Issue #2396: backport the memoryview object.

15 files changed, 1672 insertions, 26 deletions

diff --git a/Doc/c-api/buffer.rst b/Doc/c-api/buffer.rst
index 6b80ad6..ce9a4e4 100644
--- a/Doc/c-api/buffer.rst
+++ b/Doc/c-api/buffer.rst
@@ -2,10 +2,11 @@
 
 .. _bufferobjects:
 
-Buffer Objects
---------------
+Buffers and Memoryview Objects
+------------------------------
 
 .. sectionauthor:: Greg Stein <gstein@lyra.org>
+.. sectionauthor:: Benjamin Peterson
 
 
 .. index::
@@ -28,9 +29,296 @@ interface can be written to a file. There are a number of format codes to
 :cfunc:`PyArg_ParseTuple` that operate against an object's buffer interface,
 returning data from the target object.
 
+Starting from version 1.6, Python has been providing Python-level buffer
+objects and a C-level buffer API so that any builtin or used-defined type
+can expose its characteristics. Both, however, have been deprecated because
+of various shortcomings, and have been officially removed in Python 3.0 in
+favour of a new C-level buffer API and a new Python-level object named
+:class:`memoryview`.
+
+The new buffer API has been backported to Python 2.6, and the
+:class:`memoryview` object has been backported to Python 2.7. It is strongly
+advised to use them rather than the old APIs, unless you are blocked from
+doing so for compatibility reasons.
+
+
+The new-style Py_buffer struct
+==============================
+
+
+.. ctype:: Py_buffer
+
+   .. cmember:: void *buf
+
+      A pointer to the start of the memory for the object.
+
+   .. cmember:: Py_ssize_t len
+      :noindex:
+
+      The total length of the memory in bytes.
+
+   .. cmember:: int readonly
+
+      An indicator of whether the buffer is read only.
+
+   .. cmember:: const char *format
+      :noindex:
+
+      A *NULL* terminated string in :mod:`struct` module style syntax giving the
+      contents of the elements available through the buffer.  If this is *NULL*,
+      ``"B"`` (unsigned bytes) is assumed.
+
+   .. cmember:: int ndim
+
+      The number of dimensions the memory represents as a multi-dimensional
+      array.  If it is 0, :cdata:`strides` and :cdata:`suboffsets` must be
+      *NULL*.
+
+   .. cmember:: Py_ssize_t *shape
+
+      An array of :ctype:`Py_ssize_t`\s the length of :cdata:`ndim` giving the
+      shape of the memory as a multi-dimensional array.  Note that
+      ``((*shape)[0] * ... * (*shape)[ndims-1])*itemsize`` should be equal to
+      :cdata:`len`.
+
+   .. cmember:: Py_ssize_t *strides
+
+      An array of :ctype:`Py_ssize_t`\s the length of :cdata:`ndim` giving the
+      number of bytes to skip to get to a new element in each dimension.
+
+   .. cmember:: Py_ssize_t *suboffsets
+
+      An array of :ctype:`Py_ssize_t`\s the length of :cdata:`ndim`.  If these
+      suboffset numbers are greater than or equal to 0, then the value stored
+      along the indicated dimension is a pointer and the suboffset value
+      dictates how many bytes to add to the pointer after de-referencing. A
+      suboffset value that it negative indicates that no de-referencing should
+      occur (striding in a contiguous memory block).
+
+      Here is a function that returns a pointer to the element in an N-D array
+      pointed to by an N-dimesional index when there are both non-NULL strides
+      and suboffsets::
+
+          void *get_item_pointer(int ndim, void *buf, Py_ssize_t *strides,
+              Py_ssize_t *suboffsets, Py_ssize_t *indices) {
+              char *pointer = (char*)buf;
+              int i;
+              for (i = 0; i < ndim; i++) {
+                  pointer += strides[i] * indices[i];
+                  if (suboffsets[i] >=0 ) {
+                      pointer = *((char**)pointer) + suboffsets[i];
+                  }
+              }
+              return (void*)pointer;
+           }
+
+
+   .. cmember:: Py_ssize_t itemsize
+
+      This is a storage for the itemsize (in bytes) of each element of the
+      shared memory. It is technically un-necessary as it can be obtained using
+      :cfunc:`PyBuffer_SizeFromFormat`, however an exporter may know this
+      information without parsing the format string and it is necessary to know
+      the itemsize for proper interpretation of striding. Therefore, storing it
+      is more convenient and faster.
+
+   .. cmember:: void *internal
+
+      This is for use internally by the exporting object. For example, this
+      might be re-cast as an integer by the exporter and used to store flags
+      about whether or not the shape, strides, and suboffsets arrays must be
+      freed when the buffer is released. The consumer should never alter this
+      value.
+
+
+Buffer related functions
+========================
+
+
+.. cfunction:: int PyObject_CheckBuffer(PyObject *obj)
+
+   Return 1 if *obj* supports the buffer interface otherwise 0.
+
+
+.. cfunction:: int PyObject_GetBuffer(PyObject *obj, PyObject *view, int flags)
+
+      Export *obj* into a :ctype:`Py_buffer`, *view*.  These arguments must
+      never be *NULL*.  The *flags* argument is a bit field indicating what kind
+      of buffer the caller is prepared to deal with and therefore what kind of
+      buffer the exporter is allowed to return.  The buffer interface allows for
+      complicated memory sharing possibilities, but some caller may not be able
+      to handle all the complexibity but may want to see if the exporter will
+      let them take a simpler view to its memory.
+
+      Some exporters may not be able to share memory in every possible way and
+      may need to raise errors to signal to some consumers that something is
+      just not possible. These errors should be a :exc:`BufferError` unless
+      there is another error that is actually causing the problem. The exporter
+      can use flags information to simplify how much of the :cdata:`Py_buffer`
+      structure is filled in with non-default values and/or raise an error if
+      the object can't support a simpler view of its memory.
+
+      0 is returned on success and -1 on error.
+
+      The following table gives possible values to the *flags* arguments.
+
+      +------------------------------+---------------------------------------------------+
+      | Flag                         | Description                                       |
+      +==============================+===================================================+
+      | :cmacro:`PyBUF_SIMPLE`       | This is the default flag state.  The returned     |
+      |                              | buffer may or may not have writable memory.  The  |
+      |                              | format of the data will be assumed to be unsigned |
+      |                              | bytes.  This is a "stand-alone" flag constant. It |
+      |                              | never needs to be '|'d to the others. The exporter|
+      |                              | will raise an error if it cannot provide such a   |
+      |                              | contiguous buffer of bytes.                       |
+      |                              |                                                   |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_WRITABLE`     | The returned buffer must be writable.  If it is   |
+      |                              | not writable, then raise an error.                |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_STRIDES`      | This implies :cmacro:`PyBUF_ND`. The returned     |
+      |                              | buffer must provide strides information (i.e. the |
+      |                              | strides cannot be NULL). This would be used when  |
+      |                              | the consumer can handle strided, discontiguous    |
+      |                              | arrays.  Handling strides automatically assumes   |
+      |                              | you can handle shape.  The exporter can raise an  |
+      |                              | error if a strided representation of the data is  |
+      |                              | not possible (i.e. without the suboffsets).       |
+      |                              |                                                   |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_ND`           | The returned buffer must provide shape            |
+      |                              | information. The memory will be assumed C-style   |
+      |                              | contiguous (last dimension varies the             |
+      |                              | fastest). The exporter may raise an error if it   |
+      |                              | cannot provide this kind of contiguous buffer. If |
+      |                              | this is not given then shape will be *NULL*.      |
+      |                              |                                                   |
+      |                              |                                                   |
+      |                              |                                                   |
+      +------------------------------+---------------------------------------------------+
+      |:cmacro:`PyBUF_C_CONTIGUOUS`  | These flags indicate that the contiguity returned |
+      |:cmacro:`PyBUF_F_CONTIGUOUS`  | buffer must be respectively, C-contiguous (last   |
+      |:cmacro:`PyBUF_ANY_CONTIGUOUS`| dimension varies the fastest), Fortran contiguous |
+      |                              | (first dimension varies the fastest) or either    |
+      |                              | one.  All of these flags imply                    |
+      |                              | :cmacro:`PyBUF_STRIDES` and guarantee that the    |
+      |                              | strides buffer info structure will be filled in   |
+      |                              | correctly.                                        |
+      |                              |                                                   |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_INDIRECT`     | This flag indicates the returned buffer must have |
+      |                              | suboffsets information (which can be NULL if no   |
+      |                              | suboffsets are needed).  This can be used when    |
+      |                              | the consumer can handle indirect array            |
+      |                              | referencing implied by these suboffsets. This     |
+      |                              | implies :cmacro:`PyBUF_STRIDES`.                  |
+      |                              |                                                   |
+      |                              |                                                   |
+      |                              |                                                   |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_FORMAT`       | The returned buffer must have true format         |
+      |                              | information if this flag is provided. This would  |
+      |                              | be used when the consumer is going to be checking |
+      |                              | for what 'kind' of data is actually stored. An    |
+      |                              | exporter should always be able to provide this    |
+      |                              | information if requested. If format is not        |
+      |                              | explicitly requested then the format must be      |
+      |                              | returned as *NULL* (which means ``'B'``, or       |
+      |                              | unsigned bytes)                                   |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_STRIDED`      | This is equivalent to ``(PyBUF_STRIDES |          |
+      |                              | PyBUF_WRITABLE)``.                                |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_STRIDED_RO`   | This is equivalent to ``(PyBUF_STRIDES)``.        |
+      |                              |                                                   |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_RECORDS`      | This is equivalent to ``(PyBUF_STRIDES |          |
+      |                              | PyBUF_FORMAT | PyBUF_WRITABLE)``.                 |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_RECORDS_RO`   | This is equivalent to ``(PyBUF_STRIDES |          |
+      |                              | PyBUF_FORMAT)``.                                  |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_FULL`         | This is equivalent to ``(PyBUF_INDIRECT |         |
+      |                              | PyBUF_FORMAT | PyBUF_WRITABLE)``.                 |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_FULL_RO``     | This is equivalent to ``(PyBUF_INDIRECT |         |
+      |                              | PyBUF_FORMAT)``.                                  |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_CONTIG`       | This is equivalent to ``(PyBUF_ND |               |
+      |                              | PyBUF_WRITABLE)``.                                |
+      +------------------------------+---------------------------------------------------+
+      | :cmacro:`PyBUF_CONTIG_RO`    | This is equivalent to ``(PyBUF_ND)``.             |
+      |                              |                                                   |
+      +------------------------------+---------------------------------------------------+
+
+
+.. cfunction:: void PyBuffer_Release(PyObject *obj, Py_buffer *view)
+
+   Release the buffer *view* over *obj*.  This shouldd be called when the buffer
+   is no longer being used as it may free memory from it.
+
+
+.. cfunction:: Py_ssize_t PyBuffer_SizeFromFormat(const char *)
+
+   Return the implied :cdata:`~Py_buffer.itemsize` from the struct-stype
+   :cdata:`~Py_buffer.format`.
+
+
+.. cfunction:: int PyObject_CopyToObject(PyObject *obj, void *buf, Py_ssize_t len, char fortran)
+
+   Copy *len* bytes of data pointed to by the contiguous chunk of memory pointed
+   to by *buf* into the buffer exported by obj.  The buffer must of course be
+   writable.  Return 0 on success and return -1 and raise an error on failure.
+   If the object does not have a writable buffer, then an error is raised.  If
+   *fortran* is ``'F'``, then if the object is multi-dimensional, then the data
+   will be copied into the array in Fortran-style (first dimension varies the
+   fastest).  If *fortran* is ``'C'``, then the data will be copied into the
+   array in C-style (last dimension varies the fastest).  If *fortran* is
+   ``'A'``, then it does not matter and the copy will be made in whatever way is
+   more efficient.
+
+
+.. cfunction:: int PyBuffer_IsContiguous(Py_buffer *view, char fortran)
+
+   Return 1 if the memory defined by the *view* is C-style (*fortran* is
+   ``'C'``) or Fortran-style (*fortran* is ``'F'``) contiguous or either one
+   (*fortran* is ``'A'``).  Return 0 otherwise.
+
+
+.. cfunction:: void PyBuffer_FillContiguousStrides(int ndim, Py_ssize_t *shape, Py_ssize_t *strides, Py_ssize_t itemsize, char fortran)
+
+   Fill the *strides* array with byte-strides of a contiguous (C-style if
+   *fortran* is ``'C'`` or Fortran-style if *fortran* is ``'F'`` array of the
+   given shape with the given number of bytes per element.
+
+
+.. cfunction:: int PyBuffer_FillInfo(Py_buffer *view, void *buf, Py_ssize_t len, int readonly, int infoflags)
+
+   Fill in a buffer-info structure, *view*, correctly for an exporter that can
+   only share a contiguous chunk of memory of "unsigned bytes" of the given
+   length.  Return 0 on success and -1 (with raising an error) on error.
+
+
+MemoryView objects
+==================
+
+A memoryview object is an extended buffer object that could replace the buffer
+object (but doesn't have to as that could be kept as a simple 1-d memoryview
+object).  It, unlike :ctype:`Py_buffer`, is a Python object (exposed as
+:class:`memoryview` in :mod:`builtins`), so it can be used with Python code.
+
+.. cfunction:: PyObject* PyMemoryView_FromObject(PyObject *obj)
+
+   Return a memoryview object from an object that defines the buffer interface.
+
+
+Old-style buffer objects
+========================
+
 .. index:: single: PyBufferProcs
 
