BUG: fix memory leak

The OWNDATA flag was not getting changed, and as a result, there was a
memory leak. I changed strategy, and use a deallocation in the
__dealloc__ method.

cython_wrapper.pyx

@@ -13,6 +13,8 @@ http://cython.org for more information
 cdef extern from "c_code.c":
 cdef extern from "c_code.c":
     float *compute(int size)
     float *compute(int size)
 
 
+from libc.stdlib cimport free
+
 # Import the Python-level symbols of numpy
 # Import the Python-level symbols of numpy
 import numpy as np
 import numpy as np
 
 
@@ -23,6 +25,43 @@ cimport numpy as np
 # _always_ do that, or you will have segfaults
 # _always_ do that, or you will have segfaults
 np.import_array()
 np.import_array()
 
 
+# We need to build an array-wrapper class to deallocate our array when
+# the Python object is deleted.
+
+cdef class ArrayWrapper:
+    cdef void* data_ptr
+    cdef int size
+
+    cdef set_data(self, int size, void* data_ptr):
+        """ Constructor for the class.
+
+        Mallocs a memory buffer of size (n*sizeof(int)) and sets up
+        the numpy array.
+
+        Parameters:
+        -----------
+        n -- Length of the array.
+
+        Data attributes:
+        ----------------
+        data -- Pointer to an integer array.
+        alloc -- Size of the data buffer allocated.
+
+        """
+        self.data_ptr = data_ptr
+        self.size = size
+
+    def __array__(self):
+        cdef np.npy_intp shape[1]
+        shape[0] = <np.npy_intp> self.size
+        ndarray = np.PyArray_SimpleNewFromData(1, shape,
+                                np.NPY_INT, self.data_ptr)
+        return ndarray
+
+    def __dealloc__(self):
+        """ Frees the array. """
+        free(<void*>self.data_ptr)
+
 
 
 def py_compute(int size):
 def py_compute(int size):
     """ Python binding of the 'compute' function in 'c_code.c' that does
     """ Python binding of the 'compute' function in 'c_code.c' that does
@@ -32,18 +71,7 @@ def py_compute(int size):
     # Call the C function
     # Call the C function
     array = compute(size)
     array = compute(size)
 
 
-    # Create a C array to describe the shape of the ndarray
-    cdef np.npy_intp shape[1]
-    shape[0] = <np.npy_intp> size
-
-    # Use the PyArray_SimpleNewFromData function from numpy to create a
-    # new Python object pointing to the existing data
-    ndarray = np.PyArray_SimpleNewFromData(1, shape,
-                    np.NPY_INT, <void *> array)
+    array_wrapper = ArrayWrapper()
+    array_wrapper.set_data(size, <void*> array) 
 
 
-    # Tell Python that it can deallocate the memory when the ndarray
-    # object gets garbage collected
-    # As the OWNDATA flag of an array is read-only in Python, we need to
-    # call the C function PyArray_UpdateFlags
-    np.PyArray_UpdateFlags(ndarray, ndarray.flags.num | np.NPY_OWNDATA)
-    return ndarray
+    return np.array(array_wrapper)

test.py

@@ -4,4 +4,5 @@
 # License: BSD
 # License: BSD
 
 
 import cython_wrapper
 import cython_wrapper
-print cython_wrapper.py_compute(10)
+a = cython_wrapper.py_compute(10)
\ No newline at end of file
+print a