PyObject *kw)
+{
+  Py_INCREF(args);
+  return CallMethodO(OBJECT(self),py__call__,args,kw);
+}
+
+/* Code to handle accessing Wrapper objects as sequence objects */
+
+static int
+Wrapper_length(Wrapper *self)
+{
+  long l;
+  PyObject *r;
+
+  UNLESS(r=PyObject_GetAttr(OBJECT(self), py__len__)) return -1;
+  UNLESS_ASSIGN(r,PyObject_CallObject(r,NULL)) return -1;
+  l=PyInt_AsLong(r);
+  Py_DECREF(r);
+  return l;
+}
+
+static PyObject *
+Wrapper_add(Wrapper *self, PyObject *bb)
+{
+  return CallMethodO(OBJECT(self),py__add__,Build("(O)", bb) ,NULL);
+}
+
+static PyObject *
+Wrapper_mul(Wrapper *self, int  n)
+{
+  return CallMethodO(OBJECT(self),py__mul__,Build("(i)", n),NULL);
+}
+
+static PyObject *
+Wrapper_item(Wrapper *self, int  i)
+{
+  return CallMethodO(OBJECT(self),py__getitem__, Build("(i)", i),NULL);
+}
+
+static PyObject *
+Wrapper_slice(Wrapper *self, int  ilow, int  ihigh)
+{
+  return CallMethodO(OBJECT(self),py__getslice__,
+		     Build("(ii)", ilow, ihigh),NULL);
+}
+
+static int
+Wrapper_ass_item(Wrapper *self, int  i, PyObject *v)
+{
+  if (v)
+    {
+      UNLESS(v=CallMethodO(OBJECT(self),py__setitem__,
+			   Build("(iO)", i, v),NULL))
+	return -1;
+    }
+  else
+    {
+      UNLESS(v=CallMethodO(OBJECT(self),py__delitem__,
+			   Build("(i)", i),NULL))
+	return -1;
+    }
+  Py_DECREF(v);
+  return 0;
+}
+
+static int
+Wrapper_ass_slice(Wrapper *self, int  ilow, int  ihigh, PyObject *v)
+{
+  if (v)
+    {
+      UNLESS(v=CallMethodO(OBJECT(self),py__setslice__,
+			   Build("(iiO)", ilow, ihigh, v),NULL))
+	return -1;
+    }
+  else
+    {
+      UNLESS(v=CallMethodO(OBJECT(self),py__delslice__,
+			   Build("(ii)", ilow, ihigh),NULL))
+	return -1;
+    }
+  Py_DECREF(v);
+  return 0;
+}
+
+static int
+Wrapper_contains(Wrapper *self, PyObject *v)
+{
+  long c;
+
+  UNLESS(v=CallMethodO(OBJECT(self),py__contains__,Build("(O)", v) ,NULL))
+    return -1;
+  c = PyInt_AsLong(v);
+  Py_DECREF(v);
+  return c;
+}
+
+/* Support for iteration cannot rely on the internal implementation of
+   `PyObject_GetIter`, since the `self` passed into `__iter__` and
+   `__getitem__` should be acquisition-wrapped (also see LP 360761): The
+   wrapper obviously supports the iterator protocol so simply calling
+   `PyObject_GetIter(OBJECT(self))` results in an infinite recursion.
+   Instead the base object needs to be checked and the wrapper must only
+   be used when actually calling `__getitem__` or setting up a sequence
+   iterator. */
+static PyObject * 
+Wrapper_iter(Wrapper *self)
+{
+  PyObject *obj = self->obj;
+  PyObject *res;
+  if ((res=PyObject_GetAttr(OBJECT(self),py__iter__))) {
+      ASSIGN(res,PyObject_CallFunction(res,NULL,NULL));
+      if (res != NULL && !PyIter_Check(res)) {
+          PyErr_Format(PyExc_TypeError,
+                   "iter() returned non-iterator "
+                   "of type '%.100s'",
+                   res->ob_type->tp_name);
+          Py_DECREF(res);
+          res = NULL;
+      }
+  } else if (PySequence_Check(obj)) {
+      ASSIGN(res,PySeqIter_New(OBJECT(self)));
+  } else {
+      res = PyErr_Format(PyExc_TypeError, "iteration over non-sequence");
+  }
+  return res;
+}
+
+static PySequenceMethods Wrapper_as_sequence = {
+	(inquiry)Wrapper_length,		/*sq_length*/
+	(binaryfunc)Wrapper_add,		/*sq_concat*/
+	(intargfunc)Wrapper_mul,		/*sq_repeat*/
+	(intargfunc)Wrapper_item,		/*sq_item*/
+	(intintargfunc)Wrapper_slice,		/*sq_slice*/
+	(intobjargproc)Wrapper_ass_item,	/*sq_ass_item*/
+	(intintobjargproc)Wrapper_ass_slice,	/*sq_ass_slice*/
+	(objobjproc)Wrapper_contains,		/*sq_contains*/
+};
+
+/* -------------------------------------------------------------- */
+
+/* Code to access Wrapper objects as mappings */
+
+static PyObject *
+Wrapper_subscript(Wrapper *self, PyObject *key)
+{
+  return CallMethodO(OBJECT(self),py__getitem__,Build("(O)", key),NULL);
+}
+
+static int
+Wrapper_ass_sub(Wrapper *self, PyObject *key, PyObject *v)
+{
+  if (v)
+    {
+      UNLESS(v=CallMethodO(OBJECT(self),py__setitem__,
+			   Build("(OO)", key, v),NULL))
+	return -1;
+    }
+  else
+    {
+      UNLESS(v=CallMethodO(OBJECT(self),py__delitem__,
+			   Build("(O)", key),NULL))
+	return -1;
+    }
+  Py_XDECREF(v);
+  return 0;
+}
+
+static PyMappingMethods Wrapper_as_mapping = {
+  (inquiry)Wrapper_length,		/*mp_length*/
+  (binaryfunc)Wrapper_subscript,	/*mp_subscript*/
+  (objobjargproc)Wrapper_ass_sub,	/*mp_ass_subscript*/
+};
+
+/* -------------------------------------------------------------- */
+
+/* Code to access Wrapper objects as numbers */
+
+static PyObject *
+Wrapper_sub(Wrapper *self, PyObject *o)
+{
+  return CallMethodO(OBJECT(self),py__sub__,Build("(O)", o),NULL);
+}
+
+static PyObject *
+Wrapper_div(Wrapper *self, PyObject *o)
+{
+  return CallMethodO(OBJECT(self),py__div__,Build("(O)", o),NULL);
+}
+
+static PyObject *
+Wrapper_mod(Wrapper *self, PyObject *o)
+{
+  return CallMethodO(OBJECT(self),py__mod__,Build("(O)", o),NULL);
+}
+
+static PyObject *
+Wrapper_divmod(Wrapper *self, PyObject *o)
+{
+  return CallMethodO(OBJECT(self),py__divmod__,Build("(O)", o),NULL);
+}
+
+static PyObject *
+Wrapper_pow(Wrapper *self, PyObject *o, PyObject *m)
+{
+  return CallMethodO(OBJECT(self),py__pow__,Build("(OO)", o, m),NULL);
+}
+
+static PyObject *
+Wrapper_neg(Wrapper *self)
+{
+  return CallMethodO(OBJECT(self), py__neg__, NULL, NULL);
+}
+
+static PyObject *
+Wrapper_pos(Wrapper *self)
+{
+  return CallMethodO(OBJECT(self), py__pos__, NULL, NULL);
+}
+
+static PyObject *
+Wrapper_abs(Wrapper *self)
+{
+  return CallMethodO(OBJECT(self), py__abs__, NULL, NULL);
+}
+
+static PyObject *
+Wrapper_invert(Wrapper *self)
+{
+  return CallMethodO(OBJECT(self), py__invert__, NULL, NULL);
+}
+
+static PyObject *
+Wrapper_lshift(Wrapper *self, PyObject *o)
+{
+  return CallMethodO(OBJECT(self),py__lshift__,Build("(O)", o),NULL);
+}
+
+static PyObject *
+Wrapper_rshift(Wrapper *self, PyObject *o)
+{
+  return CallMethodO(OBJECT(self),py__rshift__,Build("(O)", o),NULL);
+}
+
+static PyObject *
+Wrapper_and(Wrapper *self, PyObject *o)
+{
+  return CallMethodO(OBJECT(self),py__and__,Build("(O)", o),NULL);
+}
+
+static PyObject *
+Wrapper_xor(Wrapper *self, PyObject *o)
+{
+  return CallMethodO(OBJECT(self),py__xor__,Build("(O)", o),NULL);
+}
+
+static PyObject *
+Wrapper_or(Wrapper *self, PyObject *o)
+{
+  return CallMethodO(OBJECT(self),py__or__,Build("(O)", o),NULL);
+}
+
+static int 
+Wrapper_coerce(Wrapper **self, PyObject **o)
+{
+  PyObject *m;
+
+  UNLESS (m=PyObject_GetAttr(OBJECT(*self), py__coerce__))
+    {
+      PyErr_Clear();
+      Py_INCREF(*self);
+      Py_INCREF(*o);
+      return 0;
+    }
+
+  ASSIGN(m, PyObject_CallFunction(m, "O", *o));
+  UNLESS (m) return -1;
+
+  UNLESS (PyArg_ParseTuple(m,"OO", self, o)) goto err;
+  Py_INCREF(*self);
+  Py_INCREF(*o);
+  Py_DECREF(m);
+  return 0;
+
+err:
+  Py_DECREF(m);
+  return -1;  
+}
+
+static PyObject *
+Wrapper_int(Wrapper *self)
+{
+  return CallMethodO(OBJECT(self), py__int__, NULL, NULL);
+}
+
+static PyObject *
+Wrapper_long(Wrapper *self)
+{
+  return CallMethodO(OBJECT(self), py__long__, NULL, NULL);
+}
+
+static PyObject *
+Wrapper_float(Wrapper *self)
+{
+  return CallMethodO(OBJECT(self), py__float__, NULL, NULL);
+}
+
+static PyObject *
+Wrapper_oct(Wrapper *self)
+{
+  return CallMethodO(OBJECT(self), py__oct__, NULL, NULL);
+}
+
+static PyObject *
+Wrapper_hex(Wrapper *self)
+{
+  return CallMethodO(OBJECT(self), py__hex__, NULL, NULL);
+}
+
+static int
+Wrapper_nonzero(Wrapper *self)
+{
+  long l;
+  PyObject *r;
+
+  UNLESS(r=PyObject_GetAttr(OBJECT(self), py__nonzero__))
+    {
+      PyErr_Clear();
+
+      /* Try len */
+      UNLESS(r=PyObject_GetAttr(OBJECT(self), py__len__))
+      {
+        /* No len, it's true :-) */
+        PyErr_Clear();