-More information on the buffer interface is provided in the section
+More information on the old buffer interface is provided in the section
 :ref:`buffer-structs`, under the description for :ctype:`PyBufferProcs`.
 
 A "buffer object" is defined in the :file:`bufferobject.h` header (included by
diff --git a/Doc/c-api/objbuffer.rst b/Doc/c-api/objbuffer.rst
index 7d66db2..ba6e38f 100644
--- a/Doc/c-api/objbuffer.rst
+++ b/Doc/c-api/objbuffer.rst
@@ -2,8 +2,15 @@
 
 .. _abstract-buffer:
 
-Buffer Protocol
-===============
+
+Old Buffer Protocol
+===================
+
+This section describes the legacy buffer protocol, which has been introduced
+in Python 1.6. It is still supported but deprecated in the Python 2.x series.
+Python 3.0 introduces a new buffer protocol which fixes weaknesses and
+shortcomings of the protocol, and has been backported to Python 2.6.
+See :ref:`bufferobjects` for more information.
 
 
 .. cfunction:: int PyObject_AsCharBuffer(PyObject *obj, const char **buffer, Py_ssize_t *buffer_len)
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index c19462c..5ca6e42 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -680,6 +680,13 @@ available.  They are listed here in alphabetical order.
       Added support for the optional *key* argument.
 
 
+.. function:: memoryview(obj)
+   :noindex:
+
+   Return a "memory view" object created from the given argument.  See
+   :ref:`typememoryview` for more information.
+
+
 .. function:: min(iterable[, args...][key])
 
    With a single argument *iterable*, return the smallest item of a non-empty
diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
index 03565b0..af84f4f 100644
--- a/Doc/library/stdtypes.rst
+++ b/Doc/library/stdtypes.rst
@@ -2354,6 +2354,104 @@ the particular object.
       state.
 
 
+.. _typememoryview:
+
+memoryview Types
+================
+
+:class:`memoryview`\s allow Python code to access the internal data of an object
+that supports the buffer protocol without copying.  Memory can be interpreted as
+simple bytes or complex data structures.
+
+.. class:: memoryview(obj)
+
+   Create a :class:`memoryview` that references *obj*.  *obj* must support the
+   buffer protocol.  Builtin objects that support the buffer protocol include
+   :class:`str` and :class:`bytearray` (but not :class:`unicode`).
+
+   ``len(view)`` returns the total number of bytes in the memoryview, *view*.
+
+   A :class:`memoryview` supports slicing to expose its data.  Taking a single
+   index will return a single byte.  Full slicing will result in a subview::
+
+      >>> v = memoryview('abcefg')
+      >>> v[1]
+      'b'
+      >>> v[-1]
+      'g'
+      >>> v[1:4]
+      <memory at 0x77ab28>
+      >>> str(v[1:4])
+      'bce'
+      >>> v[3:-1]
+      <memory at 0x744f18>
+      >>> str(v[4:-1])
+      'f'
+
+   If the object the memory view is over supports changing its data, the
+   memoryview supports slice assignment::
+
+      >>> data = bytearray('abcefg')
+      >>> v = memoryview(data)
+      >>> v.readonly
+      False
+      >>> v[0] = 'z'
+      >>> data
+      bytearray(b'zbcefg')
+      >>> v[1:4] = '123'
+      >>> data
+      bytearray(b'z123fg')
+      >>> v[2] = 'spam'
+      Traceback (most recent call last):
+        File "<stdin>", line 1, in <module>
+      ValueError: cannot modify size of memoryview object
+
+   Notice how the size of the memoryview object can not be changed.
+
+
+   :class:`memoryview` has two methods:
+
+   .. method:: tobytes()
+
+      Return the data in the buffer as a bytestring (an object of class
+      :class:`str`).
+
+   .. method:: tolist()
+
+      Return the data in the buffer as a list of integers. ::
+
+         >>> memoryview(b'abc').tolist()
+         [97, 98, 99]
+
+   There are also several readonly attributes available:
+
+   .. attribute:: format
+
+      A string containing the format (in :mod:`struct` module style) for each
+      element in the view.  This defaults to ``'B'``, a simple bytestring.
+
+   .. attribute:: itemsize
+
+      The size in bytes of each element of the memoryview.
+
+   .. attribute:: shape
+
+      A tuple of integers the length of :attr:`ndim` giving the shape of the
+      memory as a N-dimensional array.
+
+   .. attribute:: ndim
+
+      An integer indicating how many dimensions of a multi-dimensional array the
+      memory represents.
+
+   .. attribute:: strides
+
+      A tuple of integers the length of :attr:`ndim` giving the size in bytes to
+      access each element for each dimension of the array.
+
+   .. memoryview.suboffsets isn't documented because it only seems useful for C
+
+
 .. _typecontextmanager:
 
