add method ndarray::set_flag and corresponding test

include/boost/python/numpy/ndarray.hpp

@@ -121,6 +121,9 @@ class BOOST_NUMPY_DECL ndarray : public object
   /// @brief Return the array flags.
   bitflag get_flags() const;
 
+  /// @brief Set array flag. This can destroy the internal consistency, use with care!
+  void set_flag(bitflag flag, bool on);
+
   /// @brief Reverse the dimensions of the array.
   ndarray transpose() const;
 

src/numpy/ndarray.cpp

@@ -210,6 +210,14 @@ ndarray::bitflag ndarray::get_flags() const
   return numpy::detail::numpy_to_bitflag(get_struct()->flags);
 }
 
+void ndarray::set_flag(ndarray::bitflag flag, bool on) {
+  const int x = numpy::detail::bitflag_to_numpy(flag);
+  if (on)
+    PyArray_ENABLEFLAGS(reinterpret_cast<PyArrayObject*>(this->ptr()), x);
+  else
+    PyArray_CLEARFLAGS(reinterpret_cast<PyArrayObject*>(this->ptr()), x);
+}
+
 ndarray ndarray::transpose() const 
 {
   return ndarray(python::detail::new_reference

test/numpy/ndarray.cpp

@@ -34,6 +34,9 @@ np::ndarray reshape(np::ndarray arr,p::tuple tup) { return arr.reshape(tup);}
 Py_intptr_t shape_index(np::ndarray arr,int k) { return arr.shape(k); }
 Py_intptr_t strides_index(np::ndarray arr,int k) { return arr.strides(k); }
 
+bool is_writeable(np::ndarray arr) { return arr.get_flags() & np::ndarray::WRITEABLE; }
+void set_writeable(np::ndarray arr, bool on) { arr.set_flag(np::ndarray::WRITEABLE, on); }
+
 BOOST_PYTHON_MODULE(ndarray_ext)
 {
   np::initialize();
@@ -48,4 +51,6 @@ BOOST_PYTHON_MODULE(ndarray_ext)
   p::def("reshape", reshape);
   p::def("shape_index", shape_index);
   p::def("strides_index", strides_index);
+  p::def("is_writeable", is_writeable);
+  p::def("set_writeable", set_writeable);
 }

test/numpy/ndarray.py

@@ -107,6 +107,16 @@ def strides_check(i):
         except IndexError:
             pass
 
+    def testArrayFlags(self):
+        a = numpy.arange(24)
+        old_flags = a.flags
+        self.assertTrue(a.flags.writeable)
+        self.assertTrue(ndarray_ext.is_writeable(a))
+        ndarray_ext.set_writeable(a, False)
+        self.assertFalse(a.flags.writeable)
+        self.assertFalse(ndarray_ext.is_writeable(a))
+        ndarray_ext.set_writeable(a, True)
+        self.assertEqual(old_flags, a.flags)
 
 if __name__=="__main__":
     unittest.main()