+        return 1;
+      }
+    }
+
+  UNLESS_ASSIGN(r,PyObject_CallObject(r,NULL)) return -1;
+  l=PyInt_AsLong(r);
+  Py_DECREF(r);
+  return l;
+}
+
+static PyNumberMethods Wrapper_as_number = {
+	(binaryfunc)Wrapper_add,	/*nb_add*/
+	(binaryfunc)Wrapper_sub,	/*nb_subtract*/
+	(binaryfunc)Wrapper_mul,	/*nb_multiply*/
+	(binaryfunc)Wrapper_div,	/*nb_divide*/
+	(binaryfunc)Wrapper_mod,	/*nb_remainder*/
+	(binaryfunc)Wrapper_divmod,	/*nb_divmod*/
+	(ternaryfunc)Wrapper_pow,	/*nb_power*/
+	(unaryfunc)Wrapper_neg,		/*nb_negative*/
+	(unaryfunc)Wrapper_pos,		/*nb_positive*/
+	(unaryfunc)Wrapper_abs,		/*nb_absolute*/
+	(inquiry)Wrapper_nonzero,	/*nb_nonzero*/
+	(unaryfunc)Wrapper_invert,	/*nb_invert*/
+	(binaryfunc)Wrapper_lshift,	/*nb_lshift*/
+	(binaryfunc)Wrapper_rshift,	/*nb_rshift*/
+	(binaryfunc)Wrapper_and,	/*nb_and*/
+	(binaryfunc)Wrapper_xor,	/*nb_xor*/
+	(binaryfunc)Wrapper_or,		/*nb_or*/
+	(coercion)Wrapper_coerce,	/*nb_coerce*/
+	(unaryfunc)Wrapper_int,		/*nb_int*/
+	(unaryfunc)Wrapper_long,	/*nb_long*/
+	(unaryfunc)Wrapper_float,	/*nb_float*/
+	(unaryfunc)Wrapper_oct,		/*nb_oct*/
+	(unaryfunc)Wrapper_hex,		/*nb_hex*/
+};
+
+
+/* -------------------------------------------------------- */
+
+
+static char *acquire_args[] = {"object", "name", "filter", "extra", "explicit",
+			       "default", "containment", NULL};
+
+static PyObject *
+Wrapper_acquire_method(Wrapper *self, PyObject *args, PyObject *kw)
+{
+  PyObject *name, *filter=0, *extra=Py_None;
+  PyObject *expl=0, *defalt=0;
+  int explicit=1;
+  int containment=0;
+  PyObject *result; /* DM 2005-08-25: argument "default" ignored */
+
+  UNLESS (PyArg_ParseTupleAndKeywords(
+	     args, kw, "O|OOOOi", acquire_args+1,
+	     &name, &filter, &extra, &explicit, &defalt, &containment
+	     ))
+    return NULL;
+
+  if (expl) explicit=PyObject_IsTrue(expl);
+
+  if (filter==Py_None) filter=0;
+
+  /* DM 2005-08-25: argument "default" ignored -- fix it! */
+# if 0
+  return Wrapper_findattr(self,name,filter,extra,OBJECT(self),1,
+			  explicit || 
+			  self->ob_type==(PyTypeObject*)&Wrappertype,
+			  explicit, containment);
+# else
+  result = Wrapper_findattr(self,name,filter,extra,OBJECT(self),1,
+			  explicit || 
+			  self->ob_type==(PyTypeObject*)&Wrappertype,
+			  explicit, containment);
+  if (result == NULL && defalt != NULL) {
+    /* as "Python/bltinmodule.c:builtin_getattr" turn
+       only 'AttributeError' into a default value, such
+       that e.g. "ConflictError" and errors raised by the filter
+       are not mapped to the default value.
+    */
+    if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
+      PyErr_Clear();
+      Py_INCREF(defalt);
+      result = defalt;
+    }
+  }
+  return result;
+# endif
+}
+
+
+static PyObject *
+Wrapper_inContextOf(Wrapper *self, PyObject *args)
+{
+  PyObject *subob, *o, *c;
+  int inner=1;
+
+  UNLESS(PyArg_ParseTuple(args,"O|i",&o,&inner)) return NULL;
+
+  if (inner) {
+    /* subob = self */
+    subob = OBJECT(self);
+
+    /* o = aq_base(o) */
+    while (isWrapper(o) && WRAPPER(o)->obj) o=WRAPPER(o)->obj;
+
+    /* while 1: */
+    while (1) {
+
+      /*   if aq_base(subob) is o: return 1 */
+      c = subob;
+      while (isWrapper(c) && WRAPPER(c)->obj) c = WRAPPER(c)->obj;
+      if (c == o) return PyInt_FromLong(1);
+
+      /*   self = aq_inner(subob) */
+      /*   if self is None: break */
+      if (isWrapper(subob)) {
+        self = WRAPPER(subob);
+        while (self->obj && isWrapper(self->obj))
+          self = WRAPPER(self->obj);
+      }
+      else break;
+
+      /*   subob = aq_parent(self) */
+      /*   if subob is None: break */
+      if (self->container)
+        subob = self->container;
+      else break;
+    }
+  }
+  else {
+    /* Follow wrappers instead. */
+    c = OBJECT(self);
+    while (1) {
+      if (c==o) return PyInt_FromLong(1);
+      if (c && isWrapper(c)) c=WRAPPER(c)->container;
+      else break;
+    }
+  }
+
+  return PyInt_FromLong(0);
+}
+
+PyObject *
+Wrappers_are_not_picklable(PyObject *wrapper, PyObject *args)
+{
+  PyErr_SetString(PyExc_TypeError, 
+                  "Can't pickle objects in acquisition wrappers.");
+  return NULL;
+}
+
+static struct PyMethodDef Wrapper_methods[] = {
+  {"acquire", (PyCFunction)Wrapper_acquire_method, 
+   METH_VARARGS|METH_KEYWORDS,
+   "Get an attribute, acquiring it if necessary"},
+  {"aq_acquire", (PyCFunction)Wrapper_acquire_method, 
+   METH_VARARGS|METH_KEYWORDS,
+   "Get an attribute, acquiring it if necessary"},
+  {"aq_inContextOf", (PyCFunction)Wrapper_inContextOf, METH_VARARGS,
+   "Test whether the object is currently in the context of the argument"},
+  {"__getstate__", (PyCFunction)Wrappers_are_not_picklable, METH_VARARGS,
+   "Wrappers are not picklable"},
+  {"__reduce__", (PyCFunction)Wrappers_are_not_picklable, METH_VARARGS,
+   "Wrappers are not picklable"},
+  {"__reduce_ex__", (PyCFunction)Wrappers_are_not_picklable, METH_VARARGS,
+   "Wrappers are not picklable"},
+  {NULL,		NULL}		/* sentinel */
+};
+
+static PyExtensionClass Wrappertype = {
+  PyObject_HEAD_INIT(NULL)
+  0,					/*ob_size*/
+  "ImplicitAcquirerWrapper",		/*tp_name*/
+  sizeof(Wrapper),       		/*tp_basicsize*/
+  0,					/*tp_itemsize*/
+  /* methods */
+  (destructor)Wrapper_dealloc,		/*tp_dealloc*/
+  (printfunc)0,				/*tp_print*/
+  (getattrfunc)0,			/*tp_getattr*/
+  (setattrfunc)0,			/*tp_setattr*/
+  (cmpfunc)Wrapper_compare,    		/*tp_compare*/
+  (reprfunc)Wrapper_repr,      		/*tp_repr*/
+  &Wrapper_as_number,			/*tp_as_number*/
+  &Wrapper_as_sequence,			/*tp_as_sequence*/
+  &Wrapper_as_mapping,			/*tp_as_mapping*/
+  (hashfunc)Wrapper_hash,      		/*tp_hash*/
+  (ternaryfunc)Wrapper_call,		/*tp_call*/
+  (reprfunc)Wrapper_str,       		/*tp_str*/
+  (getattrofunc)Wrapper_getattro,	/*tp_getattr with object key*/
+  (setattrofunc)Wrapper_setattro,      	/*tp_setattr with object key*/
+  /* tp_as_buffer      */ 0,
+  /* tp_flags          */ Py_TPFLAGS_DEFAULT 
+                          | Py_TPFLAGS_BASETYPE
+                          | Py_TPFLAGS_HAVE_GC
+                          ,
+  "Wrapper object for implicit acquisition", /* Documentation string */
+  /* tp_traverse       */ (traverseproc)Wrapper_traverse,
+  /* tp_clear          */ (inquiry)Wrapper_clear,
+  /* tp_richcompare    */ (richcmpfunc)0,
+  /* tp_weaklistoffset */ (long)0,
+  (getiterfunc)Wrapper_iter,		/*tp_iter*/
+  /* tp_iternext       */ (iternextfunc)0,
+  /* tp_methods        */ Wrapper_methods,
+  /* tp_members        */ 0,
+  /* tp_getset         */ 0,
+  /* tp_base           */ 0,
+  /* tp_dict           */ 0,
+  /* tp_descr_get      */ (descrgetfunc)Wrapper_descrget,
+  /* tp_descr_set      */ 0,
+  /* tp_dictoffset     */ 0,
+  /* tp_init           */ (initproc)Wrapper__init__,
+};
+
+static PyExtensionClass XaqWrappertype = {
+  PyObject_HEAD_INIT(NULL)
+  0,					/*ob_size*/
+  "ExplicitAcquirerWrapper",		/*tp_name*/
+  sizeof(Wrapper),       		/*tp_basicsize*/
+  0,					/*tp_itemsize*/
+  /* methods */
+  (destructor)Wrapper_dealloc,		/*tp_dealloc*/
+  (printfunc)0,				/*tp_print*/
+  (getattrfunc)0,			/*tp_getattr*/
+  (setattrfunc)0,			/*tp_setattr*/
+  (cmpfunc)Wrapper_compare,    		/*tp_compare*/
+  (reprfunc)Wrapper_repr,      		/*tp_repr*/
+  &Wrapper_as_number,			/*tp_as_number*/
+  &Wrapper_as_sequence,			/*tp_as_sequence*/
+  &Wrapper_as_mapping,			/*tp_as_mapping*/
+  (hashfunc)Wrapper_hash,      		/*tp_hash*/
+  (ternaryfunc)Wrapper_call,		/*tp_call*/
+  (reprfunc)Wrapper_str,       		/*tp_str*/
+  (getattrofunc)Xaq_getattro,		/*tp_getattr with object key*/
+  (setattrofunc)Wrapper_setattro,      	/*tp_setattr with object key*/
+  /* tp_as_buffer      */ 0,
+  /* tp_flags          */ Py_TPFLAGS_DEFAULT 
+                          | Py_TPFLAGS_BASETYPE
+                          | Py_TPFLAGS_HAVE_GC