 Context Manager Types
diff --git a/Doc/tutorial/modules.rst b/Doc/tutorial/modules.rst
index f147cea..c1ff982 100644
--- a/Doc/tutorial/modules.rst
+++ b/Doc/tutorial/modules.rst
@@ -328,8 +328,8 @@ want a list of those, they are defined in the standard module
     'enumerate', 'eval', 'execfile', 'exit', 'file', 'filter', 'float',
     'frozenset', 'getattr', 'globals', 'hasattr', 'hash', 'help', 'hex',
     'id', 'input', 'int', 'intern', 'isinstance', 'issubclass', 'iter',
-    'len', 'license', 'list', 'locals', 'long', 'map', 'max', 'min',
-    'object', 'oct', 'open', 'ord', 'pow', 'property', 'quit', 'range',
+    'len', 'license', 'list', 'locals', 'long', 'map', 'max', 'memoryview',
+    'min', 'object', 'oct', 'open', 'ord', 'pow', 'property', 'quit', 'range',
     'raw_input', 'reduce', 'reload', 'repr', 'reversed', 'round', 'set',
     'setattr', 'slice', 'sorted', 'staticmethod', 'str', 'sum', 'super',
     'tuple', 'type', 'unichr', 'unicode', 'vars', 'xrange', 'zip']
diff --git a/Include/Python.h b/Include/Python.h
index 1a05116..7af6b13 100644
--- a/Include/Python.h
+++ b/Include/Python.h
@@ -92,7 +92,7 @@
 #endif
 #include "rangeobject.h"
 #include "stringobject.h"
-/* #include "memoryobject.h" */
+#include "memoryobject.h"
 #include "bufferobject.h"
 #include "bytesobject.h"
 #include "bytearrayobject.h"
diff --git a/Include/memoryobject.h b/Include/memoryobject.h
new file mode 100644
index 0000000..bf0b621
--- /dev/null
+++ b/Include/memoryobject.h
@@ -0,0 +1,74 @@
+/* Memory view object. In Python this is available as "memoryview". */
+
+#ifndef Py_MEMORYOBJECT_H
+#define Py_MEMORYOBJECT_H
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+PyAPI_DATA(PyTypeObject) PyMemoryView_Type;
+
+#define PyMemoryView_Check(op) (Py_TYPE(op) == &PyMemoryView_Type)
+
+/* Get a pointer to the underlying Py_buffer of a memoryview object. */
+#define PyMemoryView_GET_BUFFER(op) (&((PyMemoryViewObject *)(op))->view)
+/* Get a pointer to the PyObject from which originates a memoryview object. */
+#define PyMemoryView_GET_BASE(op) (((PyMemoryViewObject *)(op))->view.obj)
+
+
+PyAPI_FUNC(PyObject *) PyMemoryView_GetContiguous(PyObject *base, 
+						  int buffertype, 
+						  char fort);
+
+    /* Return a contiguous chunk of memory representing the buffer
+       from an object in a memory view object.  If a copy is made then the
+       base object for the memory view will be a *new* bytes object. 
+       
+       Otherwise, the base-object will be the object itself and no 
+       data-copying will be done. 
+
+       The buffertype argument can be PyBUF_READ, PyBUF_WRITE,
+       PyBUF_SHADOW to determine whether the returned buffer
+       should be READONLY, WRITABLE, or set to update the
+       original buffer if a copy must be made.  If buffertype is
+       PyBUF_WRITE and the buffer is not contiguous an error will
+       be raised.  In this circumstance, the user can use
+       PyBUF_SHADOW to ensure that a a writable temporary
+       contiguous buffer is returned.  The contents of this
+       contiguous buffer will be copied back into the original
+       object after the memoryview object is deleted as long as
+       the original object is writable and allows setting an
+       exclusive write lock. If this is not allowed by the
+       original object, then a BufferError is raised.
+       
+       If the object is multi-dimensional and if fortran is 'F',
+       the first dimension of the underlying array will vary the
+       fastest in the buffer.  If fortran is 'C', then the last
+       dimension will vary the fastest (C-style contiguous).  If
+       fortran is 'A', then it does not matter and you will get
+       whatever the object decides is more efficient.  
+
+       A new reference is returned that must be DECREF'd when finished.
+    */
+
+PyAPI_FUNC(PyObject *) PyMemoryView_FromObject(PyObject *base);
+
+PyAPI_FUNC(PyObject *) PyMemoryView_FromBuffer(Py_buffer *info);
+    /* create new if bufptr is NULL 
+        will be a new bytesobject in base */
+
+
+/* The struct is declared here so that macros can work, but it shouldn't
+   be considered public. Don't access those fields directly, use the macros
+   and functions instead! */
+typedef struct {
+    PyObject_HEAD
+    PyObject *base;
+    Py_buffer view;
+} PyMemoryViewObject;
+
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_MEMORYOBJECT_H */
diff --git a/Include/object.h b/Include/object.h
index c40d3620..cfca64f 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -159,21 +159,23 @@ typedef Py_ssize_t (*writebufferproc)(PyObject *, Py_ssize_t, void **);
 typedef Py_ssize_t (*segcountproc)(PyObject *, Py_ssize_t *);
 typedef Py_ssize_t (*charbufferproc)(PyObject *, Py_ssize_t, char **);
 
-/* Py3k buffer interface */
 
+/* Py3k buffer interface */
 typedef struct bufferinfo {
-	void *buf;
-	PyObject *obj;        /* borrowed reference */
-        Py_ssize_t len;
-        Py_ssize_t itemsize;  /* This is Py_ssize_t so it can be
-                                 pointed to by strides in simple case.*/
-        int readonly;
-        int ndim;
-        char *format;
-        Py_ssize_t *shape;
-        Py_ssize_t *strides;
-        Py_ssize_t *suboffsets;
-        void *internal;
+	void *buf;   
+	PyObject *obj;        /* owned reference */
+	Py_ssize_t len;
+	Py_ssize_t itemsize;  /* This is Py_ssize_t so it can be 
+			         pointed to by strides in simple case.*/
+	int readonly;
+	int ndim;
+	char *format;
+	Py_ssize_t *shape;
+	Py_ssize_t *strides;
+	Py_ssize_t *suboffsets;
+	Py_ssize_t smalltable[2];  /* static store for shape and strides of
+				      mono-dimensional buffers. */
+	void *internal;
 } Py_buffer;
 
