Merge pull request #2395 from gabrieldemarmiesse/test_buffer_2

Added tests to "Implementing the buffer protocol" part 2

docs/examples/userguide/buffer/matrix_with_buffer.pyx

+# distutils: language = c++
+
+from cpython cimport Py_buffer
+from libcpp.vector cimport vector
+
+cdef class Matrix:
+    cdef Py_ssize_t ncols
+    cdef Py_ssize_t shape[2]
+    cdef Py_ssize_t strides[2]
+    cdef vector[float] v
+
+    def __cinit__(self, Py_ssize_t ncols):
+        self.ncols = ncols
+
+    def add_row(self):
+        """Adds a row, initially zero-filled."""
+        self.v.resize(self.v.size() + self.ncols)
+
+    def __getbuffer__(self, Py_buffer *buffer, int flags):
+        cdef Py_ssize_t itemsize = sizeof(self.v[0])
+
+        self.shape[0] = self.v.size() / self.ncols
+        self.shape[1] = self.ncols
+
+        # Stride 1 is the distance, in bytes, between two items in a row;
+        # this is the distance between two adjacent items in the vector.
+        # Stride 0 is the distance between the first elements of adjacent rows.
+        self.strides[1] = <Py_ssize_t>(  <char *>&(self.v[1])
+                                       - <char *>&(self.v[0]))
+        self.strides[0] = self.ncols * self.strides[1]
+
+        buffer.buf = <char *>&(self.v[0])
+        buffer.format = 'f'                     # float
+        buffer.internal = NULL                  # see References
+        buffer.itemsize = itemsize
+        buffer.len = self.v.size() * itemsize   # product(shape) * itemsize
+        buffer.ndim = 2
+        buffer.obj = self
+        buffer.readonly = 0
+        buffer.shape = self.shape
+        buffer.strides = self.strides
+        buffer.suboffsets = NULL                # for pointer arrays only
+
+    def __releasebuffer__(self, Py_buffer *buffer):
+        pass

docs/src/userguide/buffer.rst

@@ -27,51 +27,7 @@ Implementing the buffer protocol requires adding two methods,
 ``__getbuffer__`` and ``__releasebuffer__``,
 which Cython handles specially.
 
-::
-
-    from cpython cimport Py_buffer
-    from libcpp.vector cimport vector
-
-    cdef class Matrix:
-        cdef Py_ssize_t ncols
-        cdef Py_ssize_t shape[2]
-        cdef Py_ssize_t strides[2]
-        cdef vector[float] v
-
-        def __cinit__(self, Py_ssize_t ncols):
-            self.ncols = ncols
-
-        def add_row(self):
-            """Adds a row, initially zero-filled."""
-            self.v.resize(self.v.size() + self.ncols)
-
-        def __getbuffer__(self, Py_buffer *buffer, int flags):
-            cdef Py_ssize_t itemsize = sizeof(self.v[0])
-
-            self.shape[0] = self.v.size() / self.ncols
-            self.shape[1] = self.ncols
-
-            # Stride 1 is the distance, in bytes, between two items in a row;
-            # this is the distance between two adjacent items in the vector.
-            # Stride 0 is the distance between the first elements of adjacent rows.
-            self.strides[1] = <Py_ssize_t>(  <char *>&(self.v[1])
-                                           - <char *>&(self.v[0]))
-            self.strides[0] = self.ncols * self.strides[1]
-
-            buffer.buf = <char *>&(self.v[0])
-            buffer.format = 'f'                     # float
-            buffer.internal = NULL                  # see References
-            buffer.itemsize = itemsize
-            buffer.len = self.v.size() * itemsize   # product(shape) * itemsize
-            buffer.ndim = 2
-            buffer.obj = self
-            buffer.readonly = 0
-            buffer.shape = self.shape
-            buffer.strides = self.strides
-            buffer.suboffsets = NULL                # for pointer arrays only
-
-        def __releasebuffer__(self, Py_buffer *buffer):
-            pass
+.. literalinclude:: ../../examples/userguide/buffer/matrix_with_buffer.pyx
 
 The method ``Matrix.__getbuffer__`` fills a descriptor structure,
 called a ``Py_buffer``, that is defined by the Python C-API.