+                          ,
+  "Wrapper object for implicit acquisition", /* Documentation string */
+  /* tp_traverse       */ (traverseproc)Wrapper_traverse,
+  /* tp_clear          */ (inquiry)Wrapper_clear,
+  /* tp_richcompare    */ (richcmpfunc)0,
+  /* tp_weaklistoffset */ (long)0,
+  (getiterfunc)Wrapper_iter,		/*tp_iter*/
+  /* tp_iternext       */ (iternextfunc)0,
+  /* tp_methods        */ Wrapper_methods,
+  /* tp_members        */ 0,
+  /* tp_getset         */ 0,
+  /* tp_base           */ 0,
+  /* tp_dict           */ 0,
+  /* tp_descr_get      */ (descrgetfunc)Wrapper_descrget,
+  /* tp_descr_set      */ 0,
+  /* tp_dictoffset     */ 0,
+  /* tp_init           */ (initproc)Wrapper__init__,
+};
+
+static PyObject *
+acquire_of(PyObject *self, PyObject *args)
+{
+  PyObject *inst;
+
+  UNLESS(PyArg_ParseTuple(args, "O", &inst)) return NULL;
+
+  UNLESS(PyExtensionInstance_Check(inst))
+    {
+      PyErr_SetString(PyExc_TypeError,
+		      "attempt to wrap extension method using an object that\n"
+		      "is not an extension class instance.");
+      return NULL;
+    }
+
+  return newWrapper(self, inst, (PyTypeObject *)&Wrappertype);
+}
+
+static PyObject *
+xaq_of(PyObject *self, PyObject *args)
+{
+  PyObject *inst;
+
+  UNLESS(PyArg_ParseTuple(args, "O", &inst)) return NULL;
+
+  UNLESS(PyExtensionInstance_Check(inst))
+    {
+      PyErr_SetString(PyExc_TypeError,
+		      "attempt to wrap extension method using an object that\n"
+		      "is not an extension class instance.");
+      return NULL;
+    }
+
+  return newWrapper(self, inst, (PyTypeObject *)&XaqWrappertype);
+}
+
+static struct PyMethodDef Acquirer_methods[] = {
+  {"__of__",(PyCFunction)acquire_of, METH_VARARGS, 
+   "__of__(context) -- return the object in a context"},
+  
+  {NULL,		NULL}		/* sentinel */
+};
+
+static struct PyMethodDef Xaq_methods[] = {
+  {"__of__",(PyCFunction)xaq_of, METH_VARARGS,""},
+  
+  {NULL,		NULL}		/* sentinel */
+};
+
+static PyObject *
+capi_aq_acquire(PyObject *self, PyObject *name, PyObject *filter,
+	PyObject *extra, int explicit, PyObject *defalt, int containment)
+{
+  
+  PyObject *result;
+
+  if (filter==Py_None) filter=0;
+
+  /* We got a wrapped object, so business as usual */
+  if (isWrapper(self)) 
+    return Wrapper_findattr(
+	      WRAPPER(self), name, filter, extra, OBJECT(self),1,
+	      explicit || 
+	      WRAPPER(self)->ob_type==(PyTypeObject*)&Wrappertype,
+	      explicit, containment);
+  
+  /* Not wrapped and no filter, so just getattr */
+  if (! filter) return PyObject_GetAttr(self, name);
+
+  /* Crap, we've got to construct a wrapper so we can use Wrapper_findattr */
+  UNLESS (self=newWrapper(self, Py_None, (PyTypeObject*)&Wrappertype)) 
+    return NULL;
+  
+  result=Wrapper_findattr(WRAPPER(self), name, filter, extra, OBJECT(self),
+			   1, 1, explicit, containment);
+
+  /* get rid of temp wrapper */
+  Py_DECREF(self);
+
+  return result;
+}
+
+static PyObject *
+module_aq_acquire(PyObject *ignored, PyObject *args, PyObject *kw)
+{
+  PyObject *self;
+  PyObject *name, *filter=0, *extra=Py_None;
+  PyObject *expl=0, *defalt=0;
+  int explicit=1, containment=0;
+
+  UNLESS (PyArg_ParseTupleAndKeywords(
+	     args, kw, "OO|OOOOi", acquire_args,
+	     &self, &name, &filter, &extra, &expl, &defalt, &containment
+	     ))
+    return NULL;
+
+  if (expl) explicit=PyObject_IsTrue(expl);
+
+  return capi_aq_acquire(self, name, filter, extra, explicit, defalt,
+  	containment);
+}
+
+static PyObject *
+capi_aq_get(PyObject *self, PyObject *name, PyObject *defalt, int containment)
+{
+  PyObject *result = NULL;
+  /* We got a wrapped object, so business as usual */
+  if (isWrapper(self)) 
+    result=Wrapper_findattr(WRAPPER(self), name, 0, 0, OBJECT(self), 1, 1, 1, 
+		       containment);
+  else
+    result=PyObject_GetAttr(self, name);
+
+  if (! result && defalt)
+    {
+      PyErr_Clear();
+      result=defalt;
+      Py_INCREF(result);
+    }
+  
+  return result;
+}
+
+
+static PyObject *
+module_aq_get(PyObject *r, PyObject *args)
+{
+  PyObject *self, *name, *defalt=0;
+  int containment=0;
+  
+  UNLESS (PyArg_ParseTuple(args, "OO|Oi", 
+			   &self, &name, &defalt, &containment
+			   )) return NULL;
+  return capi_aq_get(self, name, defalt, containment);
+}
+
+static int 
+capi_aq_iswrapper(PyObject *self) {
+	return isWrapper(self);
+}
+
+static PyObject *
+capi_aq_base(PyObject *self)
+{
+  PyObject *result;
+  if (! isWrapper(self)) 
+    {
+      Py_INCREF(self);
+      return self;
+    }
+  
+  if (WRAPPER(self)->obj)
+    {
+      result=WRAPPER(self)->obj;
+      while (isWrapper(result) && WRAPPER(result)->obj)
+      	result=WRAPPER(result)->obj;
+    }
+  else result=Py_None;
+  Py_INCREF(result);
+  return result;
+}
+
+static PyObject *
+module_aq_base(PyObject *ignored, PyObject *args)
+{
+  PyObject *self;
+  UNLESS (PyArg_ParseTuple(args, "O", &self)) return NULL;
+
+  return capi_aq_base(self);
+}
+
+static PyObject *
+capi_aq_parent(PyObject *self)
+{
+  PyObject *result=Py_None;
+
+  if (isWrapper(self) && WRAPPER(self)->container)
+  	result=WRAPPER(self)->container;
+
+  Py_INCREF(result);
+  return result;
+}
+
+static PyObject *
+module_aq_parent(PyObject *ignored, PyObject *args)
+{
+  PyObject *self;
+
+  UNLESS (PyArg_ParseTuple(args, "O", &self)) return NULL;
+
+  return capi_aq_parent(self);
+}
+
+static PyObject *
+capi_aq_self(PyObject *self)
+{
+  PyObject *result;
+  if (! isWrapper(self)) 
+    {
+      Py_INCREF(self);
+      return self;
+    }
+  
+  if (WRAPPER(self)->obj) result=WRAPPER(self)->obj;
+  else result=Py_None;
+
+  Py_INCREF(result);
+  return result;
+}
+
+static PyObject *
+module_aq_self(PyObject *ignored, PyObject *args)
+{
+  PyObject *self;
+  UNLESS (PyArg_ParseTuple(args, "O", &self)) return NULL;
+  return capi_aq_self(self);
+}
+
+static PyObject *
+capi_aq_inner(PyObject *self)
+{
+  PyObject *result;
+  if (! isWrapper(self)) 
+    {
+      Py_INCREF(self);
+      return self;
+    }
+
+  if (WRAPPER(self)->obj)
+    {
+      result=WRAPPER(self)->obj;
+      while (isWrapper(result) && WRAPPER(result)->obj) 
+	{
+	  self=result;
+	  result=WRAPPER(result)->obj;
+	}
+      result=self;
+    }
+  else result=Py_None;
+
+  Py_INCREF(result);
+  return result;
+}
+
+static PyObject *
+module_aq_inner(PyObject *ignored, PyObject *args)
+{
+  PyObject *self;
+
+  UNLESS (PyArg_ParseTuple(args, "O", &self)) return NULL;
+  return capi_aq_inner(self);
+}
+
+static PyObject *
+capi_aq_chain(PyObject *self, int containment)
+{
+  PyObject *result;
+
+  UNLESS (result=PyList_New(0)) return NULL;
+
+  while (1)
+    {
+      if (isWrapper(self))
+	{
+	  if (WRAPPER(self)->obj)
+	    {
+	      if (containment)
+		while (WRAPPER(self)->obj && isWrapper(WRAPPER(self)->obj))
+		  self=WRAPPER(self)->obj;
+	      if (PyList_Append(result,OBJECT(self)) < 0)
+		goto err;
+	    }
+	  if (WRAPPER(self)->container) 
+	    {
+	      self=WRAPPER(self)->container;
+	      continue;
+	    }
+	}
+      else
+	if (PyList_Append(result, self) < 0)
+	  goto err;
+
+      break;
+    }
+  
+  return result;
+err:
+  Py_DECREF(result);
+  return result;
+}
+
+static PyObject *
+module_aq_chain(PyObject *ignored, PyObject *args)
+{
+  PyObject *self;
+  int containment=0;
+
+  UNLESS (PyArg_ParseTuple(args, "O|i", &self, &containment))
+    return NULL;
+
+  return capi_aq_chain(self, containment);
+}
+
+static struct PyMethodDef methods[] = {
+  {"aq_acquire", (PyCFunction)module_aq_acquire, METH_VARARGS|METH_KEYWORDS, 
+   "aq_acquire(ob, name [, filter, extra, explicit]) -- "
+   "Get an attribute, acquiring it if necessary"
+  },
+  {"aq_get", (PyCFunction)module_aq_get, METH_VARARGS,
+   "aq_get(ob, name [, default]) -- "
+   "Get an attribute, acquiring it if necessary."