 typedef int (*getbufferproc)(PyObject *, Py_buffer *, int);
diff --git a/Lib/test/test_memoryview.py b/Lib/test/test_memoryview.py
new file mode 100644
index 0000000..c63ff5a
--- /dev/null
+++ b/Lib/test/test_memoryview.py
@@ -0,0 +1,328 @@
+"""Unit tests for the memoryview
+
+XXX We need more tests! Some tests are in test_bytes
+"""
+
+import unittest
+import sys
+import gc
+import weakref
+import array
+from test import test_support
+
+
+class AbstractMemoryTests:
+    source_bytes = b"abcdef"
+
+    @property
+    def _source(self):
+        return self.source_bytes
+
+    @property
+    def _types(self):
+        return filter(None, [self.ro_type, self.rw_type])
+
+    def check_getitem_with_type(self, tp):
+        item = self.getitem_type
+        b = tp(self._source)
+        oldrefcount = sys.getrefcount(b)
+        m = self._view(b)
+        self.assertEquals(m[0], item(b"a"))
+        self.assert_(isinstance(m[0], bytes), type(m[0]))
+        self.assertEquals(m[5], item(b"f"))
+        self.assertEquals(m[-1], item(b"f"))
+        self.assertEquals(m[-6], item(b"a"))
+        # Bounds checking
+        self.assertRaises(IndexError, lambda: m[6])
+        self.assertRaises(IndexError, lambda: m[-7])
+        self.assertRaises(IndexError, lambda: m[sys.maxsize])
+        self.assertRaises(IndexError, lambda: m[-sys.maxsize])
+        # Type checking
+        self.assertRaises(TypeError, lambda: m[None])
+        self.assertRaises(TypeError, lambda: m[0.0])
+        self.assertRaises(TypeError, lambda: m["a"])
+        m = None
+        self.assertEquals(sys.getrefcount(b), oldrefcount)
+
+    def test_getitem(self):
+        for tp in self._types:
+            self.check_getitem_with_type(tp)
+
+    def test_setitem_readonly(self):
+        if not self.ro_type:
+            return
+        b = self.ro_type(self._source)
+        oldrefcount = sys.getrefcount(b)
+        m = self._view(b)
+        def setitem(value):
+            m[0] = value
+        self.assertRaises(TypeError, setitem, b"a")
+        self.assertRaises(TypeError, setitem, 65)
+        self.assertRaises(TypeError, setitem, memoryview(b"a"))
+        m = None
+        self.assertEquals(sys.getrefcount(b), oldrefcount)
+
+    def test_setitem_writable(self):
+        if not self.rw_type:
+            return
+        tp = self.rw_type
+        b = self.rw_type(self._source)
+        oldrefcount = sys.getrefcount(b)
+        m = self._view(b)
+        m[0] = tp(b"0")
+        self._check_contents(tp, b, b"0bcdef")
+        m[1:3] = tp(b"12")
+        self._check_contents(tp, b, b"012def")
+        m[1:1] = tp(b"")
+        self._check_contents(tp, b, b"012def")
+        m[:] = tp(b"abcdef")
+        self._check_contents(tp, b, b"abcdef")
+
+        # Overlapping copies of a view into itself
+        m[0:3] = m[2:5]
+        self._check_contents(tp, b, b"cdedef")
+        m[:] = tp(b"abcdef")
+        m[2:5] = m[0:3]
+        self._check_contents(tp, b, b"ababcf")
+
+        def setitem(key, value):
+            m[key] = tp(value)
+        # Bounds checking
+        self.assertRaises(IndexError, setitem, 6, b"a")
+        self.assertRaises(IndexError, setitem, -7, b"a")
+        self.assertRaises(IndexError, setitem, sys.maxsize, b"a")
+        self.assertRaises(IndexError, setitem, -sys.maxsize, b"a")
+        # Wrong index/slice types
+        self.assertRaises(TypeError, setitem, 0.0, b"a")
+        self.assertRaises(TypeError, setitem, (0,), b"a")
+        self.assertRaises(TypeError, setitem, "a", b"a")
+        # Trying to resize the memory object
+        self.assertRaises(ValueError, setitem, 0, b"")
+        self.assertRaises(ValueError, setitem, 0, b"ab")
+        self.assertRaises(ValueError, setitem, slice(1,1), b"a")
+        self.assertRaises(ValueError, setitem, slice(0,2), b"a")
+
+        m = None
+        self.assertEquals(sys.getrefcount(b), oldrefcount)
+
+    def test_tobytes(self):
+        for tp in self._types:
+            m = self._view(tp(self._source))
+            b = m.tobytes()
+            # This calls self.getitem_type() on each separate byte of b"abcdef"
+            expected = b"".join(
+                self.getitem_type(c) for c in b"abcdef")
+            self.assertEquals(b, expected)
+            self.assert_(isinstance(b, bytes), type(b))
+
+    def test_tolist(self):
+        for tp in self._types:
+            m = self._view(tp(self._source))
+            l = m.tolist()
+            self.assertEquals(l, map(ord, b"abcdef"))
+
+    def test_compare(self):
+        # memoryviews can compare for equality with other objects
+        # having the buffer interface.
+        for tp in self._types:
+            m = self._view(tp(self._source))
+            for tp_comp in self._types:
+                self.assertTrue(m == tp_comp(b"abcdef"))
+                self.assertFalse(m != tp_comp(b"abcdef"))
+                self.assertFalse(m == tp_comp(b"abcde"))
+                self.assertTrue(m != tp_comp(b"abcde"))
+                self.assertFalse(m == tp_comp(b"abcde1"))
+                self.assertTrue(m != tp_comp(b"abcde1"))
+            self.assertTrue(m == m)
+            self.assertTrue(m == m[:])
+            self.assertTrue(m[0:6] == m[:])
+            self.assertFalse(m[0:5] == m)
+
+            # Comparison with objects which don't support the buffer API
+            self.assertFalse(m == u"abcdef")
+            self.assertTrue(m != u"abcdef")
+            self.assertFalse(u"abcdef" == m)
+            self.assertTrue(u"abcdef" != m)
+
+            # Unordered comparisons are unimplemented, and therefore give
+            # arbitrary results (they raise a TypeError in py3k)
+
+    def check_attributes_with_type(self, tp):
+        m = self._view(tp(self._source))
+        self.assertEquals(m.format, self.format)
+        self.assertEquals(m.itemsize, self.itemsize)
+        self.assertEquals(m.ndim, 1)
+        self.assertEquals(m.shape, (6,))
+        self.assertEquals(len(m), 6)
+        self.assertEquals(m.strides, (self.itemsize,))
+        self.assertEquals(m.suboffsets, None)
+        return m
+
+    def test_attributes_readonly(self):
+        if not self.ro_type:
+            return
+        m = self.check_attributes_with_type(self.ro_type)
+        self.assertEquals(m.readonly, True)
+
+    def test_attributes_writable(self):
+        if not self.rw_type:
+            return
+        m = self.check_attributes_with_type(self.rw_type)
+        self.assertEquals(m.readonly, False)
+
+    # Disabled: unicode uses the old buffer API in 2.x
+
+    #def test_getbuffer(self):
+        ## Test PyObject_GetBuffer() on a memoryview object.
+        #for tp in self._types:
+            #b = tp(self._source)
+            #oldrefcount = sys.getrefcount(b)
+            #m = self._view(b)
+            #oldviewrefcount = sys.getrefcount(m)
+            #s = unicode(m, "utf-8")
+            #self._check_contents(tp, b, s.encode("utf-8"))
+            #self.assertEquals(sys.getrefcount(m), oldviewrefcount)
+            #m = None
+            #self.assertEquals(sys.getrefcount(b), oldrefcount)
+
+    def test_gc(self):
+        for tp in self._types:
+            if not isinstance(tp, type):
+                # If tp is a factory rather than a plain type, skip
+                continue
+
+            class MySource(tp):
+                pass
+            class MyObject:
+                pass
+
+            # Create a reference cycle through a memoryview object
+            b = MySource(tp(b'abc'))
+            m = self._view(b)
+            o = MyObject()
+            b.m = m
+            b.o = o
+            wr = weakref.ref(o)
+            b = m = o = None
+            # The cycle must be broken
+            gc.collect()
+            self.assert_(wr() is None, wr())
+
+
+# Variations on source objects for the buffer: bytes-like objects, then arrays
+# with itemsize > 1.
+# NOTE: support for multi-dimensional objects is unimplemented.
+
+class BaseBytesMemoryTests(AbstractMemoryTests):
+    ro_type = bytes
+    rw_type = bytearray
+    getitem_type = bytes
+    itemsize = 1
+    format = 'B'
+
+# Disabled: array.array() does not support the new buffer API in 2.x
+
+#class BaseArrayMemoryTests(AbstractMemoryTests):
+    #ro_type = None
+    #rw_type = lambda self, b: array.array('i', map(ord, b))
+    #getitem_type = lambda self, b: array.array('i', map(ord, b)).tostring()
+    #itemsize = array.array('i').itemsize
+    #format = 'i'
+
+    #def test_getbuffer(self):
+        ## XXX Test should be adapted for non-byte buffers
+        #pass
+
+    #def test_tolist(self):
+        ## XXX NotImplementedError: tolist() only supports byte views
+        #pass
+
+
+# Variations on indirection levels: memoryview, slice of memoryview,
+# slice of slice of memoryview.
+# This is important to test allocation subtleties.
+
+class BaseMemoryviewTests:
+    def _view(self, obj):
+        return memoryview(obj)
+
+    def _check_contents(self, tp, obj, contents):
+        self.assertEquals(obj, tp(contents))
+
+class BaseMemorySliceTests:
+    source_bytes = b"XabcdefY"
+
+    def _view(self, obj):
+        m = memoryview(obj)
+        return m[1:7]
+
+    def _check_contents(self, tp, obj, contents):
+        self.assertEquals(obj[1:7], tp(contents))
+
+    def test_refs(self):
+        for tp in self._types:
+            m = memoryview(tp(self._source))
+            oldrefcount = sys.getrefcount(m)
+            m[1:2]
+            self.assertEquals(sys.getrefcount(m), oldrefcount)
+
+class BaseMemorySliceSliceTests:
+    source_bytes = b"XabcdefY"
+
+    def _view(self, obj):
+        m = memoryview(obj)
+        return m[:7][1:]
+
+    def _check_contents(self, tp, obj, contents):
+        self.assertEquals(obj[1:7], tp(contents))
+
+
+# Concrete test classes
+
+class BytesMemoryviewTest(unittest.TestCase,
+    BaseMemoryviewTests, BaseBytesMemoryTests):
+
+    def test_constructor(self):
+        for tp in self._types:
+            ob = tp(self._source)
+            self.assert_(memoryview(ob))
+            self.assert_(memoryview(object=ob))
+            self.assertRaises(TypeError, memoryview)
+            self.assertRaises(TypeError, memoryview, ob, ob)
+            self.assertRaises(TypeError, memoryview, argument=ob)
+            self.assertRaises(TypeError, memoryview, ob, argument=True)
+
+#class ArrayMemoryviewTest(unittest.TestCase,
+    #BaseMemoryviewTests, BaseArrayMemoryTests):
+
+    #def test_array_assign(self):
+        ## Issue #4569: segfault when mutating a memoryview with itemsize != 1
+        #a = array.array('i', range(10))
+        #m = memoryview(a)
+        #new_a = array.array('i', range(9, -1, -1))
+        #m[:] = new_a
+        #self.assertEquals(a, new_a)
+
+
+class BytesMemorySliceTest(unittest.TestCase,
+    BaseMemorySliceTests, BaseBytesMemoryTests):
+    pass
+
+#class ArrayMemorySliceTest(unittest.TestCase,
+    #BaseMemorySliceTests, BaseArrayMemoryTests):
+    #pass
+
+class BytesMemorySliceSliceTest(unittest.TestCase,
+    BaseMemorySliceSliceTests, BaseBytesMemoryTests):
+    pass
+
+#class ArrayMemorySliceSliceTest(unittest.TestCase,
+    #BaseMemorySliceSliceTests, BaseArrayMemoryTests):
+    #pass
+
+
+def test_main():
+    test_support.run_unittest(__name__)
+
+if __name__ == "__main__":
+    test_main()
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 4ca75b5..31a52a0 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -320,6 +320,7 @@ OBJECT_OBJS=	\
 		Objects/listobject.o \
 		Objects/longobject.o \
 		Objects/dictobject.o \
+		Objects/memoryobject.o \
 		Objects/methodobject.o \
 		Objects/moduleobject.o \
 		Objects/object.o \
@@ -617,6 +618,7 @@ PYTHON_HEADERS= \
 		Include/longintrepr.h \
 		Include/longobject.h \
 		Include/marshal.h \
+		Include/memoryobject.h \
 		Include/metagrammar.h \
 		Include/methodobject.h \
 		Include/modsupport.h \
diff --git a/Misc/NEWS b/Misc/NEWS
index a331bd7..1a7aaa6 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@ What's New in Python 2.7 alpha 1
 Core and Builtins
 -----------------
 
