Support acquiring slices from memoryviews

Cython/Utility/MemoryView.pyx

@@ -119,11 +119,6 @@ cdef class array:
         else:
             info.format = NULL
 
-        # info.obj = self
-
-    def __releasebuffer__(self, Py_buffer *info):
-        pass
-
     def __dealloc__(array self):
         if self.callback_free_data != NULL:
             self.callback_free_data(self.data)
@@ -183,6 +178,9 @@ cdef extern from *:
     int __Pyx_GetBuffer(object, Py_buffer *, int) except -1
     void __Pyx_ReleaseBuffer(Py_buffer *)
 
+    void Py_INCREF(object)
+    void Py_DECREF(object)
+
     ctypedef struct PyObject
 
     cdef struct __pyx_memoryview "__pyx_memoryview_obj":
@@ -224,6 +222,7 @@ cdef class memoryview(object):
     cdef PyThread_type_lock lock
     cdef int acquisition_count
     cdef Py_buffer view
+    cdef int flags
 
     def __cinit__(memoryview self, object obj, int flags):
         self.obj = obj
@@ -303,6 +302,10 @@ cdef class memoryview(object):
         for i, c in enumerate(bytesvalue):
             itemp[i] = c
 
+    def __getbuffer__(self, Py_buffer *info, int flags):
+        info[0] = self.view
+        info.obj = self
+
     property T:
         @cname('__pyx_memoryview_transpose')
         def __get__(self):
@@ -432,6 +435,7 @@ cdef memoryview memview_slice(memoryview memview, object indices):
     else:
         return memoryview_fromslice(&dst, new_ndim, NULL, NULL)
 
+
 #
 ### Slicing in a single dimension of a memoryviewslice
 #
@@ -673,6 +677,9 @@ cdef class _memoryviewslice(memoryview):
         def __get__(self):
             return self.from_object
 
+@cname('__pyx_memoryviewslice_check')
+cdef int __pyx_memoryviewslice_check(obj):
+    return isinstance(obj, _memoryviewslice)
 
 @cname('__pyx_memoryview_fromslice')
 cdef memoryview_fromslice({{memviewslice_name}} *memviewslice,

Cython/Utility/MemoryView_C.c

@@ -259,7 +259,7 @@ no_fail:
 }
 
 
-static CYTHON_INLINE void __pyx_fatalerror(char *fmt, ...) {
+static CYTHON_INLINE void __pyx_fatalerror(const char *fmt, ...) {
     va_list vargs;
     char msg[200];
 

Cython/Utility/TypeConversion.c

@@ -15,7 +15,7 @@ static {{struct_type_decl}} {{funcname}}(PyObject * o) {
     {{for member in var_entries:}}
         {{py:attr = "result." + member.cname}}
 
-        value = PyMapping_GetItemString(o, "{{member.name}}");
+        value = PyMapping_GetItemString(o, (char *) "{{member.name}}");
         if (!value) {
             PyErr_SetString(PyExc_ValueError, "No value specified for struct "
                                               "attribute '{{member.name}}'");

tests/run/memoryview.pyx

@@ -753,3 +753,51 @@ def test_oob():
     """
     cdef int[:, :] a = IntMockBuffer("A", range(4 * 9), shape=(4, 9))
     print a[:, 20]
+
+def test_acquire_memoryview():
+    """
+    >>> test_acquire_memoryview()
+    acquired A
+    22
+    <MemoryView of 'IntMockBuffer' object>
+    22
+    22
+    released A
+    """
+    cdef int[:, :] a = IntMockBuffer("A", range(4 * 9), shape=(4, 9))
+    cdef object b = a
+
+    print a[2, 4]
+
+    # Make sure we don't have to keep this around
+    del a
+
+    print b
+    cdef int[:, :] c = b
+    print b[2, 4]
+    print c[2, 4]
+
+def test_acquire_memoryview_slice():
+    """
+    >>> test_acquire_memoryview_slice()
+    acquired A
+    31
+    <MemoryView of 'IntMockBuffer' object>
+    31
+    31
+    released A
+    """
+    cdef int[:, :] a = IntMockBuffer("A", range(4 * 9), shape=(4, 9))
+    a = a[1:, :6]
+
+    cdef object b = a
+
+    print a[2, 4]
+
+    # Make sure we don't have to keep this around
+    del a
+
+    print b
+    cdef int[:, :] c = b
+    print b[2, 4]
+    print c[2, 4]