+  },
+  {"aq_base", (PyCFunction)module_aq_base, METH_VARARGS, 
+   "aq_base(ob) -- Get the object unwrapped"},
+  {"aq_parent", (PyCFunction)module_aq_parent, METH_VARARGS, 
+   "aq_parent(ob) -- Get the parent of an object"},
+  {"aq_self", (PyCFunction)module_aq_self, METH_VARARGS, 
+   "aq_self(ob) -- Get the object with the outermost wrapper removed"},
+  {"aq_inner", (PyCFunction)module_aq_inner, METH_VARARGS, 
+   "aq_inner(ob) -- "
+   "Get the object with alll but the innermost wrapper removed"},
+  {"aq_chain", (PyCFunction)module_aq_chain, METH_VARARGS, 
+   "aq_chain(ob [, containment]) -- "
+   "Get a list of objects in the acquisition environment"},
+  {NULL,	NULL}
+};
+
+void
+init_Acquisition(void)
+{
+  PyObject *m, *d;
+  PyObject *api;
+
+  PURE_MIXIN_CLASS(Acquirer,
+    "Base class for objects that implicitly"
+    " acquire attributes from containers\n"
+    , Acquirer_methods);
+  PURE_MIXIN_CLASS(ExplicitAcquirer,
+    "Base class for objects that explicitly"
+    " acquire attributes from containers\n"
+    , Xaq_methods);
+
+  UNLESS(ExtensionClassImported) return;
+
+  UNLESS(Acquired=PyString_FromStringAndSize(NULL,42)) return;
+  strcpy(PyString_AsString(Acquired),
+	 "<Special Object Used to Force Acquisition>");
+
+  /* Create the module and add the functions */
+  m = Py_InitModule4("_Acquisition", methods,
+	   "Provide base classes for acquiring objects\n\n"
+	   "$Id$\n",
+		     OBJECT(NULL),PYTHON_API_VERSION);
+
+  d = PyModule_GetDict(m);
+  init_py_names();
+  PyExtensionClass_Export(d,"Acquirer",AcquirerType);
+  PyExtensionClass_Export(d,"ImplicitAcquisitionWrapper",Wrappertype);
+  PyExtensionClass_Export(d,"ExplicitAcquirer",ExplicitAcquirerType);
+  PyExtensionClass_Export(d,"ExplicitAcquisitionWrapper",XaqWrappertype);
+
+  /* Create aliases */
+  PyDict_SetItemString(d,"Implicit",OBJECT(&AcquirerType));
+  PyDict_SetItemString(d,"Explicit",OBJECT(&ExplicitAcquirerType));
+  PyDict_SetItemString(d,"Acquired",Acquired);
+
+  AcquisitionCAPI.AQ_Acquire = capi_aq_acquire;
+  AcquisitionCAPI.AQ_Get = capi_aq_get;
+  AcquisitionCAPI.AQ_IsWrapper = capi_aq_iswrapper;
+  AcquisitionCAPI.AQ_Base = capi_aq_base;
+  AcquisitionCAPI.AQ_Parent = capi_aq_parent;
+  AcquisitionCAPI.AQ_Self = capi_aq_self;
+  AcquisitionCAPI.AQ_Inner = capi_aq_inner;
+  AcquisitionCAPI.AQ_Chain = capi_aq_chain;
+
+  api = PyCObject_FromVoidPtr(&AcquisitionCAPI, NULL);
+  PyDict_SetItemString(d, "AcquisitionCAPI", api);
+  Py_DECREF(api);
+}

src/Acquisition/__init__.py

+from zope.interface import classImplements
+
+from _Acquisition import *
+from interfaces import IAcquirer
+from interfaces import IAcquisitionWrapper
+
+classImplements(Explicit, IAcquirer)
+classImplements(ExplicitAcquisitionWrapper, IAcquisitionWrapper)
+classImplements(Implicit, IAcquirer)
+classImplements(ImplicitAcquisitionWrapper, IAcquisitionWrapper)

src/Acquisition/interfaces.py

+##############################################################################
+#
+# Copyright (c) 2005 Zope Corporation and Contributors. All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+"""Acquisition z3 interfaces.
+
+$Id$
+"""
+
+from zope.interface import Attribute
+from zope.interface import Interface
+
+
+class IAcquirer(Interface):
+
+    """Acquire attributes from containers.
+    """
+
+    def __of__(context):
+        """Get the object in a context.
+        """
+
+
+class IAcquisitionWrapper(Interface):
+
+    """Wrapper object for acquisition.
+    """
+
+    def aq_acquire(name, filter=None, extra=None, explicit=True, default=0,
+                   containment=0):
+        """Get an attribute, acquiring it if necessary.
+        """
+
+    def aq_inContextOf(obj, inner=1):
+        """Test whether the object is currently in the context of the argument.
+        """
+
+    aq_base = Attribute(
+        """Get the object unwrapped."""
+        )
+
+    aq_parent = Attribute(
+        """Get the parent of an object."""
+        )
+
+    aq_self = Attribute(
+        """Get the object with the outermost wrapper removed."""
+        )
+
+    aq_inner = Attribute(
+        """Get the object with all but the innermost wrapper removed."""
+        )
+
+    aq_chain = Attribute(
+        """Get a list of objects in the acquisition environment."""
+        )

src/Acquisition/setup.py

+##############################################################################
+#
+# Copyright (c) 2003 Zope Corporation and Contributors.
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+
+from distutils.core import setup, Extension
+setup(name="_Acquisition", version="2.0",
+      ext_modules=[
+         Extension("_Acquisition", ["_Acquisition.c"],
+                   include_dirs = ['.', '../ExtensionClass'],
+                   depends = ["Acquisition.h",
+                              '../ExtensionClass/ExtensionClass.h']),
+         ])
+

src/Acquisition/tests.py

+##############################################################################
+#
+# Copyright (c) 2003 Zope Corporation and Contributors.
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+"""Acquisition test cases (and useful examples)
+
+  Acquisition [1] is a mechanism that allows objects to obtain
+  attributes from their environment.  It is similar to inheritence,
+  except that, rather than traversing an inheritence hierarchy
+  to obtain attributes, a containment hierarchy is traversed.
+
+  The "ExtensionClass":ExtensionClass.html. release includes mix-in
+  extension base classes that can be used to add acquisition as a
+  feature to extension subclasses.  These mix-in classes use the
+  context-wrapping feature of ExtensionClasses to implement
+  acquisition. Consider the following example::
+
+    >>> import ExtensionClass, Acquisition
+
+    >>> class C(ExtensionClass.Base):
+    ...   color='red'
+
+    >>> class A(Acquisition.Implicit):
+    ...   def report(self):
+    ...     print self.color
+
+    >>> a = A()
+    >>> c = C()
+    >>> c.a = a
+
+    >>> c.a.report()
+    red
+
+    >>> d = C()
+    >>> d.color = 'green'
+    >>> d.a = a
+
+    >>> d.a.report()
+    green
+
+    >>> a.report() # raises an attribute error
+    Traceback (most recent call last):
+    ...
+    AttributeError: color
+
+  The class 'A' inherits acquisition behavior from
+  'Acquisition.Implicit'.  The object, 'a', "has" the color of
+  objects 'c' and 'd' when it is accessed through them, but it
+  has no color by itself.  The object 'a' obtains attributes
+  from it's environment, where it's environment is defined by
+  the access path used to reach 'a'.
+
+  Acquisition wrappers
+
+    When an object that supports acquisition is accessed through
+    an extension class instance, a special object, called an
+    acquisition wrapper, is returned.  In the example above, the
+    expression 'c.a' returns an acquisition wrapper that
+    contains references to both 'c' and 'a'.  It is this wrapper
+    that performs attribute lookup in 'c' when an attribute
+    cannot be found in 'a'.
+
+    Aquisition wrappers provide access to the wrapped objects
+    through the attributes 'aq_parent', 'aq_self', 'aq_base'.  
+    In the example above, the expressions::
+      
+       >>> c.a.aq_parent is c
+       1
+
+    and::
+
+       >>> c.a.aq_self is a
+       1
+
+    both evaluate to true, but the expression::
+
+       >>> c.a is a
+       0
+
+    evaluates to false, because the expression 'c.a' evaluates
+    to an acquisition wrapper around 'c' and 'a', not 'a' itself.
+
+    The attribute 'aq_base' is similar to 'aq_self'.  Wrappers may be
+    nested and 'aq_self' may be a wrapped object.  The 'aq_base'
+    attribute is the underlying object with all wrappers removed.
+
+  Acquisition Control
+
+    Two styles of acquisition are supported in the current
+    ExtensionClass release, implicit and explicit aquisition.
+  
+    Implicit acquisition
+    
+      Implicit acquisition is so named because it searches for
+      attributes from the environment automatically whenever an
+      attribute cannot be obtained directly from an object or
+      through inheritence.
+  
+      An attribute may be implicitly acquired if it's name does
+      not begin with an underscore, '_'.
+  
+      To support implicit acquisition, an object should inherit
+      from the mix-in class 'Acquisition.Implicit'.
+  
+    Explicit Acquisition
+  
+      When explicit acquisition is used, attributes are not
+      automatically obtained from the environment.  Instead, the
+      method 'aq_aquire' must be used, as in::
+  
+        print c.a.aq_acquire('color')
+  
+      To support explicit acquisition, an object should inherit
+      from the mix-in class 'Acquisition.Explicit'.
+
+    Controlled Acquisition
+
+      A class (or instance) can provide attribute by attribute control
+      over acquisition.  This is done by:
+
+      - subclassing from 'Acquisition.Explicit', and
+
+      - setting all attributes that should be acquired to the special
+        value: 'Acquisition.Acquired'.  Setting an attribute to this
+        value also allows inherited attributes to be overridden with
+        acquired ones.
+
+        For example, in::
+
+          >>> class E(Acquisition.Explicit):
+          ...    id = 1
+          ...    secret = 2
+          ...    color = Acquisition.Acquired
+          ...    __roles__ = Acquisition.Acquired
+
+        The *only* attributes that are automatically acquired from
+        containing objects are 'color', and '__roles__'.
+
+          >>> c = C()
+          >>> c.foo = 'foo'
+          >>> c.e = E()
+          >>> c.e.color
+          'red'
+          >>> c.e.foo
+          Traceback (most recent call last):
+          ...
+          AttributeError: foo
+
+        Note also that the '__roles__' attribute is acquired even
+        though it's name begins with an underscore:
+
+          >>> c.__roles__ = 'Manager', 'Member'
+          >>> c.e.__roles__
+          ('Manager', 'Member')
+
+        In fact, the special 'Acquisition.Acquired' value can be used
+        in 'Acquisition.Implicit' objects to implicitly acquire
+        selected objects that smell like private objects.
+
+          >>> class I(Acquisition.Implicit):
+          ...    __roles__ = Acquisition.Acquired
+
+          >>> c.x = C()
+          >>> c.x.__roles__
+          Traceback (most recent call last):
+          ...
+          AttributeError: __roles__
+
+          >>> c.x = I()
+          >>> c.x.__roles__
+          ('Manager', 'Member')
+
+    Filtered Acquisition
+
+      The acquisition method, 'aq_acquire', accepts two optional
+      arguments. The first of the additional arguments is a
+      "filtering" function that is used when considering whether to
+      acquire an object.  The second of the additional arguments is an
+      object that is passed as extra data when calling the filtering
+      function and which defaults to 'None'.
+
+      The filter function is called with five arguments:
+
+      - The object that the 'aq_acquire' method was called on,
+
+      - The object where an object was found,
+
+      - The name of the object, as passed to 'aq_acquire',
+
+      - The object found, and
+
+      - The extra data passed to 'aq_acquire'.
+
+      If the filter returns a true object that the object found is
+      returned, otherwise, the acquisition search continues.
+
+      For example, in::
+
+        >>> from Acquisition import Explicit
+        
+        >>> class HandyForTesting:
+        ...     def __init__(self, name): self.name=name
+        ...     def __str__(self):
+        ...       return "%s(%s)" % (self.name, self.__class__.__name__)
+        ...     __repr__=__str__
+        
+        >>> class E(Explicit, HandyForTesting):
+        ...     pass
+        
+        >>> class Nice(HandyForTesting):
+        ...     isNice=1
+        ...     def __str__(self):
+        ...        return HandyForTesting.__str__(self)+' and I am nice!'