+- Issue #2396: the memoryview object was backported from Python 3.1.
+
 - Fix a problem in PyErr_NormalizeException that leads to "undetected errors"
   when hitting the recursion limit under certain circumstances.
 
diff --git a/Objects/abstract.c b/Objects/abstract.c
index c67581e..e26e057 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -439,7 +439,7 @@ PyBuffer_GetPointer(Py_buffer *view, Py_ssize_t *indices)
 }
 
 
-static void
+void
 _add_one_to_index_F(int nd, Py_ssize_t *index, Py_ssize_t *shape)
 {
 	int k;
@@ -455,7 +455,7 @@ _add_one_to_index_F(int nd, Py_ssize_t *index, Py_ssize_t *shape)
 	}
 }
 
-static void
+void
 _add_one_to_index_C(int nd, Py_ssize_t *index, Py_ssize_t *shape)
 {
 	int k;
diff --git a/Objects/memoryobject.c b/Objects/memoryobject.c
new file mode 100644
index 0000000..1828cef
--- /dev/null
+++ b/Objects/memoryobject.c
@@ -0,0 +1,834 @@
+
+/* Memoryview object implementation */
+
+#include "Python.h"
+
+static Py_ssize_t
+get_shape0(Py_buffer *buf)
+{
+    if (buf->shape != NULL)
+        return buf->shape[0];
+    if (buf->ndim == 0)
+        return 1;
+    PyErr_SetString(PyExc_TypeError,
+        "exported buffer does not have any shape information associated "
+        "to it");
+    return -1;
+}
+
+static void
+dup_buffer(Py_buffer *dest, Py_buffer *src)
+{
+    *dest = *src;
+    if (src->ndim == 1 && src->shape != NULL) {
+        dest->shape = &(dest->smalltable[0]);
+        dest->shape[0] = get_shape0(src);
+    }
+    if (src->ndim == 1 && src->strides != NULL) {
+        dest->strides = &(dest->smalltable[1]);
+        dest->strides[0] = src->strides[0];
+    }
+}
+
+static int
+memory_getbuf(PyMemoryViewObject *self, Py_buffer *view, int flags)
+{
+    int res = 0;
+    /* XXX for whatever reason fixing the flags seems necessary */
+    if (self->view.readonly)
+        flags &= ~PyBUF_WRITABLE;
+    if (self->view.obj != NULL)
+        res = PyObject_GetBuffer(self->view.obj, view, flags);
+    if (view)
+        dup_buffer(view, &self->view);
+    return res;
+}
+
+static void
+memory_releasebuf(PyMemoryViewObject *self, Py_buffer *view)
+{
+    PyBuffer_Release(view);
+}
+
+PyDoc_STRVAR(memory_doc,
+"memoryview(object)\n\
+\n\
+Create a new memoryview object which references the given object.");
+
+PyObject *
+PyMemoryView_FromBuffer(Py_buffer *info)
+{
+    PyMemoryViewObject *mview;
+
+    mview = (PyMemoryViewObject *)
+        PyObject_GC_New(PyMemoryViewObject, &PyMemoryView_Type);
+    if (mview == NULL)
+        return NULL;
+    mview->base = NULL;
+    dup_buffer(&mview->view, info);
+    /* NOTE: mview->view.obj should already have been incref'ed as
+       part of PyBuffer_FillInfo(). */
+    _PyObject_GC_TRACK(mview);
+    return (PyObject *)mview;
+}
+
+PyObject *
+PyMemoryView_FromObject(PyObject *base)
+{
+    PyMemoryViewObject *mview;
+
+    if (!PyObject_CheckBuffer(base)) {
+        PyErr_SetString(PyExc_TypeError,
+            "cannot make memory view because object does "
+            "not have the buffer interface");
+        return NULL;
+    }
+
+    mview = (PyMemoryViewObject *)
+        PyObject_GC_New(PyMemoryViewObject, &PyMemoryView_Type);
+    if (mview == NULL)
+        return NULL;
+
+    mview->base = NULL;
+    if (PyObject_GetBuffer(base, &(mview->view), PyBUF_FULL_RO) < 0) {
+        Py_DECREF(mview);
+        return NULL;
+    }
+
+    mview->base = base;
+    Py_INCREF(base);
+    _PyObject_GC_TRACK(mview);
+    return (PyObject *)mview;
+}
+
+static PyObject *
+memory_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds)
+{
+    PyObject *obj;
+    static char *kwlist[] = {"object", 0};
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O:memoryview", kwlist,
+                                     &obj)) {
+        return NULL;
+    }
+
+    return PyMemoryView_FromObject(obj);
+}
+
+
+static void
+_strided_copy_nd(char *dest, char *src, int nd, Py_ssize_t *shape,
+                 Py_ssize_t *strides, Py_ssize_t itemsize, char fort)
+{
+    int k;
+    Py_ssize_t outstride;
+
+    if (nd==0) {
+        memcpy(dest, src, itemsize);
+    }
+    else if (nd == 1) {
+        for (k = 0; k<shape[0]; k++) {
+            memcpy(dest, src, itemsize);
+            dest += itemsize;
+            src += strides[0];
+        }
+    }
+    else {
+        if (fort == 'F') {
+            /* Copy first dimension first,
+               second dimension second, etc...
+               Set up the recursive loop backwards so that final
+               dimension is actually copied last.
+            */
+            outstride = itemsize;
+            for (k=1; k<nd-1;k++) {
+                outstride *= shape[k];
+            }
+            for (k=0; k<shape[nd-1]; k++) {
+                _strided_copy_nd(dest, src, nd-1, shape,
+                                 strides, itemsize, fort);
+                dest += outstride;
+                src += strides[nd-1];
+            }
+        }
+
+        else {
+            /* Copy last dimension first,
+               second-to-last dimension second, etc.
+               Set up the recursion so that the
+               first dimension is copied last
+            */
+            outstride = itemsize;
+            for (k=1; k < nd; k++) {
+                outstride *= shape[k];
+            }
+            for (k=0; k<shape[0]; k++) {
+                _strided_copy_nd(dest, src, nd-1, shape+1,
+                                 strides+1, itemsize,
+                                 fort);
+                dest += outstride;
+                src += strides[0];
+            }
+        }
+    }
+    return;
+}
+
+void _add_one_to_index_F(int nd, Py_ssize_t *index, Py_ssize_t *shape);
+void _add_one_to_index_C(int nd, Py_ssize_t *index, Py_ssize_t *shape);
+
+static int
+_indirect_copy_nd(char *dest, Py_buffer *view, char fort)
+{
+    Py_ssize_t *indices;
+    int k;
+    Py_ssize_t elements;
+    char *ptr;
+    void (*func)(int, Py_ssize_t *, Py_ssize_t *);
+
+    if (view->ndim > PY_SSIZE_T_MAX / sizeof(Py_ssize_t)) {
+        PyErr_NoMemory();
+        return -1;
+    }
+
+    indices = (Py_ssize_t *)PyMem_Malloc(sizeof(Py_ssize_t)*view->ndim);
+    if (indices == NULL) {
+        PyErr_NoMemory();
+        return -1;
+    }
+    for (k=0; k<view->ndim;k++) {
+        indices[k] = 0;
+    }
+
+    elements = 1;
+    for (k=0; k<view->ndim; k++) {
+        elements *= view->shape[k];
+    }
+    if (fort == 'F') {
+        func = _add_one_to_index_F;
+    }
+    else {
+        func = _add_one_to_index_C;
+    }
+    while (elements--) {
+        func(view->ndim, indices, view->shape);
+        ptr = PyBuffer_GetPointer(view, indices);
+        memcpy(dest, ptr, view->itemsize);
+        dest += view->itemsize;
+    }
+
+    PyMem_Free(indices);
+    return 0;
+}
+
+/*
+   Get a the data from an object as a contiguous chunk of memory (in
+   either 'C' or 'F'ortran order) even if it means copying it into a
+   separate memory area.
+
+   Returns a new reference to a Memory view object.  If no copy is needed,
+   the memory view object points to the original memory and holds a
+   lock on the original.  If a copy is needed, then the memory view object
+   points to a brand-new Bytes object (and holds a memory lock on it).
+
+   buffertype
+
+   PyBUF_READ  buffer only needs to be read-only
+   PyBUF_WRITE buffer needs to be writable (give error if not contiguous)
+   PyBUF_SHADOW buffer needs to be writable so shadow it with
+                a contiguous buffer if it is not. The view will point to
+                the shadow buffer which can be written to and then
+                will be copied back into the other buffer when the memory
+                view is de-allocated.  While the shadow buffer is
+                being used, it will have an exclusive write lock on
+                the original buffer.
+ */
+
+PyObject *
+PyMemoryView_GetContiguous(PyObject *obj, int buffertype, char fort)
+{
+    PyMemoryViewObject *mem;
+    PyObject *bytes;
+    Py_buffer *view;
+    int flags;
+    char *dest;
+
+    if (!PyObject_CheckBuffer(obj)) {
+        PyErr_SetString(PyExc_TypeError,
+                        "object does not have the buffer interface");
+        return NULL;
+    }
+
+    mem = PyObject_GC_New(PyMemoryViewObject, &PyMemoryView_Type);
+    if (mem == NULL)
+        return NULL;
+
+    view = &mem->view;
+    flags = PyBUF_FULL_RO;
+    switch(buffertype) {
+    case PyBUF_WRITE:
+        flags = PyBUF_FULL;
+        break;
+    }
+
+    if (PyObject_GetBuffer(obj, view, flags) != 0) {
+        Py_DECREF(mem);
+        return NULL;
+    }
+
+    if (PyBuffer_IsContiguous(view, fort)) {
+        /* no copy needed */
+        Py_INCREF(obj);
+        mem->base = obj;
+        _PyObject_GC_TRACK(mem);
+        return (PyObject *)mem;
+    }
+    /* otherwise a copy is needed */
+    if (buffertype == PyBUF_WRITE) {
