added .pxd for legacy Python 2 buffer interface

Cython/Includes/python.pxd

@@ -146,6 +146,7 @@ from python_getargs cimport *
 
 # Python <= 2.x
 from python_cobject cimport *
+from python_oldbuffer cimport *
 
 # Python >= 2.4
 from python_set cimport *

Cython/Includes/python_oldbuffer.pxd

+# Legacy Python 2 buffer interface.
+#
+# These functions are no longer available in Python 3, use the new
+# buffer interface instead.
+
+cdef extern from "Python.h":
+    cdef enum _:
+        Py_END_OF_BUFFER
+    #    This constant may be passed as the size parameter to
+    #    PyBuffer_FromObject() or PyBuffer_FromReadWriteObject(). It
+    #    indicates that the new PyBufferObject should refer to base object
+    #    from the specified offset to the end of its exported
+    #    buffer. Using this enables the caller to avoid querying the base
+    #    object for its length.
+
+    bint PyBuffer_Check(object p)
+    #    Return true if the argument has type PyBuffer_Type.
+
+    object PyBuffer_FromObject(object base, Py_ssize_t offset, Py_ssize_t size)
+    #    Return value: New reference.
+    #
+    #    Return a new read-only buffer object. This raises TypeError if
+    #    base doesn't support the read-only buffer protocol or doesn't
+    #    provide exactly one buffer segment, or it raises ValueError if
+    #    offset is less than zero. The buffer will hold a reference to the
+    #    base object, and the buffer's contents will refer to the base
+    #    object's buffer interface, starting as position offset and
+    #    extending for size bytes. If size is Py_END_OF_BUFFER, then the
+    #    new buffer's contents extend to the length of the base object's
+    #    exported buffer data.
+
+    object PyBuffer_FromReadWriteObject(object base, Py_ssize_t offset, Py_ssize_t size)
+    #    Return value: New reference.
+    #
+    #    Return a new writable buffer object. Parameters and exceptions
+    #    are similar to those for PyBuffer_FromObject(). If the base
+    #    object does not export the writeable buffer protocol, then
+    #    TypeError is raised.
+
+    object PyBuffer_FromMemory(void *ptr, Py_ssize_t size)
+    #    Return value: New reference.
+    #
+    #    Return a new read-only buffer object that reads from a specified
+    #    location in memory, with a specified size. The caller is
+    #    responsible for ensuring that the memory buffer, passed in as
+    #    ptr, is not deallocated while the returned buffer object
+    #    exists. Raises ValueError if size is less than zero. Note that
+    #    Py_END_OF_BUFFER may not be passed for the size parameter;
+    #    ValueError will be raised in that case.
+
+    object PyBuffer_FromReadWriteMemory(void *ptr, Py_ssize_t size)
+    #    Return value: New reference.
+    #
+    #    Similar to PyBuffer_FromMemory(), but the returned buffer is
+    #    writable.
+
+    object PyBuffer_New(Py_ssize_t size)
+    #    Return value: New reference.
+    #
+    #    Return a new writable buffer object that maintains its own memory
+    #    buffer of size bytes. ValueError is returned if size is not zero
+    #    or positive. Note that the memory buffer (as returned by
+    #    PyObject_AsWriteBuffer()) is not specifically aligned.