+        ...     __repr__=__str__
+        
+        >>> a = E('a')
+        >>> a.b = E('b')
+        >>> a.b.c = E('c')
+        >>> a.p = Nice('spam')
+        >>> a.b.p = E('p')
+        
+        >>> def find_nice(self, ancestor, name, object, extra):
+        ...     return hasattr(object,'isNice') and object.isNice
+        
+        >>> print a.b.c.aq_acquire('p', find_nice)
+        spam(Nice) and I am nice!
+
+      The filtered acquisition in the last line skips over the first
+      attribute it finds with the name 'p', because the attribute
+      doesn't satisfy the condition given in the filter.
+
+  Acquisition and methods
+
+    Python methods of objects that support acquisition can use
+    acquired attributes as in the 'report' method of the first example
+    above.  When a Python method is called on an object that is
+    wrapped by an acquisition wrapper, the wrapper is passed to the
+    method as the first argument.  This rule also applies to
+    user-defined method types and to C methods defined in pure mix-in
+    classes.
+
+    Unfortunately, C methods defined in extension base classes that
+    define their own data structures, cannot use aquired attributes at
+    this time.  This is because wrapper objects do not conform to the
+    data structures expected by these methods.
+
+  Acquiring Acquiring objects
+
+    Consider the following example::
+
+      >>> from Acquisition import Implicit
+      
+      >>> class C(Implicit):
+      ...     def __init__(self, name): self.name=name
+      ...     def __str__(self):
+      ...         return "%s(%s)" % (self.name, self.__class__.__name__)
+      ...     __repr__=__str__
+      
+      >>> a = C("a")
+      >>> a.b = C("b")
+      >>> a.b.pref = "spam"
+      >>> a.b.c = C("c")
+      >>> a.b.c.color = "red"
+      >>> a.b.c.pref = "eggs"
+      >>> a.x = C("x")
+
+      >>> o = a.b.c.x
+
+    The expression 'o.color' might be expected to return '"red"'. In
+    earlier versions of ExtensionClass, however, this expression
+    failed.  Acquired acquiring objects did not acquire from the
+    environment they were accessed in, because objects were only
+    wrapped when they were first found, and were not rewrapped as they
+    were passed down the acquisition tree.
+
+    In the current release of ExtensionClass, the expression "o.color"
+    does indeed return '"red"'.
+
+      >>> o.color
+      'red'
+
+    When searching for an attribute in 'o', objects are searched in
+    the order 'x', 'a', 'b', 'c'. So, for example, the expression,
+    'o.pref' returns '"spam"', not '"eggs"'::
+
+      >>> o.pref
+      'spam'
+
+    In earlier releases of ExtensionClass, the attempt to get the
+    'pref' attribute from 'o' would have failed.
+
+    If desired, the current rules for looking up attributes in complex
+    expressions can best be understood through repeated application of
+    the '__of__' method:
+
+    'a.x' -- 'x.__of__(a)'
+
+    'a.b' -- 'b.__of__(a)'
+
+    'a.b.x' -- 'x.__of__(a).__of__(b.__of__(a))'
+
+    'a.b.c' -- 'c.__of__(b.__of__(a))'
+
+    'a.b.c.x' --
+        'x.__of__(a).__of__(b.__of__(a)).__of__(c.__of__(b.__of__(a)))'
+
+    and by keeping in mind that attribute lookup in a wrapper
+    is done by trying to lookup the attribute in the wrapped object
+    first and then in the parent object.  In the expressions above
+    involving the '__of__' method, lookup proceeds from left to right.
+
+    Note that heuristics are used to avoid most of the repeated
+    lookups. For example, in the expression: 'a.b.c.x.foo', the object
+    'a' is searched no more than once, even though it is wrapped three
+    times.
+
+.. [1] Gil, J., Lorenz, D., 
+   "Environmental Acquisition--A New Inheritance-Like Abstraction Mechanism",
+   http://www.bell-labs.com/people/cope/oopsla/Oopsla96TechnicalProgramAbstracts.html#GilLorenz, 
+   OOPSLA '96 Proceedings, ACM SIG-PLAN, October, 1996
+
+$Id$
+"""
+
+import ExtensionClass
+import Acquisition
+
+class I(Acquisition.Implicit):
+    def __init__(self, id):
+        self.id = id
+    def __repr__(self):
+        return self.id
+
+class E(Acquisition.Explicit):
+    def __init__(self, id):
+        self.id = id
+    def __repr__(self):
+        return self.id
+
+def test_unwrapped():
+    """
+    >>> c = I('unwrapped')
+    >>> show(c)
+    unwrapped
+
+    >>> c.aq_parent
+    Traceback (most recent call last):
+    ...
+    AttributeError: aq_parent
+
+    >>> Acquisition.aq_acquire(c, 'id')
+    'unwrapped'
+    >>> Acquisition.aq_acquire(c, 'x')
+    Traceback (most recent call last):
+    ...
+    AttributeError: x
+    
+    >>> Acquisition.aq_acquire(c, 'id',
+    ...  lambda searched, parent, name, ob, extra: extra)
+    Traceback (most recent call last):
+    ...
+    AttributeError: id
+
+    >>> Acquisition.aq_acquire(c, 'id',
+    ...        lambda searched, parent, name, ob, extra: extra,
+    ...        1)
+    'unwrapped'
+
+    >>> Acquisition.aq_base(c) is c
+    1
+
+    >>> Acquisition.aq_chain(c)
+    [unwrapped]
+
+    >>> Acquisition.aq_chain(c, 1)
+    [unwrapped]
+
+    >>> Acquisition.aq_get(c, 'id')
+    'unwrapped'
+
+    >>> Acquisition.aq_get(c, 'x')
+    Traceback (most recent call last):
+    ...
+    AttributeError: x
+    >>> Acquisition.aq_get(c, 'x', 'foo')
+    'foo'
+    >>> Acquisition.aq_get(c, 'x', 'foo', 1)
+    'foo'
+
+    >>> Acquisition.aq_inner(c) is c
+    1
+
+    >>> Acquisition.aq_parent(c)
+
+    >>> Acquisition.aq_self(c) is c
+    1
+
+    
+    
+    """
+
+def test_simple():
+    """
+    >>> a = I('a')
+    >>> a.y = 42
+    >>> a.b = I('b')
+    >>> a.b.c = I('c')
+    >>> show(a.b.c)
+    c
+    |
+    b
+    |
+    a
+
+    >>> show(a.b.c.aq_parent)
+    b
+    |
+    a
+
+    >>> show(a.b.c.aq_self)
+    c
+
+    >>> show(a.b.c.aq_base)
+    c
+
+    >>> show(a.b.c.aq_inner)
+    c
+    |
+    b
+    |
+    a
+
+    >>> a.b.c.y
+    42
+
+    >>> a.b.c.aq_chain
+    [c, b, a]
+
+    >>> a.b.c.aq_inContextOf(a)
+    1
+    >>> a.b.c.aq_inContextOf(a.b)
+    1
+    >>> a.b.c.aq_inContextOf(a.b.c)
+    1
+
+
+    >>> a.b.c.aq_acquire('y')
+    42
+
+    >>> a.b.c.aq_acquire('id')
+    'c'
+
+    >>> a.b.c.aq_acquire('x')
+    Traceback (most recent call last):
+    ...
+    AttributeError: x
+    
+    >>> a.b.c.aq_acquire('id',
+    ...  lambda searched, parent, name, ob, extra: extra)
+    Traceback (most recent call last):
+    ...
+    AttributeError: id
+
+    >>> Acquisition.aq_acquire(a.b.c, 'id',
+    ...        lambda searched, parent, name, ob, extra: extra,
+    ...        1)
+    'c'
+
+    >>> Acquisition.aq_acquire(a.b.c, 'id')
+    'c'
+
+    >>> Acquisition.aq_acquire(a.b.c, 'x')
+    Traceback (most recent call last):
+    ...
+    AttributeError: x
+
+    >>> Acquisition.aq_acquire(a.b.c, 'y')
+    42
+    
+    >>> Acquisition.aq_acquire(a.b.c, 'id',
+    ...  lambda searched, parent, name, ob, extra: extra)
+    Traceback (most recent call last):
+    ...
+    AttributeError: id
+
+    >>> Acquisition.aq_acquire(a.b.c, 'id',
+    ...        lambda searched, parent, name, ob, extra: extra,
+    ...        1)
+    'c'
+
+    >>> show(Acquisition.aq_base(a.b.c))
+    c
+
+    >>> Acquisition.aq_chain(a.b.c)
+    [c, b, a]
+
+    >>> Acquisition.aq_chain(a.b.c, 1)
+    [c, b, a]
+
+    >>> Acquisition.aq_get(a.b.c, 'id')
+    'c'
+
+    >>> Acquisition.aq_get(a.b.c, 'x')
+    Traceback (most recent call last):
+    ...
+    AttributeError: x
+    >>> Acquisition.aq_get(a.b.c, 'x', 'foo')
+    'foo'
+    >>> Acquisition.aq_get(a.b.c, 'x', 'foo', 1)
+    'foo'
+
+    >>> show(Acquisition.aq_inner(a.b.c))
+    c
+    |
+    b
+    |
+    a
+
+    >>> show(Acquisition.aq_parent(a.b.c))
+    b
+    |
+    a
+
+    >>> show(Acquisition.aq_self(a.b.c))
+    c
+
+    """
+
+def test__of__exception():
+    """
+    Wrapper_findattr did't check for an exception in a user defined
+    __of__ method before passing the result to the filter. In this
+    case the 'value' argument of the filter was NULL, which caused
+    a segfault when being accessed.
+
+    >>> class UserError(Exception):
+    ...     pass
+    ...
+    >>> class X(Acquisition.Implicit):
+    ...     def __of__(self, parent):
+    ...         if Acquisition.aq_base(parent) is not parent:
+    ...             raise UserError, 'ack'
+    ...         return X.inheritedAttribute('__of__')(self, parent)
+    ...
+    >>> a = I('a')
+    >>> a.b = I('b')
+    >>> a.b.x = X('x')
+    >>> Acquisition.aq_acquire(a.b, 'x',
+    ...     lambda self, object, name, value, extra: repr(value))
+    Traceback (most recent call last):
+    ...