+        Py_DECREF(mem);
+        PyErr_SetString(PyExc_BufferError,
+                        "writable contiguous buffer requested "
+                        "for a non-contiguousobject.");
+        return NULL;
+    }
+    bytes = PyBytes_FromStringAndSize(NULL, view->len);
+    if (bytes == NULL) {
+        Py_DECREF(mem);
+        return NULL;
+    }
+    dest = PyBytes_AS_STRING(bytes);
+    /* different copying strategy depending on whether
+       or not any pointer de-referencing is needed
+    */
+    /* strided or in-direct copy */
+    if (view->suboffsets==NULL) {
+        _strided_copy_nd(dest, view->buf, view->ndim, view->shape,
+                         view->strides, view->itemsize, fort);
+    }
+    else {
+        if (_indirect_copy_nd(dest, view, fort) < 0) {
+            Py_DECREF(bytes);
+            Py_DECREF(mem);
+            return NULL;
+        }
+    }
+    if (buffertype == PyBUF_SHADOW) {
+        /* return a shadowed memory-view object */
+        view->buf = dest;
+        mem->base = PyTuple_Pack(2, obj, bytes);
+        Py_DECREF(bytes);
+        if (mem->base == NULL) {
+            Py_DECREF(mem);
+            return NULL;
+        }
+    }
+    else {
+        PyBuffer_Release(view);  /* XXX ? */
+        /* steal the reference */
+        mem->base = bytes;
+    }
+    _PyObject_GC_TRACK(mem);
+    return (PyObject *)mem;
+}
+
+
+static PyObject *
+memory_format_get(PyMemoryViewObject *self)
+{
+    return PyUnicode_FromString(self->view.format);
+}
+
+static PyObject *
+memory_itemsize_get(PyMemoryViewObject *self)
+{
+    return PyLong_FromSsize_t(self->view.itemsize);
+}
+
+static PyObject *
+_IntTupleFromSsizet(int len, Py_ssize_t *vals)
+{
+    int i;
+    PyObject *o;
+    PyObject *intTuple;
+
+    if (vals == NULL) {
+        Py_INCREF(Py_None);
+        return Py_None;
+    }
+    intTuple = PyTuple_New(len);
+    if (!intTuple) return NULL;
+    for(i=0; i<len; i++) {
+        o = PyLong_FromSsize_t(vals[i]);
+        if (!o) {
+            Py_DECREF(intTuple);
+            return NULL;
+        }
+        PyTuple_SET_ITEM(intTuple, i, o);
+    }
+    return intTuple;
+}
+
+static PyObject *
+memory_shape_get(PyMemoryViewObject *self)
+{
+    return _IntTupleFromSsizet(self->view.ndim, self->view.shape);
+}
+
+static PyObject *
+memory_strides_get(PyMemoryViewObject *self)
+{
+    return _IntTupleFromSsizet(self->view.ndim, self->view.strides);
+}
+
+static PyObject *
+memory_suboffsets_get(PyMemoryViewObject *self)
+{
+    return _IntTupleFromSsizet(self->view.ndim, self->view.suboffsets);
+}
+
+static PyObject *
+memory_readonly_get(PyMemoryViewObject *self)
+{
+    return PyBool_FromLong(self->view.readonly);
+}
+
+static PyObject *
+memory_ndim_get(PyMemoryViewObject *self)
+{
+    return PyLong_FromLong(self->view.ndim);
+}
+
+static PyGetSetDef memory_getsetlist[] ={
+    {"format",          (getter)memory_format_get,      NULL, NULL},
+    {"itemsize",        (getter)memory_itemsize_get,    NULL, NULL},
+    {"shape",           (getter)memory_shape_get,       NULL, NULL},
+    {"strides",         (getter)memory_strides_get,     NULL, NULL},
+    {"suboffsets",      (getter)memory_suboffsets_get,  NULL, NULL},
+    {"readonly",        (getter)memory_readonly_get,    NULL, NULL},
+    {"ndim",            (getter)memory_ndim_get,        NULL, NULL},
+    {NULL, NULL, NULL, NULL},
+};
+
+
+static PyObject *
+memory_tobytes(PyMemoryViewObject *self, PyObject *noargs)
+{
+    Py_buffer view;
+    PyObject *res;
+
+    if (PyObject_GetBuffer((PyObject *)self, &view, PyBUF_FULL) < 0)
+        return NULL;
+
+    res = PyBytes_FromStringAndSize(NULL, view.len);
+    PyBuffer_ToContiguous(PyBytes_AS_STRING(res), &view, view.len, 'C');
+    PyBuffer_Release(&view);
+    return res;
+}
+
+/* TODO: rewrite this function using the struct module to unpack
+   each buffer item */
+
+static PyObject *
+memory_tolist(PyMemoryViewObject *mem, PyObject *noargs)
+{
+    Py_buffer *view = &(mem->view);
+    Py_ssize_t i;
+    PyObject *res, *item;
+    char *buf;
+
+    if (strcmp(view->format, "B") || view->itemsize != 1) {
+        PyErr_SetString(PyExc_NotImplementedError, 
+                "tolist() only supports byte views");
+        return NULL;
+    }
+    if (view->ndim != 1) {
+        PyErr_SetString(PyExc_NotImplementedError, 
+                "tolist() only supports one-dimensional objects");
+        return NULL;
+    }
+    res = PyList_New(view->len);
+    if (res == NULL)
+        return NULL;
+    buf = view->buf;
+    for (i = 0; i < view->len; i++) {
+        item = PyInt_FromLong((unsigned char) *buf);
+        if (item == NULL) {
+            Py_DECREF(res);
+            return NULL;
+        }
+        PyList_SET_ITEM(res, i, item);
+        buf++;
+    }
+    return res;
+}
+
+static PyMethodDef memory_methods[] = {
+    {"tobytes", (PyCFunction)memory_tobytes, METH_NOARGS, NULL},
+    {"tolist", (PyCFunction)memory_tolist, METH_NOARGS, NULL},
+    {NULL,          NULL}           /* sentinel */
+};
+
+
+static void
+memory_dealloc(PyMemoryViewObject *self)
+{
+    _PyObject_GC_UNTRACK(self);
+    if (self->view.obj != NULL) {
+        if (self->base && PyTuple_Check(self->base)) {
+            /* Special case when first element is generic object
+               with buffer interface and the second element is a
+               contiguous "shadow" that must be copied back into
+               the data areay of the first tuple element before
+               releasing the buffer on the first element.
+            */
+
+            PyObject_CopyData(PyTuple_GET_ITEM(self->base,0),
+                              PyTuple_GET_ITEM(self->base,1));
+
+            /* The view member should have readonly == -1 in
+               this instance indicating that the memory can
+               be "locked" and was locked and will be unlocked
+               again after this call.
+            */
+            PyBuffer_Release(&(self->view));
+        }
+        else {
+            PyBuffer_Release(&(self->view));
+        }
+        Py_CLEAR(self->base);
+    }
+    PyObject_GC_Del(self);
+}
+
+static PyObject *
+memory_repr(PyMemoryViewObject *self)
+{
+    return PyUnicode_FromFormat("<memory at %p>", self);
+}
+
+/* Sequence methods */
+static Py_ssize_t
+memory_length(PyMemoryViewObject *self)
+{
+    return get_shape0(&self->view);
+}
+
+/*
+  mem[obj] returns a bytes object holding the data for one element if
+           obj fully indexes the memory view or another memory-view object
+           if it does not.
+
+           0-d memory-view objects can be referenced using ... or () but
+           not with anything else.
+ */
+static PyObject *
+memory_subscript(PyMemoryViewObject *self, PyObject *key)
+{
+    Py_buffer *view;
+    view = &(self->view);
+    
+    if (view->ndim == 0) {
+        if (key == Py_Ellipsis ||
+            (PyTuple_Check(key) && PyTuple_GET_SIZE(key)==0)) {
+            Py_INCREF(self);
+            return (PyObject *)self;
+        }
+        else {
+            PyErr_SetString(PyExc_IndexError,
+                                "invalid indexing of 0-dim memory");
+            return NULL;
+        }
+    }
+    if (PyIndex_Check(key)) {
+        Py_ssize_t result;
+        result = PyNumber_AsSsize_t(key, NULL);
+        if (result == -1 && PyErr_Occurred())
+                return NULL;
+        if (view->ndim == 1) {
+            /* Return a bytes object */
+            char *ptr;
+            ptr = (char *)view->buf;
+            if (result < 0) {
+                result += get_shape0(view);
+            }
+            if ((result < 0) || (result >= get_shape0(view))) {
+                PyErr_SetString(PyExc_IndexError,
+                                "index out of bounds");
+                return NULL;
+            }
+            if (view->strides == NULL)
+                ptr += view->itemsize * result;
+            else
+                ptr += view->strides[0] * result;
+            if (view->suboffsets != NULL &&
+                view->suboffsets[0] >= 0) {
+                ptr = *((char **)ptr) + view->suboffsets[0];
+            }
+            return PyBytes_FromStringAndSize(ptr, view->itemsize);
+        }
+        else {
+            /* Return a new memory-view object */
+            Py_buffer newview;
+            memset(&newview, 0, sizeof(newview));
+            /* XXX:  This needs to be fixed so it
+                         actually returns a sub-view
+            */
+            return PyMemoryView_FromBuffer(&newview);
+        }
+    }
+    else if (PySlice_Check(key)) {
+        Py_ssize_t start, stop, step, slicelength;
+
+        if (PySlice_GetIndicesEx((PySliceObject*)key, get_shape0(view),
+                                 &start, &stop, &step, &slicelength) < 0) {
+            return NULL;
+        }
+    