+    UserError: ack
+
+    """
+
+def test_muliple():
+    r"""
+    >>> a = I('a')
+    >>> a.color = 'red'
+    >>> a.a1 = I('a1')
+    >>> a.a1.color = 'green'
+    >>> a.a1.a11 = I('a11')
+    >>> a.a2 = I('a2')
+    >>> a.a2.a21 = I('a21')
+    >>> show(a.a1.a11.a2.a21)
+    a21
+    |
+    (a2)
+    |  \
+    |   (a2)
+    |   |  \
+    |   |   a2
+    |   |   |
+    |   |   a
+    |   |
+    |   a1
+    |   |
+    |   a
+    |
+    a11
+    |
+    a1
+    |
+    a
+
+    >>> a.a1.a11.a2.a21.color
+    'red'
+
+    >>> show(a.a1.a11.a2.a21.aq_parent)
+    (a2)
+    |  \
+    |   (a2)
+    |   |  \
+    |   |   a2
+    |   |   |
+    |   |   a
+    |   |
+    |   a1
+    |   |
+    |   a
+    |
+    a11
+    |
+    a1
+    |
+    a
+
+    >>> show(a.a1.a11.a2.a21.aq_parent.aq_parent)
+    a11
+    |
+    a1
+    |
+    a
+
+    >>> show(a.a1.a11.a2.a21.aq_self)
+    a21
+
+    >>> show(a.a1.a11.a2.a21.aq_parent.aq_self)
+    (a2)
+    |  \
+    |   a2
+    |   |
+    |   a
+    |
+    a1
+    |
+    a
+
+    >>> show(a.a1.a11.a2.a21.aq_base)
+    a21
+
+    >>> show(a.a1.a11.a2.a21.aq_inner)
+    a21
+    |
+    (a2)
+    |  \
+    |   (a2)
+    |   |  \
+    |   |   a2
+    |   |   |
+    |   |   a
+    |   |
+    |   a1
+    |   |
+    |   a
+    |
+    a11
+    |
+    a1
+    |
+    a
+
+    >>> show(a.a1.a11.a2.a21.aq_inner.aq_parent.aq_inner)
+    a2
+    |
+    a
+
+    >>> show(a.a1.a11.a2.a21.aq_inner.aq_parent.aq_inner.aq_parent)
+    a
+    
+    >>> a.a1.a11.a2.a21.aq_chain
+    [a21, a2, a11, a1, a]
+    
+    >>> a.a1.a11.a2.a21.aq_inContextOf(a)
+    1
+    
+    >>> a.a1.a11.a2.a21.aq_inContextOf(a.a2)
+    1
+
+    >>> a.a1.a11.a2.a21.aq_inContextOf(a.a1)
+    0
+    
+    >>> a.a1.a11.a2.a21.aq_acquire('color')
+    'red'
+    >>> a.a1.a11.a2.a21.aq_acquire('id')
+    'a21'
+
+    >>> a.a1.a11.a2.a21.aq_acquire('color',
+    ...     lambda ob, parent, name, v, extra: extra)
+    Traceback (most recent call last):
+    ...
+    AttributeError: color
+
+    >>> a.a1.a11.a2.a21.aq_acquire('color',
+    ...     lambda ob, parent, name, v, extra: extra, 1)
+    'red'
+    
+    >>> a.a1.y = 42
+    >>> a.a1.a11.a2.a21.aq_acquire('y')
+    42
+
+    >>> a.a1.a11.a2.a21.aq_acquire('y', containment=1)
+    Traceback (most recent call last):
+    ...
+    AttributeError: y
+
+    Much of the same, but with methods:
+
+    >>> show(Acquisition.aq_parent(a.a1.a11.a2.a21))
+    (a2)
+    |  \
+    |   (a2)
+    |   |  \
+    |   |   a2
+    |   |   |
+    |   |   a
+    |   |
+    |   a1
+    |   |
+    |   a
+    |
+    a11
+    |
+    a1
+    |
+    a
+
+    >>> show(Acquisition.aq_parent(a.a1.a11.a2.a21.aq_parent))
+    a11
+    |
+    a1
+    |
+    a
+
+    >>> show(Acquisition.aq_self(a.a1.a11.a2.a21))
+    a21
+
+    >>> show(Acquisition.aq_self(a.a1.a11.a2.a21.aq_parent))
+    (a2)
+    |  \
+    |   a2
+    |   |
+    |   a
+    |
+    a1
+    |
+    a
+
+    >>> show(Acquisition.aq_base(a.a1.a11.a2.a21))
+    a21
+
+    >>> show(Acquisition.aq_inner(a.a1.a11.a2.a21))
+    a21
+    |
+    (a2)
+    |  \
+    |   (a2)
+    |   |  \
+    |   |   a2
+    |   |   |
+    |   |   a
+    |   |
+    |   a1
+    |   |
+    |   a
+    |
+    a11
+    |
+    a1
+    |
+    a
+
+    >>> show(Acquisition.aq_inner(a.a1.a11.a2.a21.aq_inner.aq_parent))
+    a2
+    |
+    a
+
+    >>> show(Acquisition.aq_parent(
+    ...       a.a1.a11.a2.a21.aq_inner.aq_parent.aq_inner))
+    a
+    
+    >>> Acquisition.aq_chain(a.a1.a11.a2.a21)
+    [a21, a2, a11, a1, a]
+    
+    >>> Acquisition.aq_chain(a.a1.a11.a2.a21, 1)
+    [a21, a2, a]
+    
+    >>> Acquisition.aq_acquire(a.a1.a11.a2.a21, 'color')
+    'red'
+    >>> Acquisition.aq_acquire(a.a1.a11.a2.a21, 'id')
+    'a21'
+
+    >>> Acquisition.aq_acquire(a.a1.a11.a2.a21, 'color',
+    ...     lambda ob, parent, name, v, extra: extra)
+    Traceback (most recent call last):
+    ...
+    AttributeError: color
+
+    >>> Acquisition.aq_acquire(a.a1.a11.a2.a21, 'color',
+    ...     lambda ob, parent, name, v, extra: extra, 1)
+    'red'
+    
+    >>> a.a1.y = 42
+    >>> Acquisition.aq_acquire(a.a1.a11.a2.a21, 'y')
+    42
+
+    >>> Acquisition.aq_acquire(a.a1.a11.a2.a21, 'y', containment=1)
+    Traceback (most recent call last):
+    ...
+    AttributeError: y
+
+
+    """
+    
+def test_pinball():
+    r"""
+    >>> a = I('a')
+    >>> a.a1 = I('a1')
+    >>> a.a1.a11 = I('a11')
+    >>> a.a1.a12 = I('a12')
+    >>> a.a2 = I('a2')
+    >>> a.a2.a21 = I('a21')
+    >>> a.a2.a22 = I('a22')
+    >>> show(a.a1.a11.a1.a12.a2.a21.a2.a22)
+    a22
+    |
+    (a2)
+    |  \
+    |   (a2)
+    |   |  \
+    |   |   a2
+    |   |   |
+    |   |   a
+    |   |
+    |   (a2)
+    |   |  \
+    |   |   (a2)
+    |   |   |  \
+    |   |   |   a2
+    |   |   |   |
+    |   |   |   a
+    |   |   |
+    |   |   (a1)
+    |   |   |  \
+    |   |   |   (a1)
+    |   |   |   |  \
+    |   |   |   |   a1
+    |   |   |   |   |
+    |   |   |   |   a
+    |   |   |   |
+    |   |   |   a1
+    |   |   |   |
+    |   |   |   a
+    |   |   |
+    |   |   a11
+    |   |   |
+    |   |   a1
+    |   |   |
+    |   |   a
+    |   |
+    |   a12
+    |   |
+    |   (a1)
+    |   |  \
+    |   |   (a1)
+    |   |   |  \
+    |   |   |   a1
+    |   |   |   |
+    |   |   |   a
+    |   |   |
+    |   |   a1
+    |   |   |
+    |   |   a
+    |   |
+    |   a11
+    |   |
+    |   a1
+    |   |
+    |   a
+    |
+    a21
+    |
+    (a2)
+    |  \
+    |   (a2)
+    |   |  \
+    |   |   a2
+    |   |   |
+    |   |   a
+    |   |
+    |   (a1)
+    |   |  \
+    |   |   (a1)
+    |   |   |  \
+    |   |   |   a1
+    |   |   |   |
+    |   |   |   a
+    |   |   |
+    |   |   a1
+    |   |   |
+    |   |   a
+    |   |
+    |   a11
+    |   |
+    |   a1
+    |   |
+    |   a
+    |
+    a12
+    |
+    (a1)
+    |  \
+    |   (a1)
+    |   |  \
+    |   |   a1
+    |   |   |
+    |   |   a
+    |   |
+    |   a1
+    |   |
+    |   a
+    |
+    a11
+    |
+    a1
+    |
+    a
+    
+    """
+
+def test_explicit():
+    """
+    >>> a = E('a')
+    >>> a.y = 42
+    >>> a.b = E('b')
+    >>> a.b.c = E('c')
+    >>> show(a.b.c)
+    c
+    |
+    b
+    |
+    a
+
+    >>> show(a.b.c.aq_parent)
+    b
+    |
+    a
+
+    >>> show(a.b.c.aq_self)
+    c
+
+    >>> show(a.b.c.aq_base)
+    c
+
+    >>> show(a.b.c.aq_inner)
+    c
+    |
+    b
+    |
+    a
+
+    >>> a.b.c.y
+    Traceback (most recent call last):
+    ...
+    AttributeError: y
+
+    >>> a.b.c.aq_chain
+    [c, b, a]
+
+    >>> a.b.c.aq_inContextOf(a)
+    1
+    >>> a.b.c.aq_inContextOf(a.b)
+    1
+    >>> a.b.c.aq_inContextOf(a.b.c)
+    1
+
+
+    >>> a.b.c.aq_acquire('y')
+    42
+
+    >>> a.b.c.aq_acquire('id')
+    'c'
+
+    >>> a.b.c.aq_acquire('x')
+    Traceback (most recent call last):
+    ...
+    AttributeError: x
+    
+    >>> a.b.c.aq_acquire('id',
+    ...  lambda searched, parent, name, ob, extra: extra)
+    Traceback (most recent call last):
+    ...
+    AttributeError: id
+
+    >>> Acquisition.aq_acquire(a.b.c, 'id',
+    ...        lambda searched, parent, name, ob, extra: extra,
+    ...        1)
+    'c'
+
+    >>> Acquisition.aq_acquire(a.b.c, 'id')
+    'c'
+
+    >>> Acquisition.aq_acquire(a.b.c, 'x')
+    Traceback (most recent call last):
+    ...
+    AttributeError: x
+
+    >>> Acquisition.aq_acquire(a.b.c, 'y')
+    42
+    
+    >>> Acquisition.aq_acquire(a.b.c, 'id',
+    ...  lambda searched, parent, name, ob, extra: extra)
+    Traceback (most recent call last):
+    ...
+    AttributeError: id
+
+    >>> Acquisition.aq_acquire(a.b.c, 'id',
+    ...        lambda searched, parent, name, ob, extra: extra,
+    ...        1)
+    'c'
+
+    >>> show(Acquisition.aq_base(a.b.c))
+    c
+
+    >>> Acquisition.aq_chain(a.b.c)
+    [c, b, a]
+
+    >>> Acquisition.aq_chain(a.b.c, 1)
+    [c, b, a]
+
+    >>> Acquisition.aq_get(a.b.c, 'id')
+    'c'
+
+    >>> Acquisition.aq_get(a.b.c, 'x')
+    Traceback (most recent call last):
+    ...
+    AttributeError: x
+
+    >>> Acquisition.aq_get(a.b.c, 'y')
+    42
+
+    >>> Acquisition.aq_get(a.b.c, 'x', 'foo')
+    'foo'
+    >>> Acquisition.aq_get(a.b.c, 'x', 'foo', 1)
+    'foo'
+
+    >>> show(Acquisition.aq_inner(a.b.c))
+    c
+    |
+    b
+    |
+    a
+
+    >>> show(Acquisition.aq_parent(a.b.c))
+    b
+    |
+    a
+
+    >>> show(Acquisition.aq_self(a.b.c))
+    c
+
+    """
+
+def test_mixed_explicit_and_explicit():
+    """
+    >>> a = I('a')
+    >>> a.y = 42
+    >>> a.b = E('b')
+    >>> a.b.z = 3
+    >>> a.b.c = I('c')
+    >>> show(a.b.c)
+    c
+    |
+    b
+    |
+    a
+
+    >>> show(a.b.c.aq_parent)
+    b
+    |
+    a
+
+    >>> show(a.b.c.aq_self)
+    c
+
+    >>> show(a.b.c.aq_base)
+    c
+
+    >>> show(a.b.c.aq_inner)
+    c
+    |
+    b
+    |
+    a
+
+    >>> a.b.c.y
+    42
+
+    >>> a.b.c.z
+    3
+
+    >>> a.b.c.aq_chain
+    [c, b, a]
+
+    >>> a.b.c.aq_inContextOf(a)
+    1
+    >>> a.b.c.aq_inContextOf(a.b)
+    1
+    >>> a.b.c.aq_inContextOf(a.b.c)
+    1
+
+    >>> a.b.c.aq_acquire('y')
+    42
+
+    >>> a.b.c.aq_acquire('z')
+    3
+
+    >>> a.b.c.aq_acquire('z', explicit=False)
+    3
+
+    >>> a.b.c.aq_acquire('id')
+    'c'
+
+    >>> a.b.c.aq_acquire('x')
+    Traceback (most recent call last):
+    ...
+    AttributeError: x
+    
+    >>> a.b.c.aq_acquire('id',
+    ...  lambda searched, parent, name, ob, extra: extra)
+    Traceback (most recent call last):
+    ...
+    AttributeError: id
+
+    >>> Acquisition.aq_acquire(a.b.c, 'id',
+    ...        lambda searched, parent, name, ob, extra: extra,
+    ...        1)
+    'c'
+
+    >>> Acquisition.aq_acquire(a.b.c, 'id')
+    'c'
+
+    >>> Acquisition.aq_acquire(a.b.c, 'x')
+    Traceback (most recent call last):
+    ...
+    AttributeError: x
+
+    >>> Acquisition.aq_acquire(a.b.c, 'y')
+    42
+    
+    >>> Acquisition.aq_acquire(a.b.c, 'id',
+    ...  lambda searched, parent, name, ob, extra: extra)
+    Traceback (most recent call last):
+    ...
+    AttributeError: id
+
+    >>> Acquisition.aq_acquire(a.b.c, 'id',
+    ...        lambda searched, parent, name, ob, extra: extra,
+    ...        1)
+    'c'
+
+    >>> show(Acquisition.aq_base(a.b.c))
+    c
+
+    >>> Acquisition.aq_chain(a.b.c)
+    [c, b, a]
+
+    >>> Acquisition.aq_chain(a.b.c, 1)
+    [c, b, a]
+
+    >>> Acquisition.aq_get(a.b.c, 'id')
+    'c'
+
+    >>> Acquisition.aq_get(a.b.c, 'x')
+    Traceback (most recent call last):
+    ...
+    AttributeError: x
+
+    >>> Acquisition.aq_get(a.b.c, 'y')
+    42
+
+    >>> Acquisition.aq_get(a.b.c, 'x', 'foo')
+    'foo'
+    >>> Acquisition.aq_get(a.b.c, 'x', 'foo', 1)
+    'foo'
+
+    >>> show(Acquisition.aq_inner(a.b.c))
+    c
+    |
+    b
+    |
+    a
+
+    >>> show(Acquisition.aq_parent(a.b.c))
+    b
+    |
+    a
+
+    >>> show(Acquisition.aq_self(a.b.c))
+    c
+
+    """
+
+
+def old_tests():
+    """    
+    >>> from ExtensionClass import Base
+    >>> import Acquisition
+
+    >>> class B(Base):
+    ...     color='red'
+
+    >>> class A(Acquisition.Implicit):
+    ...     def hi(self):
+    ...         print "%s()" % self.__class__.__name__, self.color
+
+    >>> b=B()
+    >>> b.a=A()
+    >>> b.a.hi()
+    A() red
+    >>> b.a.color='green'
+    >>> b.a.hi()
+    A() green
+    >>> try:
+    ...     A().hi()
+    ...     raise 'Program error', 'spam'
+    ... except AttributeError: pass
+    A()
+    
+       New test for wrapper comparisons.
+    
+    >>> foo = b.a
+    >>> bar = b.a
+    >>> foo == bar
+    1
+    >>> c = A()
+    >>> b.c = c
+    >>> b.c.d = c
+    >>> b.c.d == c
+    1
+    >>> b.c.d == b.c
+    1
+    >>> b.c == c
+    1
+
+
+    >>> def checkContext(self, o):
+    ...     # Python equivalent to aq_inContextOf
+    ...     from Acquisition import aq_base, aq_parent, aq_inner
+    ...     subob = self
+    ...     o = aq_base(o)
+    ...     while 1:
+    ...         if aq_base(subob) is o: return 1
+    ...         self = aq_inner(subob)
+    ...         if self is None: break
+    ...         subob = aq_parent(self)
+    ...         if subob is None: break
+
+
+    >>> checkContext(b.c, b)
+    1
+    >>> not checkContext(b.c, b.a)
+    1
+    
+    >>> b.a.aq_inContextOf(b)
+    1
+    >>> b.c.aq_inContextOf(b)
+    1
+    >>> b.c.d.aq_inContextOf(b)
+    1
+    >>> b.c.d.aq_inContextOf(c)
+    1
+    >>> b.c.d.aq_inContextOf(b.c)
+    1
+    >>> not b.c.aq_inContextOf(foo)
+    1
+    >>> not b.c.aq_inContextOf(b.a)
+    1
+    >>> not b.a.aq_inContextOf('somestring')
+    1
+    """
+
+def test_AqAlg():
+    """
+    >>> A=I('A')
+    >>> A.B=I('B')
+    >>> A.B.color='red'
+    >>> A.C=I('C')
+    >>> A.C.D=I('D')
+
+    >>> A
+    A
+    >>> Acquisition.aq_chain(A)
+    [A]
+    >>> Acquisition.aq_chain(A, 1)
+    [A]
+    >>> map(Acquisition.aq_base, Acquisition.aq_chain(A, 1))
+    [A]
+    >>> A.C
+    C
+    >>> Acquisition.aq_chain(A.C)
+    [C, A]
+    >>> Acquisition.aq_chain(A.C, 1)
+    [C, A]
+    >>> map(Acquisition.aq_base, Acquisition.aq_chain(A.C, 1))
+    [C, A]
+
+    >>> A.C.D
+    D
+    >>> Acquisition.aq_chain(A.C.D)
+    [D, C, A]
+    >>> Acquisition.aq_chain(A.C.D, 1)
+    [D, C, A]
+    >>> map(Acquisition.aq_base, Acquisition.aq_chain(A.C.D, 1))
+    [D, C, A]
+
+    >>> A.B.C
+    C
+    >>> Acquisition.aq_chain(A.B.C)
+    [C, B, A]
+    >>> Acquisition.aq_chain(A.B.C, 1)
+    [C, A]
+    >>> map(Acquisition.aq_base, Acquisition.aq_chain(A.B.C, 1))
+    [C, A]
+
+    >>> A.B.C.D
+    D
+    >>> Acquisition.aq_chain(A.B.C.D)
+    [D, C, B, A]
+    >>> Acquisition.aq_chain(A.B.C.D, 1)
+    [D, C, A]
+    >>> map(Acquisition.aq_base, Acquisition.aq_chain(A.B.C.D, 1))
+    [D, C, A]
+    
+
+    >>> A.B.C.D.color
+    'red'
+    >>> Acquisition.aq_get(A.B.C.D, "color", None)
+    'red'
+    >>> Acquisition.aq_get(A.B.C.D, "color", None, 1)
+    
+    """
+
+def test_explicit_acquisition():
+    """
+    >>> from ExtensionClass import Base
+    >>> import Acquisition
+
+    >>> class B(Base):
+    ...     color='red'
+
+    >>> class A(Acquisition.Explicit):
+    ...     def hi(self):
+    ...         print self.__class__.__name__, self.acquire('color')
+
+    >>> b=B()
+    >>> b.a=A()
+    >>> b.a.hi()
+    A red
+    >>> b.a.color='green'
+    >>> b.a.hi()
+    A green
+
+    >>> try:
+    ...     A().hi()
+    ...     raise 'Program error', 'spam'
+    ... except AttributeError: pass
+    A
+    
+    """
+
+def test_creating_wrappers_directly():
+    """
+    >>> from ExtensionClass import Base
+    >>> from Acquisition import ImplicitAcquisitionWrapper
+
+    >>> class B(Base):
+    ...     pass
+
+
+    >>> a = B()
+    >>> a.color = 'red'
+    >>> a.b = B()
+    >>> w = ImplicitAcquisitionWrapper(a.b, a)
+    >>> w.color
+    'red'
+
+    >>> w = ImplicitAcquisitionWrapper(a.b)
+    Traceback (most recent call last):
+    ...
+    TypeError: __init__() takes exactly 2 arguments (1 given)
+
+    We can reassign aq_parent
+
+    >>> x = B()
+    >>> x.color = 'green'
+    >>> w.aq_parent = x
+    >>> w.color
+    'green'
+
+    >>> w = ImplicitAcquisitionWrapper()
+    Traceback (most recent call last):
+    ...
+    TypeError: __init__() takes exactly 2 arguments (0 given)
+
+    >>> w = ImplicitAcquisitionWrapper(obj=1)
+    Traceback (most recent call last):
+    ...
+    TypeError: kwyword arguments not allowed
+    """
+
+def test_cant_pickle_acquisition_wrappers_classic():
+    """
+    >>> import pickle
+
+    >>> class X:
+    ...     def __getstate__(self):
+    ...         return 1
+
+    We shouldn't be able to pickle wrappers:
+
+    >>> from Acquisition import ImplicitAcquisitionWrapper
+    >>> w = ImplicitAcquisitionWrapper(X(), X())
+    >>> pickle.dumps(w)
+    Traceback (most recent call last):
+    ...
+    TypeError: Can't pickle objects in acquisition wrappers.
+
+    But that's not enough. We need to defeat persistence as well. :)
+    This is tricky. We want to generate the error in __getstate__, not
+    in the attr access, as attribute errors are too-often hidden:
+
+    >>> getstate = w.__getstate__
+    >>> getstate()
+    Traceback (most recent call last):
+    ...
+    TypeError: Can't pickle objects in acquisition wrappers.