+        if (step == 1 && view->ndim == 1) {
+            Py_buffer newview;
+            void *newbuf = (char *) view->buf
+                                    + start * view->itemsize;
+            int newflags = view->readonly
+                    ? PyBUF_CONTIG_RO : PyBUF_CONTIG;
+    
+            /* XXX There should be an API to create a subbuffer */
+            if (view->obj != NULL) {
+                if (PyObject_GetBuffer(view->obj, &newview, newflags) == -1)
+                    return NULL;
+            }
+            else {
+                newview = *view;
+            }
+            newview.buf = newbuf;
+            newview.len = slicelength * newview.itemsize;
+            newview.format = view->format;
+            newview.shape = &(newview.smalltable[0]);
+            newview.shape[0] = slicelength;
+            newview.strides = &(newview.itemsize);
+            return PyMemoryView_FromBuffer(&newview);
+        }
+        PyErr_SetNone(PyExc_NotImplementedError);
+        return NULL;
+    }
+    PyErr_Format(PyExc_TypeError,
+        "cannot index memory using \"%.200s\"", 
+        key->ob_type->tp_name);
+    return NULL;
+}
+
+
+/* Need to support assigning memory if we can */
+static int
+memory_ass_sub(PyMemoryViewObject *self, PyObject *key, PyObject *value)
+{
+    Py_ssize_t start, len, bytelen, i;
+    Py_buffer srcview;
+    Py_buffer *view = &(self->view);
+    char *srcbuf, *destbuf;
+
+    if (view->readonly) {
+        PyErr_SetString(PyExc_TypeError,
+            "cannot modify read-only memory");
+        return -1;
+    }
+    if (view->ndim != 1) {
+        PyErr_SetNone(PyExc_NotImplementedError);
+        return -1;
+    }
+    if (PyIndex_Check(key)) {
+        start = PyNumber_AsSsize_t(key, NULL);
+        if (start == -1 && PyErr_Occurred())
+            return -1;
+        if (start < 0) {
+            start += get_shape0(view);
+        }
+        if ((start < 0) || (start >= get_shape0(view))) {
+            PyErr_SetString(PyExc_IndexError,
+                            "index out of bounds");
+            return -1;
+        }
+        len = 1;
+    }
+    else if (PySlice_Check(key)) {
+        Py_ssize_t stop, step;
+
+        if (PySlice_GetIndicesEx((PySliceObject*)key, get_shape0(view),
+                         &start, &stop, &step, &len) < 0) {
+            return -1;
+        }
+        if (step != 1) {
+            PyErr_SetNone(PyExc_NotImplementedError);
+            return -1;
+        }
+    }
+    else {
+        PyErr_Format(PyExc_TypeError,
+            "cannot index memory using \"%.200s\"", 
+            key->ob_type->tp_name);
+        return -1;
+    }
+    if (PyObject_GetBuffer(value, &srcview, PyBUF_CONTIG_RO) == -1) {
+        return -1;
+    }
+    /* XXX should we allow assignment of different item sizes
+       as long as the byte length is the same?
+       (e.g. assign 2 shorts to a 4-byte slice) */
+    if (srcview.itemsize != view->itemsize) {
+        PyErr_Format(PyExc_TypeError,
+            "mismatching item sizes for \"%.200s\" and \"%.200s\"", 
+            view->obj->ob_type->tp_name, srcview.obj->ob_type->tp_name);
+        goto _error;
+    }
+    bytelen = len * view->itemsize;
+    if (bytelen != srcview.len) {
+        PyErr_SetString(PyExc_ValueError,
+            "cannot modify size of memoryview object");
+        goto _error;
+    }
+    /* Do the actual copy */
+    destbuf = (char *) view->buf + start * view->itemsize;
+    srcbuf = (char *) srcview.buf;
+    if (destbuf + bytelen < srcbuf || srcbuf + bytelen < destbuf)
+        /* No overlapping */
+        memcpy(destbuf, srcbuf, bytelen);
+    else if (destbuf < srcbuf) {
+        /* Copy in ascending order */
+        for (i = 0; i < bytelen; i++)
+            destbuf[i] = srcbuf[i];
+    }
+    else {
+        /* Copy in descencing order */
+        for (i = bytelen - 1; i >= 0; i--)
+            destbuf[i] = srcbuf[i];
+    }
+
+    PyBuffer_Release(&srcview);
+    return 0;
+
+_error:
+    PyBuffer_Release(&srcview);
+    return -1;
+}
+
+static PyObject *
+memory_richcompare(PyObject *v, PyObject *w, int op)
+{
+    Py_buffer vv, ww;
+    int equal = 0;
+    PyObject *res;
+
+    vv.obj = NULL;
+    ww.obj = NULL;
+    if (op != Py_EQ && op != Py_NE)
+        goto _notimpl;
+    if (PyObject_GetBuffer(v, &vv, PyBUF_CONTIG_RO) == -1) {
+        PyErr_Clear();
+        goto _notimpl;
+    }
+    if (PyObject_GetBuffer(w, &ww, PyBUF_CONTIG_RO) == -1) {
+        PyErr_Clear();
+        goto _notimpl;
+    }
+
+    if (vv.itemsize != ww.itemsize || vv.len != ww.len)
+        goto _end;
+
+    equal = !memcmp(vv.buf, ww.buf, vv.len);
+
+_end:
+    PyBuffer_Release(&vv);
+    PyBuffer_Release(&ww);
+    if ((equal && op == Py_EQ) || (!equal && op == Py_NE))
+        res = Py_True;
+    else
+        res = Py_False;
+    Py_INCREF(res);
+    return res;
+
+_notimpl:
+    PyBuffer_Release(&vv);
+    PyBuffer_Release(&ww);
+    Py_INCREF(Py_NotImplemented);
+    return Py_NotImplemented;
+}
+
+
+static int
+memory_traverse(PyMemoryViewObject *self, visitproc visit, void *arg)
+{
+    if (self->base != NULL)
+        Py_VISIT(self->base);
+    if (self->view.obj != NULL)
+        Py_VISIT(self->view.obj);
+    return 0;
+}
+
+static int
+memory_clear(PyMemoryViewObject *self)
+{
+    Py_CLEAR(self->base);
+    PyBuffer_Release(&self->view);
+    return 0;
+}
+
+
+/* As mapping */
+static PyMappingMethods memory_as_mapping = {
+    (lenfunc)memory_length,               /* mp_length */
+    (binaryfunc)memory_subscript,         /* mp_subscript */
+    (objobjargproc)memory_ass_sub,        /* mp_ass_subscript */
+};
+
+
+/* Buffer methods */
+static PyBufferProcs memory_as_buffer = {
+    0,                                    /* bf_getreadbuffer */
+    0,                                    /* bf_getwritebuffer */
+    0,                                    /* bf_getsegcount */
+    0,                                    /* bf_getcharbuffer */
+    (getbufferproc)memory_getbuf,         /* bf_getbuffer */
+    (releasebufferproc)memory_releasebuf, /* bf_releasebuffer */
+};
+
+
+PyTypeObject PyMemoryView_Type = {
+    PyVarObject_HEAD_INIT(&PyType_Type, 0)
+    "memoryview",
+    sizeof(PyMemoryViewObject),
+    0,
+    (destructor)memory_dealloc,               /* tp_dealloc */
+    0,                                        /* tp_print */
+    0,                                        /* tp_getattr */
+    0,                                        /* tp_setattr */
+    0,                                        /* tp_compare */
+    (reprfunc)memory_repr,                    /* tp_repr */
+    0,                                        /* tp_as_number */
+    0,                                        /* tp_as_sequence */
+    &memory_as_mapping,                       /* tp_as_mapping */
+    0,                                        /* tp_hash */
+    0,                                        /* tp_call */
+    0,                                        /* tp_str */
+    PyObject_GenericGetAttr,                  /* tp_getattro */
+    0,                                        /* tp_setattro */
+    &memory_as_buffer,                        /* tp_as_buffer */
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+        Py_TPFLAGS_HAVE_NEWBUFFER,            /* tp_flags */
+    memory_doc,                               /* tp_doc */
+    (traverseproc)memory_traverse,            /* tp_traverse */
+    (inquiry)memory_clear,                    /* tp_clear */
+    memory_richcompare,                       /* tp_richcompare */
+    0,                                        /* tp_weaklistoffset */
+    0,                                        /* tp_iter */
+    0,                                        /* tp_iternext */
+    memory_methods,                           /* tp_methods */
+    0,                                        /* tp_members */
+    memory_getsetlist,                        /* tp_getset */
+    0,                                        /* tp_base */
+    0,                                        /* tp_dict */
+    0,                                        /* tp_descr_get */
+    0,                                        /* tp_descr_set */
+    0,                                        /* tp_dictoffset */
+    0,                                        /* tp_init */
+    0,                                        /* tp_alloc */
+    memory_new,                               /* tp_new */
+};
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 4c397f7..cf5e2a9 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -2304,6 +2304,8 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
 		Py_TPFLAGS_BASETYPE;
 	if (base->tp_flags & Py_TPFLAGS_HAVE_GC)
 		type->tp_flags |= Py_TPFLAGS_HAVE_GC;
+	if (base->tp_flags & Py_TPFLAGS_HAVE_NEWBUFFER)
+		type->tp_flags |= Py_TPFLAGS_HAVE_NEWBUFFER;
 
 	/* It's a new-style number unless it specifically inherits any
 	   old-style numeric behavior */
@@ -3596,6 +3598,8 @@ add_getset(PyTypeObject *type, PyGetSetDef *gsp)
 	return 0;
 }
 
+#define BUFFER_FLAGS (Py_TPFLAGS_HAVE_GETCHARBUFFER | Py_TPFLAGS_HAVE_NEWBUFFER)
+
 static void
 inherit_special(PyTypeObject *type, PyTypeObject *base)
 {
@@ -3603,9 +3607,9 @@ inherit_special(PyTypeObject *type, PyTypeObject *base)
 
 	/* Special flag magic */
 	if (!type->tp_as_buffer && base->tp_as_buffer) {
-		type->tp_flags &= ~Py_TPFLAGS_HAVE_GETCHARBUFFER;
+		type->tp_flags &= ~BUFFER_FLAGS;
 		type->tp_flags |=
-			base->tp_flags & Py_TPFLAGS_HAVE_GETCHARBUFFER;
+			base->tp_flags & BUFFER_FLAGS;
 	}
 	if (!type->tp_as_sequence && base->tp_as_sequence) {
 		type->tp_flags &= ~Py_TPFLAGS_HAVE_SEQUENCE_IN;
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 4d7dec1..0f3392a5 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -2573,7 +2573,7 @@ _PyBuiltin_Init(void)
 	SETBUILTIN("True",		Py_True);
 	SETBUILTIN("basestring",	&PyBaseString_Type);
 	SETBUILTIN("bool",		&PyBool_Type);
-	/*	SETBUILTIN("memoryview",        &PyMemoryView_Type); */
+	SETBUILTIN("memoryview",        &PyMemoryView_Type);
 	SETBUILTIN("bytearray",		&PyByteArray_Type);
 	SETBUILTIN("bytes",		&PyString_Type);
 	SETBUILTIN("buffer",		&PyBuffer_Type);