+
+    We shouldn't be able to pickle wrappers:
+
+    >>> from Acquisition import ExplicitAcquisitionWrapper
+    >>> w = ExplicitAcquisitionWrapper(X(), X())
+    >>> pickle.dumps(w)
+    Traceback (most recent call last):
+    ...
+    TypeError: Can't pickle objects in acquisition wrappers.
+
+    But that's not enough. We need to defeat persistence as well. :)
+    This is tricky. We want to generate the error in __getstate__, not
+    in the attr access, as attribute errors are too-often hidden:
+
+    >>> getstate = w.__getstate__
+    >>> getstate()
+    Traceback (most recent call last):
+    ...
+    TypeError: Can't pickle objects in acquisition wrappers.
+    """
+
+def test_cant_pickle_acquisition_wrappers_newstyle():
+    """
+    >>> import pickle
+
+    >>> class X(object):
+    ...     def __getstate__(self):
+    ...         return 1
+
+    We shouldn't be able to pickle wrappers:
+
+    >>> from Acquisition import ImplicitAcquisitionWrapper
+    >>> w = ImplicitAcquisitionWrapper(X(), X())
+    >>> pickle.dumps(w)
+    Traceback (most recent call last):
+    ...
+    TypeError: Can't pickle objects in acquisition wrappers.
+
+    But that's not enough. We need to defeat persistence as well. :)
+    This is tricky. We want to generate the error in __getstate__, not
+    in the attr access, as attribute errors are too-often hidden:
+
+    >>> getstate = w.__getstate__
+    >>> getstate()
+    Traceback (most recent call last):
+    ...
+    TypeError: Can't pickle objects in acquisition wrappers.
+
+    We shouldn't be able to pickle wrappers:
+
+    >>> from Acquisition import ExplicitAcquisitionWrapper
+    >>> w = ExplicitAcquisitionWrapper(X(), X())
+    >>> pickle.dumps(w)
+    Traceback (most recent call last):
+    ...
+    TypeError: Can't pickle objects in acquisition wrappers.
+
+    But that's not enough. We need to defeat persistence as well. :)
+    This is tricky. We want to generate the error in __getstate__, not
+    in the attr access, as attribute errors are too-often hidden:
+
+    >>> getstate = w.__getstate__
+    >>> getstate()
+    Traceback (most recent call last):
+    ...
+    TypeError: Can't pickle objects in acquisition wrappers.
+    """
+
+def test_z3interfaces():
+    """
+    >>> from zope.interface.verify import verifyClass
+
+    Explicit and Implicit implement IAcquirer:
+
+    >>> from Acquisition import Explicit
+    >>> from Acquisition import Implicit
+    >>> from Acquisition.interfaces import IAcquirer
+    >>> verifyClass(IAcquirer, Explicit)
+    True
+    >>> verifyClass(IAcquirer, Implicit)
+    True
+
+    ExplicitAcquisitionWrapper and ImplicitAcquisitionWrapper implement
+    IAcquisitionWrapper:
+
+    >>> from Acquisition import ExplicitAcquisitionWrapper
+    >>> from Acquisition import ImplicitAcquisitionWrapper
+    >>> from Acquisition.interfaces import IAcquisitionWrapper
+    >>> verifyClass(IAcquisitionWrapper, ExplicitAcquisitionWrapper)
+    True
+    >>> verifyClass(IAcquisitionWrapper, ImplicitAcquisitionWrapper)
+    True
+    """
+
+def show(x):
+    print showaq(x).strip()
+    
+def showaq(m_self, indent=''):
+    rval = ''
+    obj = m_self
+    base = getattr(obj, 'aq_base', obj)
+    try: id = base.id
+    except: id = str(base)
+    try: id = id()
+    except: pass
+
+    if hasattr(obj, 'aq_self'):
+        if hasattr(obj.aq_self, 'aq_self'):
+            rval = rval + indent + "(" + id + ")\n"
+            rval = rval + indent + "|  \\\n"
+            rval = rval + showaq(obj.aq_self, '|   ' + indent)
+            rval = rval + indent + "|\n"
+            rval = rval + showaq(obj.aq_parent, indent)
+        elif hasattr(obj, 'aq_parent'):
+            rval = rval + indent + id + "\n"
+            rval = rval + indent + "|\n"
+            rval = rval + showaq(obj.aq_parent, indent)
+    else:
+        rval = rval + indent + id + "\n"
+    return rval
+
+
+
+def test_Basic_gc():
+    """Test to make sure that EC instances participate in GC
+
+    >>> from ExtensionClass import Base
+    >>> import gc
+    >>> thresholds = gc.get_threshold()
+    >>> gc.set_threshold(0)
+
+    >>> for B in I, E:
+    ...     class C1(B):
+    ...         pass
+    ... 
+    ...     class C2(Base):
+    ...         def __del__(self):
+    ...             print 'removed'
+    ... 
+    ...     a=C1('a')
+    ...     a.b = C1('a.b')
+    ...     a.b.a = a
+    ...     a.b.c = C2()
+    ...     ignore = gc.collect()
+    ...     del a
+    ...     removed = gc.collect()
+    ...     print removed > 0
+    removed
+    True
+    removed
+    True
+
+    >>> gc.set_threshold(*thresholds)
+
+    """
+
+def test_Wrapper_gc():
+    """Test to make sure that EC instances participate in GC
+
+    >>> import gc
+    >>> thresholds = gc.get_threshold()
+    >>> gc.set_threshold(0)
+
+    >>> for B in I, E:
+    ...     class C:
+    ...         def __del__(self):
+    ...             print 'removed'
+    ... 
+    ...     a=B('a')
+    ...     a.b = B('b')
+    ...     a.a_b = a.b # circ ref through wrapper
+    ...     a.b.c = C()
+    ...     ignored = gc.collect()
+    ...     del a
+    ...     removed = gc.collect()
+    ...     removed > 0
+    removed
+    True
+    removed
+    True
+
+    >>> gc.set_threshold(*thresholds)
+
+"""
+
+
+def test_proxying():
+    """Make sure that recent python slots are proxied.
+
+    >>> import Acquisition
+    >>> class Impl(Acquisition.Implicit):
+    ...     pass
+
+    >>> class C(Acquisition.Implicit):
+    ...     def __getitem__(self, key):
+    ...         print 'getitem', key
+    ...         if key == 4:
+    ...             raise IndexError
+    ...         return key
+    ...     def __contains__(self, key):
+    ...         print 'contains', repr(key)
+    ...         return key == 5
+    ...     def __iter__(self):
+    ...         print 'iterating...'
+    ...         return iter((42,))
+
+    The naked class behaves like this:
+
+    >>> c = C()
+    >>> 3 in c
+    contains 3
+    False
+    >>> 5 in c
+    contains 5
+    True
+    >>> list(c)
+    iterating...
+    [42]
+
+    Let's put c in the context of i:
+
+    >>> i = Impl()
+    >>> i.c = c
+
+    Now check that __contains__ is properly used:
+
+    >>> 3 in i.c # c.__of__(i)
+    contains 3
+    False
+    >>> 5 in i.c
+    contains 5
+    True
+    >>> list(i.c)
+    iterating...
+    [42]
+
+    Let's let's test the same again with an explicit wrapper:
+
+    >>> import Acquisition
+    >>> class Impl(Acquisition.Explicit):
+    ...     pass
+
+    >>> class C(Acquisition.Explicit):
+    ...     def __getitem__(self, key):
+    ...         print 'getitem', key
+    ...         if key == 4:
+    ...             raise IndexError
+    ...         return key
+    ...     def __contains__(self, key):
+    ...         print 'contains', repr(key)
+    ...         return key == 5
+    ...     def __iter__(self):
+    ...         print 'iterating...'
+    ...         return iter((42,))
+
+    The naked class behaves like this:
+
+    >>> c = C()
+    >>> 3 in c
+    contains 3
+    False
+    >>> 5 in c
+    contains 5
+    True
+    >>> list(c)
+    iterating...
+    [42]
+
+    Let's put c in the context of i:
+
+    >>> i = Impl()
+    >>> i.c = c
+
+    Now check that __contains__ is properly used:
+
+    >>> 3 in i.c # c.__of__(i)
+    contains 3
+    False
+    >>> 5 in i.c
+    contains 5
+    True
+    >>> list(i.c)
+    iterating...
+    [42]
+
+    Next let's check that the wrapper's __iter__ proxy falls back
+    to using the object's __getitem__ if it has no __iter__.  See
+    https://bugs.launchpad.net/zope2/+bug/360761 .
+
+    >>> class C(Acquisition.Implicit):
+    ...     l=[1,2,3]
+    ...     def __getitem__(self, i):
+    ...         return self.l[i]
+
+    >>> c1 = C()
+    >>> type(iter(c1))
+    <type 'iterator'>
+    >>> list(c1)
+    [1, 2, 3]
+
+    >>> c2 = C().__of__(c1)
+    >>> type(iter(c2))
+    <type 'iterator'>
+    >>> list(c2)
+    [1, 2, 3]
+
+    The __iter__proxy should also pass the wrapped object as self to
+    the __iter__ of objects defining __iter__::
+
+    >>> class C(Acquisition.Implicit):
+    ...     def __iter__(self):
+    ...         print 'iterating...'
+    ...         for i in range(5):
+    ...             yield i, self.aq_parent.name
+    >>> c = C()
+    >>> i = Impl()
+    >>> i.c = c
+    >>> i.name = 'i'
+    >>> list(i.c)
+    iterating...
+    [(0, 'i'), (1, 'i'), (2, 'i'), (3, 'i'), (4, 'i')]
+
+    And it should pass the wrapped object as self to
+    the __getitem__ of objects without an __iter__::
+
+    >>> class C(Acquisition.Implicit):
+    ...     def __getitem__(self, i):
+    ...         return self.aq_parent.l[i]
+    >>> c = C()
+    >>> i = Impl()
+    >>> i.c = c
+    >>> i.l = range(5)
+    >>> list(i.c)
+    [0, 1, 2, 3, 4]
+
+    Finally let's make sure errors are still correctly raised after having
+    to use a modified version of `PyObject_GetIter` for iterator support::
+
+    >>> class C(Acquisition.Implicit):
+    ...     pass
+    >>> c = C()
+    >>> i = Impl()
+    >>> i.c = c
+    >>> list(i.c)
+    Traceback (most recent call last):
+      ...
+    TypeError: iteration over non-sequence
+
+    >>> class C(Acquisition.Implicit):
+    ...     def __iter__(self):
+    ...         return [42]
+    >>> c = C()
+    >>> i = Impl()
+    >>> i.c = c
+    >>> list(i.c)
+    Traceback (most recent call last):
+      ...
+    TypeError: iter() returned non-iterator of type 'list'
+
+    """
+
+
+import unittest
+from zope.testing.doctest import DocTestSuite, DocFileSuite
+
+def test_suite():
+    return unittest.TestSuite((
+        DocTestSuite(),
+        DocFileSuite('README.txt', package='Acquisition'),
+        ))
+
+if __name__ == '__main__':
+    unittest.main(defaultTest='test_suite')